CODEWITHSUNDEEP
androidandroid-canvasandroid-viewandroid-drawable
jion
jion

Reputation: 127

Android : How can I keep all drawings?

I want to draw some lines in android. I use SampleView class and it's onDraw, like this :

private  class SampleView extends View {

        public SampleView(Context context) {
        super(context);
        setFocusable(true);
        }
@Override
protected void onDraw(Canvas canvas) {
        p.setAntiAlias(true);
        p.setColor(Color.RED);
        p.setStyle(Paint.Style.STROKE); 
        p.setStrokeWidth(5);
        canvas.drawLine(x0, y0, x1, y1, p);
            }
}

my x0,x1,y0,y1 changes in every time that I call sv.invalidate(). every time that it is drawing new line, my previous line is cleared ... but I want to keep all lines. How can I do this?

Upvotes: 1

Views: 122

Answers (1)

Jay Snayder
Jay Snayder

Reputation: 4338

You should keep track of the lines within a Path component. Add to the path when you have a new line to draw. Then you can draw the path within the onDraw() or clear the path when you need to for whatever reason.

Path | Android Developers

One example might be something like this:

public void onDraw(Canvas canvas) 
{
    Path path = new Path();
    boolean isFirstPoint = true;
    for(Point point : points)
    {
        if(isFirstPoint)
        {
            isFirstPoint = false;
            path.moveTo(point.x, point.y);
        }
        else
        {
            path.lineTo(point.x, point.y);
        }
    }

    canvas.drawPath(path, paint);
}

But, of course, there are many ways to accomplish this. The onDraw method is meant to update frequently and draws what you tell it, you have to keep state.

Upvotes: 1

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