Android应用程序键盘（Keyboard）消息处理机制分析（22）

      Step 36. ViewRoot.finishInputEvent

         这个函数定义在frameworks/base/core/java/android/view/ViewRoot.java文件中：

public final class ViewRoot extends Handler implements ViewParent,
        View.AttachInfo.Callbacks {
    ......

    private void finishInputEvent() {
        ......

        if (mFinishedCallback != null) {
            mFinishedCallback.run();
            mFinishedCallback = null;
        } else {
            ......
        }
    }

    ......
}

         ViewRoot类里面的成员变量mFinishedCallback是在前面Step 25中由InputQueue设置的，它是一个Runnable对象，实际类型是定义在InputQueue的内部类FinishedCallback，因此，这里调用它的run方法时，接下来就会调用InputQueue的内部类FinishedCallback的run成员函数：

public final class InputQueue {
    ......

    private static class FinishedCallback implements Runnable {
        ......

        public void run() {
            synchronized (sLock) {
                ......

                nativeFinished(mFinishedToken);

                ......
            }
        }

        ......
    }

    ......
}

        这里它调用外部类InputQueue的本地方法nativeFinished来进一步处理。

       Step 37.  InputQueue.nativeFinished

        这个函数定义在frameworks/base/core/jni/android_view_InputQueue.cpp文件中：

static void android_view_InputQueue_nativeFinished(JNIEnv* env, jclass clazz,
        jlong finishedToken) {
    status_t status = gNativeInputQueue.finished(
        env, finishedToken, false /*ignoreSpuriousFinish*/);

    ......
}

        这个函数只是简单只调用NativeInputQueue的finished方法来进一处处理。

 

        Step 38. NativeInputQueue.finished

        这个函数定义在frameworks/base/core/jni/android_view_InputQueue.cpp文件中：

status_t NativeInputQueue::finished(JNIEnv* env, jlong finishedToken, bool ignoreSpuriousFinish) {
    int32_t receiveFd;
    uint16_t connectionId;
    uint16_t messageSeqNum;
    parseFinishedToken(finishedToken, &receiveFd, &connectionId, &messageSeqNum);

    { // acquire lock
        AutoMutex _l(mLock);

        ssize_t connectionIndex = mConnectionsByReceiveFd.indexOfKey(receiveFd);
        ......

        sp<Connection> connection = mConnectionsByReceiveFd.valueAt(connectionIndex);
        ......

        connection->messageInProgress = false;

        status_t status = connection->inputConsumer.sendFinishedSignal();

        ......
    } // release lock

    return OK;
}

        这个函数最重要的参数便是finishedToken了，通过它可以获得之前通知Java层的InputQueue类来处理键盘事件的Connection对象，它的值是在上面的Step 21（NativeInputQueue.handleReceiveCallback）中生成的：

finishedToken = generateFinishedToken(receiveFd, connection->id, connection->messageSeqNum);

        函数generateFinishedToken的定义如下：

jlong NativeInputQueue::generateFinishedToken(int32_t receiveFd, uint16_t connectionId,
        uint16_t messageSeqNum) {
    return (jlong(receiveFd) << 32) | (jlong(connectionId) << 16) | jlong(messageSeqNum);
}

        它的实现很简单，只是把receiveFd（前向管道的读端文件描述符）、connectionId（Client端的InputChannel对应的Connection对象在NativeInputQueue中的索引）和messageSeqNum（键盘消息的序列号）三个数值通过移位的方式编码在一个jlong值里面，即编码在上面的finishedToken参数里面。

 

        因此，在上面的finished函数里面，首先就是要对参数值finishedToken进行解码，把receiveFd、connectionId和messageSeqNum三个值分别取回来：

parseFinishedToken(finishedToken, &receiveFd, &connectionId, &messageSeqNum);

       parseFinishedToken的定义如下：

void NativeInputQueue::parseFinishedToken(jlong finishedToken,
        int32_t* outReceiveFd, uint16_t* outConnectionId, uint16_t* outMessageIndex) {
    *outReceiveFd = int32_t(finishedToken >> 32);
    *outConnectionId = uint16_t(finishedToken >> 16);
    *outMessageIndex = uint16_t(finishedToken);
}

       有了这个receiveFd和connectionId之后，就可以把相应的Connection对象取回来了：

ssize_t connectionIndex = mConnectionsByReceiveFd.indexOfKey(receiveFd);
        ......

sp<Connection> connection = mConnectionsByReceiveFd.valueAt(connectionIndex);

       接下来就是调用这个connection对象中的inputConsumer对象来发送信号通知Server端的InputChannel，应用程序这一侧处理完刚才发生的键盘事件了：

status_t status = connection->inputConsumer.sendFinishedSignal();