배경색 자동으로 바꾸기

package com.example.i310_54.myapplication08;

import android.graphics.Color;
import android.os.CountDownTimer;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    String TAG="EUNBI";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    Handler handler;
    public void f1(View view) {

         handler=new Handler(){

                          int r,g,b;
             Random rnd=new Random();
             LinearLayout ll=findViewById(R.id.ll);
            @Override
            public void handleMessage(Message msg) {

                handler.sendEmptyMessageDelayed(0,1000);

                r=rnd.nextInt(256);
                g=rnd.nextInt(256);
                b=rnd.nextInt(256);

                ll.setBackgroundColor(Color.argb(0xff,r,g,b));
                
            }
        };

        handler.sendEmptyMessage(0);
    }


    public void f2(View view) {

        handler.removeMessages(0);

        Button button3=findViewById(R.id.button3);
        button3.setEnabled(false);

    }


}