推荐一款简易的折线图，效果如下

lineview.png

使用比较简单

先去这里把View源码下载下来放入到自己的view目录 源码地址
在布局中添加:（com.sp.view.LineView根据自己放代码的位置修改）

<com.sp.view.LineView
        android:id="@+id/lineView"
        android:layout_width="match_parent"
        android:layout_height="350px" />

使用:

((LineView) headView.findViewById(R.id.lineView)).setData(
                        Arrays.asList("02-1","02-1","02-1","02-1","02-1","02-1","02-1"),
                        Arrays.asList(1.0f,2.0f,3.0f,4.0f,5.0f,6.0f,7.0f));

可以自己修改的自定义属性

    /**
     * 底部间隙大小
     */
    private float bootomDes = 10;
    /**
     * 左边间隙大小
     */
    private float leftDes = 10;
    /**
     * 纵坐标固定值分为几个间隔 默认6个
     */
    private int yGapSize = 6;
    /**
     * 背景色
     */
    private int bgColor = 0x66000000;
    /**
     * 刻度值字体大小
     */
    private int scaleTxtSize = 13;
    /**
     * 刻度字体颜色
     */
    private int scaleTxtColor = 0xffffffff;
    /**
     * 折线颜色
     */
    private int lineColor = 0xff2791dc;
    /**
     * 折线粗细层度
     */
    private int lindWidth = 2;

实现细节

onMeasure宽度为屏幕宽度或者用户设置值，高度为用户设置值否则固定为300dp

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        width = MeasureSpec.getSize(widthMeasureSpec);

        switch (heightMode) {
            case MeasureSpec.AT_MOST:
                height = dp2px(getContext(), 350);
                break;
            case MeasureSpec.EXACTLY:
                height = heightSize;
                break;
        }
        setMeasuredDimension(width, height);
    }

onDraw通过绘制底部文字，背景以及背景框，左部文字和画点和连接先

        drawBottomText(canvas);
        drawRectLineAndBg(canvas);
        drawLeftText(canvas);
        drawPointAndLine(canvas);

    private void drawPointAndLine(Canvas canvas) {
        if (xList==null||xList.size()==0){
            return;
        }
        for (int i = 0; i < yList.size(); i++) {
            x= getXPix(i);
            y= getYPix(yList.get(i));
            if (i<=yList.size()-2){
                canvas.drawLine(x,y,getXPix(i+1),getYPix(yList.get(i+1)),linePaint);
            }
            canvas.drawCircle(x, y, (float) this.DOT_OUTER_CIR_RADIUS, bigCirPaint);
            canvas.drawCircle(x, y, (float) this.DOT_INNER_CIR_RADIUS, smallCirPaint);
        }
    }

    private void drawLeftText(Canvas canvas) {
        if (yList == null || yList.size() == 0) {
            return;
        }
        canvas.save();
         max = getUpOrDownNum(getMaxOrMinNum(yList, true), 0, true);
         min = getUpOrDownNum(getMaxOrMinNum(yList, false), 0, false);
        incressFloat = increaseBy6(max, min);
        for (int i = 0; i < yGapSize+1; i++) {
            yShalfList.add(getRoundHalfUp(getUpOrDownNum(getMaxOrMinNum(yList,false),0,false)+(incressFloat*i),1));
        }
        canvas.translate((width - showLineAreaWidth) / 2, showLineAreaHeight);
        yGap = showLineAreaHeight/(yGapSize+2); //2顶部和尾部空出一个格子
        for (Float aFloat : yShalfList) {
            canvas.translate(0,-yGap);
            canvas.drawText(aFloat+" -",0,0,scaleTxtPaint);
        }
        canvas.restore();
    }

    private void drawRectLineAndBg(Canvas canvas) {
        canvas.drawLine(width - showLineAreaWidth, 0, width - showLineAreaWidth, showLineAreaHeight, linePaint);
        canvas.drawLine(width - showLineAreaWidth, showLineAreaHeight, width, showLineAreaHeight, linePaint);
        canvas.drawRect(width - showLineAreaWidth, 0, width, showLineAreaHeight, bgPaint);
    }

    private void drawBottomText(Canvas canvas) {
        if (xList == null || xList.size() == 0) {
            return;
        }
        canvas.save();
        canvas.translate(width - showLineAreaWidth, showLineAreaHeight + ((bootomDes + bottomTxtHeight) / 2) + bottomTxtHeight / 2);
        xGap = showLineAreaWidth / (xList.size() + 1);
        for (String aFloat : xList) {
            canvas.translate(xGap, 0);
            canvas.drawText(aFloat, 0, 0, scaleTxtPaint);
        }
        canvas.restore();
    }

具体查看源码吧 源码地址