tasks/src/main/java/com/faizmalkani/floatingactionbutton/FloatingActionButton.java

package com.faizmalkani.floatingactionbutton;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import org.tasks.R;

public class FloatingActionButton extends View {

    private final Paint mButtonPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final Paint mDrawablePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Bitmap mBitmap;
    private int mColor;

    public FloatingActionButton(Context context) {
        this(context, null);
    }

    public FloatingActionButton(Context context, AttributeSet attributeSet) {
        this(context, attributeSet, 0);
    }

    public FloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.FloatingActionButton);
        mColor = a.getColor(R.styleable.FloatingActionButton_tint, Color.WHITE);
        mButtonPaint.setStyle(Paint.Style.FILL);
        mButtonPaint.setColor(mColor);
        float radius, dx, dy;
        radius = a.getFloat(R.styleable.FloatingActionButton_shadowRadius, 10.0f);
        dx = a.getFloat(R.styleable.FloatingActionButton_shadowDx, 0.0f);
        dy = a.getFloat(R.styleable.FloatingActionButton_shadowDy, 3.5f);
        int color = a.getInteger(R.styleable.FloatingActionButton_shadowColor, Color.argb(100, 0, 0, 0));
        mButtonPaint.setShadowLayer(radius, dx, dy, color);

        Drawable drawable = a.getDrawable(R.styleable.FloatingActionButton_drawable);
        if (null != drawable) {
            mBitmap = ((BitmapDrawable) drawable).getBitmap();
        }
        setWillNotDraw(false);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        }
    }

    public static int darkenColor(int color) {
        float[] hsv = new float[3];
        Color.colorToHSV(color, hsv);
        hsv[2] *= 0.8f;
        return Color.HSVToColor(hsv);
    }

    public void setColor(int color) {
        mColor = color;
        mButtonPaint.setColor(mColor);
        invalidate();
    }

    public void setDrawable(Drawable drawable) {
        mBitmap = ((BitmapDrawable) drawable).getBitmap();
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawCircle(getWidth() / 2, getHeight() / 2, (float) (getWidth() / 2.6), mButtonPaint);
        if (null != mBitmap) {
            canvas.drawBitmap(mBitmap, (getWidth() - mBitmap.getWidth()) / 2,
                    (getHeight() - mBitmap.getHeight()) / 2, mDrawablePaint);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int color;
        if (event.getAction() == MotionEvent.ACTION_UP) {
            color = mColor;
        } else {
            color = darkenColor(mColor);
        }
        mButtonPaint.setColor(color);
        invalidate();
        return super.onTouchEvent(event);
    }
}