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

我们可以看到我的 Fragment.onStart 在 Activity.onStart 之前被调用。任何人都知道这种行为的原因是什么？因为当Activity移动到前台时，Activity的回调方法应该总是先调用

Activity:

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

这只是因为，您正在调用 super.onStart()，然后在您的 activity 中打印日志。所以基本上 activity 的 onStart() 首先是运行。

我猜:)

Answer 2

这是正常行为。如果您需要在开始之前在片段中做一些事情，最好重写并使用 onAttach(Context context) 方法。

Answer 3

我也遇到了同样的问题。我将其添加到我的 Fragment.onStart():

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

Fragment.onstart 在 Activity.onstart 之前被调用

Fragment.onstart is being called before Activity.onstart

android

fragment

android-lifecycle

android-fragments

android-fragmentactivity