Utility class for performing common color animations on Views. (Use of `MoreObjects` can be replaced with a turnary if you really hate Guava.)

ViewUtil.java

package foo.bar.baz;

import android.animation.ArgbEvaluator;
import android.animation.ObjectAnimator;
import android.animation.TimeInterpolator;
import android.animation.ValueAnimator;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.support.annotation.ColorInt;
import android.support.annotation.FloatRange;
import android.support.annotation.NonNull;
import android.view.View;
import android.view.ViewPropertyAnimator;
import android.widget.ImageView;
import android.widget.TextView;

import com.google.common.base.MoreObjects;

public final class ViewUtil {
    private static ColorMatrixColorFilter greyscaleFilter;
    private ViewUtil() { /* Instantiation is not allowed. */ }

    /**
     * Changes the transparency of a view over time.
     * If setting to min opacity, sets visibility to GONE at the end, otherwise sets visibility to
     * VISIBLE at the start.
     * @param view The view to animate.
     * @param alpha The new alpha value.
     * @return The animation that was created.
     */
    @NonNull
    public static ViewPropertyAnimator animateAlpha(@NonNull final View view, @FloatRange(from=0.0f, to=1.0f) float alpha,
                                                    long duration, @NonNull TimeInterpolator interpolator) {
        final ViewPropertyAnimator animator = view.animate()
                .alpha(alpha)
                .setDuration(duration)
                .setInterpolator(interpolator);
        if (alpha <= 0.f) {
            animator.withEndAction(new Runnable() {
                @Override public void run() {
                    view.setVisibility(View.GONE);
                }
            });
        } else {
            animator.withStartAction(new Runnable() {
                @Override public void run() {
                    view.setVisibility(View.VISIBLE);
                }
            });
        }
        return animator;
    }

    public static void animateTextViewColor(@NonNull TextView view, @ColorInt int newColor,
                                            long duration, @NonNull TimeInterpolator interpolator) {
        final @ColorInt int oldColor = view.getCurrentTextColor();
        final ObjectAnimator animator = ObjectAnimator.ofInt(view, "textColor",
                oldColor, newColor);
        animator.setEvaluator(new ArgbEvaluator());
        animator.setDuration(duration);
        animator.setInterpolator(interpolator);
        animator.start();
    }

    public static void animateImageViewColor(@NonNull final ImageView view, @ColorInt int newColor,
                                             long duration, @NonNull TimeInterpolator interpolator) {
        final ValueAnimator animator = ValueAnimator.ofObject(
                new ArgbEvaluator(),
                MoreObjects.firstNonNull(view.getTag(), 0xFFFFFFFF),    // Default to white if no tag set
                newColor
        );

        animator.setDuration(duration);
        animator.setInterpolator(interpolator);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                final int newColor = (int) animation.getAnimatedValue();
                view.setColorFilter(newColor);
                view.setTag(newColor);
            }
        });
        animator.start();
    }

    public static synchronized ColorMatrixColorFilter getGrayscaleColorFilter() {
        if (null == greyscaleFilter) {
            final ColorMatrix matrix = new ColorMatrix();
            matrix.setSaturation(0);
            greyscaleFilter = new ColorMatrixColorFilter(matrix);
        }
        return greyscaleFilter;
    }

    /**
     * Disables an image view and applies a monochrome color filter to it.
     * @param view The view to disable.
     */
    public static void disableAndGrayOut(@NonNull ImageView view) {
        view.setEnabled(false);
        view.setColorFilter(ViewUtil.getGrayscaleColorFilter());
    }

    /**
     * Enables an image view and clears any color filter applied to it.
     * @param view The view to enable.
     */
    public static void enableAndClearFilter(@NonNull ImageView view) {
        view.setEnabled(true);
        view.clearColorFilter();
    }

    public static void setGrayAndDisable(@NonNull ImageView view, boolean disabled) {
        if (disabled) {
            disableAndGrayOut(view);
        } else {
            enableAndClearFilter(view);
        }
    }
}