CODEWITHSUNDEEP
androidcanvas
Ankit
Ankit

Reputation: 4644

How to optimize my code for drawing on canvas

In my android app I am drawing lots of Rectangles, Lines & Arcs which frequently change on user action.

Now what I have done is created my Paint objects inside the onDraw() method so that they remain local variables and do not cause any memory issues.

But during a code review this was pointed out as a mistake. I am told that this might slow down the drawing on canvas as new() will be called each time onDraw() is called. So I am asked to make Paint objects as class variables, initialize them only once and only change their property in onDraw() and further nullify them when the screen is closed/destroyed.

I want to ask that would this be the right thing to do or things are better the way they already are because I did not find the UI slow on my screen and I doubt that this might be an unnecessary change.

Please provide suggestions.

Upvotes: 1

Views: 1183

Answers (2)

sradforth
sradforth

Reputation: 2186

Yes you should use Paint as a class member. The size of Paint is probably small, not that I've checked mind, but it is merely a settings container.

Allocating any objects in Draw is a bad idea as it can cause the GC to kick in and cause a very noticeable glitch, especially on older devices.

Upvotes: 1

David M
David M

Reputation: 2541

I have found that there is a lag for Paint paint = new Paint(); during onDraw() processing. I now make paint a class variable, and in onDraw() simply modify the attributes of the already-constructed Paint variable.

    public void onDraw(Canvas canvas) {
        mPaint.setColor(Color.BLUE);
        ...
        mPaint.setStyle(Style.FILL); 
        ...
    }

Upvotes: 2

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