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Gradient color animation

What I want to achieve:

The radial gradient that starts and ends colors smoothly changes over time from one specific color to another.

What I have tried so far:

Using ObjectAnimator like this:

        searchAnimator = ObjectAnimator.ofFloat(drawThread, new Property<DrawThread, Float>(Float.TYPE, "fraction") {
            @Override
            public Float get(DrawThread object) {
                return object.fraction;
            }

            @Override
            public void set(DrawThread object, Float value) {
                object.setFraction(value);
            }
        }, 0, 1);
        searchAnimator.setDuration(maxSearchDuration);
        searchAnimator.setInterpolator(new LinearInterpolator());

This will cause DrawThread.setFraction(value);

over time. Inside the thread, I am doing the drawing Canvas

with the SurfaceView

following:

mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setDither(true);
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
radius = (int) Math.sqrt(canvas.getWidth() / 2 * canvas.getWidth() / 2 + canvas.getHeight() / 2 * canvas.getHeight() / 2);
//calculating colors for current fraction using ARGBEvaluator
int start = (int) argbEvaluator.evaluate(fraction, colors[0].start, colors[1].start);
int end = (int) argbEvaluator.evaluate(fraction, colors[0].end, colors[1].end);
//end
mPaint.setShader(new RadialGradient(canvas.getWidth() / 2, canvas.getHeight() / 2,
      radius, start, end, Shader.TileMode.CLAMP));
canvas.drawCircle(canvas.getWidth() / 2, canvas.getHeight() / 2, radius, mPaint);

Problems:

  • The gradient is not smooth. The image looks like a low color
  • The performance is very low. I am getting aprox 16 FPS on a FullHD Snapdragon 801 device.

So what I want to ask is is any help to improve performance (even in a completely different way) and improve image quality.

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2 answers


You can animate color changes in a gradient like this:



int colorFrom = ContextCompat.getColor(this, R.color.red);
int colorTo = ContextCompat.getColor(this, R.color.blue);
ValueAnimator colorAnimation = ValueAnimator.ofObject(new ArgbEvaluator(), colorFrom, colorTo);
colorAnimation.setDuration(2000);

int color1 = ContextCompat.getColor(this, R.color.red);
int color2 = ContextCompat.getColor(this, R.color.green);
GradientDrawable gradientDrawable = new GradientDrawable(
            GradientDrawable.Orientation.TOP_BOTTOM, new int[]{color1, color2});
gradientDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);

colorAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

        @Override
        public void onAnimationUpdate(ValueAnimator animator) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                gradientDrawable.setColors(new int[]{(int) animator.getAnimatedValue(), color2});
                viewWithGradientBg.setBackground(gradientDrawable);
            }
        }

    });

colorAnimation.start();
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Perhaps this piece of pseudocode helps:



private ValueAnimator colorAnimation;

  colorAnimation = ValueAnimator.ofObject(new ArgbEvaluator(), startColor, endColor); 
                                                          // you can add more colors here 

    colorAnimation.addUpdateListener(new AnimatorUpdateListener() {

        @Override
        public void onAnimationUpdate(ValueAnimator animator) {
            yourView.setBackgroundColor((Integer) animator
                    .getAnimatedValue());
        }

    });

    colorAnimation.setDuration(maxSearchDuration);
    colorAnimation.start();
}
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