第五次作业

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:id="@+id/f">


    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="颜色选择"
        android:background="#00BCD4"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:onClick="gh"/>
</RelativeLayout>

　　

package com.example.back;
import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.RelativeLayout;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
String b="#000000";
    public void gh(View view) {
        AlertDialog dialog;
        AlertDialog.Builder builder = new AlertDialog.Builder(this)
                .setTitle("设置布局背景")
                .setIcon(R.drawable.ic_launcher_background)
                .setSingleChoiceItems(new String[]{"白色", "黑色", "红色", },
                        0,new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        // 点单选按钮时发生的事件，这里which表示你点的单选按钮是第几个
                    switch (which){
                        case 0:b="#FAF9F9" ;
                        break;
                        case 1:b="#000000" ;
                        break;
                        case 2: b="#F44336";
                        break;

                    }
                    }
                })
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        //点确定按钮时发生的事件
                        ((RelativeLayout)findViewById(R.id.f)).setBackgroundColor(Color.parseColor(b));
                    dialog.dismiss();
                    }
                })//添加“确定”按钮
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // 点取消按钮发生的事件
                        dialog.dismiss();
                    }
                });
        dialog = builder.create();
        dialog.show();
    }
}