Hey there! Let's work through your notification problems and get that daily repeating alarm sorted out step by step.

1. Replacing the Deprecated NotificationCompat.Builder #

Starting from Android API 26, notifications require a notification channel, which is why the old NotificationCompat.Builder(Context) constructor got deprecated. Here's how to update your code properly:

First, create a notification channel (you only need to run this once, like in your Application class or MainActivity's onCreate):

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    String channelId = "daily_reminder_channel";
    CharSequence channelName = "Daily Reminders";
    String channelDescription = "Channel for your daily scheduled notifications";
    int importance = NotificationManager.IMPORTANCE_DEFAULT;
    
    NotificationChannel channel = new NotificationChannel(channelId, channelName, importance);
    channel.setDescription(channelDescription);
    
    // Register the channel with the system
    NotificationManager notificationManager = getSystemService(NotificationManager.class);
    notificationManager.createNotificationChannel(channel);
}

Then build your notification using the channel-aware constructor:

Intent i = new Intent(this, MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(
    this,
    0, // Use a unique number if you have multiple PendingIntents
    i,
    PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE // FLAG_IMMUTABLE is recommended for API 31+
);

NotificationCompat.Builder builder = new NotificationCompat.Builder(this, "daily_reminder_channel")
    .setSmallIcon(R.drawable.your_notification_icon)
    .setContentTitle("Daily Check-In")
    .setContentText("It's time to take action!")
    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
    .setContentIntent(pendingIntent)
    .setAutoCancel(true);

// Show the notification
NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
notificationManager.notify(1, builder.build()); // 1 is your unique notification ID

2. Troubleshooting Red Markers in Your Manifest #

Red flags in the Android Manifest almost always point to syntax errors or missing required declarations. Here are the most common fixes to check:

• Verify your MainActivity declaration: Make sure you have a properly closed <activity> tag for MainActivity:

  <activity
      android:name=".MainActivity"
      android:exported="true"> <!-- Set to true if this is your launcher activity -->
      <intent-filter>
          <action android:name="android.intent.action.MAIN" />
          <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
  </activity>
  

• Add required permissions: For Android 13 (API 33+) and above, you need to declare the POST_NOTIFICATIONS permission in your manifest:

  <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
  

• Check for syntax typos: Hover over the red line in Android Studio—you'll get a tooltip explaining the exact error, like unclosed tags, misspelled attribute names, or missing required fields.

3. Setting Up Daily Repeating Notifications #

To make your existing PendingIntent trigger at a specific time every day, you'll use AlarmManager to schedule a repeating alarm. Here's how to do it right:

First, calculate your target trigger time (e.g., 9:00 AM every day):

Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.set(Calendar.HOUR_OF_DAY, 9);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);

// If today's target time has already passed, schedule for tomorrow
if (calendar.getTimeInMillis() < System.currentTimeMillis()) {
    calendar.add(Calendar.DAY_OF_YEAR, 1);
}

Then, you'll need a BroadcastReceiver to trigger the notification when the alarm fires (you can't directly launch a notification from AlarmManager with an Activity intent):

1. Create the receiver class:

public class DailyNotificationReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Build and show your notification here (reuse the code from section 1)
        Intent activityIntent = new Intent(context, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(
            context,
            0,
            activityIntent,
            PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE
        );

        NotificationCompat.Builder builder = new NotificationCompat.Builder(context, "daily_reminder_channel")
            .setSmallIcon(R.drawable.your_notification_icon)
            .setContentTitle("Daily Check-In")
            .setContentText("It's time to take action!")
            .setPriority(NotificationCompat.PRIORITY_DEFAULT)
            .setContentIntent(pendingIntent)
            .setAutoCancel(true);

        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(context);
        notificationManager.notify(1, builder.build());
    }
}

2. Register the receiver in your manifest:

<receiver
    android:name=".DailyNotificationReceiver"
    android:exported="false" />

Finally, schedule the repeating alarm with AlarmManager:

AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

PendingIntent alarmPendingIntent = PendingIntent.getBroadcast(
    this,
    100, // Unique request code (different from your notification ID)
    new Intent(this, DailyNotificationReceiver.class),
    PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE
);

// Use battery-friendly repeating for API 19+
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    alarmManager.setInexactRepeating(
        AlarmManager.RTC_WAKEUP,
        calendar.getTimeInMillis(),
        AlarmManager.INTERVAL_DAY,
        alarmPendingIntent
    );
} else {
    alarmManager.setRepeating(
        AlarmManager.RTC_WAKEUP,
        calendar.getTimeInMillis(),
        AlarmManager.INTERVAL_DAY,
        alarmPendingIntent
    );
}

That's all! This setup will fire your notification at your specified time every single day.

内容的提问来源于stack exchange，提问作者Mr. Benbenbenbenben