Canvas画图设置渐变色

1、线形图设置填充色为渐变色方法：

/**
 * Draws the provided path in filled mode with the provided drawable.
 *
 * @param c
 * @param filledPath
 * @param drawable
 */
protected void drawFilledPath(Canvas c, Path filledPath, Drawable drawable) {

    if (clipPathSupported()) {

        c.save();
        c.clipPath(filledPath);

        drawable.setBounds((int) mViewPortHandler.contentLeft(),
                (int) mViewPortHandler.contentTop(),
                (int) mViewPortHandler.contentRight(),
                (int) mViewPortHandler.contentBottom());
        drawable.draw(c);

        c.restore();//在canvas上设置渐变色图片
    } else {
        throw new RuntimeException("Fill-drawables not (yet) supported below API level 18, " +
                "this code was run on API level " + Utils.getSDKInt() + ".");
    }
}

渐变色图片：

最终效果:

具体代码参见：MPChartLibrary开源项目中的LineRadarRenderer.class类

2、为canvas背景设置渐变色

 final Drawable drawable = dataSet.getFillDrawable();
            c.save();
            drawable.setBounds((int) mViewPortHandler.contentLeft(),
                    (int) mViewPortHandler.contentTop(),
                    (int) mViewPortHandler.contentRight(),
                    (int) mViewPortHandler.contentBottom());
            drawable.draw(c);
//            mRenderPaint.setColor(dataSet.getColor());
            for (int j = 0; j < buffer.size(); j += 4) {

                if (!mViewPortHandler.isInBoundsLeft(buffer.buffer[j + 2]))
                    continue;

                if (!mViewPortHandler.isInBoundsRight(buffer.buffer[j]))
                    break;
                c.drawRect(buffer.buffer[j], buffer.buffer[j + 1], buffer.buffer[j + 2],
                        buffer.buffer[j + 3], mRenderPaint);
                if (drawBorder) {
                    c.drawRect(buffer.buffer[j], buffer.buffer[j + 1], buffer.buffer[j + 2],
                            buffer.buffer[j + 3], mBarBorderPaint);
                }
            }
            c.restore();

效果图：看后面背景

代码初步是在BarChartRenderer.class中做了修改。并且在

BaseDataSet.class中添加了两个接口

public Drawable getFillDrawable() {
    return mFillDrawable;
}

/**
 * Sets the drawable to be used to fill the area below the line.
 *
 * @param drawable
 */
@TargetApi(18)
public void setFillDrawable(Drawable drawable) {
    this.mFillDrawable = drawable;
}

大致是这样的修改的。具体可再优化。

3、为柱状图每个元素设置渐变色

for (int j = 0; j < buffer.size(); j += 4) {

                if (!mViewPortHandler.isInBoundsLeft(buffer.buffer[j + 2]))
                    continue;

                if (!mViewPortHandler.isInBoundsRight(buffer.buffer[j]))
                    break;

                //设置柱状图的颜色为渐变色
                LinearGradient linearGradient = new LinearGradient(0, 0, 0, 2000,Color.GREEN, Color.WHITE, Shader.TileMode.CLAMP);
                mRenderPaint.setShader(linearGradient);//目标Paint即为绘制柱的Paint

                c.drawRect(buffer.buffer[j], buffer.buffer[j + 1], buffer.buffer[j + 2],
                        buffer.buffer[j + 3], mRenderPaint);

                if (drawBorder) {
                    c.drawRect(buffer.buffer[j], buffer.buffer[j + 1], buffer.buffer[j + 2],
                            buffer.buffer[j + 3], mBarBorderPaint);
                }
            }

效果图：

代码初步是在BarChartRenderer.class中做了修改。