Android6.0 旋轉屏幕（一）WMS註冊傳感器回調

我們通常在手機上旋轉屏幕可以應用主動旋轉，也可以讓應用隨系統旋轉。這裏我們先分析應用隨系統旋轉的情況。

設置選項（旋轉屏幕）

隨系統選裝的話，我們先要在手機設置中選擇顯示項，設備旋轉時自動旋轉。最終會調用RotationPolicy.setRotationLockForAccessibility函數，我們先來看下這個函數

    public static void setRotationLockForAccessibility(Context context, final boolean enabled) {
        Settings.System.putIntForUser(context.getContentResolver(),
                Settings.System.HIDE_ROTATION_LOCK_TOGGLE_FOR_ACCESSIBILITY, enabled ? 1 : 0,
                        UserHandle.USER_CURRENT);
 
        setRotationLock(enabled, NATURAL_ROTATION);
    }

setRotationLock函數會根據參數調用WMS的freezeRotation和thawRotation函數。

    private static void setRotationLock(final boolean enabled, final int rotation) {
        AsyncTask.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    IWindowManager wm = WindowManagerGlobal.getWindowManagerService();
                    if (enabled) {
                        wm.freezeRotation(rotation);
                    } else {
                        wm.thawRotation();
                    }
                } catch (RemoteException exc) {
                    Log.w(TAG, "Unable to save auto-rotate setting");
                }
            }
        });
    }

寫入設置數據庫

我們先來看看WMS的thawRotation函數，先會調用PhoneWindowManager的setUserRotationMode函數，然後調用upateRotationUnchecked（這裏處理設備旋轉，我們下篇博客分析）。

    public void thawRotation() {
        if (!checkCallingPermission(android.Manifest.permission.SET_ORIENTATION,
                "thawRotation()")) {
            throw new SecurityException("Requires SET_ORIENTATION permission");
        }
 
        if (DEBUG_ORIENTATION) Slog.v(TAG, "thawRotation: mRotation=" + mRotation);
 
        long origId = Binder.clearCallingIdentity();
        try {
            mPolicy.setUserRotationMode(WindowManagerPolicy.USER_ROTATION_FREE,
                    777); // rot not used
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
 
        updateRotationUnchecked(false, false);//後續分析
    }

我們再來看看freezeRotation函數，只是調用PhoneWindowManager的setUserRotationMode的參數不一樣，這裏是Locked，而thawRotation傳下去的參數是free

    @Override
    public void freezeRotation(int rotation) {
        if (!checkCallingPermission(android.Manifest.permission.SET_ORIENTATION,
                "freezeRotation()")) {
            throw new SecurityException("Requires SET_ORIENTATION permission");
        }
        if (rotation < -1 || rotation > Surface.ROTATION_270) {
            throw new IllegalArgumentException("Rotation argument must be -1 or a valid "
                    + "rotation constant.");
        }
 
        if (DEBUG_ORIENTATION) Slog.v(TAG, "freezeRotation: mRotation=" + mRotation);
 
        long origId = Binder.clearCallingIdentity();
        try {
            mPolicy.setUserRotationMode(WindowManagerPolicy.USER_ROTATION_LOCKED,
                    rotation == -1 ? mRotation : rotation);
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
 
        updateRotationUnchecked(false, false);
    }

PhoneWindowManager的setUserRotationMode只是設置Settings數據庫，然後這肯定會有監聽的。

    @Override
    public void setUserRotationMode(int mode, int rot) {
        ContentResolver res = mContext.getContentResolver();
 
        // mUserRotationMode and mUserRotation will be assigned by the content observer
        if (mode == WindowManagerPolicy.USER_ROTATION_LOCKED) {
            Settings.System.putIntForUser(res,
                    Settings.System.USER_ROTATION,
                    rot,
                    UserHandle.USER_CURRENT);
            Settings.System.putIntForUser(res,
                    Settings.System.ACCELEROMETER_ROTATION,
                    0,
                    UserHandle.USER_CURRENT);
        } else {
            Settings.System.putIntForUser(res,
                    Settings.System.ACCELEROMETER_ROTATION,
                    1,
                    UserHandle.USER_CURRENT);
        }
    }

PhoneWindowManager監聽旋轉相關Settings數據項

下面就是監測Settings相關數據庫，當設置改變後會調用onChange，然後調用updateSettings和updateRotation，updateRotation就是調用WMS的updateRotationUnchecked函數，我們下篇博客分析。

    class SettingsObserver extends ContentObserver {
        SettingsObserver(Handler handler) {
            super(handler);
        }
 
        void observe() {
            // Observe all users' changes
            ContentResolver resolver = mContext.getContentResolver();
            resolver.registerContentObserver(Settings.System.getUriFor(
                    Settings.System.END_BUTTON_BEHAVIOR), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.Secure.getUriFor(
                    Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.Secure.getUriFor(
                    Settings.Secure.WAKE_GESTURE_ENABLED), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.System.getUriFor(
                    Settings.System.ACCELEROMETER_ROTATION), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.System.getUriFor(
                    Settings.System.USER_ROTATION), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.System.getUriFor(
                    Settings.System.SCREEN_OFF_TIMEOUT), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.System.getUriFor(
                    Settings.System.POINTER_LOCATION), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.Secure.getUriFor(
                    Settings.Secure.DEFAULT_INPUT_METHOD), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.Secure.getUriFor(
                    Settings.Secure.IMMERSIVE_MODE_CONFIRMATIONS), false, this,
                    UserHandle.USER_ALL);
            resolver.registerContentObserver(Settings.Global.getUriFor(
                    Settings.Global.POLICY_CONTROL), false, this,
                    UserHandle.USER_ALL);
            updateSettings();
        }
 
        @Override public void onChange(boolean selfChange) {
            updateSettings();
            updateRotation(false);
        }
    }

updateSettings中，當設置不一致的時候會調用updateOrientationListenerLp函數和updateRotation之前提過，是調用WMS的updateRotationUnchecked函數。

    public void updateSettings() {
        ......
 
            // Configure rotation lock.
            int userRotation = Settings.System.getIntForUser(resolver,
                    Settings.System.USER_ROTATION, Surface.ROTATION_0,
                    UserHandle.USER_CURRENT);
            if (mUserRotation != userRotation) {
                mUserRotation = userRotation;
                updateRotation = true;
            }
            int userRotationMode = Settings.System.getIntForUser(resolver,
                    Settings.System.ACCELEROMETER_ROTATION, 0, UserHandle.USER_CURRENT) != 0 ?
                            WindowManagerPolicy.USER_ROTATION_FREE :
                                    WindowManagerPolicy.USER_ROTATION_LOCKED;
            if (mUserRotationMode != userRotationMode) {
                mUserRotationMode = userRotationMode;
                updateRotation = true;
                updateOrientationListenerLp();
            }
            ......
        if (updateRotation) {
            updateRotation(true);
        }
    }

註冊 取消傳感器回調

updateOrientationListenerLp函數就是enable和disable傳感器。

    void updateOrientationListenerLp() {
        if (!mOrientationListener.canDetectOrientation()) {
            // If sensor is turned off or nonexistent for some reason
            return;
        }
 
        boolean disable = true;
        if (mScreenOnEarly && mAwake &&
                mKeyguardDrawComplete && mWindowManagerDrawComplete) {
            if (needSensorRunningLp()) {
                disable = false;
                //enable listener if not already enabled
                if (!mOrientationSensorEnabled) {
                    mOrientationListener.enable();
                    mOrientationSensorEnabled = true;
                }
            }
        }
        //check if sensors need to be disabled
        if (disable && mOrientationSensorEnabled) {
            mOrientationListener.disable();
            mOrientationSensorEnabled = false;
        }
    }

mOrientationListener的enable和disable函數只是註冊傳感器回調和去除傳感器回調。

    public void enable() {
        synchronized (mLock) {
            if (mSensor == null) {
                Slog.w(TAG, "Cannot detect sensors. Not enabled");
                return;
            }
            if (mEnabled == false) {
                if (LOG) {
                    Slog.d(TAG, "WindowOrientationListener enabled");
                }
                mOrientationJudge.resetLocked();
                mSensorManager.registerListener(mOrientationJudge, mSensor, mRate, mHandler);
                mEnabled = true;
            }
        }
    }
 
    /**
     * Disables the WindowOrientationListener.
     */
    public void disable() {
        synchronized (mLock) {
            if (mSensor == null) {
                Slog.w(TAG, "Cannot detect sensors. Invalid disable");
                return;
            }
            if (mEnabled == true) {
                if (LOG) {
                    Slog.d(TAG, "WindowOrientationListener disabled");
                }
                mSensorManager.unregisterListener(mOrientationJudge);
                mEnabled = false;
            }
        }
    }

這裏我們主要關心註冊傳感器的mOrientationJudge的回調。二mOrientationJudge就是OrientationSensorJudge 類型，當傳感器數據過來時會調用onSensorChanged函數，最後調用onProposedRotationChanged，這個onProposedRotationChanged是WindowOrientationListener的函數。而WindowOrientationListener是在PhoneWindowManger中新建的。

    final class OrientationSensorJudge extends OrientationJudge {
        ......
 
        @Override
        public void onSensorChanged(SensorEvent event) {
            int newRotation;
            synchronized (mLock) {
                mDesiredRotation = (int) event.values[0];
                newRotation = evaluateRotationChangeLocked();
            }
            if (newRotation >=0) {
                onProposedRotationChanged(newRotation);
            }
        }

最後就到MyOrientationListener 的onProposedRotationChanged函數，這裏就是發送了一個消息。

    class MyOrientationListener extends WindowOrientationListener {
        private final Runnable mUpdateRotationRunnable = new Runnable() {
            @Override
            public void run() {
                // send interaction hint to improve redraw performance
                mPowerManagerInternal.powerHint(PowerManagerInternal.POWER_HINT_INTERACTION, 0);
                updateRotation(false);
            }
        };
 
        MyOrientationListener(Context context, Handler handler) {
            super(context, handler);
        }
 
        @Override
        public void onProposedRotationChanged(int rotation) {
            if (localLOGV) Slog.v(TAG, "onProposedRotationChanged, rotation=" + rotation);
            mHandler.post(mUpdateRotationRunnable);
        }
    }

最後就調用其run函數，run函數先會提升性能（cpu頻率），然後調用了updateRotation，這個函數一樣就到WMS的updateRotationUnchecked函數了。