Android应用程序键盘（Keyboard）消息处理机制分析（21）
Step 30. ViewRoot.dispatchFinishedEvent
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 {
- ......
- public void dispatchFinishedEvent(int seq, boolean handled) {
- Message msg = obtainMessage(FINISHED_EVENT);
- msg.arg1 = seq;
- msg.arg2 = handled ? 1 : 0;
- sendMessage(msg);
- }
- ......
- }
和前面的Step 26一样，ViewRoot不是直接处理这个键盘事件，而是把它作为一个消息（FINISHED_EVENT）放在消息队列中去，最后，这个消息由ViewRoot的handleFinishedEvent函数来处理。 Step 31. ViewRoot.handleFinishedEvent
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 {
- ......
- void handleFinishedEvent(int seq, boolean handled) {
- final KeyEvent event = (KeyEvent)retrievePendingEvent(seq);
- ......
- if (event != null) {
- final boolean sendDone = seq >= 0;
- if (!handled) {
- deliverKeyEventToViewHierarchy(event, sendDone);
- return;
- } else if (sendDone) {
- ......
- } else {
- ......
- }
- }
- }
- ......
- }
如果InputMethodManager没有处理这个键盘事件，那么ViewRoot就会调用deliverKeyEventToViewHierarchy函数来把这个键盘事件分发给当前激活的Activity窗口来处理。
Step 32. ViewRoot.deliverKeyEventToViewHierarchy
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 deliverKeyEventToViewHierarchy(KeyEvent event, boolean sendDone) {
- try {
- if (mView != null && mAdded) {
- ......
- boolean keyHandled = mView.dispatchKeyEvent(event);
- }
- ......
- } finally {
- if (sendDone) {
- finishInputEvent();
- }
- }
- }
- ......
- }
这个函数首先会调用ViewRoot类的成员变量mView的dispatchKeyEvent来处理这个键盘事件，然后最调用ViewRoot类的finishInputEvent来处理手尾工作。
ViewRoot类的成员变量mView的类型为DecorView，它是由ActivityThread类第一次Resume当前的Activity窗口时创建的，具体可以参考ActivityThread类的handleResumeActivity成员函数，这里就不关注了。
Step 33. DecorView.dispatchKeyEvent
这个函数定义在frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindow.java文件中，它是PhoneWindow类的一个内部类：
- public class PhoneWindow extends Window implements MenuBuilder.Callback {
- ......
- private final class DecorView extends FrameLayout implements RootViewSurfaceTaker {
- ......
- @Override
- public boolean dispatchKeyEvent(KeyEvent event) {
- ......
- final Callback cb = getCallback();
- final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event)
- : super.dispatchKeyEvent(event);
- ......
- }
- ......
- }
- ......
- }
Step 34. Activity.dispatchKeyEvent
这个函数定义在frameworks/base/core/java/android/app/Activity.java文件中：
- public class Activity extends ContextThemeWrapper
- implements LayoutInflater.Factory,
- Window.Callback, KeyEvent.Callback,
- OnCreateContextMenuListener, ComponentCallbacks {
- ......
- public boolean dispatchKeyEvent(KeyEvent event) {
- ......
- View decor = mDecor;
- if (decor == null) decor = win.getDecorView();
- return event.dispatch(this, decor != null
- ? decor.getKeyDispatcherState() : null, this);
- }
- ......
- }
Step 35. KeyEvent.dispatch
这个函数定义在frameworks/base/core/java/android/view/KeyEvent.java文件中：
- public class KeyEvent extends InputEvent implements Parcelable {
- ......
- public final boolean dispatch(Callback receiver, DispatcherState state,
- Object target) {
- switch (mAction) {
- case ACTION_DOWN: {
- ......
- boolean res = receiver.onKeyDown(mKeyCode, this);
- ......
- return res;
- }
- case ACTION_UP:
- ......
- return receiver.onKeyUp(mKeyCode, this);
- case ACTION_MULTIPLE:
- final int count = mRepeatCount;
- final int code = mKeyCode;
- if (receiver.onKeyMultiple(code, count, this)) {
- return true;
- }
- ......
- return false;
- }
- return false;
- }
- ......
- }
Activity窗口处理完这个键盘事件后，层层返回，最后回到Step 32中，调用finishInputEvent事件来处理一些手尾工，下面我们将会看到这些手尾工是什么。
