Question

我正在创建一个用于显示预定通知的安卓库。例如，在下周下午4点发出通知。

我需要有一个尚未显示的预定通知的注册，所以如果我愿意，我可以取消它们。因此，每当我安排新通知时，我都会将其保存到 SharedPreferences 中。然后我开始一个 BroadcastReceiver ，当时间到来时将会超时。此时，接收方在SharedPreferences中注销通知。

当应用程序未运行时，该工作正常。 但是当应用程序运行时，接收方所做的更改不会在正在运行的应用程序中受到影响，因此我从未注册过该通知已被显示。

以下是我的示例活动代码：

public class MainActivity extends AppCompatActivity {
NotificationJSONStorage storage;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    storage = new NotificationJSONStorage(context,
            "notifications");

    // show notification in the next 10 seconds
    Calendar calendar = Calendar.getInstance();
    calendar.add(Calendar.SECOND, 10);

    sendNotification(getApplicationContext(), calendar.getTimeInMillis(), ...);
}

public int sendNotification(Context context, long dateTriggerMilliseconds, ...) {
    // create a unique notification id
    int id = UUID.randomUUID().hashCode();

    // Create an explicit intent for an Activity in your app
    Intent intent = new Intent(context, DelayedNotificationReceiver.class);
    // pass data to the receiver
    intent.putExtra("notification_id", id);
    ...

    // Set the Activity to start in a new, empty task
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(context,
            id, intent, PendingIntent.FLAG_UPDATE_CURRENT);

    AlarmManager alarm = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
    alarm.set(AlarmManager.RTC_WAKEUP, dateTriggerMilliseconds, pendingIntent);

    // adds the notification id to shared preferences
    try {
        storage.addScheduledNotification(id);
    } catch (JSONException e) {
        e.printStackTrace();
    }

    return id;
}

}

这是我的BroadcastReceiver代码：

public class DelayedNotificationReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
    // receive custom data from intent
    int id = intent.getIntExtra("notification_id", -1);
    ...

    try {
        Intent launchIntent = new Intent(context, Class.forName("my.launcher.class"));
        PendingIntent pendingIntent = PendingIntent.getActivity(context, id, launchIntent,
                PendingIntent.FLAG_UPDATE_CURRENT);

        // build the notification
        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, channelId)
                ...;

        // show the notification
        NotificationManagerCompat.from(context)
                .notify(id, builder.build());

        // removes the notification id from shared preferences
        NotificationJSONStorage storage = new NotificationJSONStorage(context,
            "notifications");
        storage.removeScheduledNotification(id);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

}

这是一个用于保存和读取SharedPreferences的通知数据的类：

public class NotificationJSONStorage {
private final String SCHEDULED_NOTIFICATIONS_KEY = "scheduled_notifications";

private Context context;
private JSONObject jsonRoot;
private String preferencesNamespace;

public NotificationJSONStorage(Context context, String preferencesNamespace) {
    this.context = context;
    this.preferencesNamespace = preferencesNamespace;
}

public void addScheduledNotification(int id) throws JSONException {
    JSONObject root = getJsonRoot();
    // do stuff with json root
    ...

    // persist it
    save(SCHEDULED_NOTIFICATIONS_KEY);
}

public boolean removeScheduledNotification(int id) throws JSONException {
    JSONObject root = getJsonRoot();
    // do stuff with json root
    ...

    // persist it
    save(SCHEDULED_NOTIFICATIONS_KEY);

    return result;
}

public JSONObject load(String key) throws JSONException {
    SharedPreferences preferences = context.getSharedPreferences(preferencesNamespace,
            Context.MODE_PRIVATE);
    String raw = preferences.getString(key, null);
    JSONObject root = null;

    if (raw != null && !raw.isEmpty()) {
        root = new JSONObject(raw);
    } else {
        root = new JSONObject();
    }

    return root;
}

public void save(String key) {
    String out = getJsonRoot().toString();
    // write to shared preferences
    SharedPreferences preferences = context.getSharedPreferences(preferencesNamespace,
            Context.MODE_PRIVATE);
    preferences.edit()
            .putString(key, out)
            .apply();
}

public JSONObject getJsonRoot() {
    if (jsonRoot == null) {
        try {
            jsonRoot = load(SCHEDULED_NOTIFICATIONS_KEY);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    return jsonRoot;
}

}

这是主要活动的Android清单：

<?xml version="1.0" encoding="utf-8"?>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

这是通知模块的Android清单：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.l33tbit.androidnotifications">
<uses-permission android:name="android.permission.SET_ALARM"/>
<uses-permission android:name="android.permission.GET_TASKS"/>
<application>
    <receiver android:name=".DelayedNotificationReceiver"/>
</application>

有什么想法吗？

Answer 1

我终于解决了这个问题。问题是当接收者改变状态时，NotificationJSONStorage类中的 jsonRoot 引用没有得到更新，因为它只被加载了一次。

我所做的是向SharedPreferences添加一个侦听器，强制在发生任何更改时重新加载json数据。

public class NotificationJSONStorage implements SharedPreferences.OnSharedPreferenceChangeListener {
private final String SCHEDULED_NOTIFICATIONS_KEY = "scheduled_notifications";

private Context context;
private JSONObject jsonRoot;
private String preferencesNamespace;
private boolean rootDirty = true;

public NotificationJSONStorage(Context context, String preferencesNamespace) {
    this.context = context;
    this.preferencesNamespace = preferencesNamespace;

    context.getSharedPreferences(preferencesNamespace, Context.MODE_PRIVATE)
            .registerOnSharedPreferenceChangeListener(this);
}

public void onDestroy() {
    context.getSharedPreferences(preferencesNamespace, Context.MODE_PRIVATE)
            .unregisterOnSharedPreferenceChangeListener(this);
}

public void addScheduledNotification(int id) throws JSONException {
    JSONObject root = getJsonRoot();
    // do stuff with json root
    ...

    // persist it
    save(SCHEDULED_NOTIFICATIONS_KEY);
}

public boolean removeScheduledNotification(int id) throws JSONException {
    JSONObject root = getJsonRoot();
    // do stuff with json root
    ...

    // persist it
    save(SCHEDULED_NOTIFICATIONS_KEY);

    return result;
}

public JSONObject load(String key) throws JSONException {
    SharedPreferences preferences = context.getSharedPreferences(preferencesNamespace,
            Context.MODE_PRIVATE);
    String raw = preferences.getString(key, null);
    JSONObject root = null;

    if (raw != null && !raw.isEmpty()) {
        root = new JSONObject(raw);
    } else {
        root = new JSONObject();
    }

    return root;
}

public void save(String key) {
    String out = getJsonRoot().toString();
    // write to shared preferences
    SharedPreferences preferences = context.getSharedPreferences(preferencesNamespace,
            Context.MODE_PRIVATE);
    preferences.edit()
            .putString(key, out)
            .apply();
}

public JSONObject getJsonRoot() {
    // also check if the data is dirty so it should be reloaded
    if (jsonRoot == null || rootDirty) {
        try {
            jsonRoot = load(SCHEDULED_NOTIFICATIONS_KEY);
            rootDirty = false;
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    return jsonRoot;
}

@Override
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
    if (key.equals(SCHEDULED_NOTIFICATIONS_KEY)) {
        rootDirty = true;
    }
}

}

主活动运行时，SharedPreferences未在BroadcastReceiver中保存

1 个答案: