GlowButton.java

package mrcpp.custombutton;

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.os.Build;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.animation.AlphaAnimation;
import android.widget.FrameLayout;
import android.widget.TextView;

public class GlowButton extends FrameLayout implements ViewTreeObserver.OnGlobalLayoutListener {

    @SuppressWarnings("unused")
    private static final String TAG = GlowButton.class.getSimpleName();

    private static final int ANIMATION_TIME = 500;

    public static final int GLOWING_COLOR = Color.parseColor("#fdb528");

    private static final int MARGIN = dp2px(8);

    private GlowView glowView;

    public TextView button;

    public GlowButton(Context context) {
        super(context);
        init(null);
    }

    public GlowButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs);
    }

    public GlowButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(attrs);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @SuppressWarnings("unused")
    public GlowButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init(attrs);
    }

    private void init(@Nullable AttributeSet attrs) {
        setBackgroundResource(0);

        glowView = new GlowView(getContext());
        glowView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        glowView.setVisibility(INVISIBLE);

        button = new TextView(getContext(), attrs);
        button.getViewTreeObserver().addOnGlobalLayoutListener(this);
        button.setVisibility(VISIBLE);
        addView(button);
        ((MarginLayoutParams) button.getLayoutParams()).setMargins(MARGIN, MARGIN, MARGIN, MARGIN);
    }

    private static int dp2px(int dp) {
        float density = Resources.getSystem().getDisplayMetrics().density;
        return Math.round(dp * density);
    }

    @Override
    public void onGlobalLayout() {
        int width = button.getWidth();
        int height = button.getHeight();
        if (width != 0 || height != 0) {
            button.getViewTreeObserver().removeOnGlobalLayoutListener(this);
            LayoutParams params = new LayoutParams(
                    width + 2 * MARGIN,
                    height + 2 * MARGIN
            );
            params.gravity = Gravity.CENTER;
            glowView.setLayoutParams(params);
            addView(glowView, 0);
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                animateGlowing(0f, 1f);
                break;
            case MotionEvent.ACTION_UP:
                animateGlowing(1f, 0f);
                break;
        }
        return super.dispatchTouchEvent(event);
    }

    private void animateGlowing(float from, float to) {
        AlphaAnimation animation = new AlphaAnimation(from, to);
        animation.setDuration(ANIMATION_TIME);
        animation.setFillAfter(true);
        glowView.startAnimation(animation);
        if (glowView.getVisibility() != VISIBLE) {
            glowView.setVisibility(VISIBLE);
        }
    }

    private static class GlowView extends View {

        private Paint paint;

        private RectF rect;

        public GlowView(Context context) {
            super(context);
            init();
        }

        public GlowView(Context context, AttributeSet attrs) {
            super(context, attrs);
            init();
        }

        public GlowView(Context context, AttributeSet attrs, int defStyleAttr) {
            super(context, attrs, defStyleAttr);
            init();
        }

        @TargetApi(Build.VERSION_CODES.LOLLIPOP)
        @SuppressWarnings("unused")
        public GlowView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
            super(context, attrs, defStyleAttr, defStyleRes);
            init();
        }

        private void init() {
            paint = new Paint();
            paint.setMaskFilter(new BlurMaskFilter(dp2px(8), BlurMaskFilter.Blur.NORMAL));
            paint.setColor(GLOWING_COLOR);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            if (rect == null) {
                rect = new RectF(MARGIN, MARGIN, getWidth() - MARGIN, getHeight() - MARGIN);
            }
            canvas.drawRoundRect(rect, dp2px(12), dp2px(12), paint);
        }
    }
}