写一段android 使用fragmeng切换界面的代码

以下是一个简单的Android应用程序，使用Fragment实现了两个界面的切换：

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 加载Fragment1
        Fragment1 fragment1 = new Fragment1();
        getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, fragment1).commit();
    }

    // 切换到Fragment2
    public void switchToFragment2() {
        Fragment2 fragment2 = new Fragment2();
        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragment2).commit();
    }

    // 切换回Fragment1
    public void switchToFragment1() {
        Fragment1 fragment1 = new Fragment1();
        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragment1).commit();
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.fragmentdemo.MainActivity">

    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

Fragment1.java

public class Fragment1 extends Fragment {

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

        Button button = (Button) view.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ((MainActivity) getActivity()).switchToFragment2();
            }
        });

        return view;
    }
}

fragment1.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Switch to Fragment 2"
        android:layout_centerInParent="true" />

</RelativeLayout>

Fragment2.java

public class Fragment2 extends Fragment {

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

        Button button = (Button) view.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ((MainActivity) getActivity()).switchToFragment1();
            }
        });

        return view;
    }
}

fragment2.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Switch to Fragment 1"
        android:layout_centerInParent="true" />

</RelativeLayout>

这个应用程序包含两个Fragment，分别是Fragment1和Fragment2。在MainActivity中，我们使用FrameLayout作为容器，用来存放Fragment。在onCreate方法中，我们加载Fragment1。当点击Fragment1中的按钮时，会调用MainActivity中的switchToFragment2方法，用来切换到Fragment2。同样，当点击Fragment2中的按钮时，会调用MainActivity中的switchToFragment1方法，用来切换回Fragment1。