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我正在玩 Android 生命周期,我发现一个似乎记录不充分的行为(或者我只是做错了什么)。

在https://developer.android.com/reference/android/app/Activity.html#onCreateOptionsMenu(android.view.Menu)中指定的 onCreateOptionsMenu 方法应该只被调用一次,但它被打印了两次在方向变化期间。

以下是创建流程日志,可以看到在 onPostResume 方法之后调用了 onCreateOptionsMenu 方法:

 [...]
 SimpleActivity >>> onStart
 SimpleActivity <<< onStart
 SimpleFragment >>> onStart
 SimpleFragment <<< onStart
 SimpleActivity >>> onPostCreate
 SimpleActivity <<< onPostCreate
 SimpleActivity >>> onResume
 SimpleActivity <<< onResume
 SimpleFragment >>> onResume
 SimpleFragment <<< onResume
 SimpleActivity >>> onPostResume
 SimpleActivity <<< onPostResume
 SimpleActivity >>> onCreateOptionsMenu
 SimpleActivity <<< onCreateOptionsMenu
 SimpleFragment >>> onCreateOptionsMenu
 SimpleFragment <<< onCreateOptionsMenu
 [...]

但是当由于方向改变而恢复状态时,它也会在 onRestoreInstanceState 方法之后调用:

 [...]
 SimpleActivity >>> onStart
 SimpleActivity <<< onStart
 SimpleFragment >>> onStart
 SimpleFragment <<< onStart
 SimpleActivity >>> onRestoreInstanceState
 SimpleActivity >>>    onCreateOptionsMenu
 SimpleActivity <<<    onCreateOptionsMenu
 SimpleFragment >>>    onCreateOptionsMenu
 SimpleFragment <<<    onCreateOptionsMenu
 SimpleActivity >>>    onPrepareOptionsMenu
 [...]
 SimpleActivity <<< onRestoreInstanceState
 SimpleActivity >>> onPostCreate
 SimpleActivity <<< onPostCreate
 SimpleActivity >>> onResume
 SimpleActivity <<< onResume
 SimpleFragment >>> onResume
 SimpleFragment <<< onResume
 SimpleActivity >>> onPostResume
 SimpleActivity <<< onPostResume
 SimpleActivity >>> onCreateOptionsMenu
 SimpleActivity <<< onCreateOptionsMenu
 SimpleFragment >>> onCreateOptionsMenu
 SimpleFragment <<< onCreateOptionsMenu
 [...]

值得注意的是,这种行为只发生在没有 Support 库的 API > 19 中。

用于记录的代码非常简单。SimpleActivity 配置内容视图并将 SimpleFragment 的实例添加到 FragmentManager(如果尚未添加):

public class SimpleActivity extends LoggerActivity {

  @Override protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fragment);
    Fragment f = getFragmentManager().findFragmentById(R.id.fragment_container);

    findViewById(R.id.btn_dialog).setOnClickListener(new View.OnClickListener() {
      @Override public void onClick(View v) {
        startActivity(new Intent(SimpleActivity.this, DialogActivity.class));
      }
    });

    findViewById(R.id.btn_activity).setOnClickListener(new View.OnClickListener() {
      @Override public void onClick(View v) {
        startActivityForResult(new Intent(SimpleActivity.this, ResultActivity.class), Utils.REQUEST_CODE);
      }
    });

    if (f == null) {
      getFragmentManager()
        .beginTransaction()
        .replace(R.id.fragment_container, new SimpleFragment())
        .commit();
    }
  }
}

//////

public class SimpleFragment extends LoggerFragment {
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    setHasOptionsMenu(true);
    super.onCreateView(inflater, container, savedInstanceState);
    View v = inflater.inflate(R.layout.fragment_layout, container, false);
    TextView txt = (TextView) v.findViewById(R.id.fragment_text);
    txt.setText(this instanceof CustomName ? ((CustomName) this).getCustomName() : getClass().getSimpleName());
    return v;
  }
}

LoggerActivity 和 LoggerFragment 实现了所有生命周期方法,并在每个方法上调用 Utils.logBeforeSuper 和 Utils.logAfterSuper。

public class LoggerActivity extends Activity {

  /* [...] */

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    Utils.logBeforeSuper(this);
    boolean b = super.onCreateOptionsMenu(menu);
    Utils.logAfterSuper(this);
    return b;
  }

  /* [...] */

}

public class LoggerFragment extends Fragment {
  /* [...] */

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    Utils.logBeforeSuper(this);
    View v = super.onCreateView(inflater, container, savedInstanceState);
    Utils.logAfterSuper(this);
    return v;
  }

  /* [...] */
}

那么,我想知道预期的行为是什么?我是否遗漏了什么或没有记录?

一些链接

完整的日志文件可以在这里找到(方向更改流程从第 108 行开始)https ://docs.google.com/spreadsheets/d/1u97W9QZIEDcJt1Q2xh5VQP4YliHjzHE0u2OlLF4y5WY/edit#gid=0

该项目托管在github上:(我没有足够的声誉添加更多链接)

Whole Project: https://github.com/TartagliaEG/android-lifecycle-tests    
LoggerActivity: /app/src/main/java/com/lifecycletests/base/loggers/LoggerActivity.java    
LoggerFragment: /app/src/main/java/com/lifecycletests/base/loggers/LoggerFragment.java    
Utils: /app/src/main/java/com/lifecycletests/utils/Utils.java    
SimpleActivity: /app/src/main/java/com/lifecycletests/simple/SimpleActivity.java    
SimpleFragment: /app/src/main/java/com/lifecycletests/simple/SimpleFragment.java
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