Looper.prepare()方法

prepare方法

public static void prepare() {prepare(true);}

prepare又调用它的重载方法，并将true作为默认形参传入，如果线程未绑定Looper对象则调用sThreadLocal.set(new Looper(quitAllowed))方法。如果已经绑定则抛出一个异常信息“每一个线程只能绑定一个Looper对象”。

private static void prepare(boolean quitAllowed) {if (sThreadLocal.get() != null) {throw new RuntimeException("Only one Looper may be created per thread");}//sThreadLocal.set(new Looper(quitAllowed))首先调用的是sThreadLocal.set()方法，以quitAllowed（也就是true）作为形参并调用Looper的有参构造然后传入一个Looper实例对象。sThreadLocal.set(new Looper(quitAllowed));
}

Looper的有参构造内以true作为形参传入并生成一个信息队列对象引用保存至mQueue成员变量，然后将当前线程引用保存至mThread成员变量。

private Looper(boolean quitAllowed) {mQueue = new MessageQueue(quitAllowed);mThread = Thread.currentThread();}

在MessageQueue有参构造中将quitAllowed（true）保存至mQuitAllowed成员变量。

MessageQueue(boolean quitAllowed) {mQuitAllowed = quitAllowed;mPtr = nativeInit();}

其实写到这里还是没有彻底弄明白，里面涉及了一些native的东西。先备注在这里以后懂了慢慢回头看。

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