廣播接收器到來時更改菜單項圖標

Question

我的操作欄上有兩個菜單項，一個菜單項顯示藍牙已打開，另一個菜單項顯示藍牙已打開。 我想在網絡關閉和藍牙關閉時將圖像更改為其他圖像。 因此，將圖像從打開更改為關閉，反之亦然。 我有一個broadCastReceiver，它告訴我何時有網絡。 現在，當我嘗試從廣播接收器中調用menuItem並從那里更改其圖像時，我總是收到null異常。

這是我的廣播接收器：

private BroadcastReceiver broadcastBufferReceiverCheckConnection = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent bufferIntent) {
        isInternetPresent = ConnectionDetector.isConnectingToInternet();
        MenuItem iconNetwork = menu.findItem(R.id.iconNetwork);
        if (isInternetPresent == false) {
            iconNetwork.setIcon(R.drawable.network_disconnected);
        } else {
            iconNetwork.setIcon(R.drawable.network_connected);
        }
    }
};

這是我onCreateOptionMenu：

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    this.menu = menu;
    super.onCreateOptionsMenu(menu);
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

我知道問題可能在於菜單值，但我無法弄清楚如何解決此問題。 這也是我的logcat：

05-06 11:08:57.958: E/AndroidRuntime(16077): FATAL EXCEPTION: main
05-06 11:08:57.958: E/AndroidRuntime(16077): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.net.conn.CONNECTIVITY_CHANGE flg=0x8000010 (has extras) } in petrolina.pptaviation.MainActivity$1@4147ecc0
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:798)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.os.Handler.handleCallback(Handler.java:725)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.os.Handler.dispatchMessage(Handler.java:92)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.os.Looper.loop(Looper.java:153)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.app.ActivityThread.main(ActivityThread.java:5299)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at java.lang.reflect.Method.invokeNative(Native Method)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at java.lang.reflect.Method.invoke(Method.java:511)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at dalvik.system.NativeStart.main(Native Method)
05-06 11:08:57.958: E/AndroidRuntime(16077): Caused by: java.lang.NullPointerException
05-06 11:08:57.958: E/AndroidRuntime(16077):    at petrolina.pptaviation.MainActivity$1.onReceive(MainActivity.java:417)
05-06 11:08:57.958: E/AndroidRuntime(16077):    at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:788)
05-06 11:08:57.958: E/AndroidRuntime(16077):    ... 9 more

Answer 1

這是更新菜單項的正確方法

private BroadcastReceiver broadcastBufferReceiverCheckConnection = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent bufferIntent) {
            isInternetPresent = ConnectionDetector.isConnectingToInternet();
            invalidateOptionsMenu();//Activity method
    }
};

並覆蓋另一種方法

public boolean onPrepareOptionsMenu(Menu menu) {
       MenuItem iconNetwork = menu.findItem(R.id.iconNetwork);
       if (iconNetwork != null) {
           iconNetwork.setIcon(isInternetPresent ? R.drawable.network_connected : R.drawable.network_disconnected);
       }
       return true;
    }