android 返回键完全退出程序

主页面中覆盖onKeyDown方法

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if(keyCode == KeyEvent.KEYCODE_BACK){
ShowDialog.showExitDialog(MainActivity.this);
}
return true;
}

ShowDialog.java

public class ShowDialog{

public static void showExitDialog(Activity context){
//实例化一个关于退出的警示对话框
final AlertDialog exitDialog = new AlertDialog.Builder(context).create();
exitDialog.setTitle("提示");
exitDialog.setMessage("是否退出程序");

//点击“是”的时候触发的事件
exitDialog.setButton("是", new AlertDialog.OnClickListener(){

public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
exitDialog.dismiss();
System.out.println("the wopai program exit");
System.exit(0);

}

});

//点击“否”的时候触发的事件
exitDialog.setButton2("否", new AlertDialog.OnClickListener(){

public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
exitDialog.dismiss();
}

});
//显示对话框
exitDialog.show();
}

}