grunk grunk - 5 months ago 21
Android Question

How to define a pixel independent height in an onDraw() method

I have extended View to build a custom widget. I would like to define the height of the widget with an independ pixel unit.
I think it could be done by multiplying the pixel density by the desired height , but i don't know how to do that.

What i have so far (minimized) :

public class Timeline extends View
{

@Override
protected void onDraw(Canvas canvas) {
//super.onDraw(canvas);
int canvasWidth = canvas.getWidth();
this.widgetWith = canvasWidth;


this.setBackgroundGradientNoVideo();
RectF rect = new RectF();
rect.set(0, 0, canvasWidth, 50);
//Dessin d'un rectangle de fond
canvas.drawRoundRect(rect, 10, 10, this.paint);

}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// TODO Auto-generated method stub
//super.onMeasure(widthMeasureSpec, 50);
this.setMeasuredDimension(widthMeasureSpec, 50);
this.widgetWith = MeasureSpec.getSize(widthMeasureSpec);
}
}


So i would like to change the lines

this.setMeasuredDimension(widthMeasureSpec, 50);


and

rect.set(0, 0, canvasWidth, 50);


To something pixel independent.

Thanks

Answer

multiply your pixel values by getResources().getDisplayMetrics().density to make pixels density-independent. If you draw text, you might want to use scaledDensity instead.

density = 1 on mdpi, 1.5 on hdpi, and 0.75 on ldpi i believe.

To complete the answer, some source code: Either use int px = getResources().getDisplayMetrics().density * dp; when dealing with views or images or, when dealing with text, int px = getResources().getDisplayMetrics().scaledDensity * sp;

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