包重新开发(package development without restarting)

 您使用错误的逻辑来绘制线，如果您调用invalidate()您将请求调用draw() ，这将重置您的画布。 
 
 试试这个版本的课程： 
 
public class BreakDownBar extends View {
    private List<Point> points = new ArrayList<>();
    private Path path = new Path();
    private Paint p = new Paint();

    public BreakDownBar(Context context) {
        super(context);
        p.setStrokeWidth(5);
        p.setStyle(Paint.Style.STROKE);
        p.setColor(Color.BLACK);
    }

    public void addPoint(Point point) {
        points.add(point);
        //this will request a call to draw(canvas) method
        invalidate();
    }

    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);
        //move to the first point in the list
        path.moveTo(points.get(0).getX(), points.get(0).getY());
        for (int i = 1; i < points.size(); i++) {
            path.lineTo(points.get(i).getX(), points.get(i).getY());
        }
        canvas.drawPath(path, p);
    }
}
 
 然后在你的代码中你可以做到 
 
BreakDownBar bar = new BreakDownBar(context);
bar.addPoint(new Point(100f, 200f))
bar.addPoint(new Point(200f, 300f))
bar.addPoint(new Point(400f, 200f))
 
 如果这对您有用，请告诉我。 

You are using a bad logic to draw the line, if you call invalidate() you will request a call to draw() and this will reset your canvas.
 
Try with this version of your class:
 
public class BreakDownBar extends View {
    private List<Point> points = new ArrayList<>();
    private Path path = new Path();
    private Paint p = new Paint();

    public BreakDownBar(Context context) {
        super(context);
        p.setStrokeWidth(5);
        p.setStyle(Paint.Style.STROKE);
        p.setColor(Color.BLACK);
    }

    public void addPoint(Point point) {
        points.add(point);
        //this will request a call to draw(canvas) method
        invalidate();
    }

    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);
        //move to the first point in the list
        path.moveTo(points.get(0).getX(), points.get(0).getY());
        for (int i = 1; i < points.size(); i++) {
            path.lineTo(points.get(i).getX(), points.get(i).getY());
        }
        canvas.drawPath(path, p);
    }
}
 
Then in your code you can simply do
 
BreakDownBar bar = new BreakDownBar(context);
bar.addPoint(new Point(100f, 200f))
bar.addPoint(new Point(200f, 300f))
bar.addPoint(new Point(400f, 200f))
 
Let me know if this works for you.