当有多个activity时，随时随地退出当前程序

当有3个activity时，在第三个activity想退出程序，那么就要按back键3次才能退出，那么怎么直接退出呢。

1、创建一个专门的集合类来管理所有活动

package com.yuanlp.taskstack;

import android.app.Activity;

import java.util.ArrayList;
import java.util.List;

/**
* Created by 原立鹏 on 2017/6/27.
*/

public class ActivityCollector {
public static List<Activity> activityList=new ArrayList<Activity>();

public  static void addActivity(Activity activity){
activityList.add(activity);
}

public static void removeActivity(Activity activity){
activityList.remove(activity);

}

public static void finshiAll(){
for (Activity activity: activityList){
if (!activity.isFinishing()){ //判断当前activity是否被干掉了
activity.finish();
}
}
activityList.clear();
}
}

2、创建一个java的类，BaseActivity，继承AppCompatActivity。为什么不直接写成activity呢，因为我们不需要讲BaseActivity在Manifext.xml里注册。

package com.yuanlp.taskstack;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

/**
* Created by 原立鹏 on 2017/6/27.
*/

public class BaseActivity  extends AppCompatActivity{
private static final String TAG = "BaseActivity";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

Log.d(TAG, getClass().getSimpleName());  //获取当前活动的名称
ActivityCollector.addActivity(this);  //调用自己写的activity的集合类，把当前activity加入到list中

}

protected void onDestroy(){
super.onDestroy();
ActivityCollector.removeActivity(this); //每当当前activity销毁时，去除当前activity
}
}

3、让3个activity都继承BaseActivity,这样之前写的三个activity也不会报错。

package com.yuanlp.taskstack;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class MainActivity extends BaseActivity {
private static final String TAG = "MainActivity";
@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
Log.d(TAG, "Task id is: "+getTaskId());  //输出当前返回栈的ID
setContentView(R.layout.activity_main);
}

@Override
protected void onStart() {
super.onStart();
Log.d(TAG, "onStart: ");
}

@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume: ");
}

@Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause: ");
}

@Override
protected void onStop() {
super.onStop();
Log.d(TAG, "onStop: ");
}

@Override
protected void onRestart() {
super.onRestart();
Log.d(TAG, "onRestart: ");
}

@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy: ");
}

public void open1(View view){

Intent intent=new Intent(this,MainActivity.class);
startActivity(intent);
}

public void open2(View view){
Intent intent =new Intent(this,SecondActivity.class);
startActivity(intent);
}
}

4、在第三个activity中加入一个按钮，点击后退出程序。

package com.yuanlp.taskstack;

import android.os.Bundle;
import android.util.Log;
import android.view.View;

public class ThirdActivity extends BaseActivity {
private static final String TAG = "ThirdActivity";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "Task id is"+getTaskId());
setContentView(R.layout.activity_third);
}

public void exitApp(View view){
ActivityCollector.finshiAll();  //退出
android.os.Process.killProcess(android.os.Process.myPid());  //杀死当前进程
}
}