第五次作业

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rel"
    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/but"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="换色"
        android:background="@drawable/ic_launcher_background"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:textSize="50sp"
        android:textColor="#000000"
        >
    </Button>


</RelativeLayout>

MainActivity

package com.example.color;

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;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    Button but;
    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        inter();
        View.OnClickListener but1=new but1();
        but.setOnClickListener(but1);
    }
    public  void inter(){
        but=findViewById(R.id.but);
    }
    class but1 implements View.OnClickListener{
        String bj="#ffffff";
        public void onClick(View view){
            AlertDialog dialog;
            AlertDialog.Builder builder=new AlertDialog.Builder(MainActivity.this)
                    .setTitle("设置主题背景")
                    .setIcon(R.drawable.ic_launcher_background)
                    .setSingleChoiceItems(new String[]{"红", "橙", "黄", "绿",},
                            2, new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int i) {
                                    switch(i){
                                        case 0:bj="#fff44336";
                                            break;
                                        case 1:bj="#ff9800";
                                            break;
                                        case 2:bj="#ffeb3b";
                                            break;
                                        case 3:bj="#87f332";
                                            break;
                                    }
                                }
                            })
                    .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int i) {
                            ((RelativeLayout)findViewById(R.id.rel)).setBackgroundColor
                                    (Color.parseColor(bj));
                        }
                    })
                    .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int i) {
                            dialog.dismiss();
                        }
                    });
            dialog=builder.create();
            dialog.show();
        }
    }
}