本文基于Android 12。
InputEvent经过inputflinger读取后，通过Inputchannel发送到Java层的InputEventReceiver对象，输入事件和View的状态强相关，事件发送需要确定当前的焦点App，焦点Window（View），事件接收者是谁，所以InputEventReceiver对象也在View的创建流程中被初始化，ViewRootImpl中通过InputChannel参数实例化WindowInputEventReceiver，其覆盖了父类InputEventReceiver的onInputEvent()方法。
一、WindowInputEventReceiver
// ViewRootImpl.java
final class WindowInputEventReceiver extends InputEventReceiver {
public WindowInputEventReceiver(InputChannel inputChannel, Looper looper) {
super(inputChannel, looper);
}
@Override
public void onInputEvent(InputEvent event) {
enqueueInputEvent(event, this, 0, true);
}
}
调用enqueueInputEvent方法。
// ViewRootImpl.java
QueuedInputEvent mPendingInputEventHead;
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
QueuedInputEvent last = mPendingInputEventTail;
if (last == null) {
mPendingInputEventHead = q;
mPendingInputEventTail = q;
} else {
last.mNext = q;
mPendingInputEventTail = q;
}
mPendingInputEventCount += 1;
doProcessInputEvents();
}
enqueueInputEvent对事件通过mPendingInputEventHead变量维护一个事件队列，doProcessInputEvents()进行下一步处理。
// ViewRootImpl.java
void doProcessInputEvents() {
while (mPendingInputEventHead != null) {
QueuedInputEvent q = mPendingInputEventHead;
mPendingInputEventHead = q.mNext;
if (mPendingInputEventHead == null) {
mPendingInputEventTail = null;
}
q.mNext = null;
deliverInputEvent(q);
}
}
doProcessInputEvents对mPendingInputEventHead队列中所有事件进行分发。
// ViewRootImpl.java
private void deliverInputEvent(QueuedInputEvent q) {
try {
InputStage stage;
if (q.shouldSendToSynthesizer()) {
stage = mSyntheticInputStage;
} else {
stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;
}
if (stage != null) {
handleWindowFocusChanged();
stage.deliver(q);
} else {
finishInputEvent(q);
}
}
}
将事件交给InputStage处理，InputStage是Android实现事件责任链的基类，deliver()方法中处理是否传递给下一个阶段：forward()，或者结束事件的传递：finish()。
二、InputState
// ViewRootImpl.java
abstract class InputStage {
public final void deliver(QueuedInputEvent q) {
if ((q.mFlags & QueuedInputEvent.FLAG_FINISHED) != 0) {
forward(q);
} else if (shouldDropInputEvent(q)) {
finish(q, false);
} else {
traceEvent(q, Trace.TRACE_TAG_VIEW);
final int result;
try {
result = onProcess(q);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
apply(q, result);
}
}
}
InputStage是一个抽象类，deliver方法中调用了onProcess(q)，子类覆盖onProcess方法实现自己的操作逻辑。
在ViewRootImpl的setView方法中定义了InputState的责任链：
// ViewRootImpl.java
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView,
int userId) {
// Set up the input pipeline.
CharSequence counterSuffix = attrs.getTitle();
mSyntheticInputStage = new SyntheticInputStage();
InputStage viewPostImeStage = new ViewPostImeInputStage(mSyntheticInputStage);
InputStage nativePostImeStage = new NativePostImeInputStage(viewPostImeStage,
"aq:native-post-ime:" + counterSuffix);
InputStage earlyPostImeStage = new EarlyPostImeInputStage(nativePostImeStage);
InputStage imeStage = new ImeInputStage(earlyPostImeStage,
"aq:ime:" + counterSuffix);
InputStage viewPreImeStage = new ViewPreImeInputStage(imeStage);
InputStage nativePreImeStage = new NativePreImeInputStage(viewPreImeStage,
"aq:native-pre-ime:" + counterSuffix);
mFirstInputStage = nativePreImeStage;
mFirstPostImeInputStage = earlyPostImeStage;
}
从实例化的顺序可知事件传递阶段的流程：
nativePreImeStage->viewPreImeStage->imeStage->earlyPostImeStage->nativePostImeStage->viewPostImeStage->mSyntheticInputStage
关于各个InputStage的官方说明：
| InputState | Description |
|---|---|
| NativePreImeInputStage | Delivers pre-ime input events to a native activity. Does not support pointer events. |
| ViewPreImeInputStage | Delivers pre-ime input events to the view hierarchy. Does not support pointer events. |
| ImeInputStage | Delivers input events to the ime. Does not support pointer events. |
| EarlyPostImeInputStage | Performs early processing of post-ime input events. |
| NativePostImeInputStage | Delivers post-ime input events to a native activity. |
| ViewPostImeInputStage | Delivers post-ime input events to the view hierarchy. |
| SyntheticInputStage | Performs synthesis of new input events from unhandled input events. |
可参考文章：https://blog.csdn.net/vviccc/article/details/93377708
一般用户接触到最多的Activity和View属于ViewPostImeInputStage阶段。
三、ViewPostImeInputStage
// ViewRootImpl.java
final class ViewPostImeInputStage extends InputStage {
@Override
protected int onProcess(QueuedInputEvent q) {
if (q.mEvent instanceof KeyEvent) {
return processKeyEvent(q);
} else {
final int source = q.mEvent.getSource();
if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
return processPointerEvent(q);
} else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
return processTrackballEvent(q);
} else {
return processGenericMotionEvent(q);
}
}
}
}
processKeyEvent处理KeyEvent，MotionEvent有两种情况，触屏操作的MotionEvent调用processPointerEvent处理，轨迹球操作的MotionEvent调用processTrackballEvent处理。
接着查看processPointerEvent方法：
// ViewRootImpl.java
private int processPointerEvent(QueuedInputEvent q) {
final MotionEvent event = (MotionEvent)q.mEvent;
boolean handled = mView.dispatchPointerEvent(event);
maybeUpdatePointerIcon(event);
maybeUpdateTooltip(event);
return handled ? FINISH_HANDLED : FORWARD;
}
调用mView.dispatchPointerEvent(event)方法。文章来源：https://www.toymoban.com/news/detail-433237.html
// View.java
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
public final boolean dispatchPointerEvent(MotionEvent event) {
if (event.isTouchEvent()) {
return dispatchTouchEvent(event);
} else {
return dispatchGenericMotionEvent(event);
}
}
终于到了熟悉的dispatchTouchEvent(event)方法。接下来就是熟悉onInterceptTouchEvent()，onTouchEvent()。文章来源地址https://www.toymoban.com/news/detail-433237.html
到了这里，关于Android InputEventReceiver事件接收流程分析的文章就介绍完了。如果您还想了解更多内容，请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章，希望大家以后多多支持TOY模板网！
