Android 返回键返回到指定的Activity

按后退键的时候，让程序退出。

实现起来的思路：

1.捕获后退键被按了这个事件。

Java代码

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {

if(keyCode == KeyEvent.KEYCODE_BACK ){
//DO SOMETHING
return true;
}
return false;
}

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {

    	if(keyCode == KeyEvent.KEYCODE_BACK ){
    		//DO SOMETHING  
    		return true;
    	}
    	return false;
    }

2-1.通过intent返回都主屏幕中

Java代码

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) { // 按下的如果是BACK，同时没有重复

Intent home = new Intent(Intent.ACTION_MAIN);
home.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
home.addCategory(Intent.CATEGORY_HOME);
startActivity(home);
}
return super.onKeyDown(keyCode, event);
}

@Override  
  public boolean onKeyDown(int keyCode, KeyEvent event) {  
   if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) { // 按下的如果是BACK，同时没有重复  
    Intent home = new Intent(Intent.ACTION_MAIN);  
    home.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);  
    home.addCategory(Intent.CATEGORY_HOME);  
    startActivity(home);  
   }  
   return super.onKeyDown(keyCode, event);  
  }

2-2.记录所有打开的activity，关闭的时候将所有的activity关闭

使用单例模式创建一个Activity管理对象，该对象中有一个Activity容器专门负责存储新开启的每一个Activity

MyApplication类（储存每一个Activity，并实现关闭所有Activity的操作

Java代码

public class MyApplication extends Application {


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

private MyApplication()
{
}
//单例模式中获取唯一的MyApplication实例

public static MyApplication getInstance()
{
if(null == instance)
{
instance = new MyApplication();
}
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);

}
}

public class MyApplication extends Application {

 private List<Activity> activityList = new LinkedList<Activity>(); 
 private static MyApplication instance;
 
            private MyApplication()
            {
            }
             //单例模式中获取唯一的MyApplication实例 
             public static MyApplication getInstance()
             {
                            if(null == instance)
                          {
                             instance = new MyApplication();
                          }
                 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);

            }
}

在每一个Activity中的onCreate方法里添加该Activity到MyApplication对象实例容器中

Java代码

MyApplication.getInstance().addActivity(this);

MyApplication.getInstance().addActivity(this);

在需要结束所有Activity的时候调用exit方法

Java代码

MyApplication.getInstance().exit();