Fragment 基本使用

Fragment 表示 Activity 中一种行为或用户界面的一部分，它有自己的生命周期接收自己的输入事件，也可以在 Activity 运行时添加或删除事件。

Fragment 生命周期

• 管理 Fragment 的生命周期非常类似管理 Activity 的生命周期
  
• Activity 布局文件中添加 fragment，启动 Activity 生命周期执行顺序。
  
• Activity 布局文件中添加 fragment，按 back 键生命周期执行顺序。
  
• 测试代码

1. MainActivity

public class MainActivity {
   
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate: ");
        setContentView(R.layout.activity_main);
        if (findViewById(R.id.ll_content) != null) {
            if (savedInstanceState != null) {
                return;
            }
            HeadlinesFragment headlinesFragment = new HeadlinesFragment();
            headlinesFragment.setArguments(getIntent().getExtras());
            getSupportFragmentManager().beginTransaction().add(R.id.ll_content,headlinesFragment).commit();
        }
    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG, "onStart: ");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG, "onResume: ");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG, "onPause: ");
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG, "onStop: ");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy: ");
    }
}

2. activity_main.xml

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

3. 需要添加的 HeadlinesFragment

public class HeadlinesFragment extends ListFragment {

    private static final String TAG = "HeadlinesFragment";
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate: ");
        setListAdapter(new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_activated_1,
                titles));
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        Log.d(TAG, "onCreateView: ");
        return super.onCreateView(inflater, container, savedInstanceState);
    }

    @Override
    public void onListItemClick(@NonNull ListView l, @NonNull View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
    }

    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
        Log.d(TAG, "onAttach: ");
    }

    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG, "onStart: ");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d(TAG, "onResume: ");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d(TAG, "onPause: ");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d(TAG, "onStop: ");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d(TAG, "onDestroyView: ");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d(TAG, "onDetach: ");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy: ");
    }
}