我做了一些关于调查活动切换生命周期的实验，发现会出现“黑屏”的情况。如果我错了，请纠正我。

两项活动A

03-06 13:04:52.811: I/LOG(32125): pause A begin
03-06 13:04:53.811: I/LOG(32125): pause A return
03-06 13:04:53.813: I/LOG(32125): focus A begin
03-06 13:04:58.813: I/LOG(32125): focus A return

In the window, shows the view of Activity A.

03-06 13:04:58.829: I/LOG(32125): create B begin
03-06 13:04:58.845: I/LOG(32125): create B return
03-06 13:04:58.846: I/LOG(32125): start B begin
03-06 13:04:59.847: I/LOG(32125): start B return

The view of Act A is hide, it is now shown by Activity B, but it's actually a "black screen" rather than the "actual genereated layout" in Activity B

03-06 13:04:59.847: I/LOG(32125): resume B begin
03-06 13:05:00.847: I/LOG(32125): resume B return
03-06 13:05:00.968: I/LOG(32125): focus B begin
03-06 13:05:05.968: I/LOG(32125): focus B return

Until this point, the "actual generated layout" of Activity B is shown here.

03-06 13:05:06.044: I/LOG(32125): A onSaveInstance
03-06 13:05:06.044: I/LOG(32125): stop A begin
03-06 13:05:07.044: I/LOG(32125): stop A return

下面是我活动A中的代码

@Override
protected void onStart() {
    super.onStart();
    Log.i("LOG","start B begin");
    try {
        Thread.sleep(5000,0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("LOG","start B return");
}

@Override
protected void onResume() {
    super.onResume();
    Log.i("LOG","resume B begin");
    try {
        Thread.sleep(5000,0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("LOG","resume B return");
}

@Override
protected void onStop() {
    super.onStop();
    Log.i("LOG","stop B begin");
    try {
        Thread.sleep(3000,0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("LOG","stop B return");
}

@Override
protected void onPause() {
    super.onPause();
    Log.i("LOG", "pause B begin");
    try {
        Thread.sleep(3000,0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("LOG","pause B return");
}

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    Log.i("LOG","focus B begin");
    try {
        Thread.sleep(5000,0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    Log.i("LOG","focus B return");
}

从上面的实验中，我提出了一些结论和设计策略。

1. 不要在简历上做太多事情

但是，也有这样的场景：
一个图表应用程序。用户在活动中看到“图表（布局）”，但最新的数据还没有填写，因为第二个线程仍在获取数据（可能是因为它太重了）。

此时，用户将看到一个空白图表。为了避免这种情况，我们可以在创建活动之前获取数据。在上一个活动中或在应用程序开始时执行此操作。为了流畅的用户体验。

有没有人也发现这个“黑屏”陷阱？还是我理解错误？非常感谢！