Android开发中可能被忽视的bug

java.lang.IllegalArgumentException

• 异常：Receiver not registered

• 出现情况：偶现

• 问题原因：广播在没有注册的情况下就调用注销广播方法。

• 问题场景：平时大多动态注册广播，都是把广播注册写在Activity的onCreate方法里面，把注销写在onDestory里面，这样可以保证调用广播注销方法时，该广播一定是被注册过的，但是在其它地方使用，可能由于代码逻辑不够严谨，而出现注销时，广播并没有被注册。

• 问题衍生：

  1. 如果多次调用注销广播也是会报异常的：

      "Unregistering Receiver " + r+ " that was already unregistered"
     

• 源码位置：

  1. 文件路径：android.app.ReceiverRestrictedContext.java

   @Override
   public void unregisterReceiver(BroadcastReceiver receiver) {
       if (mPackageInfo != null) {
           IIntentReceiver rd = mPackageInfo.forgetReceiverDispatcher(
                   getOuterContext(), receiver);
           try {
               ActivityManager.getService().unregisterReceiver(rd);
           } catch (RemoteException e) {
               throw e.rethrowFromSystemServer();
           }
       } else {
           throw new RuntimeException("Not supported in system context");
       }
  
   public IIntentReceiver forgetReceiverDispatcher(Context context,
           BroadcastReceiver r) {
       ...
           if (context == null) {
               throw new IllegalStateException("Unbinding Receiver " + r
                       + " from Context that is no longer in use: " + context);
           } else {
               throw new IllegalArgumentException("Receiver not registered: " + r);
           }
       }
   } ```