系统调用 onPause 和 onStop

Question

当系统调用onPause 和onStop 活动生命周期方法时，我有一个困惑。我看到通过从我的活动导航到另一个应用程序，这里系统正在调用onPause 和onStop，当我再次启动我的应用程序的另一个活动时，系统正在调用onPause 和onStop 方法

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    startActivity(new Intent(this, SecondActivity.class));
}

这里answer 说“当一个 Activity 将控制权转移到另一个 Activity 时调用 onPause()，当 Activity 处于完成模式时调用 onStop() 方法。”这对我来说似乎是错误的，当我开始另一个活动时，两者都在调用，我只是开始了活动并没有完成它，但仍然 onPause 和 onStop 方法正在调用。

Doc 说“当您的活动时间不长时，它会调用 onStop”我很好，它会调用 onStop

当您的 Activity 不再可见并被另一个 Activity 隐藏但仍然onPause 也在调用但为什么？？

Answer 1

为简单起见，这里是来自 android developers documentation 的小信息。

Activity Lifecycle

Activities in the system are managed as an activity stack. When a new activity is
started, it is placed on the top of the stack and becomes the running activity -- 
the previous activity always remains below it in the stack, and will not come to the
foreground again until the new activity exits.

An activity has essentially four states:

If an activity in the foreground of the screen (at the top of the stack), it is active or running.
If an activity has lost focus but is still visible (that is, a new non-full-sized or transparent activity has focus on top of your activity), it is paused. A paused activity is completely alive (it maintains all state and member information and remains attached to the window manager), but can be killed by the system in extreme low memory situations.
If an activity is completely obscured by another activity, it is stopped. It still retains all state and member information, however, it is no longer visible to the user so its window is hidden and it will often be killed by the system when memory is needed elsewhere.
If an activity is paused or stopped, the system can drop the activity from memory by either asking it to finish, or simply killing its process. When it is displayed again to the user, it must be completely restarted and restored to its previous state.

请参考this生命周期演示应用。这对理解 Activity 生命周期非常有帮助。

正如 Raghunandan 所建议的，你必须阅读this。

添加：

例如：当用户从 Activity A 遍历到 Activity B（全屏非透明）时，发生以下事情

1. Activity A 的状态变为暂停状态（在 Activity A 上调用 onPause）
2. 然后活动 A 的状态从暂停状态变为停止状态（调用 onStop 活动 A) 。 onStop 被调用是因为 Activity B 是全屏的 不透明的活动。 （如果 Activity B 不是全尺寸或透明的，则不会在 Activity A 上调用 onStop）

onPause 保证在 Activity A 上被调用（无论 Activity B 是非全尺寸透明还是全尺寸）。 onStop 只会在 Activity A 被全尺寸的 Activity B 完全覆盖时调用。

因此，在 onPause 中，您可以根据需要保存 Activity 的状态或其他一些有用信息。

祝你好运:)