首先声明，此自定义LineChart并非本人定义，而是在他人（io.github.kntryer.linechart）基础上修改的，因原来的LineChart如果点只有两三个点的时候折线会超出下边界，我修改之后则不会再出现这种情况。 同时我给折线图添加了上下padding使图标更加美观。看效果。

LineChart.java:
public class LineChart extends View {

    private int mWidth, mHeight;//View 的宽和高

    private float mFontSize = 12;//字体的大小
    private float mStrokeWidth = 1.5f;//线条的宽度
    private float mPointRadius = 2;//点的半径
    private int mDateTextColor = Color.parseColor("#cfcfcf");//日期字体颜色
    private int mDarkColor = Color.parseColor("#5b7fdf");//点、线的颜色(深色)
    private int mLightColor = Color.parseColor("#d5d8f7");//点、线的颜色(浅色)
    private int mShapeColor = Color.parseColor("#f3f6fd");//阴影的颜色

    private String[] mXItems;//X轴的文字
    private int[] mPoints;//点的数组，-1表示该日还没到
    private int mLength = 7;//最大比例

    private Paint mDatePaint = new Paint();//日期画笔
    private Paint mPointPaint = new Paint();//点画笔
    private Paint mLinePaint = new Paint();//线条画笔
    private Paint mShapePaint = new Paint();//阴影部分画笔

    private int max = 7;
    private Context mContext;

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

    public LineChart(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LineChart(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mContext = context;
        TypedArray typedArray = mContext.getTheme().obtainStyledAttributes(attrs, R.styleable.LineChart, 0, 0);
        try {
            mDateTextColor = typedArray.getColor(R.styleable.LineChart_DateTextColor, mDateTextColor);
            mDarkColor = typedArray.getColor(R.styleable.LineChart_DarkColor, mDarkColor);
            mLightColor = typedArray.getColor(R.styleable.LineChart_LightColor, mLightColor);
            mShapeColor = typedArray.getColor(R.styleable.LineChart_ShapeColor, mShapeColor);
            mFontSize = typedArray.getDimensionPixelSize(R.styleable.LineChart_FontSize,
                    (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, mFontSize, mContext.getResources().getDisplayMetrics()));
            mStrokeWidth = typedArray.getDimensionPixelSize(R.styleable.LineChart_StrokeWidth,
                    (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, mStrokeWidth, mContext.getResources().getDisplayMetrics()));
            mPointRadius = typedArray.getDimensionPixelSize(R.styleable.LineChart_PointRadius,
                    (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, mPointRadius, mContext.getResources().getDisplayMetrics()));
        } finally {
            typedArray.recycle();
        }

        initPaint();
    }

    private void initPaint() {
        //日期画笔
        mDatePaint.setTextSize(mFontSize);
        mDatePaint.setColor(mDateTextColor);
        //点画笔
        mPointPaint.setTextSize(mFontSize);
        mPointPaint.setColor(mDarkColor);
        //线画笔
        mLinePaint.setAntiAlias(true);
        mLinePaint.setStrokeWidth(mStrokeWidth);//设置线条宽度
        mLinePaint.setStyle(Paint.Style.FILL);
        mLinePaint.setColor(mDarkColor);
        //阴影部分画笔
        mShapePaint.setAntiAlias(true);
        mShapePaint.setStyle(Paint.Style.FILL);
        mShapePaint.setColor(mShapeColor);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        mWidth = widthSize;
        mHeight = heightSize;
        if (heightMode == MeasureSpec.AT_MOST) {
            mHeight = mWidth / 7 * 7;
        }
        setMeasuredDimension(mWidth, mHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        if (mXItems == null) {
            mXItems = new String[]{"日", "一", "二", "三", "四", "五", "六"};
            mPoints = new int[]{0, -1, -1, -1, -1, -1, -1};
            mLength = mXItems.length;
        }

        //最大比例
        for (int i = 0; i < mLength; i++) {
            if (mPoints[i] > max) {
                max = mPoints[i];
            }
        }
        //原点坐标
        int xOrigin = (int) (0.25 * mWidth / mLength);
        int yOrigin = (int) (mHeight - 3 * mFontSize);
        // X轴
        canvas.drawLine(xOrigin, yOrigin, mWidth - xOrigin, yOrigin, mLinePaint);
        Path xpath = new Path();
        xpath.moveTo(mWidth - xOrigin - mFontSize / 3, yOrigin + mFontSize / 3);
        xpath.lineTo(mWidth - xOrigin, yOrigin);
        xpath.lineTo(mWidth - xOrigin - mFontSize / 3, yOrigin - mFontSize / 3);
        xpath.close();
        canvas.drawPath(xpath, mLinePaint);
        // Y轴
        canvas.drawLine(xOrigin, yOrigin, xOrigin, mFontSize, mLinePaint);
        Path ypath = new Path();
        ypath.moveTo(xOrigin - mFontSize / 3, mFontSize + mFontSize / 3);
        ypath.lineTo(xOrigin, mFontSize);
        ypath.lineTo(xOrigin + mFontSize / 3, mFontSize + mFontSize / 3);
        ypath.close();
        canvas.drawPath(ypath, mLinePaint);


        int[] xPoints = new int[mLength];//x轴的刻度集合
        int[] yPoints = new int[mLength];//y轴的刻度集合

        for (int i = 0; i < mLength; i++) {
            //获取点的坐标
            xPoints[i] = (int) ((i + 0.5) * (mWidth / mLength));
            yPoints[i] = (int) ((max - (mPoints[i] == -1 ? 0 : mPoints[i])) * ((mHeight - 6 * mFontSize) / max));

            if (i > 0) {
                //画一个实心梯形,阴影部分
                Path path = new Path();
                path.moveTo(xPoints[i - 1], yOrigin - mStrokeWidth);
                path.lineTo(xPoints[i - 1], yPoints[i - 1] + 3 * mFontSize - mStrokeWidth);
                path.lineTo(xPoints[i], yPoints[i] + 3 * mFontSize - mStrokeWidth);
                path.lineTo(xPoints[i], yOrigin - mStrokeWidth);
                path.close();
                canvas.drawPath(path, mShapePaint);
            }
            //画出日期
            canvas.drawText(mXItems[i], (int) ((i + 0.5) * mWidth / mLength) - mFontSize / 2, mHeight - mFontSize, mDatePaint);
        }

        for (int i = 0; i < mLength; i++) {
            if (mPoints[i] == -1) {
                mLinePaint.setColor(mLightColor);
                mPointPaint.setColor(mLightColor);
            } else {
                mLinePaint.setColor(mDarkColor);
                mPointPaint.setColor(mDarkColor);
            }
            if (i > 0) {
                //画连线
                canvas.drawLine(xPoints[i - 1], yPoints[i - 1] + 3 * mFontSize, xPoints[i], yPoints[i] + 3 * mFontSize, mLinePaint);
            }
            //画点的数值
            canvas.drawText(String.valueOf(mPoints[i]).equals("-1") ? " " : String.valueOf(mPoints[i]), xPoints[i] - mFontSize / 2, yPoints[i] + 2 * mFontSize, mPointPaint);
        }

        for (int i = 0; i < mLength; i++) {
            if (mPoints[i] == -1) {
                mLinePaint.setColor(mLightColor);
                mPointPaint.setColor(mLightColor);
            } else {
                mLinePaint.setColor(mDarkColor);
                mPointPaint.setColor(mDarkColor);
            }
            //画点
            if (!(yOrigin ==( 3 * mFontSize + yPoints[i])))
                canvas.drawCircle(xPoints[i], yPoints[i] + 3 * mFontSize, mPointRadius, mPointPaint);
        }
    }

    public void setData(List<LineChartData> dataList) {
        mLength = dataList.size();
        if (mLength > 0) {
            mXItems = new String[mLength];
            mPoints = new int[mLength];
            for (int i = 0; i < mLength; i++) {
                mPoints[i] = dataList.get(i).getPoint();
                mXItems[i] = dataList.get(i).getItem();
            }
        }
        invalidate();
    }
}

LineChartData.java:
public class LineChartData {

    private int point;
    private String item;

    public int getPoint() {
        return point;
    }

    public void setPoint(int point) {
        this.point = point;
    }

    public String getItem() {
        return item;
    }

    public void setItem(String item) {
        this.item = item;
    }
}
main_activity.xml
<io.github.kntryer.linechart.LineChart
    android:id="@+id/line_chart_week"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:background="@color/white"
    app:DarkColor="@color/blue_dark"
    app:LightColor="@color/blue"
    app:ShapeColor="@color/blue_light" />
MainActivity.java

public class MainActivity extends AppCompatActivity {

    private LineChart mWeekLineChart;

    private String[] mWeekItems = new String[]{"一", "二", "三","四","五","六"};
    private int[] mWeekPoints = new int[]{60, 100, 111,300, 298, -1};


    private List<LineChartData> dataList1 = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mWeekLineChart = (LineChart) findViewById(R.id.line_chart_week);

        for (int i = 0; i < mWeekItems.length; i++) {
            LineChartData data = new LineChartData();
            data.setItem(mWeekItems[i]);
            data.setPoint(mWeekPoints[i]);
            dataList1.add(data);
        }
        mWeekLineChart.setData(dataList1);
    }

}

    以上只是我个人根据项目需要进行的简单改造，欢迎交流指教。

    源码在这：http://download.csdn.net/detail/qq_32371277/9873522