完成這樣的效果

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
 

    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn1"
        android:text="彈出對話方塊"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="myAlert"/>


</LinearLayout>

package com.example.eightalertdialog;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void myAlert(View view) {
        //建立AlertDialog構建器
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        //通過構建器進行鏈式設定
        builder.setIcon(R.drawable.ic_android_black_24dp)
                .setTitle("我是一個對話方塊")
                .setMessage("今天天氣怎麼樣呀")
                .create()
                .show();
    }
}
 

完成如下效果

package com.example.eightalertdialog;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Build;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void myAlert(View view) {
        //建立AlertDialog構建器
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        //通過構建器進行鏈式設定
        builder.setIcon(R.drawable.ic_android_black_24dp)
                .setTitle("我是一個對話方塊")
                .setMessage("今天天氣怎麼樣呀")
                .setPositiveButton("確定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                })
                .setNeutralButton("中間按鈕", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        
                    }
                })
                .create()
                .show();
    }
}