android中如何退出应用程序

<span style="font-size:18px;">public boolean onKeyDown(int keyCode, KeyEvent event) {

if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {

// 确认对话框

final AlertDialog isExit = new AlertDialog.Builder(this).create();

// 对话框标题

isExit.setTitle("系统提示");

// 对话框消息

isExit.setMessage("确定要退出吗?");

// 实例化对话框上的按钮点击事件监听

DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog, int which) {

switch (which) {

case AlertDialog.BUTTON1:// "确认"按钮退出程序

NotificationManager notificationManager = (NotificationManager) MainActivity.this 

                   .getSystemService(NOTIFICATION_SERVICE); 

notificationManager.cancel(0); 

String packagename = getPackageName();

ActivityManager manager = (ActivityManager)getSystemService(ACTIVITY_SERVICE); 

finish();

if(getSystemVersion()<8){

 

manager.restartPackage(getPackageName()); 

}else{

manager.killBackgroundProcesses(packagename); 

}

 

break;

case AlertDialog.BUTTON2:// "取消"第二个按钮取消对话框

isExit.cancel();

break;

default:

break;

}

}

};

// 注册监听

isExit.setButton("确定", listener);

isExit.setButton2("取消", listener);

// 显示对话框

isExit.show();

return false;

}

return false;

}</span>