ObjectAnimator animate LinearLayout width

In situations where there isn't a simple property getter/setter you should use ValueAnimator and perform the animation manually.

Assuming:

• v is the view you're animating
• END_WIDTH is the target width of the view in pixels.
• DURATION is the desired length of the animation in milliseconds.

Your code should look something like this:

    ValueAnimator anim = ValueAnimator.ofInt(v.getMeasuredWidth(), END_WIDTH);
    anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        @Override
        public void onAnimationUpdate(ValueAnimator valueAnimator) {
            int val = (Integer) valueAnimator.getAnimatedValue();
            ViewGroup.LayoutParams layoutParams = v.getLayoutParams();
            layoutParams.width = val;
            v.setLayoutParams(layoutParams);
        }
    });
    anim.setDuration(DURATION);
    anim.start(); 

For what it's worth this works. After you change the width on the layout params you have to reset the layout params object.

private class WidthEvaluator extends IntEvaluator {

    private View v;
    public WidthEvaluator(View v) {
        this.v = v;
    }

    @Override
    public Object evaluate(float fraction, Object startValue, Object endValue) {
        int num = (Integer)super.evaluate(fraction, startValue, endValue);
        ViewGroup.LayoutParams params = v.getLayoutParams();
        params.width = num;
        v.setLayoutParams(params);
        return num;
    }
}

// your client code
ValueAnimator.ofObject(new WidthEvaluator(box), box.getWidth(), v.getWidth()).start();

I've created a small library ViewPropertyObjectAnimator that can do that in a very simple way (and uses a similar approach to this proposed by Tomer Weller).

You could achieve this animation with (assuming the mLinearLayout is the animated View and mEndWidth is the end value of the View's width):

ViewPropertyObjectAnimator.animate(mLinearLayout).width(mEndWidth).start();

You have made a mistake

 params.weight = myWidth;

I think it is params.width not params.weight