【唤醒屏幕总结】java.lang.RuntimeException: WakeLock under-locked target

最近线上的项目遇到了这样的错误

java.lang.RuntimeException: WakeLock under-locked target
	at android.os.PowerManager$WakeLock.release(PowerManager.java:2665)
	at android.os.PowerManager$WakeLock.release(PowerManager.java:2627)
	at com.driving.driver.android.kepplive.PowerManagerUtil$1.run(PowerManagerUtil.java:86)
	at java.lang.Thread.run(Thread.java:933)"

经过一顿查找资料分析，是由于设置了mWakelock.acquire();默认计数形式唤醒屏幕，这种情况下还需要设置 mWakelock.setReferenceCounted(false); 不然的话，很容易引起以下异常：

java.lang.RuntimeException: WakeLock under-locked

原理：

       acquire() 函数如下：

            public void acquire () {
                synchronized (mToken) {
                    if (!mRefCounted || mCount++ == 0) {
                        try {
                            mService.acquireWakeLock(mFlags, mToken, mTag);
                        } catch (RemoteException e) {
                        }
                        mHeld = true;
                    }
                }
            }

　　    release() 函数如下：

            public void release () {
                release(0);
            }

            public void release ( int flags){
                synchronized (mToken) {
                    if (!mRefCounted || --mCount == 0) {
                        try {
                            mService.releaseWakeLock(mToken, flags);
                        } catch (RemoteException e) {
                        }
                        mHeld = false;
                    }
                    if (mCount < 0) {
                        throw new RuntimeException("WakeLock under-locked " + mTag);
                    }
                }
            }

看到了吗？报错就抱在release（int flags）中，mCount为负数了，抛除了异常

我们再看下：setReferenceCounted(boolean flags);

public void setReferenceCounted(boolean value){
            mRefCounted = value;
}

 这个函数的作用是是不是需要计算锁的数量，设置为false时，在release（）的时候，不管你acquire()了多少回，可以releaseWakeLock掉

public class PowerManagerUtil {
    public static final String TAG = "PowerManagerUtil";

    //使用volatile关键字保其可见性
    volatile private static PowerManagerUtil instance = null;

    private PowerManagerUtil() {
    }

    public static PowerManagerUtil getInstance() {
        try {
            if (instance != null) {//懒汉式

            } else {
                //创建实例之前可能会有一些准备性的耗时工作
                Thread.sleep(300);
                synchronized (PowerManagerUtil.class) {
                    if (instance == null) {//二次检查
                        instance = new PowerManagerUtil();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return instance;
    }

    
    public boolean isScreenOn(final Context context) {
        try {
            Method isScreenMethod = PowerManager.class.getMethod("isScreenOn", new Class[]{});
            PowerManager pm = (PowerManager) context.getSystemService(POWER_SERVICE);
            boolean screenState = (Boolean) isScreenMethod.invoke(pm);
            return screenState;
        } catch (Exception e) {
            return true;
        }
    }

    
    @SuppressLint("InvalidWakeLockTag")
    public void wakeUpScreen(final Context context) {
        try {
            if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
                PowerManager pm = (PowerManager) context.getSystemService(POWER_SERVICE);
                
                PowerManager.WakeLock mWakelock = pm.newWakeLock(
                        PowerManager.PARTIAL_WAKE_LOCK
                                | PowerManager.SCREEN_DIM_WAKE_LOCK, TAG);
                
                mWakelock.setReferenceCounted(false);
                mWakelock.acquire();
                if (mWakelock.isHeld()) {//如果已获得唤醒锁但尚未释放，则返回true。
                    mWakelock.release();
                }
                // FIXME: 注意：WakeLock的设置是 Activiy 级别的，不是针对整个Application应用的。所以application下有多个activity一定需要注意下！
            }
        } catch (Exception e) {

        }
    }

}