项目中有个需求，使用的是折线图，但是要求当y轴的值为0的时候 不与前后的点进行连接，但是MpChart 默认是完全连接的。

image.png

我需要的效果是这样的

device-2019-06-09-175642.png

下面说实现方式：

 LineDataSet支持设置渲染模式  默认是以下几种（其中第一个是笔者自己添加的，为了实现图2的效果）
public enum Mode {
    /**
     * 这个zero是我根据需求自己添加的
     */
    LINEAR_DISCONNECT_ZERO,
    LINEAR,
    STEPPED,
    CUBIC_BEZIER,
    HORIZONTAL_BEZIER
}

图表的绘制在LineChartRenderer类中，

 switch (dataSet.getMode()) {
        default:

        case LINEAR:
        case STEPPED:
            drawLinear(c, dataSet);
            break;
        case LINEAR_DISCONNECT_ZERO:
            drawLinearDisConnectZero(c,dataSet);
            break;
        case CUBIC_BEZIER:
            drawCubicBezier(dataSet);
            break;

        case HORIZONTAL_BEZIER:
            drawHorizontalBezier(dataSet);
            break;


    }

自己创建的绘制方法 其实重点就是 y值为0的话跳出 绘制 （ //实现这个效果重点就是这行代码
if (e1.getY()==0||e2.getY()==0) continue;）

     private void drawLinearDisConnectZero(Canvas c, @NonNull ILineDataSet dataSet) {

    int entryCount = dataSet.getEntryCount();

    final int pointsPerEntryPair = 2;

    Transformer trans = mChart.getTransformer(dataSet.getAxisDependency());

    float phaseY = mAnimator.getPhaseY();

    mRenderPaint.setStyle(Paint.Style.STROKE);

    Canvas canvas = c;

    mXBounds.set(mChart, dataSet);

          // if drawing filled is enabled
      //        if (dataSet.isDrawFilledEnabled() && entryCount > 0) {
    //            drawLinearFill(c, dataSet, trans, mXBounds);
        //        }

    // more than 1 color
    if (dataSet.getColors().size() > 1) {

        if (mLineBuffer.length <= pointsPerEntryPair * 2)
            mLineBuffer = new float[pointsPerEntryPair * 4];

        for (int j = mXBounds.min; j <= mXBounds.range + mXBounds.min; j++) {

            Entry e = dataSet.getEntryForIndex(j);
            if (e == null) continue;

            mLineBuffer[0] = e.getX();
            mLineBuffer[1] = e.getY() * phaseY;

            if (j < mXBounds.max) {

                e = dataSet.getEntryForIndex(j + 1);

                if (e == null) break;


                    mLineBuffer[2] = e.getX();
                    mLineBuffer[3] = e.getY() * phaseY;


            } else {
                mLineBuffer[2] = mLineBuffer[0];
                mLineBuffer[3] = mLineBuffer[1];
            }

            trans.pointValuesToPixel(mLineBuffer);

            if (!mViewPortHandler.isInBoundsRight(mLineBuffer[0]))
                break;

            // make sure the lines don't do shitty things outside
            // bounds
            if (!mViewPortHandler.isInBoundsLeft(mLineBuffer[2])
                    || (!mViewPortHandler.isInBoundsTop(mLineBuffer[1]) && !mViewPortHandler
                    .isInBoundsBottom(mLineBuffer[3])))
                continue;

            // get the color that is set for this line-segment
            mRenderPaint.setColor(dataSet.getColor(j));

            canvas.drawLines(mLineBuffer, 0, pointsPerEntryPair * 2, mRenderPaint);
        }

    } else { // only one color per dataset

        if (mLineBuffer.length < Math.max((entryCount) * pointsPerEntryPair, pointsPerEntryPair) * 2)
            mLineBuffer = new float[Math.max((entryCount) * pointsPerEntryPair, pointsPerEntryPair) * 4];

        Entry e1, e2;

        e1 = dataSet.getEntryForIndex(mXBounds.min);

        if (e1 != null) {


            int j = 0;
            for (int x = mXBounds.min; x <= mXBounds.range + mXBounds.min; x++) {

                e1 = dataSet.getEntryForIndex(x == 0 ? 0 : (x - 1));
                e2 = dataSet.getEntryForIndex(x);

            //实现这个效果重点就是这行代码
                if (e1.getY()==0||e2.getY()==0) continue;
                if (e1 == null || e2 == null) continue;

                mLineBuffer[j++] = e1.getX();
                mLineBuffer[j++] = e1.getY() * phaseY;



                mLineBuffer[j++] = e2.getX();
                mLineBuffer[j++] = e2.getY() * phaseY;
            }

            if (j > 0) {
                trans.pointValuesToPixel(mLineBuffer);

                final int size = Math.max((mXBounds.range + 1) * pointsPerEntryPair, pointsPerEntryPair) * 2;

                mRenderPaint.setColor(dataSet.getColor());

                    canvas.drawLines(mLineBuffer, 0, size, mRenderPaint);

            }
        }
    }

    mRenderPaint.setPathEffect(null);


}