为什么我的 BroadcastReceiver 的 onReceive 中的 intent.getAction() 返回 null？答案

【问题标题】：Why does intent.getAction() in onReceive of my BroadcastReceiver returns null?为什么我的 BroadcastReceiver 的 onReceive 中的 intent.getAction() 返回 null？
【发布时间】：2019-11-08 05:47:56
【问题描述】：

我想在特定的时钟时间触发 BroadcastReceiver 的 onReceive 函数。触发事件时，创建 IntentFilter 和/或注册 BroadcastReceiver 的片段不存在。这可能是 onReceive 方法中的 intent.getAction 返回 null 的原因吗？我的代码有什么错误？使用 BroadcastReceiver 的 onReceive 方法的 intent 参数的正确方法是什么？

当我显式调用 sendBroadcast 方法时，一切正常。但这会立即执行 onReceive。我希望它在指定的时间执行。

AddEditReminderFragment.java


    public class AddEditReminderFragment extends Fragment {
    ...
    public static final String NOTIFICATION_INTENT_ACTION = BuildConfig.APPLICATION_ID + ".NOTIFICATION_INTENT_ACTION";
    private AlarmManager alarmManager;
    private AlarmReceiver alarmReceiver = new AlarmReceiver();

    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
        ...
        alarmManager = (AlarmManager) getActivity().getSystemService(Context.ALARM_SERVICE);
        ...
    }

    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        ...
        saveReminder();
        ...
    }

    private void saveReminder() {
        ...
        Intent alarmIntent = new Intent(getActivity(), AlarmReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(getActivity(), 0, alarmIntent, 0);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            alarmManager.setAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, alarmDateTime.getTimeInMillis(), pendingIntent);
        } else {
            alarmManager.set(AlarmManager.RTC_WAKEUP, alarmDateTime.getTimeInMillis(), pendingIntent);
        } 
LocalBroadcastManager.getInstance(getActivity()).registerReceiver(alarmReceiver, new IntentFilter(NOTIFICATION_INTENT_ACTION));
        getFragmentManager().popBackStack();
    }

    public void onDestroyView() {
        super.onDestroyView();
LocalBroadcastManager.getInstance(getActivity()).unregisterReceiver(alarmReceiver);
    }
    ...
    }

AlarmReceiver.java


    public class AlarmReceiver extends BroadcastReceiver {

    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        Log.i("rahul", "Broadcast received: " + action);
        if (action.equals(AddEditReminderFragment.NOTIFICATION_INTENT_ACTION)) {
            sendNotification(context, intent.getStringExtra("notificationTitle"));
        }
    }
    ...
    }

AndroidManifest.xml


    ...
    <receiver android:name=".receivers.AlarmReceiver"
              android:enabled="true">
        <intent-filter>
            <action android:name="com.example.todo.NOTIFICATION_INTENT_ACTION" />
        </intent-filter>
    </receiver>
    ...

期望 Logcat 输出显示意图操作，但实际输出如下：

由搜索字符串“rahul”过滤的 Logcat 详细输出

06-26 11:47:56.011 4321-4321/com.example.todo I/rahul: Broadcast received: null

【问题讨论】：

标签： android android-intent broadcastreceiver intentfilter

【解决方案1】：

您需要在您用来创建PendingIntent 的Intent 上设置操作。

 Intent alarmIntent = new Intent(getActivity(), AlarmReceiver.class);
 alarmIntent.setAction("com.example.todo.NOTIFICATION_INTENT_ACTION");
 PendingIntent pendingIntent = PendingIntent.getBroadcast(getActivity(), 0, alarmIntent, 0);

Action 用于区分要执行的操作，以防您想在单个BroadcastReceiver 中执行不同的任务。

【讨论】：