在 Main Activity 中使用 BroadcastReceiver 更新 Widget

Question

我正在开发一个包含时钟的 android 小部件。到目前为止，我能够成功地将时钟设置为当前时间，但无法更新它。我正在使用Intent.ACTION_TIME_TICK 广播接收器。 我在onEnable() 中注册广播接收器并在onDeleted() 上删除。接收器正在正确注册和取消注册，但是当我更新views 时出现问题。这是我正在使用的代码

@Override
public void onEnabled(final Context context) {

    // TODO Auto-generated method stub
    System.out.println("Entering onstart");
    _broadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context ctx, Intent intent) {
            System.out.println("Registering BroadCast");
            if (intent.getAction().compareTo(Intent.ACTION_TIME_TICK) == 0) {

                System.out.println(_sdfWatchTime.format(new Date()));
                //class to get drawable images that will be used to denote hours and minutes
                GetDrawableResources getDrawableResources = new GetDrawableResources();
                int time[] = new int[new GetTime().getTime(context
                        .getApplicationContext()).length];
                //class to get each digit of time seperatly eg 10:10, separating 1 0 1 0 working correctly
                time = new GetTime().getTime(context
                        .getApplicationContext());

                //changing views
                for (int i = 0; i < awID.length; i++) {
                    System.out.println("awID for " + awID[i]);
                    RemoteViews views = new RemoteViews(
                            context.getApplicationContext().getPackageName(),
                            R.layout.activity_main);

                    views.setImageViewResource(R.id.ivHour0,
                            getDrawableResources.setTimeDrawable(time[0]));
                    views.setImageViewResource(R.id.ivHour1,
                            getDrawableResources.setTimeDrawable(time[1]));
                    views.setImageViewResource(R.id.ivMinute0,
                            getDrawableResources.setTimeDrawable(time[2]));
                    views.setImageViewResource(R.id.ivMinute1,
                            getDrawableResources.setTimeDrawable(time[3]));
                    //problem is pointing to line below
                    awm.updateAppWidget(awID[i], views);

                }

            }
        }
    };
    context.getApplicationContext().registerReceiver(_broadcastReceiver,
            new IntentFilter(Intent.ACTION_TIME_TICK));
    super.onEnabled(context);
}

@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager,
        int[] appWidgetIds) {
    // TODO Auto-generated method stub
    super.onUpdate(context, appWidgetManager, appWidgetIds);

    final int N = appWidgetIds.length; // more than 1 same widget added
    awID = new int[N];
    awID = appWidgetIds;
    awm = appWidgetManager;

    for (int t : awID) {
        System.out.println("awID onUpdate" + t);
    }

}

我遇到的错误

    06-28 11:27:00.078: E/AndroidRuntime(453): FATAL EXCEPTION: main
06-28 11:27:00.078: E/AndroidRuntime(453): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.intent.action.TIME_TICK flg=0x40000004 (has extras) } in com.itcse.weather.MainActivity$1@40520228
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:722)
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.os.Handler.handleCallback(Handler.java:587)
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.os.Handler.dispatchMessage(Handler.java:92)
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.os.Looper.loop(Looper.java:123)
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-28 11:27:00.078: E/AndroidRuntime(453):  at java.lang.reflect.Method.invokeNative(Native Method)
06-28 11:27:00.078: E/AndroidRuntime(453):  at java.lang.reflect.Method.invoke(Method.java:507)
06-28 11:27:00.078: E/AndroidRuntime(453):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-28 11:27:00.078: E/AndroidRuntime(453):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-28 11:27:00.078: E/AndroidRuntime(453):  at dalvik.system.NativeStart.main(Native Method)
06-28 11:27:00.078: E/AndroidRuntime(453): Caused by: java.lang.NullPointerException
06-28 11:27:00.078: E/AndroidRuntime(453):  at com.itcse.weather.MainActivity$1.onReceive(MainActivity.java:57)
06-28 11:27:00.078: E/AndroidRuntime(453):  at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:709)
06-28 11:27:00.078: E/AndroidRuntime(453):  ... 9 more

更新 null 错误被移除，代码运行成功但视图没有更新。

Answer 1

您的 MainActivity 第 57 行出现 NullPointerException：

com.itcse.weather.MainActivity$1.onReceive(MainActivity.java:57)

你应该在那里放一个断点，看看什么是空的。

如果你不能让你的调试器停在那里（有时发生在接收器中），把 Debug.waitForDebugger();在你的断点之前。