java - getWindow().getAttributes() 期间出现 NullpointerException；

Question

我正在尝试获取 Android 中的屏幕亮度。

场景是这样的:A 类调用 B 类的函数:

A类:

if(condition is true){
  ClassB.function();
}

B类:

function(){
WindowManager.LayoutParams screenBrightness = getWindow()
                    .getAttributes();
screenBrightness.screenBrightness = 1;
screenBrightness.flags |= WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON;
screenBrightness.flags |= WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD;
screenBrightness.flags |= WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED;
getWindow().setAttributes(screenBrightness);
}

收到的异常如下:

06-15 13:36:30.476: E/AndroidRuntime(8873): FATAL EXCEPTION: main
06-15 13:36:30.476: E/AndroidRuntime(8873): java.lang.NullPointerException
06-15 13:36:30.476: E/AndroidRuntime(8873):     at function(B.java:68)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at something.run(A.java:104)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at android.os.Handler.handleCallback(Handler.java:587)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at android.os.Handler.dispatchMessage(Handler.java:92)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at android.os.Looper.loop(Looper.java:130)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at android.app.ActivityThread.main(ActivityThread.java:3701)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at java.lang.reflect.Method.invokeNative(Native Method)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at java.lang.reflect.Method.invoke(Method.java:507)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
06-15 13:36:30.476: E/AndroidRuntime(8873):     at dalvik.system.NativeStart.main(Native Method)

有人之前遇到过这个问题吗？

Answer 1

我在调用 transaction.commit() 时遇到了这个问题。

将其更改为 transaction.commitAllowingStateLoss() 后问题就消失了。