How to set drawable on background of View? Android

Question

I have next code in my custom view that extends EditText:

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

                int count = getLineCount();
                Canvas cvs= new Canvas();
                Drawable dr = this.getBackground();
                Rect r = mRect;
                Paint paint = mPaint;
                mTextPaint.setTextSize(this.getTextSize());
                Paint PaintText = mTextPaint;

                for (int i = 0; i < count; i++) {
                    int baseline = getLineBounds(i, r);
                    cvs.drawText(Integer.toString(i+1), r.left, baseline + 1, PaintText);
                    cvs.drawLine(r.left, baseline + 1, r.right, baseline + 1, paint); 
                }
                cvs.drawLine(PaintText.measureText(Integer.toString(count)), this.getTop(), PaintText.measureText(Integer.toString(count)), this.getBottom(), paint);
                dr.setBounds(0, 0, this.getRight(), this.getBottom());
                dr.draw(cvs);
                this.setBackgroundDrawable(dr);
            }

Why is there nothing on backgroind of this view?

Termininja · Accepted Answer · 2016-12-17 10:29:11Z

protected void onDraw(Canvas canvas) {
    Bitmap bitmap = Bitmap.createBitmap(this.getWidth(), this.getHeight(), Bitmap.Config.ARGB_8888);
    int count = getLineCount();
    Canvas cvs= new Canvas(bitmap);
    cvs.drawColor(Color.rgb(245, 245, 245));
    Rect r = mRect;
    Paint paint = mPaint;
    mTextPaint.setTextSize(this.getTextSize());
    Paint PaintText = mTextPaint;

    for (int i = 0; i < count; i++) {
        int baseline = getLineBounds(i, r);
        cvs.drawText(Integer.toString(i+1), 2, baseline + 1, PaintText);
        cvs.drawLine(2, baseline + 1, r.right, baseline + 1, paint); 
    }

    cvs.drawLine(PaintText.measureText(Integer.toString(count))+3, this.getTop(), PaintText.measureText(Integer.toString(count))+3, this.getBottom(), paint);

    this.setBackgroundDrawable(new BitmapDrawable(getContext().getResources(), bitmap));
    this.setPadding((int) (PaintText.measureText(Integer.toString(count))+7),3,3,3); 
    super.onDraw(canvas);
}

Michael · Accepted Answer · 2011-03-26 20:54:31Z

3

I think you're trying to do something that can be done easier. However, your code doesn't work because:

You don't set a Bitmap for your Canvas object.
I think that you want to move content of the Canvas to the Drawable but in fact your code performs an opposite action. Actually, you draw the Drawable on the Canvas object. Try this:

    Bitmap bitmap = Bitmap.createBitmap(this.getWidth(), this.getHeight(),
        Bitmap.Config.ARGB_8888);
    Canvas cvs = new Canvas(bitmap);
    // Your drawing stuff without dr.setBounds() and dr.draw()
    this.setBackgroundDrawable(
        new BitmapDrawable(getContext().getResources(), bitmap));

answered Mar 26, 2011 at 20:54

Michael

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8 Comments

Divers Over a year ago

Thank you so much, but now I have 2 problems: 1. Its black color of this bitmap. 2. android:padding acts on this background ( . I just want to set left padding for text in this view - i.imgur.com/1doN8.png

Michael Over a year ago

Use Canvas.drawColor() to change color of Bitmap. Can you please describe your goal in detail?

Divers Over a year ago

I doing custom edittext with linenumbering, but the problem is that user's text is superimposed on top draw the text, as you can see on the picture.

Michael Over a year ago

So as far as I understand, padding of the EditText changes when new background drawable is set.

Divers Over a year ago

I just want to set padding only for text.

|

Amplify91 · Accepted Answer · 2011-03-28 04:53:43Z

1

You do not need to create a new Canvas object. onDraw creates one for you and sets it in its own bitmap. Just use the name of the canvas specified in the parameters (in this case, canvas).

onDraw is called everytime your view is created or invalidate() is called. And in your onDraw() method, you are creating a NEW canvas object. If you are using this code for anything graphically intense (like a game) then you are leaking memory. Even if you only draw your view once, this is not the best way to do so. Use the canvas provided in the onDraw() parameters.

answered Mar 28, 2011 at 4:53

Amplify91

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