Create 同步处理消息.md

blogs/Android/Framework/Interview/技巧心得相关/同步处理消息.md

@@ -0,0 +1,59 @@
+---
+怎么同步处理消息？
+---
+
+```c++
+status_t Client::createSurface(const String&& name, ...){
+    sp<MessageBase> msg = new MessageCreateLayer(mFlinger.get(), name, this, w, h, format, flags, handle, gbp);
+    mFlinger->postMessageSync(msg);
+    return static_cast<MessageCreateLayer*>(msg.get())->getResult();
+}
+status_t postMessageSync(const sp<MessageBase>& msg, ...){
+    mEventQueue.postMessage(msg, reltime);
+    msg.wait();
+}
+class MessageCreateLayer:public MessageBase{
+    status_t getResult() const{return result;}
+    virtual bool handler(){
+        result = flinger->createLayer(name, client,w, h, format, ...);
+        return true;
+    }
+}
+```
+
+```java
+public final boolean runWithScissors(final Runnable r, long timeout){
+	if(Looper.myLooper()==mLooper){
+		r.run();
+		return true;
+	}
+    BlockingRunnable br = new BlockingRunnable(r);
+    return br.postAndWait(this, timeout);
+}
+private static final class BlockingRunnable implements Runnable{
+    public BlockingRunnable(Runnable task){
+        mTask = task;
+    }
+    
+    @Override
+    public void run(){
+        mTask.run();
+        mDone = true;
+        notifyAll();
+    }
+}
+public boolean postAndWait(Handler handler, ...){
+    if(!handler.post(this)){
+        return false;
+    }
+    while(!mDone){
+        wait();
+    }
+    return true;
+}
+```
+
+#### 总结
+
+1. 同步等待消息的处理
+2. Binder 调用统一切换工作线程