Handler常见两种用法

1.Handler在Android的两个功能

　　1.1表示未来某时做某事

      1.2线程间通信

2.演示源码如下：

package com.example.datastrorage;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class HandlerActivity extends AppCompatActivity {
    private Handler mHandler=null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_handler);
//延迟功能
//        mHandler.postDelayed(new Runnable() {
//            @Override
//            public void run() {
//                Toast.makeText(HandlerActivity.this, "我是handler!", Toast.LENGTH_SHORT).show();
//            }
//        },3000);
        mHandler=new Handler(){
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                switch(msg.what){
                    case 1:
                        Toast.makeText(HandlerActivity.this, "线程间通信成功", Toast.LENGTH_SHORT).show();
                        break;
                }
            }
        };

        new Thread(){
            @Override
            public void run() {
                super.run();
                Message msg=new Message();
                msg.what=1;
                mHandler.sendMessage(msg);
            }
        }.start();

    }
}