安卓通知点击 : Fragment transition when app not in foreground

Question

当应用程序在前台并收到通知时， Activity 上的 fragment 转换会顺利进行，没有任何问题。如果应用程序在后台运行，则应用程序会崩溃，因为在 Activity 进入前台之前会触发 fragment 转换!

通知创建代码:

    Intent intent = new Intent(this, MainActivity.class);
    if(newsData == true) {
      intent.putExtra("displayNews", true);
      } else {
      intent.putExtra("displayMessage", true);
      }
      intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);

      final PendingIntent contentIntent = PendingIntent.getActivity(this, 0, intent, 0);

    final NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)
        .setSmallIcon(R.drawable.ic_launcher)
        .setContentTitle(this.getApplicationContext().getString(R.string.app_name))
        .setStyle(new NotificationCompat.BigTextStyle().bigText(msg)).setContentText(msg);

    mBuilder.setContentIntent(contentIntent);
    mBuilder.setAutoCancel(true);
    mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());

接收通知的MainActivity:

 @Override
    protected void onNewIntent(final Intent intent) {
        final Bundle extras = intent.getExtras();
        if (intent.getExtras().get("displayNews") != null) {
          showFragment(context, "newsFragment", false);
        } else {
            showFragment(context, "messageFragment", false);
        }
    }

    public void showFragment(final FragmentActivity context, final String selectedItem, final boolean reverseAnimation) {

        final Fragment switchFragment = getFragment(selectedItem);
        final FragmentManager fragmentManager = context.getSupportFragmentManager();
        final Fragment fragment = fragmentManager.findFragmentByTag(selectedItem);
        if (fragment == null) {
          final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
          if (!reverseAnimation) {
            fragmentTransaction.setCustomAnimations(R.anim.abc_fade_in, R.anim.slide_out_left);
          } else {
            fragmentTransaction.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right);
          }
          fragmentTransaction.replace(R.id.content_frame, switchFragment, selectedItem);
          fragmentTransaction.commit();
        }
  }

如何在 MainActivity 中等待 Activity 在开始 fragment 转换之前到达前台？

错误日志:

Application has been shut down. Please inspect exception trace for more details.
java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

Answer 1

最终(如评论中所示)使用了正确的解决方案。

fragmentTransaction.replace(R.id.content_frame, switchFragment, selectedItem);
      fragmentTransaction.commitAllowingStateLoss();