实现RunOnUiThread和RunOnUiThreadBlock

现在需要实现一个工具类，RunUtils，这个类中包含runOnUiThread(Context context, Runnable runnable)和runOnUiThreadBlock(Context context, Runnable runnable)两个方法。两个方法都使runnable在UI线程执行，runOnUiThread立即返回，runOnUiThreadBlock等待runnable执行完毕后才返回。

根据context创建一个Handler，这个Handler用于发送消息。runOnUiThread这个方法不需要同步，runOnUiThreadBlock需要同步。

RunUtils内容

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package com.letv.handlertest;   import android.content.Context; import android.os.Handler; import android.os.Message; import android.util.Log;   import java.lang.ref.WeakReference;   public class RunUtils {       private static final int WHAT_BLOCK = 0x1001;       private static WeakReference<Context> weakContext;     private static WeakReference<Handler> weakHandler;     private static Object lock = new Object();       private static void init(Context context){         if(RunUtils.weakContext == null ||                 (RunUtils.weakContext!=null && RunUtils.weakContext.get()!=context) ){             RunUtils.weakContext = new WeakReference<Context>(context);               Handler handler = new Handler(context.getMainLooper()) {                 @Override                 public void dispatchMessage(Message msg) {                     if(msg.what == WHAT_BLOCK){                         Log.i(MainActivity.TAG, "what block");                         synchronized (lock){                             super.dispatchMessage(msg);                             lock.notify();                             Log.i(MainActivity.TAG, "notify");                         }                     }                     else{                         super.dispatchMessage(msg);                         Log.i(MainActivity.TAG, "what not block");                     }                 }             };             weakHandler = new WeakReference<Handler>(handler);             handler = null;         }     }       public static void runOnUiThread(Context context, Runnable runnable){         init(context);         weakHandler.get().post(runnable);         Log.i(MainActivity.TAG, "run ui over!");     }       public static void runOnUiThreadBlock(Context context, Runnable runnable){         init(context);           Message msg = Message.obtain(weakHandler.get(), runnable);         msg.what = WHAT_BLOCK;         msg.sendToTarget();           synchronized (lock){             Log.i(MainActivity.TAG, "begin wait!");             try {                 lock.wait();             } catch (InterruptedException e) {                 e.printStackTrace();             }             Log.i(MainActivity.TAG, "run ui block over!");         }     }   }

　　主类MainActivity内容

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package com.letv.handlertest;   import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.TextView;   public class MainActivity extends Activity implements View.OnClickListener {       public static final String TAG = "HandlerTest";       private Button btnRunOnUiThread, btnRunOnUiThreadBlock;     private TextView tvShow1, tvShow2; //    private RunUtilsB utils;       @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         initView();   //        utils = new RunUtilsB(this);     }       private void initView(){         btnRunOnUiThread = (Button)findViewById(R.id.btnRunOnUiThread);         btnRunOnUiThreadBlock = (Button)findViewById(R.id.btnRunOnUiThreadBlock);         tvShow1 = (TextView)findViewById(R.id.tvShow1);         tvShow2 = (TextView)findViewById(R.id.tvShow2);           btnRunOnUiThread.setOnClickListener(this);         btnRunOnUiThreadBlock.setOnClickListener(this);     }       private void runUi(){         new Thread(new Runnable() {             @Override             public void run() {                 RunUtils.runOnUiThread(MainActivity.this, new Runnable() {                     @Override                     public void run() {                         try {                             Thread.sleep(2000);                         } catch (InterruptedException e) {                             e.printStackTrace();                         }                         tvShow1.setText("run ui");                     }                 });             }         }).start();     }       private void runUiBlock(){         new Thread(new Runnable() {             @Override             public void run() {                 RunUtils.runOnUiThreadBlock(MainActivity.this, new Runnable() {                     @Override                     public void run() {                         try {                             Thread.sleep(2000);                         } catch (InterruptedException e) {                             e.printStackTrace();                         }                         tvShow2.setText("run ui block");                     }                 });             }         }).start();     }       @Override     public void onClick(View v) {         if(v == btnRunOnUiThread){             runUi();         }         else if(v == btnRunOnUiThreadBlock){             runUiBlock();         }     } }

 

运行结果正常。点击RunOnUiThread实现2s后更新textView1的值，点击调用后立马返回，点击RunOnUiThreadBlock后实现2s后更新textView2的值，更新完后才返回。