[Android]ActivityやFragmentからFragmentを呼ぶ

目的

ActivityやFragmentからFragmentを呼ぶときの実装メモ

実装方法

ソースコード

以下のように簡単なActivityとFragment2つを作りました。

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Button activityButton = findViewById(R.id.button);
        activityButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                FragmentManager fragmentManager = getSupportFragmentManager();
                if(fragmentManager != null) {
                    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                    fragmentTransaction.addToBackStack(null);
                    fragmentTransaction.replace(R.id.content1, Fragment1.newInstance());
                    fragmentTransaction.commit();
                }
            }
        });

    }
}

public class Fragment1 extends Fragment {

    public static Fragment1 newInstance(){
        //インスタンス生成
        Fragment1 category = new Fragment1();
        return category;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View fragment1 = inflater.inflate(R.layout.fragment1, container, false);
        return fragment1;
    }

    @Override
    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        
        Button fragment1Button = view.findViewById(R.id.button1);
        fragment1Button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                FragmentManager fragmentManager = getChildFragmentManager();
                if(fragmentManager != null) {
                    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

                    fragmentTransaction.replace(R.id.contentFragment1, Fragment2.newInstance());
                    fragmentTransaction.addToBackStack(null);
                    fragmentTransaction.commit();
                }
            }
        });

    }
}

public class Fragment2 extends Fragment {

    public static Fragment2 newInstance(){
        //インスタンス生成
        Fragment2 category = new Fragment2();
        return category;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View fragment2 = inflater.inflate(R.layout.fragment2, container, false);
        return fragment2;
    }
}

レイアウトXmlファイルは以下のようなものとしました。
Fragmentもほぼ一緒なので省略します。

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/content1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#FF5722">
        <Button
            android:id="@+id/button"
            android:layout_width="120dp"
            android:layout_height="wrap_content"
            android:text="Activity"
            android:layout_centerInParent="true"
            />
    </RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>