Android待机状态更新

Android的待机状态管理由PowerManagerService.java管理

主要的状态更新方法在下面贴出代码, 注释写的很清楚, 第一次看系统源码感觉还比较爽

主要是更新唤醒, 屏幕休眠以及其他的一些状态, 然后系统根据更新的状态进行一些操作, 比如系统睡眠, 进入屏保, 或者电源模式变更等等.

 /**
     * Updates the global power state based on dirty bits recorded in mDirty.
     *
     * This is the main function that performs power state transitions.
     * We centralize them here so that we can recompute the power state completely
     * each time something important changes, and ensure that we do it the same
     * way each time.  The point is to gather all of the transition logic here.
     */
    private void updatePowerStateLocked() {
        if (!mSystemReady || mDirty == 0) {
            return;
        }
        if (!Thread.holdsLock(mLock)) {
            Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
        }

        // Phase 0: Basic state updates.
        updateIsPoweredLocked(mDirty);
        updateStayOnLocked(mDirty);

        // Phase 1: Update wakefulness.
        // Loop because the wake lock and user activity computations are influenced
        // by changes in wakefulness.
        final long now = SystemClock.uptimeMillis();
        int dirtyPhase2 = 0;
        for (;;) {
            int dirtyPhase1 = mDirty;
            dirtyPhase2 |= dirtyPhase1;
            mDirty = 0;

            updateWakeLockSummaryLocked(dirtyPhase1);
            updateUserActivitySummaryLocked(now, dirtyPhase1);
            if (!updateWakefulnessLocked(dirtyPhase1)) {
                break;
            }
        }

        // Phase 2: Update dreams and display power state.
        updateDreamLocked(dirtyPhase2);
        updateDisplayPowerStateLocked(dirtyPhase2);

        // Phase 3: Send notifications, if needed.
        if (mDisplayReady) {
            sendPendingNotificationsLocked();
        }

        // Phase 4: Update suspend blocker.
        // Because we might release the last suspend blocker here, we need to make sure
        // we finished everything else first!
        updateSuspendBlockerLocked();
    }

调用updatePowerStateLocked()方法的地方有:

可以发现, 基本都是接受到一些系统广播之后进行调用(以handle开头的方法), 以及系统设置后调用(set开头的方法), 来更新电源状态, 还有一些接口回调, 主要是给用户的一些操作

先是public的回调方法, 回调方法把任务传递到内部的private方法(Internal结尾), 还有接收的native方法(Native结尾), 最后都是通过Locked结尾的方法调用updatePowerStateLocked()更新状态.