handler延时tiaozhuan

package com.example.lenovo.mnyk01;

import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private static final int FLAG = 123;

    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

           if(msg.what==FLAG){
               Intent intent = new Intent(MainActivity.this,ShowActivity.class);
               startActivity(intent);
           }
        }
    };

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

     TextView txt = findViewById(R.id.text);

    handler.sendEmptyMessageDelayed(FLAG,3000);

    }
}