一、Activity生命周期

正常流程生命周期

1、创建一个页面

04-26 17:28:11.851 2951-2951/com.demo.xp D/MainActivity: onCreate
04-26 17:28:12.090 2951-2951/com.demo.xp D/MainActivity: onStart
04-26 17:28:12.093 2951-2951/com.demo.xp D/MainActivity: onResume

2、启动另一个页面

04-26 17:28:18.285 2951-2951/com.demo.xp D/MainActivity: onPause
04-26 17:28:18.290 2951-2951/com.demo.xp D/Main2Activity: onCreate
04-26 17:28:18.299 2951-2951/com.demo.xp D/Main2Activity: onStart
04-26 17:28:18.300 2951-2951/com.demo.xp D/Main2Activity: onResume
04-26 17:28:19.027 2951-2951/com.demo.xp D/MainActivity: onStop

3、按下back键返回第一个界面

04-26 17:28:32.524 2951-2951/com.demo.xp D/Main2Activity: onPause
04-26 17:28:32.543 2951-2951/com.demo.xp D/MainActivity: onRestart
04-26 17:28:32.543 2951-2951/com.demo.xp D/MainActivity: onStart
04-26 17:28:32.544 2951-2951/com.demo.xp D/MainActivity: onResume
04-26 17:28:33.056 2951-2951/com.demo.xp D/Main2Activity: onStop
04-26 17:28:33.059 2951-2951/com.demo.xp D/Main2Activity: onDestroy

4、按下home键

04-26 17:33:24.801 2951-2951/com.demo.xp D/MainActivity: onPause
04-26 17:33:24.961 2951-2951/com.demo.xp D/MainActivity: onStop

异常流程生命周期

1、资源相关的系统配置发生改变导致Activity被杀死并重新创建。

2、资源内存不足导致优先级低的Activity被杀死。

二、屏幕切换时的生命周期

1、API=25,默认情况下竖屏切横屏

2、API=25,默认情况下横屏切竖屏

3、API=25,设置Activity的android:configChanges="orientation"时

4、API=25,设置Activity的android:configChanges="orientation|keyboardHidden"时，切横屏、竖屏只会执行一次生命周期。

04-26 17:57:01.519 17721-17721/com.demo.xp D/MainActivity: onPause
04-26 17:57:01.521 17721-17721/com.demo.xp D/MainActivity: onStop
04-26 17:57:01.521 17721-17721/com.demo.xp D/MainActivity: onDestroy
04-26 17:57:01.539 17721-17721/com.demo.xp D/MainActivity: onCreate
04-26 17:57:01.553 17721-17721/com.demo.xp D/MainActivity: onStart
04-26 17:57:01.556 17721-17721/com.demo.xp D/MainActivity: onResume

5、API=25,当设置android:configChanges="orientation|keyboardHidden|screenSize"切屏不会重新调用各个生命周期。

自从Android 3.2（API 13），在设置Activity的android:configChanges="orientation|keyboardHidden"后，还是一样会重新调用各个生命周期的。因为screen size也开始跟着设备的横竖切换而改变。因此，阻止程序在运行时重新加载Activity，除了设置"orientation"，你还必须加上"ScreenSize"。

三、Activity启动模式

见：https://github.com/XieXiePro/LearnDemo
Android四种启动模式：

1、standard,默认为此模式

04-26 18:59:11.773 7154-7154/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 21 hasCode:44123917
04-26 18:59:11.773 7154-7154/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 18:59:14.701 7154-7154/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 21 hasCode:125095489
04-26 18:59:14.701 7154-7154/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:00:58.932 7154-7154/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 21 hasCode:212299573
04-26 19:00:58.932 7154-7154/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:01:05.019 7154-7154/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 21 hasCode:118245998
04-26 19:01:05.019 7154-7154/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp

2、singleTop

04-26 19:39:33.792 31605-31605/com.demo.xp I/BaseActivity: onCreate：SingleTopActivity TaskId: 23 hasCode:56583874
04-26 19:39:33.794 31605-31605/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:39:55.269 31605-31605/com.demo.xp I/BaseActivity: onNewIntent：SingleTopActivity TaskId: 23 hasCode:56583874
04-26 19:39:55.270 31605-31605/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:39:56.133 31605-31605/com.demo.xp I/BaseActivity: onNewIntent：SingleTopActivity TaskId: 23 hasCode:56583874
04-26 19:39:56.133 31605-31605/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp

3、singleInstance

04-26 19:45:51.273 5664-5664/com.demo.xp I/BaseActivity: onCreate：SingleInstanceActivity TaskId: 29 hasCode:234473767
04-26 19:45:51.274 5664-5664/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:45:55.186 5664-5664/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 28 hasCode:116954427
04-26 19:45:55.187 5664-5664/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:45:58.868 5664-5664/com.demo.xp I/BaseActivity: onNewIntent：SingleInstanceActivity TaskId: 29 hasCode:234473767
04-26 19:45:58.868 5664-5664/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:46:07.095 5664-5664/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 28 hasCode:234710287
04-26 19:46:07.097 5664-5664/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:46:12.733 5664-5664/com.demo.xp I/BaseActivity: onNewIntent：SingleInstanceActivity TaskId: 29 hasCode:234473767
04-26 19:46:12.734 5664-5664/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp

4、singleTask

04-26 19:58:30.703 8423-8423/com.demo.xp I/BaseActivity: onCreate：SingleTaskActivity TaskId: 32 hasCode:74078356
04-26 19:58:30.703 8423-8423/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:58:33.920 8423-8423/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 32 hasCode:136280344
04-26 19:58:33.920 8423-8423/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:58:38.181 8423-8423/com.demo.xp I/BaseActivity: onNewIntent：SingleTaskActivity TaskId: 32 hasCode:74078356
04-26 19:58:38.181 8423-8423/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:58:41.067 8423-8423/com.demo.xp I/BaseActivity: onCreate：StandardActivity TaskId: 32 hasCode:238283109
04-26 19:58:41.067 8423-8423/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp
04-26 19:58:43.832 8423-8423/com.demo.xp I/BaseActivity: onNewIntent：SingleTaskActivity TaskId: 32 hasCode:74078356
04-26 19:58:43.832 8423-8423/com.demo.xp I/BaseActivity: taskAffinity:com.demo.xp

四、安全退出所有的Activity

SingTask的应用：
　　可以用来退出整个应用。

将主Activity设为SingTask模式，然后在要退出的Activity中转到主Activity，然后重写主Activity的onNewIntent函数，并在函数中加上一句finish。

退出单个Activity方法：

调用finish

杀死该进程：killprocess(Process.mId)

终止正在运行的虚拟机：system.exit()

退出整个应用：

制造抛异常导致整个程序退出

将所有的activity放入到一个list中，然后在需要退出的时候，将所有的activity，finish掉

通过广播来完成退出功能

通过广播来完成退出功能，具体实现过程是这样的：在每个Activity创建时（onCreate时）给Activity注册一个广播接收器，当退出时发送该广播即可。

@Override

protected void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       IntentFilter filter = new IntentFilter();

       filter.addAction("finish");

       registerReceiver(mFinishReceiver, filter);

       ……

}

private BroadcastReceiver mFinishReceiver = new BroadcastReceiver() {

    @Override

    public void onReceive(Context context, Intent intent) {

           if("finish".equals(intent.getAction())) {

              Log.e("#########", "I am " + getLocalClassName()

                     + ",now finishing myself...");

              finish();

       }

    }

};

定义一个Application类来存储Activity对象的引用

package com.demo.xp;

import android.app.Activity;
import android.app.Application;

import java.util.LinkedList;
import java.util.List;

/**
 * Created by xp on 17/4/27.
 */

public class AppApplication extends Application {

    private List<Activity> activityList = new LinkedList<>();
    private static AppApplication instance;


    // 单例模式中获取唯一的ExitApplication实例
    public static AppApplication getInstance() {
        if (null == instance) {
            instance = new AppApplication();
        }
        return instance;

    }

    // 添加Activity到容器中
    public void addActivity(Activity activity) {
        activityList.add(activity);
    }

    // 遍历所有Activity并finish

    public void exit() {

        for (Activity activity : activityList) {
            activity.finish();
        }

        System.exit(0);

    }
}

参考：
Android入门：Activity四种启动模式
彻底弄懂Activity四大启动模式