move-android-view-along-path.java

        final View target = findViewById(R.id.target);

        // Create path you would like your view to follow
        Path p = new Path();
        RectF circle = new RectF(0, 0, 400f, 400f);
        p.arcTo(circle, 0, 180);
        p.arcTo(circle, 180, 180);

        final PathMeasure pm = new PathMeasure(p, false);

        // Animating from 0 to our path length
        ValueAnimator animator = ValueAnimator.ofFloat(0, pm.getLength());
        // This will hold current position
        final float[] pos = new float[2];
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                // Getting current length on the path
                float v = (float) animation.getAnimatedValue();

                // Getting current position..
                pm.getPosTan(v, pos, null);

                // ..and applying it
                target.setTranslationX(pos[0]);
                target.setTranslationY(pos[1]);
            }
        });

        animator.setDuration(3000);
        animator.setRepeatMode(ValueAnimator.RESTART);
        animator.setRepeatCount(ValueAnimator.INFINITE);
        animator.setInterpolator(new LinearInterpolator());
        animator.start();