[TOC]
我们知道，MPAndroidChart这个依赖库的图表的所有绘制都在renderer中，所有我们找到LineChartRender，找到drawCircles（）方法，这就是绘制圆点的方法，好了，现在开始修改。
1.复制LineChartRender，命名为LineChartCircleRenderer，添加代码：
/**
* 显示原点的x轴的对应的数组
*/
private static List<Integer> mCirclePointPositions = new ArrayList<>();
/**
* 设置显示哪个x轴对应的原点
*
* @param positions 显示原点的数据所在的位置的集合
*/
public static void setCirclePoints(List<Integer> positions) {
mCirclePointPositions = positions;
}修改drawCircles()方法：
/**
* 画圆点 -- x轴值对应的y值的小圆圈
*
* @param c
*/
protected void drawCircles(Canvas c) {
mRenderPaint.setStyle(Paint.Style.FILL);
float phaseY = mAnimator.getPhaseY();
mCirclesBuffer[0] = 0;
mCirclesBuffer[1] = 0;
List<ILineDataSet> dataSets = mChart.getLineData().getDataSets();
for (int i = 0; i < dataSets.size(); i++) {
ILineDataSet dataSet = dataSets.get(i);
if (!dataSet.isVisible() || !dataSet.isDrawCirclesEnabled() ||
dataSet.getEntryCount() == 0)
continue;
mCirclePaintInner.setColor(dataSet.getCircleHoleColor());
Transformer trans = mChart.getTransformer(dataSet.getAxisDependency());
mXBounds.set(mChart, dataSet);
float circleRadius = dataSet.getCircleRadius();
float circleHoleRadius = dataSet.getCircleHoleRadius();
boolean drawCircleHole = dataSet.isDrawCircleHoleEnabled() &&
circleHoleRadius < circleRadius &&
circleHoleRadius > 0.f;
boolean drawTransparentCircleHole = drawCircleHole &&
dataSet.getCircleHoleColor() == ColorTemplate.COLOR_NONE;
DataSetImageCache imageCache;
if (mImageCaches.containsKey(dataSet)) {
imageCache = mImageCaches.get(dataSet);
} else {
imageCache = new DataSetImageCache();
mImageCaches.put(dataSet, imageCache);
}
boolean changeRequired = imageCache.init(dataSet);
// only fill the cache with new bitmaps if a change is required
if (changeRequired) {
imageCache.fill(dataSet, drawCircleHole, drawTransparentCircleHole);
}
int boundsRangeCount = mXBounds.range + mXBounds.min;
for (int j = mXBounds.min; j <= boundsRangeCount; j++) {
// TODO: 2017/11/13 改动位置
if (mCirclePointPositions.contains(j)) {
Entry e = dataSet.getEntryForIndex(j);
if (e == null)
break;
mCirclesBuffer[0] = e.getX();
mCirclesBuffer[1] = e.getY() * phaseY;
trans.pointValuesToPixel(mCirclesBuffer);
if (!mViewPortHandler.isInBoundsRight(mCirclesBuffer[0]))
break;
if (!mViewPortHandler.isInBoundsLeft(mCirclesBuffer[0]) ||
!mViewPortHandler.isInBoundsY(mCirclesBuffer[1]))
continue;
Bitmap circleBitmap = imageCache.getBitmap(j);
if (circleBitmap != null) {
c.drawBitmap(circleBitmap, mCirclesBuffer[0] - circleRadius, mCirclesBuffer[1] - circleRadius, null);
}
}
}
}
}其实就是在Entry e = dataSet.getEntryForIndex(j);外包加了一层我们写的if判断，判断只有当位置是我们传入的列表的位置时，才显示。
2.复制LineChart，命名为LineCircleChart，把所有的LineChartRender替换成LineChartCircleRenderer。
public class LineCircleChart extends BarLineChartBase<LineData> implements LineDataProvider {
public LineCircleChart(Context context) {
super(context);
}
public LineCircleChart(Context context, AttributeSet attrs) {
super(context, attrs);
}
public LineCircleChart(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
protected void init() {
super.init();
mRenderer = new LineChartCircleRenderer(this, mAnimator, mViewPortHandler);
}
@Override
public LineData getLineData() {
return mData;
}
@Override
protected void onDetachedFromWindow() {
// releases the bitmap in the renderer to avoid oom error
if (mRenderer != null && mRenderer instanceof LineChartCircleRenderer) {
((LineChartCircleRenderer) mRenderer).releaseBitmap();
}
super.onDetachedFromWindow();
}
}3.使用线性图的时候使用刚改好的LineCircleChart，并调用我们在renderer中添加的方法。
//设置那几个位置的圆点显示
List<Integer> position = new ArrayList<>();
position.add(0);
position.add(3);
position.add(6);
LineChartCircleRenderer.setCirclePoints(position);注意：使用的时候请注意是否开启绘制圆点：
//绘制x轴对应的y轴数据值的圆点
lineDataSet.setDrawCircles(true);
//绘制的圆点是否是空心
lineDataSet.setDrawCircleHole(false);
//圆点的填充颜色
lineDataSet.setCircleColor(Color.BLACK);
//圆点的半径
lineDataSet.setCircleRadius(5f);特别强调：文中使用的是3.0.2版本的MPAndroid。