Eventhandler机制

1) Eventhandle初始化：
vim frameworks/base/core/java/android/hardware/Camera.java
private int cameraInitVersion(int cameraId, int halVersion) {
    mShutterCallback = null;
    mRawImageCallback = null;
    mJpegCallback = null;
    mPreviewCallback = null;
    mPostviewCallback = null;
    mUsingPreviewAllocation = false;
    mZoomListener = null;
    /* ### QC ADD-ONS: START */
    mCameraDataCallback = null;
    mCameraMetaDataCallback = null;
    /* ### QC ADD-ONS: END */
    Looper looper;
    if ((looper = Looper.myLooper()) != null) { //获得当前线程looper
        mEventHandler = new EventHandler(this, looper); //mEventHandler用于和looper交互
    } else if ((looper = Looper.getMainLooper()) != null) {
        mEventHandler = new EventHandler(this, looper);
    } else {
        mEventHandler = null;
    }
    return native_setup(new WeakReference<Camera>(this), cameraId, halVersion,
            ActivityThread.currentOpPackageName());
}
  2) 向线程队列发送数据：
private static void postEventFromNative(Object camera_ref, //该函数在jni中被调用（C++调用java接口函数）
                                        int what, int arg1, int arg2, Object obj)
{
    Camera c = (Camera)((WeakReference)camera_ref).get();
    if (c == null)
        return;
    if (c.mEventHandler != null) {
        Message m = c.mEventHandler.obtainMessage(what, arg1, arg2, obj); //组合队列信息
        c.mEventHandler.sendMessage(m); //发送数据
    }
}
3) 接收队列数据：
private class EventHandler extends Handler
{
    private final Camera mCamera;
    public EventHandler(Camera c, Looper looper) {
        super(looper);
        mCamera = c;
    }
    @Override
    public void handleMessage(Message msg) {
        switch(msg.what) {
        …...
        case CAMERA_MSG_OBJECT_TRACKING:
            if (mObjectTrackingFWCallback != null) {
                Log.e(TAG, "jay test call back");  //将数据传递给callback函数
                mObjectTrackingFWCallback.onObjectTrackingFWCallback((ObjectTrackingResult)msg.obj, mCamera);
            }
            return;
         ……
        }
    }
}

文章来源: blog.csdn.net，作者：简一商业，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/liwei16611/article/details/51315868