View Animation (Resizing a Ball)

Question

hi,

i am trying to do this:

1) user long touches the screen, 2) a circle/ball pops up (centered around the user's finger) and grows in size as long as the user is touching the screen 3) once the user lets go of the finger, the ball (now in its final size) will bounce around.

i think i have the bouncing around figure out from the DivideAndConquer example, but i am not sure how to animate the ball's growth. i looked at various view flipper examples such as this:

http://www.inter-fuser.com/2009/08/android-animations-3d-flip.html

but it seems like view flipper is best for swapping two static pictures. i wasn't able to find a good view animator example other than the flippers. also, i would prefer to use images as opposed to just a circle. can someone point me in the right direction?

thanks.

Answer 1

If you're using a bitmap on a canvas to draw it

http://developer.android.com/reference/android/graphics/Canvas.html#drawBitmap(android.graphics.Bitmap, android.graphics.Matrix, android.graphics.Paint)

Use a scale matrix, the identity multiplied by the scalar of the size you want the image to be.

Answer 2

Here are two simple tutorials to help you get started with drawing basic animations including touch input: balls bouncing randomly around the screen and basic drag and drop.

In brief: You're right, ViewFlipper is really not suited for this. You want to draw on a Canvas by making your own custom View. This is the basic framework for 2D graphics. Canvases let you draw image files, solid colors and other things to the screen, while applying transformations ot them at the same time. Handling the user input (i.e. the finger on the screen) is done via the onTouchEvent(...) method, which lets you do something when the finger touches the screen, moves on the screen or lifts off. Have a play with those two tutorials, they should give you the basics.