Troubleshooting

Hardware and software support for touch input changed rapidly over time. This reference does not maintain a list of every device an operating system and software combination that supports multitouch. However, it provides guidance on using the discovery API to determine if your application is deployed on a device that supports multitouch, and provides tips for troubleshooting your OpenFL code.

OpenFL responds to touch events based on information the device, operating system, or containing software (such as a browser) passes to the runtime. This dependency on the software environment complicates documenting multitouch compatibility. Some devices interpret a gesture or touch motion differently than another device. Is rotation defined by two fingers rotating at the same time? Is rotation one finger drawing a circle on a screen? Depending on the hardware and software environment, the rotation gesture could be either, or something entirely different. So, the device tells the operating system the user input, then the operating system passes that information to the runtime. If the runtime is inside a browser, the browser software sometimes interprets the gesture or touch event and does not pass the input to the runtime. This behavior is similar to the behavior of keyboard shortcuts or hotkeys: you try to use a specific key combination to get OpenFL to do something inside the browser and the browser keeps opening a menu instead.

Individual API and classes mention if they're not compatible with specific operating systems. You can explore individual API entries here, starting with the Multitouch class: https://api.openfl.org/openfl/ui/Multitouch.html.

Here are some common gesture and touch descriptions:

Pan
Move a finger left-to-right or right-to-left. Some devices require two fingers to pan.

Rotate
Touch two fingers down, then move them around in a circle (as if they're both simultaneously tracing an imaginary circle on a surface). The pivot point is set at the midpoint between the two finger touch points.

Swipe
Move three fingers left-to-right or right-to-left, top-to-bottom, or bottom-to-top, quickly.

Zoom
Touch two fingers down, then move them away from each other to zoom in and toward each other to zoom out.

Press-and-tap
Move or press one finger, then tap the surface with another.

Each device has its own documentation about the gestures the device supports and how to perform each gesture on that device. In general, the user must remove all fingers from contact with the device between gestures, depending upon the operating system.

If you find your application is not responding to touch events or gestures, test the following:

1. Do you have event listeners for touch or gesture events attached to an object class that inherits from the InteractiveObject class? Only InteractiveObject instances can listen for touch and gesture events

2. Start simple and see what does work, first (the following code example is from the API entry for Multitouch.inputMode:

   Multitouch.inputMode = MultitouchInputMode.TOUCH_POINT;
   
   var mySprite:Sprite = new Sprite();
   mySprite.graphics.beginFill(0x336699);
   mySprite.graphics.drawRect(0,0,40,40);
   addChild(mySprite);
   
   var myTextField:TextField = new TextField();
   
   mySprite.addEventListener(TouchEvent.TOUCH_TAP, taplistener);
   
   function taplistener(e:TouchEvent):Void {
       myTextField.text = "I've been tapped";
       myTextField.y = 50;
       addChild(myTextField);
   }
   

   Tap the rectangle. If this example works, then you know your environment supports a simple tap. Then you can try more complicated handling.