CropImage中为什么使用CountDownLatch难道不阻塞UI线程吗?

Question

    private void startFaceDetection() {
        if (isFinishing()) {
            return;
        }        mImageView.setImageBitmapResetBase(mBitmap, true);        Util.startBackgroundJob(this, null, getResources().getString(Res.string.running_face_detection), new Runnable() {
            public void run() {
                final CountDownLatch latch = new CountDownLatch(1);
                final Bitmap b = mBitmap;
                mHandler.post(new Runnable() {
                    public void run() {
                        if (b != mBitmap && b != null) {
                            mImageView.setImageBitmapResetBase(b, true);
                            mBitmap.recycle();
                            mBitmap = b;
                        }
                        if (mImageView.getScale() == 1.0f) {
                            mImageView.center(true, true);
                        }
                        latch.countDown();
                    }
                });
                try {
                    latch.await();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                mRunFaceDetection.run();
            }
        }, mHandler);
    }

Answer 1

调用CountDownLatch里面的方法的线程不是主线程吧？根据代码看都是在new的一个Runnable中调用的喎。不过不确定，有牛人详细说明么？哈！