How to programmatically create background for LinearLayout

Question

I have a LinearLayout which I would like to set a background programmatically. This background should be very simple, just two rectangles one next to each other. The width of the rectangles is only known at runtime. What would be the best way?

    ShapeDrawable done = new ShapeDrawable(new RectShape());
    done.setBounds(new Rect(0, 0, 0, 0));
    done.getPaint().setColor(Color.GREEN);

    ShapeDrawable remaining = new ShapeDrawable(new RectShape());
    remaining.setBounds(new Rect(20, 0, 0, 0));
    remaining.getPaint().setColor(Color.RED);

    LayerDrawable composite = new LayerDrawable(new Drawable[]{remaining, done});
    weightRow.setBackgroundDrawable(composite);

I have tried to create a compound drawable like this, where I've expected the remaining rectangle to start at position 20, but it just fills the whole layout.

I haven't worked with LayerDrawable much/in a while, but from what I remember, drawable containers like LayerDrawable may maintain or consolidate state among all the drawables in that container (like bounds). — Karakuri
– Karakuri, Commented May 21, 2013 at 7:04

Martin Petransky · Accepted Answer · 2013-05-21 08:23:25Z

1

I'll answer my own question. After reading more posts I've realized, that simulating the android:top, left, ... from xml drawable, you should use the setLayerInset(int index, int l, int t, int r, int b) of the LayerDrawable on the layer you want to shift.

ShapeDrawable done = new ShapeDrawable();
done.getPaint().setColor(Color.GREEN);

ShapeDrawable remaining = new ShapeDrawable(new RectShape());
remaining.getPaint().setColor(Color.RED);

LayerDrawable composite = new LayerDrawable(new Drawable[]{done, remaining});
composite.setLayerInset(1, 0, 0, 100, 0);

layout.setBackgroundDrawable(composite);

answered May 21, 2013 at 8:23

Martin Petransky

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Karakuri · Accepted Answer · 2013-05-20 21:57:20Z

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You can make a custom class that extends ShapeDrawable. Implement the onDraw() method to define how it should draw itself; you cant programmatically draw your rectangular regions using the Canvas and Paint APIs. You can then define a method to set the widths of those regions at runtime.

In your Activity, make a new instance of this class and call setBackgroundDrawable() on the LinearLayout.

answered May 20, 2013 at 21:57

Karakuri

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3 Comments

Martin Petransky Over a year ago

Hi, thanks for the answer, I've already tried that, but the trouble is that it scales the border between the rectangles so it looks blurry and i want a nice sharp edge.

Karakuri Over a year ago

Wouldn't that have to do with your drawing code? I can't think of a better way to accomplish what you want, unless you just put two Views inside a LinearLayout and change their layout weights at runtime (which is much more expensive as it requires an entire traversal of the view hierarchy to re-measure and layout the views before the redraw, whereas my suggestion only involves the redraw)

Martin Petransky Over a year ago

Its a scaling issue i believe, the border between the rectangles is lets say antialiased.. Anyway.. I have the screen width, so the scaling on x-axis won't happen.. So I'll make it that way. But i would still like to see comment on my question. Shouldn't it work ? I believe it should.

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