Android Tutorial [Advanced] Using a custom view written with Kotlin


Using Kotlin libraries is similar to using Java libraries. The only difference is that we need to add references to two additional libraries:
#AdditionalJar: kotlin-stdlib-1.3.21
#AdditionalJar: kotlin-stdlib-jdk7-1.3.21

As an example, I wanted to show how to use this open source project, without writing a wrapper:

The first step is to get the jar or AAR library from the maven repository. I like the direct approach. (The indirect approach is to create an Android Studio project based on the instructions and then find the downloaded resource.)

1. Get the compiled library

The setup instructions from that page:
allprojects {
   repositories {
       maven { url '' }

dependencies {
   implementation 'com.github.iammert:CameraVideoButton:0.2'
This can be translated to:
Follow this link to see the list of files available.

We can then download the aar file:
The other interesting file is the POM file. It lists the other dependencies. Note that the other dependencies might depend on more resources.

2. Calling the constructor

We need to look in the code and find the constructor:
The B4A code:
Dim ctxt As JavaObject
CameraVideoButton.InitializeNewInstance("com.iammert.library.cameravideobuttonlib.CameraVideoButton", _
     Array(ctxt, Null, 0))

Once we see that it is working we translate the example code and also create the listener:
Dim duration As Long = 10000
CameraVideoButton.RunMethod("setVideoDuration", Array(duration))
CameraVideoButton.RunMethod("enableVideoRecording", Array(True))
CameraVideoButton.RunMethod("enablePhotoTaking", Array(True))
Dim listener As Object = CameraVideoButton.CreateEventFromUI("com.iammert.library.cameravideobuttonlib.CameraVideoButton.ActionListener", _
   "VideoListener", Null)
CameraVideoButton.RunMethod("setActionListener", Array(listener))
Activity.AddView(CameraVideoButton, 50%x - 50dip, 100%y - 120dip, 100dip, 100dip)

Sub VideoListener_Event (MethodName As String, Args() As Object) As Object
   Return Null
End Sub

Note that the duration parameter type is Long. I first wrote Array(10000) and it failed with a class cast exception.

At this point everything worked but I wasn't able to change the "recording color" value. The library doesn't provide a method to set it programmatically. It is extracted from the view's XML declaration:
recordingColor = typedArray.getColor(R.styleable.CameraVideoButton_cvb_recording_color, Color.WHITE)

We can set it by creating a custom theme with the manifest editor:
SetApplicationAttribute(android:theme, "@style/Theme")

CreateResource(values, theme.xml,
    <style name="Theme" parent="@android:style/Theme.Material">
        <item name="cvb_recording_color">#ffff0000</item>
Note that the material theme is only available on Android 5+. I've set minSdkVersion to 21 (Android 5). It shouldn't be difficult to use an AppCompat theme instead or to to create a different theme based on the Android version if you want to support Android 4 devices:

The project is attached.


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