android4.4 锁屏灭屏时间的设置

屏幕自动灭屏的时间和userActivity事件相关，而这个灭屏时间的获取是在PowerManagerService中getScreenOffTimeoutLocked函数。

    private int getScreenOffTimeoutLocked() {        int timeout = mScreenOffTimeoutSetting;        if (isMaximumScreenOffTimeoutFromDeviceAdminEnforcedLocked()) {            timeout = Math.min(timeout, mMaximumScreenOffTimeoutFromDeviceAdmin);        }        if (mUserActivityTimeoutOverrideFromWindowManager >= 0) {            timeout = (int)Math.min(timeout, mUserActivityTimeoutOverrideFromWindowManager);        }        return Math.max(timeout, MINIMUM_SCREEN_OFF_TIMEOUT);    }

我们先来看下mScreenOffTimeoutSetting这个变量，如果没有设置的话，默认是DEFAULT_SCREEN_OFF_TIMEOUT常量为15秒。

        mScreenOffTimeoutSetting = Settings.System.getIntForUser(resolver,                Settings.System.SCREEN_OFF_TIMEOUT, DEFAULT_SCREEN_OFF_TIMEOUT,                UserHandle.USER_CURRENT);

而keyguard的灭屏时间和mUserActivityTimeoutOverrideFromWindowManager值有关。

下面我们来看看这个值是哪里来的？

我在WMS的performLayoutAndPlaceSurfacesLockedInner函数中，会调用如下函数。

            mPowerManager.setUserActivityTimeoutOverrideFromWindowManager(                    mInnerFields.mUserActivityTimeout);

这个函数最终就会设置mUserActivityTimeoutOverrideFromWindowManager。

    public void setUserActivityTimeoutOverrideFromWindowManager(long timeoutMillis) {        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);        final long ident = Binder.clearCallingIdentity();        try {            setUserActivityTimeoutOverrideFromWindowManagerInternal(timeoutMillis);        } finally {            Binder.restoreCallingIdentity(ident);        }    }    private void setUserActivityTimeoutOverrideFromWindowManagerInternal(long timeoutMillis) {        synchronized (mLock) {            if (mUserActivityTimeoutOverrideFromWindowManager != timeoutMillis) {                mUserActivityTimeoutOverrideFromWindowManager = timeoutMillis;                mDirty |= DIRTY_SETTINGS;                updatePowerStateLocked();            }        }    }

而在WMS调用PowerManagerService的setUserActivityTimeoutOverrideFromWindowManager的参数mInnerFields.mUserActivityTimeout其实也是WindowState的mAttrs（WindowManager.LayoutParams）的userActivityTimeout变量。

mInnerFields.mUserActivityTimeout = w.mAttrs.userActivityTimeout;

而这个变量就是在KeyguardViewManager.java中设置的，因此到这里我们就知道这个值就是在Keyguard窗口起来的时候设置的，而由于这个值默认值是-1，其他窗口起来时，也把窗口的userActivityTimeout设置到PowerManagerService中去了，这时mUserActivityTimeoutOverrideFromWindowManager为-1。也就是说只有在keyguard的时候这个值才不是-1.

    private void updateUserActivityTimeoutInWindowLayoutParams() {        // Use the user activity timeout requested by the keyguard view, if any.        if (mKeyguardView != null) {            long timeout = mKeyguardView.getUserActivityTimeout();            if (timeout >= 0) {                mWindowLayoutParams.userActivityTimeout = timeout;                return;            }        }        // Otherwise, use the default timeout.        mWindowLayoutParams.userActivityTimeout = KeyguardViewMediator.AWAKE_INTERVAL_DEFAULT_MS;    }

而我们修改锁屏的时间，就是先修改KeyguardViewMediator.AWAKE_INTERVAL_DEFAULT_MS这个值。

然后在PowerManagerService中的getScreenOffTimeoutLocked函数中，当这个时候在锁屏界面时，因为是keyguard界面，这时候WMS会调用PowerManagerService的setUserActivityTimeoutOverrideFromWindowManager函数来设置mUserActivityTimeoutOverrideFromWindowManager，因此这个时候mUserActivityTimeoutOverrideFromWindowManager不为-1.这个时候我们可以将timeout直接设置为mUserActivityTimeoutOverrideFromWindowManager（Keyguard设置的屏幕锁屏时间），而不用和PowerManagerService现在的timeout对比，最后在锁屏的时候灭屏的timeout就会变成我们设置的时间了。

    private int getScreenOffTimeoutLocked() {        int timeout = mScreenOffTimeoutSetting;        if (isMaximumScreenOffTimeoutFromDeviceAdminEnforcedLocked()) {            timeout = Math.min(timeout, mMaximumScreenOffTimeoutFromDeviceAdmin);        }        if (mUserActivityTimeoutOverrideFromWindowManager >= 0) {            timeout = (int)mUserActivityTimeoutOverrideFromWindowManager;//设置为keyguard设置的timeout        }        int lockedtimeout = Math.max(timeout, MINIMUM_SCREEN_OFF_TIMEOUT);        return lockedtimeout;    }