android - Activity 生命周期示例

Question

我已经阅读了大量教程并看过大量示例，但我很难理解 Activity 生命周期。我明白会发生什么，我的问题是我似乎无法弄清楚应该如何编码。例如，假设我有一个简单的应用程序，一旦按下按钮，它就会添加两个数字。我知道要为 onCreate 方法编写什么代码，但我不知道要添加什么 onPause、onRestart 等。我会只删除变量的内容吗？任何帮助将不胜感激。

Answer 1

我创建了一个示例来帮助您理解 Activity 的生命周期。在您第一次启动屏幕时，将调用以下三个生命周期方法:

onCreate()
onStart()
onResume()

每当我们在应用程序运行时按下后退按钮时，都会调用以下生命周期方法:

onPause()
onStop()
onDestroy()

当我们在应用程序运行时按下主页按钮时，将调用以下生命周期方法:

onPause()
onStop()

当我们在按下主页按钮后恢复应用程序时，将调用以下生命周期方法:

onRestart()
onStart()
onResume()

我想这对你有帮助。

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toast.makeText(this, "Activity is created", Toast.LENGTH_SHORT).show();
    Log.i("onCreate():","Activity is created");
}

@Override
protected void onStart() {
    // TODO Auto-generated method stub
    super.onStart();
    Toast.makeText(this, "Activity is started", Toast.LENGTH_SHORT).show();
    Log.i("onStart():","Activity started");
}

@Override
protected void onRestart() {
    // TODO Auto-generated method stub
    super.onRestart();
    Toast.makeText(this, "Activity is Restarted", Toast.LENGTH_SHORT).show();
    Log.i("onRestart():","Activity Restarted");
}

@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
    Toast.makeText(this, "Activity is Resumed", Toast.LENGTH_SHORT).show();
    Log.i("onResume():","Activity Resumed");
}

@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    Toast.makeText(this, "Activity is Paused", Toast.LENGTH_SHORT).show();
    Log.i("onPause():","Activity paused");
}

@Override
protected void onStop() {
    // TODO Auto-generated method stub
    super.onStop();
    Toast.makeText(this, "Activity is Stopped", Toast.LENGTH_SHORT).show();
    Log.i("onStop():","Activity stopped");
}

@Override
protected void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
    Toast.makeText(this, "Activity is Destroyed", Toast.LENGTH_SHORT).show();
    Log.i("onDestroy():","Activity destroyed");
}

}