Android7.0 PowerManagerService(4) Power按鍵流程
阿新 • • 發佈：2019-01-28
按鍵的處理主要由InputManagerService負責，屬於Android輸入系統的流程。在這篇部落格裡，我們只關注與Power鍵相關的內容。InputManagerService處理的按鍵事件，最終將會傳遞到PhoneWindowManager的interceptKeyBeforeQueueing函式。
我們就從這個函式開始，逐步進行分析。
public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
if (!mSystemBooted) {
// If we have not yet booted, don't let key events do anything. 接下來，我們分別看一下interceptPowerKeyDown和interceptPowerKeyUp函式。
一、interceptPowerKeyDown
interceptPowerKeyDown用於處理按下Power鍵(還未鬆手釋放)對應的事件。
private void interceptPowerKeyDown(KeyEvent event, boolean interactive) {
// Hold a wake lock until the power key is released.
// mPowerKeyWakeLock為PARTIAL_WAKE_LOCK級別的鎖
if (!mPowerKeyWakeLock.isHeld()) {
//將呼叫到PMS的acquire WakeLock流程
mPowerKeyWakeLock.acquire();
}
// Cancel multi-press detection timeout.
//處理多次按power鍵的場景
//每次power up時，傳送MSG_POWER_DELAYED_PRESS的延遲訊息
//如果延遲訊息被處理，說明一次完整的Power鍵處理結束（按下去，彈起來）
//在延遲訊息被處理前，再次按power鍵，就檢測到多次點選了
//實際上，原生終端不支援該場景
if (mPowerKeyPressCounter != 0) {
mHandler.removeMessages(MSG_POWER_DELAYED_PRESS);
}
// Detect user pressing the power button in panic when an application has
// taken over the whole screen.
// 從註釋來看及mHiddenNavPanic的程式碼，覺得像是處理“誤觸”的
boolean panic = mImmersiveModeConfirmation.onPowerKeyDown(interactive,
SystemClock.elapsedRealtime(), isImmersiveMode(mLastSystemUiFlags));
if (panic) {
mHandler.post(mHiddenNavPanic);
}
// Latch power key state to detect screenshot chord.
// 如果當前是亮屏狀態，且滿足觸發截圖的條件，觸發截圖功能
if (interactive && !mScreenshotChordPowerKeyTriggered
&& (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
mScreenshotChordPowerKeyTriggered = true;
mScreenshotChordPowerKeyTime = event.getDownTime();
interceptScreenshotChord();
}
// Stop ringing or end call if configured to do so when power is pressed.
TelecomManager telecomManager = getTelecommService();
boolean hungUp = false;
if (telecomManager != null) {
if (telecomManager.isRinging()) {
// Pressing Power while there's a ringing incoming
// call should silence the ringer.
//如果有電話撥入，且電話鈴聲響起，按Power鍵，設定電話響鈴靜音
telecomManager.silenceRinger();
} else if ((mIncallPowerBehavior
& Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0
&& telecomManager.isInCall() && interactive) {
// Otherwise, if "Power button ends call" is enabled,
// the Power button will hang up any current active call.
//如果正在接聽電話，且配置了Power鍵結束通話電話的話，按Power按鍵結束通話正在接聽的電話
hungUp = telecomManager.endCall();
}
}
GestureLauncherService gestureService = LocalServices.getService(
GestureLauncherService.class);
boolean gesturedServiceIntercepted = false;
if (gestureService != null) {
//手勢對應的服務，嘗試攔截處理Power鍵動作事件
gesturedServiceIntercepted = gestureService.interceptPowerKeyDown(event, interactive,
mTmpBoolean);
if (mTmpBoolean.value && mGoingToSleep) {
mCameraGestureTriggeredDuringGoingToSleep = true;
}
}
// If the power key has still not yet been handled, then detect short
// press, long press, or multi press and decide what to do.
// Power鍵事件的處理，就像處理螢幕上的點選事件一樣，也依賴於事件分發機制
// 如果已經被消耗掉了，就不會再被繼續處理
mPowerKeyHandled = hungUp || mScreenshotChordVolumeDownKeyTriggered
|| mScreenshotChordVolumeUpKeyTriggered || gesturedServiceIntercepted;
//Power鍵事件未被消耗掉
if (!mPowerKeyHandled) {
//螢幕還是亮的
if (interactive) {
// When interactive, we're already awake.
// Wait for a long press or for the button to be released to decide what to do.
//1、 判斷是否支援長按的行為
if (hasLongPressOnPowerBehavior()) {
//2、 亮屏時，長按Power鍵將觸發MSG_POWER_LONG_PRESS訊息
Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg,
ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
}
} else {
//此時螢幕是熄滅狀態
//3、先喚醒系統，這個會呼叫到PMS的wakeUp
wakeUpFromPowerKey(event.getDownTime());
//支援熄屏長按，mSupportLongPressPowerWhenNonInteractive讀資原始檔得到，預設為false
if (mSupportLongPressPowerWhenNonInteractive && hasLongPressOnPowerBehavior()) {
Message msg = mHandler.obtainMessage(MSG_POWER_LONG_PRESS);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg,
ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());
mBeganFromNonInteractive = true;
} else {
//預設返回1
final int maxCount = getMaxMultiPressPowerCount();
if (maxCount <= 1) {
//息屏時，按下power鍵（不彈起），僅消耗掉該事件
mPowerKeyHandled = true;
} else {
mBeganFromNonInteractive = true;
}
}
}
}
}1、hasLongPressOnPowerBehavior
hasLongPressOnPowerBehavior負責判斷終端是否支援長按的行為：
private boolean hasLongPressOnPowerBehavior() {
return getResolvedLongPressOnPowerBehavior() != LONG_PRESS_POWER_NOTHING;
}
private int getResolvedLongPressOnPowerBehavior() {
//取決與系統屬性"factory.long_press_power_off"，此處預設為false
if (FactoryTest.isLongPressOnPowerOffEnabled()) {
return LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM;
}
return mLongPressOnPowerBehavior;
}從上面的程式碼可以看出，終端是否支援長按行為，最終將由mLongPressOnPowerBehavior決定。
.........
mLongPressOnPowerBehavior = mContext.getResources().getInteger(
com.android.internal.R.integer.config_longPressOnPowerBehavior);
.........mLongPressOnPowerBehavior將在PhoneWindowManager初始化時，通過讀取資原始檔得到，一般情況下應該為1。
於是，hasLongPressOnPowerBehavior的值返回true，即終端支援Power鍵長按。
2、MSG_POWER_LONG_PRESS的處理
從上面的程式碼，我們知道亮屏時按Power鍵，會觸發延遲的MSG_POWER_LONG_PRESS訊息。
如果在MSG_POWER_LONG_PRESS超時前，Power鍵未被釋放掉，那麼此次操作被定義為長按Power鍵。
MSG_POWER_LONG_PRESS對應的處理函式為powerLongPress：
private void powerLongPress() {
//也是由資原始檔得到，預設為1，即LONG_PRESS_POWER_GLOBAL_ACTIONS
final int behavior = getResolvedLongPressOnPowerBehavior();
switch (behavior) {
case LONG_PRESS_POWER_NOTHING:
break;
case LONG_PRESS_POWER_GLOBAL_ACTIONS:
mPowerKeyHandled = true;
//感覺這裡是：終端對接收的事件處理後，給使用者一個反饋資訊
//performHapticFeedbackLw主要進行震動反饋，例如按鍵後，終端震動一下
//不同的事件，定義了不同的震動模式
if (!performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false)) {
//如果沒有震動反饋，這裡嘗試進行聲音的反饋，例如響一下按鍵音
performAuditoryFeedbackForAccessibilityIfNeed();
}
//彈出選擇關機還是重啟的對話方塊
showGlobalActionsInternal();
break;
.........
}
}3、wakeUpFromPowerKey
在息屏的狀態下按下Power鍵，將呼叫wakeUpFromPowerKey函式喚醒系統：
private void wakeUpFromPowerKey(long eventTime) {
//從config.xml來看，mAllowTheaterModeWakeFromPowerKey預設為true
wakeUp(eventTime, mAllowTheaterModeWakeFromPowerKey, "android.policy:POWER");
}
private boolean wakeUp(long wakeTime, boolean wakeInTheaterMode, String reason) {
//取資料庫的值
final boolean theaterModeEnabled = isTheaterModeEnabled();
//按Power鍵時，條件返回false
if (!wakeInTheaterMode && theaterModeEnabled) {
return false;
}
//看來喚醒時，將退出劇院模式
if (theaterModeEnabled) {
Settings.Global.putInt(mContext.getContentResolver(),
Settings.Global.THEATER_MODE_ON, 0);
}
//最終將呼叫到PMS的wakeUp函式
mPowerManager.wakeUp(wakeTime, reason);
return true;
}我們跟進一下PMS的wakeUp函式：
public void wakeUp(long eventTime, String reason, String opPackageName) {
..........
try {
wakeUpInternal(eventTime, reason, uid, opPackageName, uid);
} finally {
...............
}
}
private void wakeUpInternal(long eventTime, String reason, int uid, String opPackageName,
int opUid) {
synchronized (mLock) {
//更新Wakefullness的狀態為WAKEFULNESS_AWAKE，記錄一次UserActivity
if (wakeUpNoUpdateLocked(eventTime, reason, uid, opPackageName, opUid)) {
//如之前部落格所述，對整個電源狀態進行一次調整，將在需要時點亮螢幕
updatePowerStateLocked();
}
}
}二、interceptPowerKeyUp
interceptPowerKeyUp處理鬆開Power鍵後的流程：
private void interceptPowerKeyUp(KeyEvent event, boolean interactive, boolean canceled) {
//事件被取消，或者在按下Power鍵時，該事件已被消耗掉
//那麼就不用繼續處理
final boolean handled = canceled || mPowerKeyHandled;
mScreenshotChordPowerKeyTriggered = false;
//退出截圖
cancelPendingScreenshotChordAction();
//取消MSG_POWER_LONG_PRESS事件，即在一定事件內Power鍵彈起，則表示這一次不是長按Power鍵
cancelPendingPowerKeyAction();
//從之前的程式碼，我們知道除了特殊功能外
//滅屏按Power鍵或亮屏長按時，均會消耗掉Power事件
//因此，只有亮屏短按Power鍵需要進行處理
if (!handled) {
// Figure out how to handle the key now that it has been released.
// 記錄短按的次數
mPowerKeyPressCounter += 1;
final int maxCount = getMaxMultiPressPowerCount();
final long eventTime = event.getDownTime();
if (mPowerKeyPressCounter < maxCount) {
// This could be a multi-press. Wait a little bit longer to confirm.
// Continue holding the wake lock.
// 與之前interceptPowerKeyDown，處理Power鍵被多次按下場景對應
// 每次被按下，均傳送MSG_POWER_DELAYED_PRESS訊息
// 實際上maxCount為1，該不會進入該分支
Message msg = mHandler.obtainMessage(MSG_POWER_DELAYED_PRESS,
interactive ? 1 : 0, mPowerKeyPressCounter, eventTime);
msg.setAsynchronous(true);
mHandler.sendMessageDelayed(msg, ViewConfiguration.getDoubleTapTimeout());
return;
}
//1、No other actions. Handle it immediately.
powerPress(eventTime, interactive, mPowerKeyPressCounter);
}
// 2、Done. Reset our state.
finishPowerKeyPress();
}1、powerPress
我們跟進一下powerPress函式：
private void powerPress(long eventTime, boolean interactive, int count) {
if (mScreenOnEarly && !mScreenOnFully) {
Slog.i(TAG, "Suppressed redundant power key press while "
+ "already in the process of turning the screen on.");
return;
}
if (count == 2) {
//原生不進入
powerMultiPressAction(eventTime, interactive, mDoublePressOnPowerBehavior);
} else if (count == 3) {
//原生不進入
powerMultiPressAction(eventTime, interactive, mTriplePressOnPowerBehavior);
} else if (interactive && !mBeganFromNonInteractive) {
//亮屏時，將進入該分支
//mShortPressOnPowerBehavior被配置為1
switch (mShortPressOnPowerBehavior) {
case SHORT_PRESS_POWER_NOTHING:
break;
case SHORT_PRESS_POWER_GO_TO_SLEEP:
//最終呼叫到PMS的goToSleep函式
mPowerManager.goToSleep(eventTime,
PowerManager.GO_TO_SLEEP_REASON_POWER_BUTTON, 0);
break;
...............
}
}
}從上面的程式碼可以看出，在亮屏狀態下，短按一下Power鍵，最終將呼叫到PMS的goToSleep函式，使終端進入到休眠狀態，與實際情況一致。
我們跟進一下PMS的goToSleep函式：
public void goToSleep(long eventTime, int reason, int flags) {
............
try {
goToSleepInternal(eventTime, reason, flags, uid);
} finally {
...............
}
}
private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {
synchronized (mLock) {
//沒有觸發使用者事件，將mWakefullness置為WAKEFULNESS_DOZING
if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {
//執行整體的電源狀態更新，將熄滅螢幕
updatePowerStateLocked();
}
}2、finishPowerKeyPress
每當處理一次完整的Power鍵按下、彈出操作後，interceptPowerKeyUp呼叫finishPowerKeyPress進行最後的狀態復位操作：
private void finishPowerKeyPress() {
mBeganFromNonInteractive = false;
mPowerKeyPressCounter = 0;
if (mPowerKeyWakeLock.isHeld()) {
mPowerKeyWakeLock.release();
}
}從程式碼可以看出，主要的工作其實就是將狀態變數恢復為初始值，同時釋放掉最初申請的鎖。
三、總結
整個Power按鍵的主要處理流程如上圖所示。結合手機的實際情況，整個邏輯還是非常好理解的。