Fragment.onstart在Activity.onstart之前被调用

Question

MMuzammil: MainActivity:in onCreate
MMuzammil: FirstFragment:in onAttach
MMuzammil: FirstFragment:in onCreate
MMuzammil: FirstFragment:in onCreateView
MMuzammil: FirstFragment:in onActivityCreated
MMuzammil: FirstFragment:in onStart <----
MMuzammil: MainActivity:in onStart <----
MMuzammil: MainActivity:in onResume
MMuzammil: FirstFragment:in onResume

如我们所见，我的Fragment.onStart是在Activity.onStart之前被调用的。有人知道这种行为的原因是什么吗？因为当活动转移到前台时，活动的回调方法应该总是首先调用

活性：

public class MainActivity extends AppCompatActivity {

public static final String TAG = "MMuzammil";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Log.d(TAG, "MainActivity:in onCreate");
    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new FirstFragment()).commit();
}

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

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

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

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

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

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

Answer 1

这仅仅是因为您正在调用super.onStart()，然后在活动中打印日志。因此，基本上，您的活动的onStart()首先运行。

我猜:)

Answer 2

这是正常行为。如果您需要在启动之前以片段的形式完成某件事情，最好重写并使用onAttach(上下文上下文)方法。

Answer 3

我也有同样的问题。我把这个添加到我的Fragment.onStart()中

override fun onStart() {
    super.onStart()
    launch {
        requireActivity().lifecycle.withStarted {
            // do work
        }
    }
}