Android生命周期的学习

package cn.com;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class AndroidLifecycle extends Activity {

	public void onCreate(Bundle savedInstanceState) {
		System.out.println("First Activity =======onCreate()========");

		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		Button btn = (Button) findViewById(R.id.Button01);
		btn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent();
				intent.setClass(AndroidLifecycle.this, Second.class);
				startActivity(intent);
			}
		});
	}

	// Called after onCreate — or after onRestart when the activity had been
	// stopped, but is now again being displayed to the user. It will be
	// followed by onResume
	protected void onStart() {
		System.out.println("First Activity =======onStart()========");
		super.onStart();
	}

	// Called after onRestoreInstanceState, onRestart, or onPause, for your
	// activity to start interacting with the user
	protected void onResume() {
		System.out.println("First Activity =======onResume()========");
		super.onResume();
	}

	// Called as part of the activity lifecycle when an activity is going into
	// the background, but has not (yet) been killed
	protected void onPause() {
		System.out.println("First Activity =======onPause()========");
		super.onPause();
	}

	// Called when you are no longer visible to the user. You will next receive
	// either onRestart, onDestroy, or nothing, depending on later user
	// activity.
	protected void onStop() {
		System.out.println("First Activity =======onStop()========");
		super.onStop();
	}

	// Perform any final cleanup before an activity is destroyed
	protected void onDestroy() {
		System.out.println("First Activity =======onDestroy()========");
		super.onDestroy();
	}

	// Called after onStop when the current activity is being re-displayed to
	// the user (the user has navigated back to it). It will be followed by
	// onStart and then onResume
	protected void onRestart() {
		System.out.println("First Activity =======onRestart()========");
		super.onRestart();
	}

}

package cn.com;

import android.app.Activity;
import android.os.Bundle;

public class Second extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main1);
		System.out.println("Second Activity =======onCreate()========");
	}

	// Called after onCreate — or after onRestart when the activity had been
	// stopped, but is now again being displayed to the user. It will be
	// followed by onResume
	protected void onStart() {
		System.out.println("Second Activity =======onStart()========");
		super.onStart();
	}

	// Called after onRestoreInstanceState, onRestart, or onPause, for your
	// activity to start interacting with the user
	protected void onResume() {
		System.out.println("Second Activity =======onResume()========");
		super.onResume();
	}

	// Called as part of the activity lifecycle when an activity is going into
	// the background, but has not (yet) been killed
	protected void onPause() {
		System.out.println("Second Activity =======onPause()========");
		super.onPause();
	}

	// Called when you are no longer visible to the user. You will next receive
	// either onRestart, onDestroy, or nothing, depending on later user
	// activity.
	protected void onStop() {
		System.out.println("Second Activity =======onStop()========");
		super.onStop();
	}

	// Perform any final cleanup before an activity is destroyed
	protected void onDestroy() {
		System.out.println("Second Activity =======onDestroy()========");
		super.onDestroy();
	}

	// Called after onStop when the current activity is being re-displayed to
	// the user (the user has navigated back to it). It will be followed by
	// onStart and then onResume
	protected void onRestart() {
		System.out.println("Second Activity =======onRestart()========");
		super.onRestart();
	}

}

我们知道,在第一个Activity启动的时候,依次运行
onCreate()-->onStart()-->onResume(),当点击按钮启动第二个activity的时候,我们可以看到第一个activity的onPause()调用了,但是这个时候第一个activity还可以看到,没有被完全遮盖住,稍后第二个activitiy启动了,所以又依次调用了第二个activity的onCreate()-->onStart()-->onResume();这个时候第一个activity就完全不可见了,不可与user进行交互操作了,所以这个时候我们就看到第一个activity的onStop()方法就被调用了,但这个时候我们如果点击手机的back键,第2个activity就会调用onPause()方法,但是第一个activity又重新调回到最前面,所以现在调用的是onRestart()-->onStart()-->onResume();而这个时候第2个activity在第一个activity调用了onResume()后,又变的不可与user进行交互了,就调用了onStop()方法,这个时候我们要注意的是它又接着调用了onDestory()方法,因为activity是栈的原理,先进后出,第2个activity由于是后进(后显示出来),所以现在出去的话,就直接onDestory()掉了,如果这个时候我们在点击back退出的话,就会在依次调用第一个activity的
onPause()-->onStop()-->onDestory()方法;
    以上说的估计看起来不是很明白,请见谅,我有个视频地址,是一个叫陈川的讲的,讲的还不错,贴上地址:http://u.youku.com/user_video/id_UMjYxMzI0MjQ4.html
里面的第7,8讲讲的很清楚,希望对学习的朋友有所帮助!!!

生命周期的在补充点:
Active/Runing一个新 Activity 启动入栈后,它在屏幕最前端,处于栈的最顶端,此时它处于可见并可和用户交互的激活状态.
Paused 当 Activity 被另一个透明或者 Dialog 样式的 Activity 覆盖时的状态.此时它依然与窗口管理器保持连接,系统继续维护其内部状态,所以它仍然可见,但它已经失去了焦点故不可与用户交互.
Stoped 当 Activity 被另外一个 Activity 覆盖、失去焦点并不可见时处于 Stoped状态.
Killed Activity 被系统杀死回收或者没有被启动时处于 Killed状态.
   

评论

2 楼 owennet 2010-10-07  

讲的挺清楚了，谢谢

1 楼 beeb00 2010-09-20  

写的好，学习了