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有两个例子，代码ppt上都有。
自己新建工程,默认是relativeLayout，改成LinearLayout，第一例子xml不用管，就写MainActivity.java就行

package com.example.dialog_test;

import java.util.Calendar;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;

import android.content.DialogInterface;
import android.view.Menu;

import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;
import android.widget.Toast;

public class MainActivity extends Activity {

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

        AlertDialog.Builder dlg = new AlertDialog.Builder(MainActivity.this);//上下文内容
        dlg.setTitle("警示对话框");
        dlg.setMessage("这里是警示内容");
        // dlg.setIcon();这个自己加icon图片
        //new DialogInterface.OnClickListener() 需要自己写对按钮的响应,也可以是null
        dlg.setNegativeButton("取消", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // TODO Auto-generated method stub
                Toast.makeText(MainActivity.this, "取消", Toast.LENGTH_LONG)
                        .show();

            }
        });
        dlg.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // TODO Auto-generated method stub
                Toast.makeText(MainActivity.this, "确定", Toast.LENGTH_LONG)
                        .show();
            }

        });
        dlg.setNeutralButton("查看详情", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface arg0, int arg1) {
                // TODO Auto-generated method stub
                Toast.makeText(MainActivity.this, String.valueOf(arg1),
                        Toast.LENGTH_LONG).show();
            }
        });
        dlg.create();
        dlg.show();```
第二个例子

AlertDialog.Builder dlg = new AlertDialog.Builder(MainActivity.this);
dlg.setTitle("警示对话框");
//dlg.setMessage("这里是警示内容");
// dlg.setIcon();
//需要自己写对按钮的响应

     dlg.setSingleChoiceItems(R.array.gongsi, 0, new    //R.array.gongsi是在values里的Strings.xml里写
     DialogInterface.OnClickListener() {
    
     @Override
     public void onClick(DialogInterface arg0, int which) {
     // TODO Auto-generated method stub
     String strMsg = "选中了"+String.valueOf(which);
     Toast.makeText(MainActivity.this, strMsg, Toast.LENGTH_LONG).show();
    
     }
     });
     dlg.create();
     dlg.show();```