Display的syncExec和asyncExec
背景
一直在用Display.syncExec(Runnable)和Display.asyncExec(Runnable)，只简单知道同步用前者，异步用后者，而且代码也工作的很好，今天把它后面的源代码都了一遍，有了更清楚的认识。
1，每个Display会关联一个Thread（在Shell或Eclipse环境中一般即为UI主线程），Display.readAndDispatch()方法可以用来处理OS发送过来的消息，也可以处理自身的消息队列，代码片段如下
protected void asyncExec (Runnable runnable) {if (runnable == null) {//TEMPORARY CODEif (!IS_CARBON) {display.wake ();return;}}addLast (new RunnableLock (runnable));}protected void syncExec (Runnable runnable) {RunnableLock lock = null;synchronized (Device.class) {if (display == null || display.isDisposed ()) SWT.error (SWT.ERROR_DEVICE_DISPOSED);if (!display.isValidThread ()) {if (runnable == null) {display.wake ();return;}lock = new RunnableLock (runnable);/* * Only remember the syncThread for syncExec. */lock.thread = Thread.currentThread();addLast (lock);}}if (lock == null) {if (runnable != null) runnable.run ();return;}synchronized (lock) {boolean interrupted = false;while (!lock.done ()) {try {lock.wait ();} catch (InterruptedException e) {interrupted = true;}}if (interrupted) {Compatibility.interrupt();}if (lock.throwable != null) {SWT.error (SWT.ERROR_FAILED_EXEC, lock.throwable);}}}??6，当在一个UI主线程中打开一个Dialog时，就会嵌套进入到另一个Shell的消息循环，但他们都用主线程的Display，都在主线程中。