Android：在图片资源上书写并在不同设备上保持相同大小

Question

I have been looking for days on how to fix my issue and haven't really found an answer. So I apologize in advance if there already is a similar question.

My problem is simple. I want the user to input a name, and this name will be written on an image, in some kind of little box. (The image is then shared in an intent and everything, anyway...)

The image is a png in my drawable folder. So it should always have the same size in pixels on any kind of device. I load the png on a bitmap, use canvas on that bitmap, create a paint and myPaint.setTextSize(100) (setTextSize takes pixels so in this case it is 100 pixels) and then drawText on the canvas using that paint to have the same text size (in pixel) from whatever device is used.

The result is that writing "MyName" on one device fits perfectly, but on a smaller device would go out of the box, and on a larger device also.

I tried to use dp or sp, even if I knew it wouldn't change anything because we aren't talking about a layout, but a drawable png that has a fixed size.'

I have no issue with the position of the text or anything; only the size of it.

So anyway, I don't know where this change of textsize from one device to another comes from. Maybe I am not taking care of some kind of detail. I hope you guys can help me out.

                    Context context = getBaseContext();
                    Resources resources = context.getResources();
                    Bitmap card = BitmapFactory.decodeResource(resources, R.drawable.card);

                    android.graphics.Bitmap.Config bitmapConfig = card.getConfig();
                    if(bitmapConfig == null) {
                        bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888;
                    }
                    // Converting to mutable
                    card = card.copy(bitmapConfig, true);

                    Canvas canvas = new Canvas(card);
                    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
                    // text color
                    paint.setColor(Color.WHITE);
                    paint.setFakeBoldText(true);
                    paint.setTextAlign(Paint.Align.CENTER);
                    // text size in pixels
                    paint.setTextSize(100);

                    // Name Position
                    float xName = (float) (0.744 * card.getWidth() );
                    float yName = (float) (0.680424 * (card.getHeight() - (paint.ascent()/2)));
                    String name = editName.getText().toString();
                    canvas.drawText(name, xName, yName, paint);

Answer 1

Try this.

/**
     * Sets the text size for a Paint object so a given string of text will be a
     * given width.
     * 
     * @param paint
     *            the Paint to set the text size for
     * @param desiredWidth
     *            the desired width
     * @param text
     *            the text that should be that width
     */
    private static void setTextSizeForWidth(Paint paint, float desiredWidth,
            String text) {

        // Pick a reasonably large value for the test. Larger values produce
        // more accurate results, but may cause problems with hardware
        // acceleration. But there are workarounds for that, too; refer to
        // http://stackoverflow.com/questions/6253528/font-size-too-large-to-fit-in-cache
        final float testTextSize = 48f;

        // Get the bounds of the text, using our testTextSize.
        paint.setTextSize(testTextSize);
        Rect bounds = new Rect();
        paint.getTextBounds(text, 0, text.length(), bounds);

        // Calculate the desired size as a proportion of our testTextSize.
        float desiredTextSize = testTextSize * desiredWidth / bounds.width();

        // Set the paint for that size.
        paint.setTextSize(desiredTextSize);
    }

Answer 2

I was able to fix this issue by using density. Not really sure how it works, but it gets the job done so...

Resources resources = context.getResources();
float scale = resources.getDisplayMetrics().density;
paint.setTextSize(30 * scale);