此處記錄按鍵事件從Framework到應用層的傳遞流程。WMS中接收到消息后，會調用ViewRootImpl中的dispatchInputEvent方法，
附上核心流程圖
Android按鍵事件流程
輸入事件認識
Android所有輸入事件都會封裝為InputEvent事件然后進行分發，InputEvent又分為兩種類型，實體按鍵事件(KeyEvent)，觸摸事件(MotionEvent)。這些事件流入到上層之后才會進行分別進行處理。
下面源碼分析
按鍵事件流入
InputEvent就包含了KeyEvent,接下來就看該輸入事件如何傳遞和分別處理的，首先是ViewRootImpl的dispatchInputEvent方法
frameworks/base/core/java/android/view/ViewRootImpl.java
public void dispatchInputEvent(InputEvent event) {
dispatchInputEvent(event, null);
}
public void dispatchInputEvent(InputEvent event, InputEventReceiver receiver) {
SomeArgs args = SomeArgs.obtain();
args.arg1 = event;
args.arg2 = receiver; // 此處receiver為null
Message msg = mHandler.obtainMessage(MSG_DISPATCH_INPUT_EVENT, args);
msg.setAsynchronous(true);
//發送MSG_DISPATCH_INPUT_EVENT消息
mHandler.sendMessage(msg);
}
mHandler是其內部類ViewRootHandler,接收到消息如下
final class ViewRootHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
...
case MSG_DISPATCH_INPUT_EVENT: {
SomeArgs args = (SomeArgs)msg.obj;
InputEvent event = (InputEvent)args.arg1;
InputEventReceiver receiver = (InputEventReceiver)args.arg2;
enqueueInputEvent(event, receiver, 0, true);
args.recycle();
} break;
}
}
走enqueueInputEvent方法
void enqueueInputEvent(InputEvent event,
InputEventReceiver receiver, int flags, boolean processImmediately) {
adjustInputEventForCompatibility(event);
// 1. 將輸入事件event封裝為QueuedInputEvent
QueuedInputEvent q = obtainQueuedInputEvent(event, receiver, flags);
// Always enqueue the input event in order, regardless of its time stamp.
// We do this because the application or the IME may inject key events
// in response to touch events and we want to ensure that the injected keys
// are processed in the order they were received and we cannot trust that
// the time stamp of injected events are monotonic.
QueuedInputEvent last = mPendingInputEventTail;
if (last == null) {
mPendingInputEventHead = q;
mPendingInputEventTail = q;
} else {
// 2. 追加新事件到mPendingInputEventTail上,形成事件鏈表
last.mNext = q;
mPendingInputEventTail = q;
}
mPendingInputEventCount += 1;
if (processImmediately) {
// 3. 處理輸入事件
doProcessInputEvents();
} else {
scheduleProcessInputEvents();
}
}
void doProcessInputEvents() {
// Deliver all pending input events in the queue.
while (mPendingInputEventHead != null) {
QueuedInputEvent q = mPendingInputEventHead;
mPendingInputEventHead = q.mNext;
if (mPendingInputEventHead == null) {
mPendingInputEventTail = null;
}
q.mNext = null;
...
// 4. 分發QueuedInputEvent隊列中的所有事件
deliverInputEvent(q);
}
...
}
InputEvent事件會形成一個事件鏈表，最后循環分發鏈表隊列中的事件
private void deliverInputEvent(QueuedInputEvent q) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onInputEvent(q.mEvent, 0);
}
// 關于InputStage下面詳解，它表示了輸入事件的一個分發階段,eg: ime之前處理，ime處理，ime之后處理等
InputStage stage;
if (q.shouldSendToSynthesizer()) {
stage = mSyntheticInputStage;
} else {
// 是否跳過鍵盤消息(IME),如果true,返回EarlyPostImeInputStage對象，否則返回NativePreImeInputStage對象
stage = q.shouldSkipIme() ? mFirstPostImeInputStage : mFirstInputStage;
}
if (stage != null) {
stage.deliver(q);
} else {
finishInputEvent(q);
}
}
NativePreImeInputStage是在ViewRootImpl中的setView()創建，而setview方法是在完成view繪制時調用的。
ViewRootImpl.java
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
if (mView == null) {
mView = view;
...
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;
}
}
}
先接著看deliverInputEvent方法中的stage.deliver(q);
abstract class InputStage {
/**
* Delivers an event to be processed.
*/
public final void deliver(QueuedInputEvent q) {
/// M: [ANR] Add for monitoring stage status. {
ViewDebugManager.getInstance().debugInputStageDeliverd(this,
System.currentTimeMillis());
/// }
// 當前事件還沒有處理，因此不包含FLAG_FINISHED標致
if ((q.mFlags & QueuedInputEvent.FLAG_FINISHED) != 0) {
forward(q);
// 一般不會丟棄輸入事件
} else if (shouldDropInputEvent(q)) {
finish(q, false);
} else {
ViewDebugManager.getInstance().debugInputDispatchState(q.mEvent, this.toString());
// 1. 執行apply方法，傳入onProcess的返回結果，該方法由子類重寫
apply(q, onProcess(q));
}
}
...
/**
* Applies a result code from {@link #onProcess} to the specified event.
*/
protected void apply(QueuedInputEvent q, int result) {
if (result == FORWARD) {
forward(q);
} else if (result == FINISH_HANDLED) {
finish(q, true);
} else if (result == FINISH_NOT_HANDLED) {
finish(q, false);
} else {
throw new IllegalArgumentException("Invalid result: " + result);
}
}
/**
* Called when an event is ready to be processed.
* @return A result code indicating how the event was handled.
*/
protected int onProcess(QueuedInputEvent q) {
return FORWARD;
}
...
}
上面提到的所有InputState都繼承自InputStage
如果不跳過IME消息，則inputStage為NativePreImeInputStage，其是由ViewPreImeInputStage，ImeInputStage，EarlyPostImeInputStage，NativePostImeInputStage，ViewPostImeInputStage，SyntheticInputStage作為嵌套參數構成的，所以調用NativePreImeInputStage的deliver(q)，會依次調用到每個InputState的子類的onProcess()方法
這里先介紹下InputStage
InputStage
輸入事件的傳遞過程如下，每個前面處理事件的階段都有攔截傳遞的能力。
- NativePreImeInputStage 分發早于IME的InputEvent事件到NativeActivity中去處理, NativeActivity和普通acitivty的功能區別不大,只是很多代碼都在native層去實現,這樣執行效率更高,并且NativeActivity在游戲開發中很實用。 不支持觸摸事件。
- ViewPreImeInputStage 分發早于IME的InputEvent到View框架處理，會調用acitivity的所有view的onkeyPreIme方法,這樣就給View在輸入法處理key事件之前先得到消息并處理的機會。 不支持觸摸事件
- ImeInputStage 分發InputEvent到IME處理 ImeInputStage的onProcess方法會調用InputMethodManager的dispatchInputEvent方法處理消息。 不支持觸摸事件。
- EarlyPostImeInputStage 輸入法之后輸入事件就會流到該階段，此時 屏幕上有焦點的View會高亮顯示,用來提示用戶焦點所在。支持觸摸事件。
- NativePostImeInputStage 分發InputEvent事件到NativeActivity,為了讓IME處理完消息后能先于普通的Activity處理消息。此時支持觸摸事件。
- ViewPostImeInputStage 分發InputEvent事件到View框架，支持觸摸事件。
- SyntheticInputStage 未處理的InputEvent都會傳到這個階段,例如手機上的虛擬按鍵消息
所有InputStage類的構造方法都會傳入一個InputStage類的變量,這樣最終會形成流水線線式的處理結構,也就是采用了責任鏈模式，每經過一個InputStage對象的處理都會進行判斷,看是否還需要將 events繼續向前傳輸,如果需要就調用forward()函數讓該變量中存儲的下一個InputStage對象處理該events,如果不需要就調用finish()函數結束events的傳輸
我們所關心的View框架的輸入事件，故著重分析ViewPostImeInputStage
/**
* Delivers post-ime input events to the view hierarchy.
*/
final class ViewPostImeInputStage extends InputStage {
...
@Override
protected int onProcess(QueuedInputEvent q) {
if (q.mEvent instanceof KeyEvent) {
// 處理按鍵事件
return processKeyEvent(q);
} else {
// else中處理觸摸事件,觸摸事件又會根據不同類型的觸摸做不同的處理，例如鼠標觸摸，軌跡球(Android很早的一種交互方式，現在沒有手機用)觸摸,一般的手指觸摸
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);
}
}
}
}
此處我們分析按鍵事件
private int processKeyEvent(QueuedInputEvent q) {
// 轉為KeyEvent事件
final KeyEvent event = (KeyEvent)q.mEvent;
// Deliver the key to the view hierarchy.
// 1. 先由DecorView進行按鍵事件派發
if (mView.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
...
int groupNavigationDirection = 0;
// 根據TAB和SHIFT鍵的按下來判斷焦點方向為向前還是向后
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.
if (event.getAction() == KeyEvent.ACTION_DOWN
&& !KeyEvent.metaStateHasNoModifiers(event.getMetaState())
&& event.getRepeatCount() == 0
&& !KeyEvent.isModifierKey(event.getKeyCode())
&& groupNavigationDirection == 0) {
// 交由DecorView處理快捷鍵分發
if (mView.dispatchKeyShortcutEvent(event)) {
return FINISH_HANDLED;
}
...
}
// mFallbackEventHandler會處理系統的一些按鍵，針對的是所有窗口
// Apply the fallback event policy.
if (mFallbackEventHandler.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
...
// Handle automatic focus changes.
if (event.getAction() == KeyEvent.ACTION_DOWN) {
if (groupNavigationDirection != 0) {
if (performKeyboardGroupNavigation(groupNavigationDirection)) {
return FINISH_HANDLED;
}
} else {
// 2. 處理鍵盤的上下左右的焦點查找
if (performFocusNavigation(event)) {
return FINISH_HANDLED;
}
}
}
return FORWARD;
}
注釋1處，mView處理按鍵事件， mView具體指的是？ 如果是Activity和Dialog，mView就是DecorView，是所有view的根;如果是Toast,mView是id為com.android.internal.R.id.message,這點在Toast.makeText方法中可以看出。此處只分析Activity。
本文主要分析View框架的按鍵事件派發
按鍵事件派發
1. DecorView.dispatchKeyEvent方法
DecorView.java
@Override
public 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.
// 快捷按鍵處理
if ((mWindow.mPanelChordingKey > 0) && (mWindow.mPanelChordingKey != keyCode)) {
boolean handled = dispatchKeyShortcutEvent(event);
if (handled) {
return true;
}
}
// 快捷按鍵處理
// If a panel is open, perform a shortcut on it without the
// chorded panel key
if ((mWindow.mPreparedPanel != null) && mWindow.mPreparedPanel.isOpen) {
if (mWindow.performPanelShortcut(mWindow.mPreparedPanel, keyCode, event, 0)) {
return true;
}
}
}
if (!mWindow.isDestroyed()) {
// cb是Activiy或者Dialog，我們只分析Activity
// mFeatureId在installDecor是構造的DecorView傳入的為-1,故調用Activity的dispatchKeyEvent
final Window.Callback cb = mWindow.getCallback();
final boolean handled = cb != null && mFeatureId < 0 ? cb.dispatchKeyEvent(event)
: super.dispatchKeyEvent(event);
if (handled) {
return true;
}
}
return isDown ? mWindow.onKeyDown(mFeatureId, event.getKeyCode(), event)
: mWindow.onKeyUp(mFeatureId, event.getKeyCode(), event);
}
2. Activity的dispatchKeyEvent
Activity.java
public boolean dispatchKeyEvent(KeyEvent event) {
onUserInteraction();
// Let action bars open menus in response to the menu key prioritized over
// the window handling it
final int keyCode = event.getKeyCode();
// 如果按鍵是menu事件，則先回調Actionbar的onMenuKeyEvent()事件處理，如果返回沒有處理才會繼續往下走
if (keyCode == KeyEvent.KEYCODE_MENU &&
mActionBar != null && mActionBar.onMenuKeyEvent(event)) {
return true;
}
Window win = getWindow();
// 1. 調用Phonewindow的superDispatchKeyEvent,最終會調用到DecorView的dispatchKeyEvent方法中
if (win.superDispatchKeyEvent(event)) {
return true;
}
View decor = mDecor;
if (decor == null) decor = win.getDecorView();
// 2. 如果Phonewindow 分發后返回false，則交由KeyEvent派發事件，調用Activity的onKeyDown/Up()方法
return event.dispatch(this, decor != null
? decor.getKeyDispatcherState() : null, this);
}
繼續分析注釋1，看如何派發輸入事件到ViewGroup
PhoneWindow.java
@Override
public boolean superDispatchKeyEvent(KeyEvent event) {
// mDecor是DecorView
return mDecor.superDispatchKeyEvent(event);
}
發現又進入到DecorView，但這次調用的方法是superDispatchKeyEvent
DecorView.java
public boolean superDispatchKeyEvent(KeyEvent event) {
// Give priority to closing action modes if applicable.
// 對BACK按鍵做處理，如果存在ActionMode則先退出ActionMode,ActionMode相當于一個臨時的ActionBar,具體使用還是google吧,此處不是重點
if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
final int action = event.getAction();
// Back cancels action modes first.
if (mPrimaryActionMode != null) {
if (action == KeyEvent.ACTION_UP) {
mPrimaryActionMode.finish();
}
return true;
}
}
// 1. DecorView父類是FrameLayout，但其沒有實現dispatchKeyEvent方法，故該處調用的是ViewGroup的方法
return super.dispatchKeyEvent(event);
}
注釋1會調用其父類ViewGroup的dispatchKeyEvent()方法
3. ViewGroup的dispatchKeyEvent
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onKeyEvent(event, 1);
}
// 1. 如果viewgroup獲得焦點且邊界確定，則調用父view的也就是View的dispatchKeyEvent
if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
== (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
if (super.dispatchKeyEvent(event)) {
return true;
}
} else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
== PFLAG_HAS_BOUNDS) {
// 2. 交由獲取焦點的子view進行按鍵事件的派發
if (mFocused.dispatchKeyEvent(event)) {
return true;
}
}
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 1);
}
return false;
}
注釋2中mFocused存在于每個ViewGroup,其標識了ViewGroup的直接子View是否擁有或者包含焦點，通過mFocused.dispatchKeyEvent即可遞歸調用找到最終獲取焦點的View，然后調用該View的dispatchKeyEvent()方法,如注釋1.
4. View的dispatchKeyEvent
View.java
public boolean dispatchKeyEvent(KeyEvent event) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onKeyEvent(event, 0);
}
// Give any attached key listener a first crack at the event.
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
// 1. 當對view設置了OnKeyListener,且該view處于enabled狀態，則調用OnKeyListener的onKey()方法
if (li != null && li.mOnKeyListener != null && (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnKeyListener.onKey(this, event.getKeyCode(), event)) {
return true;
}
// 2. KeyEvent派發事件，receiver為view,會回調View的onKeyDown/Up()方法
if (event.dispatch(this, mAttachInfo != null
? mAttachInfo.mKeyDispatchState : null, this)) {
return true;
}
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
return false;
}
注釋1中對View是否設置了OnKeyListener做了判斷，如果設置，則先回調onKey()方法
注釋2，在onKey()返回false情況下會通過KeyEvent的dispatch方法調用View的onKeyDown/Up()方法。
KeyEvent的dispatch(),該方法在View#dispatchKeyEvent()方法中，如果onKey()返回false會調用，參數傳入的是View;該方法也會在Activity#dispatchKeyEvent()方法中win.superDispatchKeyEvent()方法返回false后進行調用，只不過參數傳入的是Activity，最終會調用Activity或者View的onKeyDown/Up()方法。
KeyEvent.java
public final boolean dispatch(Callback receiver, DispatcherState state,
Object target) {
switch (mAction) {
case ACTION_DOWN: {
mFlags &= ~FLAG_START_TRACKING;
// 1. 執行Activity或者View的onKeyDown()方法
boolean res = receiver.onKeyDown(mKeyCode, this);
if (state != null) {
if (res && mRepeatCount == 0 && (mFlags&FLAG_START_TRACKING) != 0) {
state.startTracking(this, target);
} else if (isLongPress() && state.isTracking(this)) {
try {
if (receiver.onKeyLongPress(mKeyCode, this)) {
state.performedLongPress(this);
res = true;
}
} catch (AbstractMethodError e) {
}
}
}
return res;
}
case ACTION_UP:
if (state != null) {
state.handleUpEvent(this);
}
// 2. 執行Activity或者View的onKeyUp()方法
return receiver.onKeyUp(mKeyCode, this);
...
}
return false;
}
receiver可能是Activity對象，也可能是view對象，具體情況具體分析
View對象的onKeyDown(),onKeyUp()
public boolean onKeyDown(int keyCode, KeyEvent event) {
// isConfirmKey中會對keycode判斷是否是KEYCODE_DPAD_CENTER,KEYCODE_ENTER,KEYCODE_SPACE,KEYCODE_NUMPAD_ENTER幾個表示確定的鍵，也就是可以觸發點擊作用的鍵
if (KeyEvent.isConfirmKey(keyCode)) {
// 如果view處于DISABLED狀態，則直接返回true
if ((mViewFlags & ENABLED_MASK) == DISABLED) {
return true;
}
if (event.getRepeatCount() == 0) {
// Long clickable items don't necessarily have to be clickable.
// View的CLICKABLE 和 LONG_CLICABLE是獨立的，互不影響
final boolean clickable = (mViewFlags & CLICKABLE) == CLICKABLE
|| (mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE;
if (clickable || (mViewFlags & TOOLTIP) == TOOLTIP) {
// For the purposes of menu anchoring and drawable hotspots,
// key events are considered to be at the center of the view.
final float x = getWidth() / 2f;
final float y = getHeight() / 2f;
if (clickable) {
// 設置按下狀態，比如更換view顏色，切換圖片等
setPressed(true, x, y);
}
// 該方法做的事情是發送一個可以判斷長按時間的演示runnable，時間一到則執行長按操作
checkForLongClick(0, x, y);
return true;
}
}
}
return false;
}
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (KeyEvent.isConfirmKey(keyCode)) {
if ((mViewFlags & ENABLED_MASK) == DISABLED) {
return true;
}
if ((mViewFlags & CLICKABLE) == CLICKABLE && isPressed()) {
setPressed(false);
if (!mHasPerformedLongPress) {
// This is a tap, so remove the longpress check
// 抬起時移除長按消息即可，如果沒有觸發長按，則長按消息會被移除
removeLongPressCallback();
if (!event.isCanceled()) {
// 回調OnClickListener的onClick()方法
return performClick();
}
}
}
}
return false;
}
如果View設置了onClickListener()方法，則按下enter鍵后抬起時會執行onClick()方法
如果View的onKeyDown/Up()也返回false，則dispatchKeyEvent()方法會一直返回至Activity中，交由其onKeyDown/Up()處理
Activity對象的onKeyDown(),onKeyUp()
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
if (getApplicationInfo().targetSdkVersion
>= Build.VERSION_CODES.ECLAIR) {
// >= android2.1則跟蹤按鍵傳遞過程
event.startTracking();
} else {
// android2.1之前按下返回鍵直接返回
onBackPressed();
}
return true;
}
...
return handled;
}
}
public boolean onKeyUp(int keyCode, KeyEvent event) {
// 如果android版本>= 2.1 回調onBackPressed()方法退出Activity
if (getApplicationInfo().targetSdkVersion
>= Build.VERSION_CODES.ECLAIR) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.isTracking()
&& !event.isCanceled()) {
onBackPressed();
return true;
}
}
return false;
}
如果Activity里面的任何view、布局都沒有處理按鍵，就會傳遞到Activity的onKeyDown，onKeyUp。比如，當在EditText中輸入文字時，Activity的onKeyDown，onKeyUp不會接收到按鍵事件，因為EditText有自己的處理按鍵事件的方法，如果此時把焦點從EditText移走，onKeyDown，onKeyUp就會接收到按鍵事件。
Activity中onKeyDown/Up()也不做處理返回false時，事件一路返回至DecorView的dispatchKeyEvent()方法中，此時繼續調用PhoneWindow的onKeyDown/Up()方法
PhoneWindow的onKeyDown/Up()
PhoneWindow.java
protected boolean onKeyDown(int featureId, int keyCode, KeyEvent event) {
final KeyEvent.DispatcherState dispatcher =
mDecor != null ? mDecor.getKeyDispatcherState() : null;
switch (keyCode) {
case KeyEvent.KEYCODE_VOLUME_UP:
case KeyEvent.KEYCODE_VOLUME_DOWN:
case KeyEvent.KEYCODE_VOLUME_MUTE: {
// If we have a session send it the volume command, otherwise
// use the suggested stream.
if (mMediaController != null) {
int direction = 0;
switch (keyCode) {
case KeyEvent.KEYCODE_VOLUME_UP:
direction = AudioManager.ADJUST_RAISE;
break;
case KeyEvent.KEYCODE_VOLUME_DOWN:
direction = AudioManager.ADJUST_LOWER;
break;
case KeyEvent.KEYCODE_VOLUME_MUTE:
direction = AudioManager.ADJUST_TOGGLE_MUTE;
break;
}
mMediaController.adjustVolume(direction, AudioManager.FLAG_SHOW_UI);
} else {
MediaSessionLegacyHelper.getHelper(getContext()).sendVolumeKeyEvent(
event, mVolumeControlStreamType, false);
}
return true;
}
// These are all the recognized media key codes in
// KeyEvent.isMediaKey()
case KeyEvent.KEYCODE_MEDIA_PLAY:
case KeyEvent.KEYCODE_MEDIA_PAUSE:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
case KeyEvent.KEYCODE_MUTE:
case KeyEvent.KEYCODE_HEADSETHOOK:
case KeyEvent.KEYCODE_MEDIA_STOP:
case KeyEvent.KEYCODE_MEDIA_NEXT:
case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
case KeyEvent.KEYCODE_MEDIA_REWIND:
case KeyEvent.KEYCODE_MEDIA_RECORD:
case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD: {
if (mMediaController != null) {
if (mMediaController.dispatchMediaButtonEvent(event)) {
return true;
}
}
return false;
}
case KeyEvent.KEYCODE_MENU: {
onKeyDownPanel((featureId < 0) ? FEATURE_OPTIONS_PANEL : featureId, event);
return true;
}
case KeyEvent.KEYCODE_BACK: {
if (event.getRepeatCount() > 0) break;
if (featureId < 0) break;
// Currently don't do anything with long press.
if (dispatcher != null) {
dispatcher.startTracking(event, this);
}
return true;
}
}
return false;
}
onKeyDown/onKeyUp方法主要針對當前獲得焦點的窗口對一些特殊按鍵進行處理，包括音量+/-,多媒體控制按鍵,MENU,BACK
總結
按鍵事件從Framework層到View框架整體流程如流程圖，我們主要關心是Activity,ViewGroup和View的事件派發。
Activity可以通過dispatchKeyEvent()將KeyEvent派發給ViewGroup直到找到獲取焦點的View(當然可能就是ViewGroup獲取焦點),獲取焦點的View先去判斷OnKeyListener存在與否，存在回調onKey(),如果不存在或者返回false，則回調其onKeyDown/Up()方法，onClick()方法在onKeyUp()方法中會進行回調，此時如果還是返回false，則Activity中的onKeyDown/Up()方法得以調用，最后沒有處理則交給PhoneWindow的onKeyDown/Up()。我們也可以通過重寫對應方法來達到事件消費,也就是不繼續走剩余事件傳遞流程。
注意：PhoneFallbackEventHandler在ViewRoolImpl中提到過，其也是對特殊按鍵進行處理，但是那是針對所有的窗口，包括當前獲得焦點的窗口，而PhoneWindow只針對當前獲得焦點的窗口。PhoneFallbackEventHandler是在使用代碼如下
ViewRootImpl.java
private int processKeyEvent(QueuedInputEvent q) {
...
// Apply the fallback event policy. mFallbackEventHandler就是PhoneFallbackEventHandler
if (mFallbackEventHandler.dispatchKeyEvent(event)) {
return FINISH_HANDLED;
}
...
}
PhoneFallbackEventHandler
public boolean dispatchKeyEvent(KeyEvent event) {
final int action = event.getAction();
final int keyCode = event.getKeyCode();
if (action == KeyEvent.ACTION_DOWN) {
return onKeyDown(keyCode, event);
} else {
return onKeyUp(keyCode, event);
}
}
boolean onKeyDown(int keyCode, KeyEvent event) {
final KeyEvent.DispatcherState dispatcher = mView.getKeyDispatcherState();
switch (keyCode) {
case KeyEvent.KEYCODE_VOLUME_UP:
case KeyEvent.KEYCODE_VOLUME_DOWN:
case KeyEvent.KEYCODE_VOLUME_MUTE: {
MediaSessionLegacyHelper.getHelper(mContext).sendVolumeKeyEvent(
event, AudioManager.USE_DEFAULT_STREAM_TYPE, false);
return true;
}
case KeyEvent.KEYCODE_MEDIA_PLAY:
case KeyEvent.KEYCODE_MEDIA_PAUSE:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
/* Suppress PLAY/PAUSE toggle when phone is ringing or in-call
* to avoid music playback */
if (getTelephonyManager().getCallState() != TelephonyManager.CALL_STATE_IDLE) {
return true; // suppress key event
}
case KeyEvent.KEYCODE_MUTE:
case KeyEvent.KEYCODE_HEADSETHOOK:
case KeyEvent.KEYCODE_MEDIA_STOP:
case KeyEvent.KEYCODE_MEDIA_NEXT:
case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
case KeyEvent.KEYCODE_MEDIA_REWIND:
case KeyEvent.KEYCODE_MEDIA_RECORD:
case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD:
case KeyEvent.KEYCODE_MEDIA_AUDIO_TRACK: {
handleMediaKeyEvent(event);
return true;
}
case KeyEvent.KEYCODE_CALL: {
...
}
}
主要是針對音量鍵，媒體相關，Call和Camera鍵進行處理。
特殊按鍵處理
第一次攔截在interceptKeyBeforeQueueing中，
result &= ~ACTION_PASS_TO_USER或者0，將會攔截事件，不在向下傳遞
第二次在攔截在interceptKeyBeforeDispatching，
return -1，事件將被攔截不在向下傳遞
例如對Home鍵做操作,由于Home并不會下發至View,故應用是無法監聽,但我們可以在interceptKeyBeforeDispatching中對其進行客制化,例如將其remap返回鍵KEYCODE_BACK下發,這時PhoneWindowManager就會收到被remap后的KEYCODE_BACK,進而最后交由View框架處理.
PhoneWindowManager.java
public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {
final boolean keyguardOn = keyguardOn();
final int keyCode = event.getKeyCode();
final int repeatCount = event.getRepeatCount();
final int metaState = event.getMetaState();
final int flags = event.getFlags();
final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
......
if (keyCode == KeyEvent.KEYCODE_HOME) {
// If we have released the home key, and didn't do anything else
// while it was pressed, then it is time to go home!
if (!down) {
// wangyannan begin
Log.i("wangyannan","foreground");
/**
*通過inputManager注入KEYCODE_BACK事件，相當于在按home鍵時接收到的為back事件
*/
InputManager inputManager = (InputManager) mContext.getSystemService(Context.INPUT_SERVICE);
KeyEvent ke1 = new KeyEvent(event.getDownTime(), event.getEventTime(),
KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_BACK, event.getRepeatCount());
KeyEvent ke2 = new KeyEvent(event.getDownTime(), event.getEventTime(),
KeyEvent.ACTION_UP, KeyEvent.KEYCODE_BACK, event.getRepeatCount());
inputManager.injectInputEvent(ke1, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);
inputManager.injectInputEvent(ke2, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);
return -1;
}
//wangyannan end
cancelPreloadRecentApps();
......
handleShortPressOnHome();
return -1;//返回-1則不響應home鍵
}
......
}
}
//wangyannan begin
例如某個Activity監聽按鍵,對HOME鍵做處理
XXXActivity.java
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
switch (keyCode){
case KeyEvent.KEYCODE_BACK:
// 如果該條件成立,則為系統原本的按鍵事件,否則為重定向的時間
if(event.getFlags()!=0&&event.getDeviceId()!=-1&&event.getSource()!=0){
//實際接收到的back事件
Toast.makeText(this,"沒有重定向",Toast.LENGTH_SHORT).show();
}else{
//接受到的back事件為代碼中注入的back事件
Toast.makeText(this,"重定向",Toast.LENGTH_SHORT).show();
}
return ture;
}
return super.onKeyDown(keyCode, event);
}
