Dynamically create / draw images to put in android view

Question

I\'m not sure I\'m doing this the \"right\" way, so I\'m open to other options as well. Here\'s what I\'m trying to accomplish:

I want a view which contains a graph.

Answer 1

First off, it is never a waste of time writing code if you learned something from it. :-)

There is unfortunately still no support for drawing vector images in Android. So bitmap is what you get.

I think the bit you are missing is that you can create a Canvas any time you want to draw on a bitmap. You don't have to wait for onDraw to give you one.

So at some point (from onCreate, when data changes etc), create your own Bitmap of whatever size you want.

Here is some psuedo code (not tested)

Bitmap mGraph;

void init() {
    // look at Bitmap.Config to determine config type
    mGraph = new Bitmap(width, height, config);
    Canvas c = new Canvas(mybits);
    // use Canvas draw routines to draw your graph
}

// Then in onDraw you can draw to the on screen Canvas from your bitmap.
protected void onDraw(Canvas canvas) {
    Rect dstRect = new Rect(0,0,viewWidth, viewHeight);
    Rect sourceRect = new Rect();
    // do something creative here to pick the source rect from your graph bitmap
    // based on zoom and pan 
    sourceRect.set(10,10,100,100);

    // draw to the screen
    canvas.drawBitmap(mGraph, sourceRect, dstRect, graphPaint);
}

Hope that helps a bit.