Wacom One Standard Pen, how to handle these buttons in android

Now, I am coding yet another app for Galaxy Tab (S6 Lite/S8+) with S Pen. To make this app minimum UI parts, I decided to get and test this Wacom One Standard Pen that has two buttons. I got this and I felt a little anxiety if android could not handle these buttons? But it was Okay. In this entry I will show you how to handle these buttons in Android View class.

As a result: this pen's 1st button has the same functionality S Pen button and 2nd button is as eraser. It makes sense.

How to handle these buttons in Android View

In the extended class such as android.view.View various pen touch event called back to onTouchEvent function.

private companion object {
    val ACTION_DOWN_WITH_1ST_BUTTON = 211
    val ACTION_MOVE_WITH_1ST_BUTTON = 213
    val ACTION_UP_WITH_1ST_BUTTON   = 212
    val ACTION_CANCEL_WITH_1ST_BUTTON = 214
}

override fun onTouchEvent(motionEvent: MotionEvent): Boolean {
    val actionMasked = motionEvent.actionMasked

    val eraser: Boolean = 0.until(motionEvent.pointerCount).filter { pointerIndex->
        motionEvent.getToolType(pointerIndex)==MotionEvent.TOOL_TYPE_ERASER
    }.size>0

    if( !eraser ){
        when(actionMasked){
            //
            // Pen Input without any buttons pressed 
            //
            MotionEvent.ACTION_DOWN->{}
            MotionEvent.ACTION_MOVE->{}
            MotionEvent.ACTION_UP -> {}
            MotionEvent.ACTION_CANCEL-> {}

            //
            // Pen Input with 1st buttons pressed ( SPen 1st button or Wacom One Standard Pen 1st button )
            //
            ACTION_DOWN_WITH_1ST_BUTTON->{}
            ACTION_MOVE_WITH_1ST_BUTTON->{}
            ACTION_UP_WITH_1ST_BUTTON -> {}
            ACTION_CANCEL_WITH_1ST_BUTTON-> {}

            //
            else -> {}
        }
    } else {
        when(actionMasked){
            //
            // Wacom One Standard Pen Input with 2nd button pressed 
            //
            MotionEvent.ACTION_DOWN->{}
            MotionEvent.ACTION_MOVE->{}
            MotionEvent.ACTION_UP -> {}
            MotionEvent.ACTION_CANCEL-> {}

            //
            else -> {}
        }
    }

    return true
}

About 1st button:

• Just checking the motionEvent.actionMasked value when pen stroking (action down, move, and up )
  • Without pressed 1st button: The value is 0 = MotionEvent.ACTION_DOWN, 2 = MotionEvent.ACTION_MOVE, 1 = MotionEvent.ACTION_UP and 3 = MotionEvent.ACTION_CANCEL.
  • With pressed 1st button: The value is 211, 213, 212 or 214.

Update: Galaxy tab S6Lite is Okay, but S8+ is NG. This code does not work properly on S8+. To capture this 1st button on S8+ use motionEvent.getButtonState() instead of using actionMasked value.

About 2nd button:

• Even if with pressed 2nd button, the motionEvent.actionMasked value is 0,2,1 or 3.
• Instead of checking motionEvent.actionMasked value, do check ToolType. When pressed 2nd button motionEvent.getToolType(0) has MotionEvent.TOOL_TYPE_ERASER.

MotionEvent.getButonState()

Another way to check which any button pressed, use motionEvent.getButtonState().

In details, see MotionEvent API.

You can check it this code:

when( motionEvent.getButtonState() ){
    0 -> {
        // no spen/wacom one button pressed
    }
    MotionEvent.BUTTON_STYLUS_PRIMARY -> {
        // spen/wacom one 1st button pressed
    }
    MotionEvent.BUTTON_STYLUS_SECONDARY -< {
        // NG: it is wrong. -> wacom one 2nd button pressed
    }
    else -> {
        //
    }
}

Update: Even if Wacom One Pen 2nd button pressed, it does not point motionEvent.getButtonState() value this MotionEvent.BUTTON_STYLUS_SECONDARY. To capture this 2nd button action, use motionEvent.getToolType instead of using motionEvent.getButtonState() value.

Wrap up

Wacom One Standard Pen works well on Galaxy Tab S6Lite/ S8+. If using these buttons, I could get rid of the pen/lasso/eraser tool switcher UI from the app.