关于android的Activity是如何触摸事件框架简析(一)
2015-01-06
最近做项目会修改导事件分发，所以对系统这部分代码进行了一定的研究，对android的框架的流的过程发出来供大家参考下. 所有代码研究基于android4.2.2_R1
Activity与windowMnager打交道的过程
首先是我们如何开启一个ActivityThread的，在ActivityThread中我们做了什么:
在ActivityThread中会最先调用的是handleLaunchActivity-->handleResumeActivity;
final void handleResumeActivity(IBinder token, boolean clearHide, boolean isForward,
boolean reallyResume) {
.......
if (r.window == null && !a.mFinished && willBeVisible) {
r.window = r.activity.getWindow();
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
l.softInputMode |= forwardBit;
if (a.mVisibleFromClient) {
a.mWindowAdded = true;
wm.addView(decor, l);
}
......
}核心代码就是上面的通过windowManager添加View, 这里的wm实体其实是WindowMnagerGlobal,查看addView:
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
......
ViewRootImpl root;
View panelParentView = null;
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
......
// do this last because it fires off messages to start doing things
try {
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
synchronized (mLock) {
final int index = findViewLocked(view, false);
if (index >= 0) {
removeViewLocked(index, true);
}
}
throw e;
}
}这里是new出了一个新的ViewRootImpl调用了setView方法: ViewRootImpl.java
/**
* We have one child
*/
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
......
try {
mOrigWindowType = mWindowAttributes.type;
mAttachInfo.mRecomputeGlobalAttributes = true;
collectViewAttributes();
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mInputChannel);
} catch (RemoteException e) {
mAdded = false;
mView = null;
mAttachInfo.mRootView = null;
mInputChannel = null;
mFallbackEventHandler.setView(null);
unscheduleTraversals();
setAccessibilityFocus(null, null);
throw new RuntimeException("Adding window failed", e);
} finally {
if (restore) {
attrs.restore();
}
}
.......
if (mInputChannel != null) {
if (mInputQueueCallback != null) {
mInputQueue = new InputQueue(mInputChannel);
mInputQueueCallback.onInputQueueCreated(mInputQueue);
} else {
mInputEventReceiver = new WindowInputEventReceiver(mInputChannel,
Looper.myLooper());
}
}
}核心代码就是 mWindowSession.addToDisplay(),
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
int viewVisibility, int displayId, Rect outContentInsets,
InputChannel outInputChannel) {
return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,
outContentInsets, outInputChannel);
}就是一个aidl调用，最终是调用的WindowManagerService的addWindow方法：
public int addWindow(Session session, IWindow client, int seq,
WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
Rect outContentInsets, InputChannel outInputChannel) {
......
if (outInputChannel != null && (attrs.inputFeatures
& WindowManager.LayoutParams.INPUT_FEATURE_NO_INPUT_CHANNEL) == 0) {
String name = win.makeInputChannelName();
InputChannel[] inputChannels = InputChannel.openInputChannelPair(name);
win.setInputChannel(inputChannels[0]);
inputChannels[1].transferTo(outInputChannel);
mInputManager.registerInputChannel(win.mInputChannel, win.mInputWindowHandle);
}
......
}这里打开了一对inputChannel一个作为server端，一个作为client端，并且注册到inputManager里头.这个inputChannel其实就是pipe,我们看看他们是怎么生成的： inputChannel.java
/**
* Creates a new input channel pair. One channel should be provided to the input
* dispatcher and the other to the application's input queue.
* @param name The descriptive (non-unique) name of the channel pair.
* @return A pair of input channels. They are symmetric and indistinguishable.
*/
public static InputChannel[] openInputChannelPair(String name) {
if (name == null) {
throw new IllegalArgumentException("name must not be null");
}
if (DEBUG) {
Slog.d(TAG, "Opening input channel pair '" + name + "'");
}
return nativeOpenInputChannelPair(name);
}natvie层对应代码： android_view_inputchannel.cpp
static jobjectArray android_view_InputChannel_nativeOpenInputChannelPair(JNIEnv* env,
jclass clazz, jstring nameObj) {
const char* nameChars = env->GetStringUTFChars(nameObj, NULL);
String8 name(nameChars);
env->ReleaseStringUTFChars(nameObj, nameChars);
sp<InputChannel> serverChannel;
sp<InputChannel> clientChannel;
status_t result = InputChannel::openInputChannelPair(name, serverChannel, clientChannel);
if (result) {
String8 message;
message.appendFormat("Could not open input channel pair. status=%d", result);
jniThrowRuntimeException(env, message.string());
return NULL;
}
jobjectArray channelPair = env->NewObjectArray(2, gInputChannelClassInfo.clazz, NULL);
if (env->ExceptionCheck()) {
return NULL;
}
jobject serverChannelObj = android_view_InputChannel_createInputChannel(env,
new NativeInputChannel(serverChannel));
if (env->ExceptionCheck()) {
return NULL;
}
jobject clientChannelObj = android_view_InputChannel_createInputChannel(env,
new NativeInputChannel(clientChannel));
if (env->ExceptionCheck()) {
return NULL;
}
env->SetObjectArrayElement(channelPair, 0, serverChannelObj);
env->SetObjectArrayElement(channelPair, 1, clientChannelObj);
return channelPair;
}主要关注函数openInputChannelPair
status_t InputChannel::openInputChannelPair(const String8& name,
sp<InputChannel>& outServerChannel, sp<InputChannel>& outClientChannel) {
int sockets[2];
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets)) {
status_t result = -errno;
ALOGE("channel '%s' ~ Could not create socket pair. errno=%d",
name.string(), errno);
outServerChannel.clear();
outClientChannel.clear();
return result;
}
int bufferSize = SOCKET_BUFFER_SIZE;
setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &bufferSize, sizeof(bufferSize));
setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &bufferSize, sizeof(bufferSize));
String8 serverChannelName = name;
serverChannelName.append(" (server)");
outServerChannel = new InputChannel(serverChannelName, sockets[0]);
String8 clientChannelName = name;
clientChannelName.append(" (client)");
outClientChannel = new InputChannel(clientChannelName, sockets[1]);
return OK;
}这里就可以发现双方是通过一个共享内存，socket的方式通信。这时候我们就已经初步的了解 Activity与windowManagerService是如何建立联系的.
Activity接收事件过程
在ViewRootImpl中，我们会创建一个WindowInputEventReceiver，WindowInputEventReceiver的初始化会使用inputchannel和主线程的looper,继承于InputEventReceiver:
**
* Creates an input event receiver bound to the specified input channel.
*
* @param inputChannel The input channel.
* @param looper The looper to use when invoking callbacks.
*/
public InputEventReceiver(InputChannel inputChannel, Looper looper) {
if (inputChannel == null) {
throw new IllegalArgumentException("inputChannel must not be null");
}
if (looper == null) {
throw new IllegalArgumentException("looper must not be null");
}
mInputChannel = inputChannel;
mMessageQueue = looper.getQueue();
mReceiverPtr = nativeInit(this, inputChannel, mMessageQueue);
mCloseGuard.open("dispose");
}会调用底层的nativeInit： android_view_InputEventReceiver.cpp
static jint nativeInit(JNIEnv* env, jclass clazz, jobject receiverObj,
jobject inputChannelObj, jobject messageQueueObj) {
sp<InputChannel> inputChannel = android_view_InputChannel_getInputChannel(env,
inputChannelObj);
if (inputChannel == NULL) {
jniThrowRuntimeException(env, "InputChannel is not initialized.");
return 0;
}
sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, messageQueueObj);
if (messageQueue == NULL) {
jniThrowRuntimeException(env, "MessageQueue is not initialized.");
return 0;
}
sp<NativeInputEventReceiver> receiver = new NativeInputEventReceiver(env,
receiverObj, inputChannel, messageQueue);
status_t status = receiver->initialize();
if (status) {
String8 message;
message.appendFormat("Failed to initialize input event receiver. status=%d", status);
jniThrowRuntimeException(env, message.string());
return 0;
}
receiver->incStrong(gInputEventReceiverClassInfo.clazz); // retain a reference for the object
return reinterpret_cast<jint>(receiver.get());
}这里其实是拿到上层的looper和上层的inputchannel去生成一个NativeInputEventReceiver，在看看NativeInputEventReceiver的作用:
NativeInputEventReceiver::NativeInputEventReceiver(JNIEnv* env,
jobject receiverObj, const sp<InputChannel>& inputChannel,
const sp<MessageQueue>& messageQueue) :
mReceiverObjGlobal(env->NewGlobalRef(receiverObj)),
mInputConsumer(inputChannel), mMessageQueue(messageQueue),
mBatchedInputEventPending(false) {
#if DEBUG_DISPATCH_CYCLE
ALOGD("channel '%s' ~ Initializing input event receiver.", getInputChannelName());
#endif
}status_t NativeInputEventReceiver::initialize() {
int receiveFd = mInputConsumer.getChannel()->getFd();
mMessageQueue->getLooper()->addFd(receiveFd, 0, ALOOPER_EVENT_INPUT, this, NULL);
return OK;
}NativeInputEventReceiver实际上就是生成了一个mInputConsumer,并且调用initialize，将inputChannel的fd挂载到looper中去监听事件，回调函数为handleEvent：
int NativeInputEventReceiver::handleEvent(int receiveFd, int events, void* data) {
if (events & (ALOOPER_EVENT_ERROR | ALOOPER_EVENT_HANGUP)) {
ALOGE("channel '%s' ~ Publisher closed input channel or an error occurred. "
"events=0x%x", getInputChannelName(), events);
return 0; // remove the callback
}
if (!(events & ALOOPER_EVENT_INPUT)) {
ALOGW("channel '%s' ~ Received spurious callback for unhandled poll event. "
"events=0x%x", getInputChannelName(), events);
return 1;
}
JNIEnv* env = AndroidRuntime::getJNIEnv();
status_t status = consumeEvents(env, false /*consumeBatches*/, -1);
mMessageQueue->raiseAndClearException(env, "handleReceiveCallback");
return status == OK || status == NO_MEMORY ? 1 : 0;
}status_t NativeInputEventReceiver::consumeEvents(JNIEnv* env,
bool consumeBatches, nsecs_t frameTime) {
.......
if (!skipCallbacks) {
jobject inputEventObj;
switch (inputEvent->getType()) {
case AINPUT_EVENT_TYPE_KEY:
#if DEBUG_DISPATCH_CYCLE
ALOGD("channel '%s' ~ Received key event.", getInputChannelName());
#endif
inputEventObj = android_view_KeyEvent_fromNative(env,
static_cast<KeyEvent*>(inputEvent));
break;
case AINPUT_EVENT_TYPE_MOTION:
#if DEBUG_DISPATCH_CYCLE
ALOGD("channel '%s' ~ Received motion event.", getInputChannelName());
#endif
inputEventObj = android_view_MotionEvent_obtainAsCopy(env,
static_cast<MotionEvent*>(inputEvent));
break;
default:
assert(false); // InputConsumer should prevent this from ever happening
inputEventObj = NULL;
}
if (inputEventObj) {
#if DEBUG_DISPATCH_CYCLE
ALOGD("channel '%s' ~ Dispatching input event.", getInputChannelName());
#endif
env->CallVoidMethod(mReceiverObjGlobal,
gInputEventReceiverClassInfo.dispatchInputEvent, seq, inputEventObj);
if (env->ExceptionCheck()) {
ALOGE("Exception dispatching input event.");
skipCallbacks = true;
}
} else {
ALOGW("channel '%s' ~ Failed to obtain event object.", getInputChannelName());
skipCallbacks = true;
}
}
if (skipCallbacks) {
mInputConsumer.sendFinishedSignal(seq, false);
}
}
}这里会回调到java层上的InputEventReceiver的dispatchInputEvent：
// Called from native code.
@SuppressWarnings("unused")
private void dispatchInputEvent(int seq, InputEvent event) {
mSeqMap.put(event.getSequenceNumber(), seq);
onInputEvent(event);
}这里的onInputEvent(event)方法已经被WindowInputEventReceiver复写了:
@Override
public void onInputEvent(InputEvent event) {
enqueueInputEvent(event, this, 0, true);
}这里往下翻一点就知道这个队列做了什么事情:
private void deliverInputEvent(QueuedInputEvent q) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "deliverInputEvent");
try {
if (q.mEvent instanceof KeyEvent) {
deliverKeyEvent(q);
} else {
final int source = q.mEvent.getSource();
if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
deliverPointerEvent(q);
} else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
deliverTrackballEvent(q);
} else {
deliverGenericMotionEvent(q);
}
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
}这里讲底层的inputEvent分成各种不同的类型去区别对待.
这里就能看到View是如何接收事件的整个过程的
结论
1.androd的底层实现是通过socket和共享内存的方式，这种写法也可以采用在我们自己的多进程通信上使用，值得学习 2.底层所有的event其实都是一样的，都是inputEvent，上层会根据source再分成keyEvent,MotionEvent等，用于不同的用处 3.所有View的起点其实就是dispatchPointerEvent()，这个是分发事件的起点.
参考blog
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