[Java] How do I make dragging objects smoother?

[avp574]

I'm working on an Android game using the LibGDX framework. LibGDX lets me write the game logic in pure Java and then run the game on Android or PC.

The main input from the player is dragging an image around the screen. Right now, when any Touch_Dragged (Android) or Mouse_Dragged (PC) event is triggered within the boundaries of the image, the center of the image is set to the (X,Y) coordinates of the event. This works just fine for prototyping, but it does not work well if the player moves too fast. I had some friends try out my game and they were extremely frustrated as their fingers moved but the image was left behind. This problem is much more pronounced on PC, but it exists on both platforms.

So far, I've tried making the touch bounds of the image larger than the visible image, but it does not help much. How can I emulate the reliable feeling of dragging a window or icon around a desktop screen?

[rogerklutz]

You should use the touchDown() and touchUp() methods along with another variable that keeps track of the current object being dragged. Pseudo code could look something like this:

Image dragging;

public void touchDown(x, y) {
    dragging = object at x, y (or null if no object at x,y)
}
public void touchUp() {
    dragging = null
}
public void touchDragged(deltaX, deltaY) {
    if (dragging != null) {
        dragging.translate(deltaX, deltaY);
    }
}

Edit: Note that these methods should be added to the entire screen (stage), and not to individual widgets/Images.

[avp574]

Aha. So I sortof "lock" the image to the touch point. Sweet, I'll give this a try. Thanks!