解开广播员

Question

在我的应用中，我的服务将广播员注册到 onStart() 方法：

public void onStart() {
    if(something....) {
        IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        screenReceiver = new ScreenReceiver();
        registerReceiver(screenReceiver, filter);
    } else {
        if(screenReceiver != null) {
            unregisterReceiver(screenReceiver);
        }
    }
}

它正常工作。但是我会在内部注册这位广播员 else 我收到这个错误：

01-25 09:30:03.730: ERROR/AndroidRuntime(11748): FATAL EXCEPTION: main
01-25 09:30:03.730: ERROR/AndroidRuntime(11748): java.lang.RuntimeException: Unable to start service com.myservice.Service@460ce7d8 with Intent { cmp=com.myservice/.Service (has extras) }: java.lang.IllegalArgumentException: Receiver not registered: com.myreceiver.ScreenReceiver@46079370
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3063)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread.access$3600(ActivityThread.java:125)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2096)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.os.Looper.loop(Looper.java:123)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread.main(ActivityThread.java:4627)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at java.lang.reflect.Method.invoke(Method.java:521)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at dalvik.system.NativeStart.main(Native Method)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748): Caused by: java.lang.IllegalArgumentException: Receiver not registered: com.myreceiver.ScreenReceiver@46079370
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread$PackageInfo.forgetReceiverDispatcher(ActivityThread.java:793)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ContextImpl.unregisterReceiver(ContextImpl.java:814)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.content.ContextWrapper.unregisterReceiver(ContextWrapper.java:331)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at com.myservice.Service.onStart(Service.java:291)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.Service.onStartCommand(Service.java:420)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3053)
01-25 09:30:03.730: ERROR/AndroidRuntime(11748):     ... 10 more

你能帮助我吗？

Answer 1

修改您的代码如下

public void onStart() {
    if(something....) {
        IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
        filter.addAction(Intent.ACTION_SCREEN_OFF);
        screenReceiver = new ScreenReceiver();
        registerReceiver(screenReceiver, filter);
    } else {
        if(screenReceiver != null) {
            unregisterReceiver(screenReceiver);
            screenReceiver = null;
        }
    }
}

呼叫UnregisterReceiver（）不会将ScreenReceiver设置为null，并且当控件到达该块时，可能并不总是注册您的接收器的情况。例如，考虑按照顺序考虑

1. if(something...) 是真的，因此ScreenReceiver已实例化和注册。
2. if(something...) 这次是错误的，因此没有注册的ScreenReceiver。
3. if(something...) 再次是错误的，在这里，ScreenReceiver在步骤1中实例化，因此它不是空的，但在步骤2中未注册，因此“未注册的接收器：com.myreceiver.screenreceiver@46079370”。

设置后 screenReceiver 为了无效，请考虑以上3个步骤的顺序。它将正确执行。