Android 中keyEvent的消息处理

本文主要是介绍Android 中keyEvent的消息处理，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1. ViewRootImpl.deliverKeyEvent(QueuedInputEvent q)

1. 如果mView为空或者mAdded为false，就直接调用finishInputEvent。

2. mView.dispatchKeyEventPreIme(event)，在传递给IME之前做一些预处理。因为对于View来说，如果有输入窗口存在的话，会先将按键消息派发到输入窗口，只有当输入窗口没有处理这个事件，才会派发到真正的视图。因此如果想要在输入法截取事件前处理该消息，则可以重载这个方法去处理一些特定的按键消息。

3. 如果有IME窗口存在，就把这个传递给IME进行处理。imm.dispatchKeyEvent(mView.getContext(), seq, event, mInputMethodCallback);

4. deliverKeyEventPostIme(q); 将消息派发给真正的视图。

    private void deliverKeyEvent(QueuedInputEvent q) {final KeyEvent event = (KeyEvent)q.mEvent;if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onKeyEvent(event, 0);}if ((q.mFlags & QueuedInputEvent.FLAG_DELIVER_POST_IME) == 0) {// If there is no view, then the event will not be handled.if (mView == null || !mAdded) {finishInputEvent(q, false);return;}if (LOCAL_LOGV) Log.v(TAG, "Dispatching key " + event + " to " + mView);// Perform predispatching before the IME.if (mView.dispatchKeyEventPreIme(event)) {finishInputEvent(q, true);return;}// Dispatch to the IME before propagating down the view hierarchy.// The IME will eventually call back into handleImeFinishedEvent.if (mLastWasImTarget) {InputMethodManager imm = InputMethodManager.peekInstance();if (imm != null) {final int seq = event.getSequenceNumber();if (DEBUG_IMF) Log.v(TAG, "Sending key event to IME: seq="+ seq + " event=" + event);imm.dispatchKeyEvent(mView.getContext(), seq, event, mInputMethodCallback);return;}}}// Not dispatching to IME, continue with post IME actions.deliverKeyEventPostIme(q);}

1.2 ViewRootImpl.deliverKeyEventPostIme(q);

1. mView.dispatchKeyEvent(event); 将事件派发到View视图。因为mView就是一个DecorView,所以就是调用DecorView的dispatchKeyEvent的方法。

    private void deliverKeyEventPostIme(QueuedInputEvent q) {final KeyEvent event = (KeyEvent)q.mEvent;... ...// If the key's purpose is to exit touch mode then we consume it and consider it handled.if (checkForLeavingTouchModeAndConsume(event)) {finishInputEvent(q, true);return;}// Make sure the fallback event policy sees all keys that will be delivered to the// view hierarchy.mFallbackEventHandler.preDispatchKeyEvent(event);// Deliver the key to the view hierarchy.if (mView.dispatchKeyEvent(event)) {finishInputEvent(q, true);return;}// If the Control modifier is held, try to interpret the key as a shortcut.if (event.getAction() == KeyEvent.ACTION_DOWN&& event.isCtrlPressed()&& event.getRepeatCount() == 0&& !KeyEvent.isModifierKey(event.getKeyCode())) {if (mView.dispatchKeyShortcutEvent(event)) {finishInputEvent(q, true);return;}}// Apply the fallback event policy.if (mFallbackEventHandler.dispatchKeyEvent(event)) {finishInputEvent(q, true);return;}// Handle automatic focus changes.if (event.getAction() == KeyEvent.ACTION_DOWN) {int direction = 0;switch (event.getKeyCode()) {case KeyEvent.KEYCODE_DPAD_LEFT:if (event.hasNoModifiers()) {direction = View.FOCUS_LEFT;}break;case KeyEvent.KEYCODE_DPAD_RIGHT:if (event.hasNoModifiers()) {direction = View.FOCUS_RIGHT;}break;case KeyEvent.KEYCODE_DPAD_UP:if (event.hasNoModifiers()) {direction = View.FOCUS_UP;}break;case KeyEvent.KEYCODE_DPAD_DOWN:if (event.hasNoModifiers()) {direction = View.FOCUS_DOWN;}break;case KeyEvent.KEYCODE_TAB:if (event.hasNoModifiers()) {direction = View.FOCUS_FORWARD;} else if (event.hasModifiers(KeyEvent.META_SHIFT_ON)) {direction = View.FOCUS_BACKWARD;}break;}if (direction != 0) {View focused = mView.findFocus();if (focused != null) {View v = focused.focusSearch(direction);if (v != null && v != focused) {// do the math the get the interesting rect// of previous focused into the coord system of// newly focused viewfocused.getFocusedRect(mTempRect);if (mView instanceof ViewGroup) {((ViewGroup) mView).offsetDescendantRectToMyCoords(focused, mTempRect);((ViewGroup) mView).offsetRectIntoDescendantCoords(v, mTempRect);}if (v.requestFocus(direction, mTempRect)) {playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));finishInputEvent(q, true);return;}}// Give the focused view a last chance to handle the dpad key.if (mView.dispatchUnhandledMove(focused, direction)) {finishInputEvent(q, true);return;}}}}// Key was unhandled.finishInputEvent(q, false);}

1.2.1 DecorView.dispatchKeyEvent(KeyEvent event)

1. 如果是Down事件，首先会判断是不是Shortcut事件也就是快捷键按钮或者特殊事件，如果是就会调用dispatchKeyShortcutEvent和performPanelShortcut进行一些处理然后返回。

2. 如果不是快捷键按钮，就调用Callback Activity的cb.dispatchKeyEvent(event)去处理。Activity的dispatchKeyEvent中其实也还是去调用PhoneWindow中的superDispatchKeyEvent， PhoneWindow最终还是调用mDecor.superDispatchKeyEvent(event);

        @Overridepublic boolean dispatchKeyEvent(KeyEvent event) {final int keyCode = event.getKeyCode();final int action = event.getAction();final boolean isDown = action == KeyEvent.ACTION_DOWN;if (isDown && (event.getRepeatCount() == 0)) {// First handle chording of panel key: if a panel key is held// but not released, try to execute a shortcut in it.if ((mPanelChordingKey > 0) && (mPanelChordingKey != keyCode)) {boolean handled = dispatchKeyShortcutEvent(event);if (handled) {return true;}}// If a panel is open, perform a shortcut on it without the// chorded panel keyif ((mPreparedPanel != null) && mPreparedPanel.isOpen) {if (performPanelShortcut(mPreparedPanel, keyCode, event, 0)) {return true;}}}if (!isDestroyed()) {final Callback cb = getCallback();final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event): super.dispatchKeyEvent(event);if (handled) {return true;}}return isDown ? PhoneWindow.this.onKeyDown(mFeatureId, event.getKeyCode(), event): PhoneWindow.this.onKeyUp(mFeatureId, event.getKeyCode(), event);}

1.2.1.2 DecorView.mDecor.superDispatchKeyEvent(event);

1. 调用父类的dispatchKeyEvent。

       public boolean superDispatchKeyEvent(KeyEvent event) {if (super.dispatchKeyEvent(event)) {return true;}// Not handled by the view hierarchy, does the action bar want it// to cancel out of something special?if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {final int action = event.getAction();// Back cancels action modes first.if (mActionMode != null) {if (action == KeyEvent.ACTION_UP) {mActionMode.finish();}return true;}// Next collapse any expanded action views.if (mActionBar != null && mActionBar.hasExpandedActionView()) {if (action == KeyEvent.ACTION_UP) {mActionBar.collapseActionView();}return true;}}return false;}

1.2.1.2.1 ViewGroup.dispatchKeyEvent(KeyEvent event)

1. mPrivateFlags 是在View中定义的，标志当前View的属性。这里吧的FOCUSED 和HAS_BOUNDS表示当前的View是否是focused和有bounds的。一般的View和ViewGroup都会有HAS_BOUNDS, 而mFocused记录这当前ViewGroup中处于focus的View。

例如：如果A包含B，B又包含C，如果C是一个View，C的mPrivateFlags就是 FOCUSED | HAS_BOUNDS那么B的mPrivateFlags就是FOCUSED，mFocused就是C，同理A的mPrivateFlags也是FOCUSED，mFocused就是B。

2. 所以一般情况下，ViewGroup通过mFocused.dispatchKeyEvent()递归把Event传到View。

    public boolean dispatchKeyEvent(KeyEvent event) {if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onKeyEvent(event, 1);}if ((mPrivateFlags & (FOCUSED | HAS_BOUNDS)) == (FOCUSED | HAS_BOUNDS)) {if (super.dispatchKeyEvent(event)) {return true;}} else if (mFocused != null && (mFocused.mPrivateFlags & HAS_BOUNDS) == HAS_BOUNDS) {if (mFocused.dispatchKeyEvent(event)) {return true;}}if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onUnhandledEvent(event, 1);}return false;}

1.2.1.2.1.2 View.dispatchKeyEvent()

如果mFocused是ViewGroup那么还是调用1.2.1.2.1；如果是View，那么就调用View的dispatchKeyEvent。

1. 如果有注册Listener，就直接调用Listener的onKey去相应，然后返回。

2. 如果没有注册Listener，就调用KeyEvent.dispatch去做最后的处理

    public boolean dispatchKeyEvent(KeyEvent event) {if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onKeyEvent(event, 0);}// Give any attached key listener a first crack at the event.//noinspection SimplifiableIfStatementListenerInfo li = mListenerInfo;if (li != null && li.mOnKeyListener != null && (mViewFlags & ENABLED_MASK) == ENABLED&& li.mOnKeyListener.onKey(this, event.getKeyCode(), event)) {return true;}if (event.dispatch(this, mAttachInfo != null? mAttachInfo.mKeyDispatchState : null, this)) {return true;}if (mInputEventConsistencyVerifier != null) {mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);}return false;}

1.2.1.2.1.2.2 KeyEvent.dispatch

1. KeyEvent.dispatch会根据Action的类型调用receiver的对应的onXXX函数去处理。（receiver通常都是View）

2. 如果所有的View都没有处理这个KeyEvent，那么会最终通过KeyEvent调用Activity的onXXX函数。

    public final boolean dispatch(Callback receiver, DispatcherState state,Object target) {switch (mAction) {case ACTION_DOWN: {mFlags &= ~FLAG_START_TRACKING;if (DEBUG) Log.v(TAG, "Key down to " + target + " in " + state+ ": " + this);boolean res = receiver.onKeyDown(mKeyCode, this);if (state != null) {if (res && mRepeatCount == 0 && (mFlags&FLAG_START_TRACKING) != 0) {if (DEBUG) Log.v(TAG, "  Start tracking!");state.startTracking(this, target);} else if (isLongPress() && state.isTracking(this)) {try {if (receiver.onKeyLongPress(mKeyCode, this)) {if (DEBUG) Log.v(TAG, "  Clear from long press!");state.performedLongPress(this);res = true;}} catch (AbstractMethodError e) {}}}return res;}case ACTION_UP:if (DEBUG) Log.v(TAG, "Key up to " + target + " in " + state+ ": " + this);if (state != null) {state.handleUpEvent(this);}return receiver.onKeyUp(mKeyCode, this);case ACTION_MULTIPLE:final int count = mRepeatCount;final int code = mKeyCode;if (receiver.onKeyMultiple(code, count, this)) {return true;}if (code != KeyEvent.KEYCODE_UNKNOWN) {mAction = ACTION_DOWN;mRepeatCount = 0;boolean handled = receiver.onKeyDown(code, this);if (handled) {mAction = ACTION_UP;receiver.onKeyUp(code, this);}mAction = ACTION_MULTIPLE;mRepeatCount = count;return handled;}return false;}return false;}