代码实现最简单Handler

package com.studio.handlerproject;import android.nfc.Tag;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.TextView;public class MainActivity extends AppCompatActivity {    private static final String TAG = "MainActivity";    @Override    protected void onCreate(Bundle savedInstanceState) {        /**         * UI线程         */        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        final TextView textView = (TextView) findViewById(R.id.textView);        //创建Handler        final Handler handler = new Handler() {            @Override            public void handleMessage(Message msg) {                super.handleMessage(msg);                /**                 * 主线程接到子线程发出来的消息，处理                 */                //处理消息                Log.i(TAG, "handleMessage: " + msg.what);                if (msg.what == 1001) {                    textView.setText("imooc");                }            }        };        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                //  有可能要做大量耗时操作                /**                 * 子线程                 */                new Thread(new Runnable() {                    @Override                    public void run() {                        try {                            Thread.sleep(2000);                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                        /**                         * 通知UI更新                         */                        handler.sendEmptyMessage(1001);                    }                }).start();            }        });    }}