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Call Prefix Filter is an Android app that filters incoming phone calls.
Getting started
Getting started
The app requests runtime permissions on new Android releases. A simple guide.
Install the app and launch it.
In version 1.x.x and 2.0.x, the app needs permission to read the phone state. Please grant the runtime permission in Marshmallow and newer.
Starting from version 3.0.0, the app requests the call screener role in Android 10 or newer. Please select Call Prefix Filter as the default caller ID app.
The app can let through the numbers in the contact list. To support this feature, it needs the permission to read the contacts. Please grant the runtime permission in Marshmallow and newer.
If the app is not permitted to access the contacts, Android 10 or newer does not block calls which are in the user's contacts. Highly recommend granting the permission to the app.
When the setting is done, the app will go to the main screen.
Main screen
Main screen
In the main screen, the entered filter rules are listed.
Each filter rule has 3 entities:
icon for block or allow
country code
number prefix
Asterisk is added to denote number wildcard.
When a prefix is not specified an exact number, it is shown followed by an asterisk.
When a country code is not specified, it is shown as an asterisk.
Starting from version 1.7.0, you may swipe sideways across the screen to bring up the call log page.
There are several buttons for filter setup.
Floating add button
Floating add button
Press the add button to add a filter rule in the dialog box.
In the add dialog box, enter the number prefix for the filter rule.
A country code may also be specified. It is placed before the prefix with a + sign. The use of this field may complicate the filter design. The detail is given in this link.
You may select whether the prefix be blocked or allowed.
The prefix can be selected an exact number.
In the shown dialog box, the incoming number that starts with 398765 is blocked.
Edit button
Edit button
Press the edit button to edit a filter rule.
The edit dialog box is similar to the add dialog box.
Remove button
Remove button
Press the remove button to remove a filter rule.
You will be prompted to confirm the removal.
Menu button
Menu button
Press the menu button to bring up the options menu.
How the filter rules work
How the filter rules work
A separate page is dedicated to illustrate how the filter works. --> link
Rule sorting
Rule sorting
The filter rule list has 3 sorting options.
No sorting
Sort by prefix
Sort by country code and prefix
Notification
Notification
Starting from version 1.5.0, the app no longer posts a separate notification for each blocked call. Instead, only one notification is posted for the last incoming call.
Starting from version 1.5.0, clicking the notification brings up the app's call log page.
Troubleshooting
Troubleshooting
To get the app blocking calls, the app has to be started.
It is easy to get the app started. Run the app once.
Android should be able to keep the app started after a power off and restart.
Some Android variants have an auto-start management feature. You may need to manually enable this app.
When the app suffers a crash, it may be stopped.
The App info page shows whether the app is running. You should be able to find the app in Android Settings Apps page.
Starting from version 3.0.0, check the call log page to see if the app handles any incoming call.
The app needs to be the default call ID app in Android 10 and newer.
Figure 1. App is started.
Figure 2. App is stopped.
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