B4A Library LockScreen: Create your own lockscreen with just 5 lines of code

Periklis Koutsogiannis

Active Member
Licensed User
version 2.0 requires B4A version 3.80[Android-L compatible]

Introduction

One of the most wanted features since the birth of android is the lockscreen. After a long and exhausting 2 weeks research, I did not find a single complete functional lockscreen example that can address all aspects of a stable lockscreen. Just do a search in GitHub and you will understand what I mean.

The difficult part was the testing and as mentioned before, to address every single lockscreen system requirement with the minimum amount of complexity and code while keeping in mind that we are playing in B4A and not in eclipse. And in the end, offer the B4A community a fully encapsulated library that contains 100% of the lockscreen functionality (permissions, services, listeners, auto restart when killed, handling the keyguard and phone calls, waking/locking the device and so on) leaving you enough space for your creativity and app logic.

Latest package (library files and samples)
https://www.dropbox.com/s/ju1z09r90lx5m4g/lockscreen.zip

Compiled demos (APK)
sample1 (5LinesOfCode), sample2 (push button lockscreen), sample3 (slide button lockscreen), sample4 (sliding panel lockscreen)

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Getting started
  • Extract the contents of the package anywhere in your hard disk
  • Copy the lockscreen.jar and lockscreen.xml to your B4A libraries folder
  • Explore the samples


Creating a lockscreen app with just 5 lines of code (based on samples\sample1)

Create 2 activities. One to be your main (configuration) activity and one that will be your actual lockscreen activity.

Copy the Assets folder from any of the samples folder to your project root and in the main activity's project attributes add the following lines:
B4X:
'Kitkat transparent status/navigation bars support with custom theme and DeviceAdmin XML
#AdditionalRes: ..\Assets
In the main activity's attributes add the following magic line:
B4X:
    #Extends: com.datasteam.b4a.system.lockscreen.MainActivity
In the lockscreen activity's attributes add the following magic line:
B4X:
    #Extends: com.datasteam.b4a.system.lockscreen.LockScreenActivity

Now let's write the actual code.

1. Declare a LockscreenController object in Sub Process_Globals of the Main activity
B4X:
Sub Process_Globals
    Dim Controller As LockScreenController
End Sub
2. Load the main layout
B4X:
Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("Main")
End Sub
3. Drop a button in your main layout and create the click handler that will show the lockscreen
B4X:
Sub BtnPreview_Click
    StartActivity(LockScreen)
End Sub
4. Load the layout of the lockscreen activity
B4X:
Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("LockScreen")
End Sub
5. Drop a button in your lockscreen layout and create the click handler that will unlock the lockscreen
B4X:
Sub BtnUnlock_Click
    Main.Controller.Unlock
End Sub

Done with just 5 lines of code!

Add the following text to your manifest to complete the setup.
IMPORTANT: In the meta-data node and in the android:value field, put the name of your lockscreen activity so that the library engine will find it and launch it when needed.
B4X:
AddPermission(android.permission.GET_TASKS)
AddPermission(android.permission.WAKE_LOCK)
AddPermission(android.permission.DISABLE_KEYGUARD)
AddPermission(android.permission.RECEIVE_BOOT_COMPLETED)
AddPermission(android.permission.READ_PHONE_STATE)

'IMPORTANT: The android:value of meta-data contains the *NAME* of your lockscreen activity!
AddApplicationText(
    <meta-data android:name="lockscreen_activity" android:value="LockScreen"/>)
SetActivityAttribute(
    LockScreen, "android:theme", "@style/Theme.Lockscreen")
AddApplicationText(
    <service android:name="com.datasteam.b4a.system.lockscreen.LockScreenService">
        <intent-filter >
            <action android:name="com.datasteam.b4a.system.lockscreen.LockScreenService" />
        </intent-filter >
    </service>)
AddApplicationText(
    <receiver android:name="com.datasteam.b4a.system.lockscreen.LockScreenDeviceAdminReceiver" android:permission="android.permission.BIND_DEVICE_ADMIN" >
        <meta-data
            android:name="android.app.device_admin"
            android:resource="@xml/lockscreen_admin" />
        <intent-filter>
            <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
        </intent-filter>
    </receiver>
    <receiver android:name="com.datasteam.b4a.system.lockscreen.LockScreenBootReceiver" >
       <intent-filter >
            <action android:name="android.intent.action.BOOT_COMPLETED" />
       </intent-filter>
    </receiver>)
AddApplicationText(
    <activity android:name="com.datasteam.b4a.system.lockscreen.LockScreenHomeResetActivity" android:label="HomeReset" android:theme="@android:style/Theme.NoDisplay" android:enabled="false" android:taskAffinity="" android:stateNotNeeded="true" android:excludeFromRecents="true" android:launchMode="singleTask" android:configChanges="keyboard|keyboardHidden|orientation">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.HOME" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>)
AddApplicationText(
    <activity android:name="com.datasteam.b4a.system.lockscreen.LockScreenHomeActivity" android:theme="@android:style/Theme.NoDisplay" android:enabled="false" android:taskAffinity="" android:stateNotNeeded="true" android:excludeFromRecents="true" android:configChanges="keyboard|keyboardHidden|orientation" android:label="$LABEL$ Launcher">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.HOME" />
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>)
That's all! Run your project and see your first lockscreen app in full swing!

There is only one non-visual class exposed in the library: LockScreenController. This class will be used to enable/disable the lockscreen and save/load its settings. Explore the SlideButton and SlidePanel samples to see how it is used.

If you want to wake the device from any of your services, use the LockScreenController.Wake method and the LockScreenController.Lock method from your lockscreen activity to lock the device.

The SlidePanel sample uses the excellent ClsSlidingSidebar class (included in sample4) from [B]Informatix[/B] (Frédéric Leneuf-Magaud).

Now, go get the NotificationListener library from [B]Erel[/B] and the Clocks library from [B]Agraham[/B] (or use this nice clock trick) and you will soon have the next lockscreen app hit!


Blocking the Home Button

Well-designed and top google play store Lockscreen apps block the home button by allowing the user to set the lockscreen as the home launcher (and the lockscreen will launch the actual launcher). This method is also implemented through the LockScreenController.HomeBlockerEnabled property. See sample2 for detailed usage instructions.


Known issues

Third party lockscreens rely on the stock lockscreen when it comes for security. You can set your stock lockscreen pattern or pin security and when the 3rd party lockscreen unlocks, your stock security lockscreen will appear. Custom lockscreens disable the swipe keyguard only. There is no gain in "recreating the wheel" since stock lockscreens provide proven security.

--

That's all for now folks! :D

Version history:

2.0
  • Fixed: FC and incorrect handling of phone state changes (ringing, offhook)
  • Added: HomeBlocker functionality through LockScreenController.HomeBlockerEnabled property
  • Updated: Samples, manifest code and forum tutorial
1.1
  • Renamed: LockScreenConfigurator class renamed to LockScreenController
  • Added: LockScreenController.LockNow method which uses the DeviceAdmin Api (use the latest updated manifest code)
  • Samples updated to the latest version
1.0
  • Initial version
 
Last edited:

ivan.tellez

Active Member
Licensed User
Hi

Maybe Im doing something wrong or Im confused about the concept of the lockScreen. :confused:

It supose that the lockscreen should regulate immediate access to a device by requiring that the user perform a certain action in order to receive access, like a password, a button press or a gesture.

So I suposed that the device should be Locked and only could be unlocked with actions in the LockScreen.

But when compiling the project, it shows the "lockScreen", but this is dissmised if I press the home buton. also when soing a swipe gesture from top of the screen to botom, it shows the notifications panel and lauch apps from here, so, the device its not really "locked".

I Tested other "lockscreen apps" and have the same issue, its a way to create an app that truly locks the screen?
 
Last edited:

Periklis Koutsogiannis

Active Member
Licensed User
Third party lockscreens rely on the stock lockscreen when it comes for security. You can set your stock lockscreen pattern or pin security and when the 3rd party lockscreen unlocks, your stock security lockscreen appear. Custom lockescreens disable the swipe keyguard only. No lockscreen developer will "recreate the wheel" since stock lockscreens provide proven security.

Regarding the home button, most lockscreens block the home button by allowing the user to set the lockscreen as the home launcher (and the lockscreen will launch the actual launcher) which is up to the lockscreen developer to implement for now.

http://stackoverflow.com/questions/22298322/home-button-override-in-android

:)
 
Last edited:

Reids

Member
Licensed User
I got following error while tried to compile the source :

B4X:
Parsing code.                          0.02
Compiling code.                        0.09
Compiling layouts code.                0.02
Generating R file.                      Error
..\Assets\values-v19\styles.xml:5: error: Error: No resource found that matches the given name: attr 'android:windowTranslucentNavigation'.
..\Assets\values-v19\styles.xml:4: error: Error: No resource found that matches the given name: attr 'android:windowTranslucentStatus'.
but solved by removing following line on Asset\values-v19\styles.xml
B4X:
        <item name="android:windowTranslucentStatus">true</item>
        <item name="android:windowTranslucentNavigation">true</item>
This library is very great!! I Like It!
 

Periklis Koutsogiannis

Active Member
Licensed User
Update: 1.1

  • Renamed: LockScreenConfigurator class renamed to LockScreenController
  • Added: LockScreenController.LockNow method which uses the DeviceAdmin Api (use the latest updated manifest code)
  • Samples updated to the latest version
@ivan.tellez :D
 
Last edited:

ivan.tellez

Active Member
Licensed User
Hi, thanks for the LockNow

Im afraid @Reids is right, the proyect causes an error, that is because 'android:windowTranslucentNavigation'. And 'android:windowTranslucentStatus'. are only available on API 19 (KitKat)

I compiled changing the Paths of the android.jar to android-19\android.jar
 

susu

Well-Known Member
Licensed User
On my LG Optimus G Pro, I can press Home button to pass lockscreen. Is it normal?
 

ivan.tellez

Active Member
Licensed User
Im testing the demo in my Galaxy S4.

There is some random problems on incomming calls. The app just quits (LockR has a problem and has to close) and no loger appears the lockscreen until i open the config again.

Any ideas?
 
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