public class MainActivity extends Activity {
//定义一个变量，来标识是否退出
private static boolean isExit=false;
Handler handler=newHandler(){
@Override
public void handleMessage(Message msg){
super.handleMessage(msg);
isExit=false;
}
};
@Override
public boolean onKeyDown(int keyCode,KeyEvent event){
if(keyCode==KeyEvent.KEYCODE_BACK){
exit();
returnfalse;
}
returnsuper.onKeyDown(keyCode,event);
}
private void exit(){
if(!isExit){
isExit=true;
Toast.makeText(getApplicationContext(),"再按一
退出程序",Toast.LENGTH_SHORT).show();
//利用handler延迟发送更改状态信息
handler.sendEmptyMessageDelayed(0,2000);
}
else{
finish();
System.exit(0);
}
}
