25. 09. 2018
ALERT: This article might be outdated and not fit for your needs. In order to enjoy its updated version, visit Android Guide To: Drawing Text Over Bitmap
This improves method from my previous blog post to work with multiline text. The StaticLayout class does the trick.
Measure height of multiline text
To center text vertically we need to know text height. Instantiate StaticLayout with text width according to your needs, for us it is simple the width of Bitmap/Canvas minus 16dp padding. The getHeight() then returns height of text.
Positioning text on Canvas
There are four simple steps to position text on Canvas:
- Save the current matrix and clip with
Canvas.save()
. - Apply translation to Canvas matrix with
Canvas.translate(x,y)
. - Draw StaticLayout on Canvas with
StaticLayout.draw(canvas)
. - Revert matrix translation with
Canvas.restore()
method.
Complete source code
public Bitmap drawMultilineTextToBitmap(Context gContext, int gResId, String gText) { // prepare canvas Resources resources = gContext.getResources(); float scale = resources.getDisplayMetrics().density; Bitmap bitmap = BitmapFactory.decodeResource(resources, gResId); android.graphics.Bitmap.Config bitmapConfig = bitmap.getConfig(); // set default bitmap config if none if(bitmapConfig == null) { bitmapConfig = android.graphics.Bitmap.Config.ARGB_8888; } // resource bitmaps are imutable, // so we need to convert it to mutable one bitmap = bitmap.copy(bitmapConfig, true); Canvas canvas = new Canvas(bitmap); // new antialiased Paint TextPaint paint=new TextPaint(Paint.ANTI_ALIAS_FLAG); // text color - #3D3D3D paint.setColor(Color.rgb(61, 61, 61)); // text size in pixels paint.setTextSize((int) (14 * scale)); // text shadow paint.setShadowLayer(1f, 0f, 1f, Color.WHITE); // set text width to canvas width minus 16dp padding int textWidth = canvas.getWidth() - (int) (16 * scale); // init StaticLayout for text StaticLayout textLayout = new StaticLayout( gText, paint, textWidth, Layout.Alignment.ALIGN_CENTER, 1.0f, 0.0f, false); // get height of multiline text int textHeight = textLayout.getHeight(); // get position of text's top left corner float x = (bitmap.getWidth() - textWidth)/2; float y = (bitmap.getHeight() - textHeight)/2; // draw text to the Canvas center canvas.save(); canvas.translate(x, y); textLayout.draw(canvas); canvas.restore(); return bitmap; }