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Android按键事件传递流程(二)
应用层接收按键事件
上篇文章讲到了ViewRootImpl中的processKeyEvent这个方法
private int processKeyEvent(QueuedInputEvent q) {
final KeyEvent event = (KeyEvent)q.mEvent;
if (mUnhandledKeyManager.preViewDispatch(event)) {
return FINISH_HANDLED;
}
// Deliver the key to the view hierarchy.
//把按键事件传给了view处理，转交给应用层
if (mView.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
if (shouldDropInputEvent(q)) {
return FINISH_NOT_HANDLED;
}
// This dispatch is for windows that don't have a Window.Callback. Otherwise,
// the Window.Callback usually will have already called this (see
// DecorView.superDispatchKeyEvent) leaving this call a no-op.
if (mUnhandledKeyManager.dispatch(mView, event)) {
return FINISH_HANDLED;
}
int groupNavigationDirection = 0;
if (event.getAction() == KeyEvent.ACTION_DOWN
&& event.getKeyCode() == KeyEvent.KEYCODE_TAB) {
if (KeyEvent.metaStateHasModifiers(event.getMetaState(), KeyEvent.META_META_ON)) {
groupNavigationDirection = View.FOCUS_FORWARD;
} else if (KeyEvent.metaStateHasModifiers(event.getMetaState(),
KeyEvent.META_META_ON | KeyEvent.META_SHIFT_ON)) {
groupNavigationDirection = View.FOCUS_BACKWARD;
}
}
// If a modifier is held, try to interpret the key as a shortcut.
//处理Ctrl组合按键
if (event.getAction() == KeyEvent.ACTION_DOWN
&& !KeyEvent.metaStateHasNoModifiers(event.getMetaState())
&& event.getRepeatCount() == 0
&& !KeyEvent.isModifierKey(event.getKeyCode())
&& groupNavigationDirection == 0) {
if (mView.dispatchKeyShortcutEvent(event)) {
return FINISH_HANDLED;
}
if (shouldDropInputEvent(q)) {
return FINISH_NOT_HANDLED;
}
}
// Apply the fallback event policy.
//处理所有的回退按键事件，主要是一些未处理的特殊按键，例如拍照键、拨号键等。如果特殊按键没有在PhoneWindowManager、view树、窗口中处理，就会传到此处。
if (mFallbackEventHandler.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
if (shouldDropInputEvent(q)) {
return FINISH_NOT_HANDLED;
}
// Handle automatic focus changes.
//处理方向键和TAB键，找到获取焦点的view并将按键传递过去，如果view都没有焦点，就会找一个最适合的view并把按键传递过去。
if (event.getAction() == KeyEvent.ACTION_DOWN) {
if (groupNavigationDirection != 0) {
if (performKeyboardGroupNavigation(groupNavigationDirection)) {
return FINISH_HANDLED;
}
} else {
if (performFocusNavigation(event)) {
return FINISH_HANDLED;
}
}
}
return FORWARD;
}
应用层按键事件的传递
...
//把按键事件传给了view处理，转交给应用层
if (mView.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
...
事件传递给了mView的dispatchKeyEvent方法，mView是DecorView对象。
可以这样理解：
先找到当前获取焦点的窗口，把事件发送到窗口，窗口在启动Activity时会被创建，最终事件就传递到了窗口中所有view的根类DecorView。
这里主要讲解两部分，mView的创建和事件传递流程。
1. mView的创建过程
Activity的启动流程中handleResumeActivity方法
...
if (r.window == null && !a.mFinished && willBeVisible) {
//返回一个PhoneWindow对象
r.window = r.activity.getWindow();
//获取DectorView对象
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
//创建了一个与Activity对应的WindowManagerImpl对象。
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
l.softInputMode |= forwardBit;
if (r.mPreserveWindow) {
a.mWindowAdded = true;
r.mPreserveWindow = false;
// Normally the ViewRoot sets up callbacks with the Activity
// in addView->ViewRootImpl#setView. If we are instead reusing
// the decor view we have to notify the view root that the
// callbacks may have changed.
ViewRootImpl impl = decor.getViewRootImpl();
if (impl != null) {
impl.notifyChildRebuilt();
}
}
if (a.mVisibleFromClient) {
if (!a.mWindowAdded) {
a.mWindowAdded = true;
//调用WindowManagerImpl对象的addView方法
wm.addView(decor, l);
} else {
// The activity will get a callback for this {@link LayoutParams} change
// earlier. However, at that time the decor will not be set (this is set
// in this method), so no action will be taken. This call ensures the
// callback occurs with the decor set.
a.onWindowAttributesChanged(l);
}
}
// If the window has already been added, but during resume
// we started another activity, then don't yet make the
// window visible.
} else if (!willBeVisible) {
if (localLOGV) Slog.v(TAG, "Launch " + r + " mStartedActivity set");
r.hideForNow = true;
}
...
r.activity.getWindow() r.activity就是最新启动的Activity对象，通过getWindow()返回mWindow对象。
wm.addView(decor, l);
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mContext.getDisplayNoVerify(), mParentWindow,
mContext.getUserId());
}
其中mGlobal是WindowManagerGlobal的单例对象。
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow, int userId) {
...
ViewRootImpl root;
...
// do this last because it fires off messages to start doing things
try {
root.setView(view, wparams, panelParentView, userId);
} catch (RuntimeException e) {
// BadTokenException or InvalidDisplayException, clean up.
if (index >= 0) {
removeViewLocked(index, true);
}
throw e;
}
}
root是ViewRootImpl对象，调用其setView方法把DecorView对象传递过去并赋值给mView,详细请看源码ViewRootImpl.java。
mView就是与Activity对应的DecorView对象，在创建PhoneWindow对象时创建的。
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