statelist - Android: How to create a StateListDrawable programmatically

Question

I have a GridView to display some objects, and visually each of the objects will have an image icon and a text label. I also want the image icon to have some "push and pop" effect when clicked, that is, when pressed, the image will move a small distance to the bottom right direction, and when released get back to its original position.

The objects (and their image icons) are from some dynamic sources. My intuition is to create a StateListDrawable for each item, which will have two states: pressed or not. For GridView item view, I would use a Button, which can accomodate a Drawable and a label, that perfectly satisfies my requirment.

I defined an item class to wrap up the original object:

public class GridItem<T> {

    public static final int ICON_OFFSET = 4;

    private StateListDrawable mIcon;
    private String mLabel;
    private T mObject;

    public Drawable getIcon() {
        return mIcon;
    }

    public void setIcon(Drawable d) {
        if (null == d) {
            mIcon = null;
        }else if(d instanceof StateListDrawable) {
            mIcon = (StateListDrawable) d;
        } else {
            InsetDrawable d1 = new InsetDrawable(d, 0, 0, ICON_OFFSET, ICON_OFFSET);
            InsetDrawable d2 = new InsetDrawable(d, ICON_OFFSET, ICON_OFFSET, 0, 0);
            mIcon = new StateListDrawable();
            mIcon.addState(new int[] { android.R.attr.state_pressed }, d2);
            mIcon.addState(StateSet.WILD_CARD, d1);
            //This won't help either: mIcon.addState(new int[]{}, d1);
        }
    }

    public String getLabel() {
        return mLabel;
    }

    public void setLabel(String l) {
        mLabel = l;
    }

    public T getObject() {
        return mObject;
    }

    public void setObject(T o) {
        mObject = o;
    }

}

Now the problem is, when I touch a grid item, the icon "moves" quite as I have expected, but it won't restore its original position when my finger lifts up leaving the item.

My question is: how to programmatically create a StateListDrawable equivalent to one inflated from an XML resource like

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true"
          android:drawable="@drawable/image_pressed" />  
    <item android:drawable="@drawable/image_normal" />
</selector>

?

Answer 1

if your drawables are just bitmaps, you could draw them programmatically, for now it should help, however I wonder what is the problem with InsetDrawable usage here, basically use prepared BitmapDrawables that are drawn programatically, you would need to modify your method to accept bitmaps b

        Bitmap bc1 = Bitmap.createBitmap(b.getWidth() + ICON_OFFSET, b.getHeight() + ICON_OFFSET, Bitmap.Config.ARGB_8888);
        Canvas c1 = new Canvas(bc1);
        c1.drawBitmap(b, 0, 0, null);
        Bitmap bc2 = Bitmap.createBitmap(b.getWidth() + ICON_OFFSET, b.getHeight() + ICON_OFFSET, Bitmap.Config.ARGB_8888);
        Canvas c2 = new Canvas(bc2);
        c2.drawBitmap(b, ICON_OFFSET, ICON_OFFSET, null);

        mIcon = new StateListDrawable();
        mIcon.addState(new int[] { android.R.attr.state_pressed },  new BitmapDrawable(bc2));
        mIcon.addState(StateSet.WILD_CARD, new BitmapDrawable(bc1));