How to prepare curve translate animation for android?

Question

There are 4 types of animations in android - rotate, alpha,scale and translate. I want to prepare curved translate animation.

Is it possible.?

Answer 1

What Android version do you use? Since API level 11 you can use custom Animators which can easily implement your curve translation.

If you use a version below that there is afaik only the possibility to manually concatenate multiple linear translations using the translate animation and setting animation listeners

EDIT:

Example:

View view;
animator = ValueAnimator.ofFloat(0, 1); // values from 0 to 1
animator.setDuration(5000); // 5 seconds duration from 0 to 1
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener()
{
    @Override
    public void onAnimationUpdate(ValueAnimator animation) {
        float value = ((Float) (animation.getAnimatedValue()))
                    .floatValue();
        // Set translation of your view here. Position can be calculated
        // out of value. This code should move the view in a half circle.
        view.setTranslationX((float)(200.0 * Math.sin(value*Math.PI)));
        view.setTranslationY((float)(200.0 * Math.cos(value*Math.PI)));
    }
});

I hope it works. Just copied & pasted (and shortened and changed) the code from one of my apps.

Answer 2

Here are the animators I use:

Purpose: Move View "view" along Path "path"

Android v21+:

// Animates view changing x, y along path co-ordinates
ValueAnimator pathAnimator = ObjectAnimator.ofFloat(view, "x", "y", path)

Android v11+:

// Animates a float value from 0 to 1 
ValueAnimator pathAnimator = ValueAnimator.ofFloat(0.0f, 1.0f);

// This listener onAnimationUpdate will be called during every step in the animation
// Gets called every millisecond in my observation  
pathAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

float[] point = new float[2];

@Override
    public void onAnimationUpdate(ValueAnimator animation) {
        // Gets the animated float fraction
        float val = animation.getAnimatedFraction();

        // Gets the point at the fractional path length  
        PathMeasure pathMeasure = new PathMeasure(path, true);
        pathMeasure.getPosTan(pathMeasure.getLength() * val, point, null);

        // Sets view location to the above point
        view.setX(point[0]);
        view.setY(point[1]);
    }
});

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