AlertDialog

AlertDialog也就处对话框。
使用方式分为6种：

简单dialog
列表dialog
单选dialog
多选dialog
自定义dialog
使用adapter的dialog

举例第一种的使用
代码：

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.mipmap.ic_launcher_round);

        builder.setTitle("桃子");
        builder.setMessage("喜欢吃桃子吗?");

        builder.setPositiveButton("yes",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "想吃", Toast.LENGTH_SHORT).show();
            }
        });
        builder.setNegativeButton("不喜欢吃",null);
        builder.setNeutralButton("不知道",null);

        AlertDialog alertDialog = builder.create();
        alertDialog.show();

实战

activity_main.xml文件:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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">



    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="简单dialog"
            android:onClick="dialog_1"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="列表dialog"
            android:onClick="dialog_2"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="单选的dialog"
            android:onClick="dialog_3"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="多选dialog"
            android:onClick="dialog_4"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="自定义dialog"
            android:onClick="dialog_5"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="使用adapter的dialog"
            android:onClick="dialog_6"/>
    </LinearLayout>
</android.support.constraint.ConstraintLayout>

代码:

package com.example.user.alertdiog;

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

public class MainActivity extends AppCompatActivity {

    int index;
    private String [] fru = {"苹果","桃子","西红柿","芒果","数学老师"};
    boolean[] flag = {false,false,false,false,false};

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

    public void dialog_1(View v){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.mipmap.ic_launcher_round);

        builder.setTitle("桃子");
        builder.setMessage("喜欢吃桃子吗?");

        builder.setPositiveButton("yes",new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "想吃", Toast.LENGTH_SHORT).show();
            }
        });
        builder.setNegativeButton("不喜欢吃",null);
        builder.setNeutralButton("不知道",null);

        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void dialog_2(View v){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("请选择");
        builder.setItems(fru, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "选择了"+fru[which], Toast.LENGTH_SHORT).show();
            }
        });

        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void dialog_3(View v){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("请选择");
        builder.setSingleChoiceItems(fru, index, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                index = which;
            }
        });
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "选择了"+fru[index], Toast.LENGTH_SHORT).show();
            }
        });
        builder.setNegativeButton("取消",null);
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void dialog_4(View v){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("请选择");
        builder.setMultiChoiceItems(fru, flag, new DialogInterface.OnMultiChoiceClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which, boolean isChecked) {
                flag[which] = isChecked;
            }
        });

        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                StringBuffer str = new StringBuffer();
                for (int i = 0; i < fru.length; i++) {
                    if (flag[i]) {
                        str.append(fru[i] + " ");
                    }
                }
                Toast.makeText(MainActivity.this, "选择了" + str.toString(), Toast.LENGTH_SHORT).show();
            }
        });
        builder.setNegativeButton("取消",null);
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void dialog_5(View v){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("爱吃的水果");
        final EditText et = new EditText(this);
        et.setHint("哦我爱吃的水果是什么");
        et.setSingleLine(true);
        builder.setView(et);
        builder.setNegativeButton("取消",null);
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                String password = et.getText().toString();
                if (password.equals("桃子")) {
                    Toast.makeText(MainActivity.this, "正确", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(MainActivity.this, "错误", Toast.LENGTH_SHORT).show();
                }
            }
        });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void dialog_6(View v){
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, fru);
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("水果超市");
        builder.setAdapter(adapter, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "选择了"+fru[which], Toast.LENGTH_SHORT).show();
            }
        });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }
}

运行效果: