Android 实现返回键退出弹出确认对话框

实现效果：



实现代码：

package com.example.android12_zhangkai;

import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

private long firstTime=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode==KeyEvent.KEYCODE_BACK){
AlertDialog.Builder builder=new AlertDialog.Builder(this);
builder.setTitle("提示：");
builder.setMessage("您确定退出？");

//设置确定按钮
builder.setNegativeButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
//设置取消按钮
builder.setPositiveButton("容我再想想",null);
//显示提示框
builder.show();
}
return super.onKeyDown(keyCode, event);
}

}