Fragments

Os fragmentos foram criados com o objetivo modularizar a parte gráfica do app. Cada uma dessas partes possui seu próprio layout, clico de vida e necessitam de uma atividade. Conforme consta na documentação oficial, Google Developers (2021), "Um fragmento representa uma parte reutilizável da IU do seu app. Um fragmento define e gerencia o próprio layout, tem o próprio ciclo de vida e pode processar os próprios eventos de entrada. Fragmentos não podem existir por conta própria" .

Referências do texto entre aspas:

GOOGLE DEVELOPERS. Fragmentos. Disponível em: https://developer.android.com/guide/fragments#videos. Acesso em: 04 de ago. 2024.

Os fragmentos também possuem um ciclo de vida, sendo que o método mais relevante é o onCreateView que será chamado para criar a interface gráfica personalizada no arquivo de layout especifico do fragmento. O método retorna uma View que representa a raiz do layout do fragmento. Para a activity o fragmento será visto como mais uma view inserida em seu layout.

Métodos do ciclo de vida:

onAttach(Context context): o fragmento é anexado ao contexto da activity;
onCreate(Bundle savedInstanceState): cria o fragmento, pode ser usado para passar informações vinculadas ao objeto Bundle;
onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState): retorna a View criada a partir do layout personalizado do fragmento;
onViewCreated(View view, Bundle savedInstanceState):invocado logo após a criação da View. Pode ser usado para adicionar eventos, ou outras configurações de interface gráfica;
onStart(): a mesma tarefa definida na activity, ou seja, está visível, mas não aceita solicitações do usuário;
onResume(): a mesma tarefa definida na activity, ou seja, visível e responde ao usuário;
onPause(): a mesma tarefa definida na activity, ou seja, é chamado quando o fragmento está parcialmente visível;
onStop(): a mesma tarefa definida na activity, ou seja, é chamado quando o fragmento não está mais visível;
onDestroyView(): método chamado quando a view do fragmento é destruída. Pode ser usado para liberar recursos associados à interface do usuário;
onDestroy(): chamado para encerrar o fragmento;
onDetach(): o fragmento é desassociado da activity.
Referência: GOOGLE DEVELOPERS. Ciclo de Vida dos Fragmentos. Disponível em:https://developer.android.com/guide/fragments/lifecycle?hl=pt-br. Acessado em: 26 ago. 2024.

Exemplos práticos (estático):

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
    <color name="red">#CE3D3D</color>
    <color name="green">#4CAF50</color>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <fragment
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:name="com.example.fragment_01.Tela1"
    android:id="@+id/tela1"/>
    <fragment
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:name="com.example.fragment_01.Tela2"
    android:id="@+id/tela2"/>
</LinearLayout>

MainActivity.java

import android.os.Bundle;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

tela1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:background="@color/green"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextNome"
        android:hint="Digite seu nome"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/buttonNome"
        android:text="CLICK"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textViewNome"/>
</LinearLayout>

Tela1.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Tela1 extends Fragment {
    private EditText editText;
    private Button button;
    private TextView textView;
    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.tela1,container,
                false);
        return view;
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        editText = view.findViewById(R.id.editTextNome);
        button = view.findViewById(R.id.buttonNome);
        textView = view.findViewById(R.id.textViewNome);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textView.setText(editText.getText().toString());
            }
        });
    }
}

tela2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:background="@color/red"
    android:layout_height="match_parent">
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextCurso"
        android:hint="Digite o curso"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/buttonCurso"
        android:text="CLICK"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textViewCurso"/>
</LinearLayout>

Tela2.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Tela2 extends Fragment {
    private EditText editText;
    private Button button;
    private TextView textView;
    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.tela2, container, false);
        return view;
    }//method
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        editText = view.findViewById(R.id.editTextCurso);
        button = view.findViewById(R.id.buttonCurso);
        textView = view.findViewById(R.id.textViewCurso);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textView.setText(editText.getText().toString());
            }
        });
    }
}

Exemplos práticos (dinâmico):

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
    <color name="green">#4CAF50</color>
    <color name="orange">#FF9800</color>
    <color name="blue">#00BCD4</color>
    <color name="red">#E91E63</color>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/orange"
    tools:context=".MainActivity">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:layout_width="0dp"
            android:layout_weight="1"
            android:text="Tela1"
            android:onClick="trocar"
            android:id="@+id/buttonTela1"
            android:layout_height="wrap_content"/>
        <Button
            android:layout_width="0dp"
            android:layout_weight="1"
            android:text="Tela2"
            android:onClick="trocar"
            android:id="@+id/buttonTela2"
            android:layout_height="wrap_content"/>
    </LinearLayout>
    <FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/red"
    android:id="@+id/telaPrincipal" />
</LinearLayout>

MainActivity.java

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
    private Button buttonTela1,buttonTela2;
    private FragmentManager fm;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        buttonTela1 = findViewById(R.id.buttonTela1);
        buttonTela2 = findViewById(R.id.buttonTela2);
        fm = getSupportFragmentManager();
        // Carrega a tela 1
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.telaPrincipal, new Tela1());
        ft.commit();
    }
    public void trocar(View view){
        if(view.getId() == R.id.buttonTela1){
            FragmentTransaction ft = fm.beginTransaction();
            ft.replace(R.id.telaPrincipal, new Tela1());
            ft.commit();  //confirmar
        }
        if(view.getId() == R.id.buttonTela2){
            FragmentTransaction ft = fm.beginTransaction();
            ft.replace(R.id.telaPrincipal, new Tela2());
            ft.commit();
        }
    }//
}

tela1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="@color/green"
    android:orientation="vertical"
    android:layout_height="match_parent">
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextNome"
        android:hint="Digite seu nome"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/buttonNome"
        android:text="CLICK"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textViewNome" />
</LinearLayout>

Tela1.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Tela1 extends Fragment {
    private EditText editText;
    private Button button;
    private TextView textView;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.tela1,container, false);
        return view;
    }//method
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        editText = view.findViewById(R.id.editTextNome);
        button = view.findViewById(R.id.buttonNome);
        textView = view.findViewById(R.id.textViewNome);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textView.setText(editText.getText().toString());
            }
        });
    }
}

tela2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="@color/blue"
    android:orientation="vertical"
    android:layout_height="match_parent">
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editTextCurso"
        android:hint="Digite o curso"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/buttonCurso"
        android:text="CLICK"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textViewCurso" />
</LinearLayout>

Tela2.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Tela2 extends Fragment {
    private EditText editText;
    private Button button;
    private TextView textView;
    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.tela2,container,false);
        return view;
    }//method
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        editText = view.findViewById(R.id.editTextCurso);
        button = view.findViewById(R.id.buttonCurso);
        textView = view.findViewById(R.id.textViewCurso);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textView.setText(editText.getText().toString());
            }
        });
    }
}

Veja que na documentação oficial(https://developer.android.com/guide/fragments/create?hl=pt-br), que a tag para adicionar o fragmento foi atualizada para <androidx.fragment.app.FragmentContainerView>. A mesma tag pode ser usada tanto para adicionar o fragmento via XML como programaticamente. A diferença é que para adicionar via XML, deve ser usado o atributo name, passando o nome da classe java que estende a classe Fragment. Caso deseje adicionar de forma dinâmica use o atributo id.

Por exemplo: no arquivo activity_main.xml a nova tag adicionada ficaria assim:

<androidx.fragment.app.FragmentContainerView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:id="@+id/tela" />

Na classe MainActivity, coloque o gerenciamento de fragmento no método onCreate.

protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   getSupportFragmentManager().beginTransaction()
           .setReorderingAllowed(true)
           .add(R.id.tela, FragmentActivity.class,null)
           .commit();
}

Exemplos práticos (FragContentView):

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
    <color name="green">#4CAF50</color>
    <color name="orange">#FF9800</color>
    <color name="blue">#00BCD4</color>
    <color name="red">#E91E63</color>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/orange"
    tools:context=".MainActivity">
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/telaPrincipal"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/green"
        tools:layout="@layout/tela1" />
</LinearLayout>

tela1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center"
    android:padding="24dp"
    android:background="@android:color/holo_blue_light">
    <TextView
        android:id="@+id/textViewMensagem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Olá, você está na Tela 1!"
        android:textSize="20sp"
        android:textColor="@android:color/white" />
    <Button
        android:id="@+id/buttonMensagem"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Clique aqui"
        android:layout_marginTop="16dp" />
</LinearLayout>

Tela1.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class Tela1 extends Fragment {
    private TextView textView;
    private Button button;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.tela1, container, false);
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        textView = view.findViewById(R.id.textViewMensagem);
        button = view.findViewById(R.id.buttonMensagem);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textView.setText("Você clicou no botão da Tela 1!");
            }
        });
    }
}

MainActivity.java

import android.os.Bundle;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.telaPrincipal, new Tela1());
        ft.commit();
    }
}

Exemplo mostrando a interação do clico de vida da Activity e dos Fragments:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <FrameLayout
            android:id="@+id/fragment_container"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" />
        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Trocar Fragmento" />
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

fragment_imagem.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ImagemFragment">
    <ImageView
        android:id="@+id/imagem"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher_foreground"
        tools:srcCompat="@tools:sample/avatars" />
</FrameLayout>

fragment_lista.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ListaFragment">
    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</FrameLayout>

MainActivity.java

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
    private boolean controleFragment = true;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //permite que você exiba visualizações atrás da barra de status
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        //insets barra de status no topo da tela
        // ou a barra de navegação na parte inferior.
        //garantir que o conteúdo da tela
        // não fique oculto ou sobreposto por esses elementos do sistema.
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });
        Log.i("Activity","Criada");
        if (savedInstanceState == null) {
            mostrar(new ImagemFragment());
        }
        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // Alterna entre os fragmentos
                if (controleFragment) {
                    mostrar(new ListaFragment());
                } else {
                    mostrar(new ImagemFragment());
                }
                controleFragment = !controleFragment;
            }
        });
    }//
    private void mostrar(Fragment fragment) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container, fragment);
        fragmentTransaction.commit();
    }
    @Override
    protected void onPause() {
        super.onPause();
        Log.i("Activity","Pausada");
    }
    @Override
    protected void onResume() {
        super.onResume();
        Log.i("Activity","Pronta");
    }
    @Override
    protected void onStart() {
        super.onStart();
        Log.i("Activity","Inicializada");
    }
    @Override
    protected void onStop() {
        super.onStop();
        Log.i("Activity","Parada");
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.i("Activity","Destruída");
    }
}//

ImagemFragment.java

import android.content.Context;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class ImagemFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        Log.e("Fragment","criando a view");
        return inflater.inflate(R.layout.fragment_imagem,
                container, false);
    }//
    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
        Log.e("Fragment","anexado");
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("Fragment","criado");
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Log.e("Fragment","view já criada");
    }
    @Override
    public void onStart() {
        super.onStart();
        Log.e("Fragment","inicializado");
    }
    @Override
    public void onResume() {
        super.onResume();
        Log.e("Fragment","pronto");
    }
    @Override
    public void onStop() {
        super.onStop();
        Log.e("Fragment","parado");
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.e("Fragment","destroi o fragmento");
    }
    @Override
    public void onDetach() {
        super.onDetach();
        Log.e("Fragment","desassocia o fragmento à actividade");
    }
    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.e("Fragment","destroi a view do fragmento");
    }
    @Override
    public void onPause() {
        super.onPause();
        Log.e("Fragment","pausado");
    }
}//class

ListaFragment.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class ListaFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_lista, container,
                false);
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        ListView listView = view.findViewById(R.id.list_view);
        String[] items = {"Java", "Python", "Kotlin"};
        ArrayAdapter<String> adapter = new ArrayAdapter<>(getContext(),
                android.R.layout.simple_list_item_1, items);
        listView.setAdapter(adapter);
    }
}

Exemplos práticos (Passando valor da activity para o fragmento):

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <androidx.fragment.app.FragmentContainerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</LinearLayout>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (savedInstanceState == null) {
            Bundle bundle = new Bundle();
            bundle.putInt("number", 10);
            getSupportFragmentManager().beginTransaction()
                    .setReorderingAllowed(true)
                    .add(R.id.fragment_container_view,
                            ExampleFragment.class, bundle)
                    .commit();
        }
    }
}

example_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:padding="16dp">
    <TextView
        android:id="@+id/textViewHello"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Texto padrão"
        android:textSize="20sp"/>
</LinearLayout>

ExampleFragment.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class ExampleFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.example_fragment, container, false);
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Bundle bundle = getArguments();
        if (bundle != null) {
            Integer msg = bundle.getInt("number");
            TextView textViewHello = view.findViewById(R.id.textViewHello);
            textViewHello.setText(msg.toString());
        }
    }
}

Exemplos práticos (Comunicação entre Fragment e Activity):

fragment_mensagem.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="16dp">
    <EditText
        android:id="@+id/editTextMensagem"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Digite algo" />
    <Button
        android:id="@+id/buttonEnviar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Enviar" />
</LinearLayout>

FragmentMensagem.java

import android.content.Context;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
public class FragmentMensagem extends Fragment {
    private EditText editText;
    private Button button;
    private EnviarMensagemListener listener;
    // Interface de comunicação com a Activity
    public interface EnviarMensagemListener {
        void onMensagemEnviada(String texto);
    }
    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
        if (context instanceof EnviarMensagemListener) {
            listener = (EnviarMensagemListener) context;
        }
    }
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_mensagem, container, false);
        editText = view.findViewById(R.id.editTextMensagem);
        button = view.findViewById(R.id.buttonEnviar);
        button.setOnClickListener(v -> {
            String texto = editText.getText().toString();
            if (listener != null) {
                listener.onMensagemEnviada(texto);
            }
        });
        return view;
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/containerFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

MainActivity.java

import android.os.Bundle;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity
        implements FragmentMensagem.EnviarMensagemListener {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.containerFragment,
                            new FragmentMensagem())
                    .commit();
        }
    }
    @Override
    public void onMensagemEnviada(String texto) {
        Toast.makeText(this, "Recebido do Fragmento: "
                + texto, Toast.LENGTH_SHORT).show();
    }
}

Exemplos práticos (maneiras de trocar os fragmentos):

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="black">#FF000000</color>
    <color name="white">#FFFFFFFF</color>
    <color name="green">#8BC34A</color>
    <color name="blue">#00BCD4</color>
</resources>

fragment_one.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/green">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Fragmento 1"
        android:gravity="center"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium" />
</FrameLayout>

fragment_two.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/blue">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="Fragmento 2"
        android:gravity="center"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium" />
</FrameLayout>

FragmentOne.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class FragmentOne extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_one, container, false);
    }
}

FragmentTwo.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class FragmentTwo extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_two, container, false);
    }
}

ActivityMain.java

import android.os.Bundle;
import android.view.View;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
public class MainActivity extends AppCompatActivity {
    FragmentManager fragmentManager;
    FragmentTransaction transaction;
    boolean adicionado = false;
    Fragment fragmentOne, fragmentTwo;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fragmentManager = getSupportFragmentManager();
        fragmentOne = new FragmentOne();
        fragmentTwo = new FragmentTwo();
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, fragmentOne)
                .commit();
        findViewById(R.id.buttonTrocar).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                transaction = fragmentManager.beginTransaction();
                transaction.replace(R.id.container, fragmentTwo);
                transaction.commit();
            }
        });
        findViewById(R.id.buttonRetornar).
                setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        transaction = fragmentManager.beginTransaction();
                        transaction.replace(R.id.container, fragmentTwo);
                        transaction.addToBackStack(null); // permite voltar para a tela anterior
                        transaction.commit();
                    }
                });
        findViewById(R.id.buttonOcultar).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                transaction = fragmentManager.beginTransaction();
                if (!adicionado) {
                    // Adiciona o fragmento2 e esconde o fragmento1
                   //ambos ficam na memória
                    transaction.hide(fragmentOne);
                    transaction.add(R.id.container, fragmentTwo);
                    adicionado = true;
                } else {
                    // Alterna entre os dois
                    if (fragmentTwo.isHidden()) {
                        transaction.hide(fragmentOne);
                        transaction.show(fragmentTwo);
                    } else {
                        transaction.hide(fragmentTwo);
                        transaction.show(fragmentOne);
                    }
                }
                transaction.commit();
            }
        });
    }
}

Exemplos práticos (lista com 4 itens e cada item é mostrado usando fragmentos):

strings.xml

<resources>
    <string name="app_name">FragLista</string>
    <!-- Nomes das Estrelas -->
    <string name="estrela_1_nome">Estrela 1</string>
    <string name="estrela_2_nome">Estrela 2</string>
    <string name="estrela_3_nome">Estrela 3</string>
    <!-- Descrições das Estrelas -->
    <string name="estrela_1_descricao">Descrição detalhada da Estrela 1.</string>
    <string name="estrela_2_descricao">Descrição detalhada da Estrela 2.</string>
    <string name="estrela_3_descricao">Descrição detalhada da Estrela 3.</string>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

MainActivity.java

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class MainActivity extends AppCompatActivity implements EstrelaAdapter.OnItemClickListener {
    private RecyclerView recyclerView;
    private EstrelaAdapter estrelaAdapter;
    private List<Estrela> estrelas;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        EstrelaRepositorio estrelaRepositorio = new EstrelaRepositorio(this);
        estrelas = estrelaRepositorio.getStars();
        estrelaAdapter = new EstrelaAdapter(estrelas, this);
        recyclerView.setAdapter(estrelaAdapter);
    }
    @Override
    public void onItemClick(Estrela estrela) {
        // Ao clicar em um item da lista, abrir a DetalheActivity
        Intent intent = new Intent(MainActivity.this, DetalheActivity.class);
        intent.putExtra("estrela_nome", estrela.getNome());
        intent.putExtra("estrela_descricao", estrela.getDescricao());
        startActivity(intent);
    }
}

Estrela.java

public class Estrela {
    private String nome;
    private String descricao;
    public Estrela(String nome, String descricao) {
        this.nome = nome;
        this.descricao = descricao;
    }
    public String getNome() {
        return nome;
    }
    public void setNome(String nome) {
        this.nome = nome;
    }
    public String getDescricao() {
        return descricao;
    }
    public void setDescricao(String descricao) {
        this.descricao = descricao;
    }
    @Override
    public String toString() {
        return "Estrela{" +
                "nome='" + nome + '\'' +
                '}';
    }
}

EstrelaRepositorio.java

import android.content.Context;
import android.content.res.Resources;
import java.util.ArrayList;
import java.util.List;
public class EstrelaRepositorio {
    private Context context;
    public EstrelaRepositorio(Context context) {
        this.context = context;
    }
    public List<Estrela> getStars() {
        List<Estrela> estrelas = new ArrayList<>();
        Resources res = context.getResources();
        estrelas.add(new Estrela(res.getString(R.string.estrela_1_nome), res.getString(R.string.estrela_1_descricao)));
        estrelas.add(new Estrela(res.getString(R.string.estrela_2_nome), res.getString(R.string.estrela_2_descricao)));
        estrelas.add(new Estrela(res.getString(R.string.estrela_3_nome), res.getString(R.string.estrela_3_descricao)));
        return estrelas;
    }
}

EstrelaAdapter.java

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class EstrelaAdapter extends
        RecyclerView.Adapter<EstrelaAdapter.StarViewHolder> {
    private List<Estrela> estrelas;
    private OnItemClickListener listener;
    public interface OnItemClickListener {
        void onItemClick(Estrela estrela);
    }
    public EstrelaAdapter(List<Estrela> estrelas, OnItemClickListener listener) {
        this.estrelas = estrelas;
        this.listener = listener;
    }
    @Override
    public StarViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false);
        return new StarViewHolder(view);
    }
    @Override
    public void onBindViewHolder(StarViewHolder holder, int position) {
        Estrela estrela = estrelas.get(position);
        holder.textView.setText(estrela.getNome());
    }
    @Override
    public int getItemCount() {
        return estrelas.size();
    }
    class StarViewHolder extends RecyclerView.ViewHolder {
        TextView textView;
        public StarViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(android.R.id.text1);
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    listener.onItemClick(estrelas.get(getAdapterPosition()));
                }
            });
        }
    }
}

activity_detalhe.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

DetalheActivity.java

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
public class DetalheActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detalhe);
        String estrelaNome = getIntent().getStringExtra("estrela_nome");
        String estrelaDescricao = getIntent().getStringExtra("estrela_descricao");
        EstrelaFragment fragmento = EstrelaFragment.newInstance(estrelaNome, estrelaDescricao);
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.fragment_container, fragmento)
                .commit();
    }
}

fragment_estrela.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">
    <TextView
        android:id="@+id/textviewNomeEstrela"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
        android:textStyle="bold" />
    <TextView
        android:id="@+id/textViewDescricao"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="@style/TextAppearance.AppCompat.Medium"
        android:layout_marginTop="8dp"/>
</LinearLayout>

EstrelaFragment.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
public class EstrelaFragment extends Fragment {
    private static final String ARG_NOME = "nome";
    private static final String ARG_DESCRICAO = "descricao";
    private String estrelaNome;
    private String estrelaDescricao;
    public static EstrelaFragment newInstance(String nome, String descricao) {
        EstrelaFragment fragment = new EstrelaFragment();
        Bundle args = new Bundle();
        args.putString(ARG_NOME, nome);
        args.putString(ARG_DESCRICAO, descricao);
        fragment.setArguments(args);
        return fragment;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            estrelaNome = getArguments().getString(ARG_NOME);
            estrelaDescricao = getArguments().getString(ARG_DESCRICAO);
        }
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_estrela, container, false);
        return view;
    }
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        TextView textViewNome = view.findViewById(R.id.textviewNomeEstrela);
        TextView textViewDescricao = view.findViewById(R.id.textViewDescricao);
        textViewNome.setText(estrelaNome);
        textViewDescricao.setText(estrelaDescricao);
    }
}