第五次作业

<?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"
    android:orientation="vertical"
    tools:context=".MainActivity"
    android:background="@color/colorPrimaryDark"
    android:id="@+id/txt1">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="多选对话框!"
        android:id="@+id/tv"
        android:gravity="center"
        android:textColor="#FFFDB371"
        android:textSize="20dp"
        android:layout_marginTop="30dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="200dp"
        android:text="设置背景颜色"
        android:layout_gravity="center"
        android:textSize="25dp"
        android:onClick="test"
        />

</LinearLayout>

package com.example.mytest;

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

import android.content.DialogInterface;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {
    String [] a={"#87CEFF","#7D26CD","#F08080","#FF4040","#FFC125"};
    int b=0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }
    public void test(View view){
        final AlertDialog dialog;
        AlertDialog.Builder builder=new AlertDialog.Builder(this)
                .setTitle("设置背景颜色")
                .setIcon(R.drawable.ic_launcher_background)
                .setSingleChoiceItems(new String[]{"蓝色", "紫色", "粉色", "红色", "黄色"}, b, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int which) {
                        b=which;
                    }
                })
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    findViewById(R.id.txt1).setBackgroundColor(Color.parseColor(a[b]));
                    dialog.dismiss();
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                    }
                });
                dialog=builder.create();
                dialog.show();
    }
}