sandalone sandalone - 1 year ago 96
Java Question

Why does BitmapFactory.decodeByteArray return null?

It's the simple code and instead of getting result to set the Bitmap, I get null. Can anyone tell me where I am making a mistake?

String test = "test";
byte[] byteA = test.getBytes();
Bitmap bmp = BitmapFactory.decodeByteArray(byteA, 0, byteA.length); //<- I get null here
ImageView image = (ImageView) findViewById(;


Ok, so I cannot convert text to image like I thought I could. How about this way? Will this create a bitmap?

Paint paint = new Paint();

Bitmap bm = Bitmap.createBitmap(16, 16, Bitmap.Config.ALPHA_8);
float x = bm.getWidth();
float y = bm.getHeight();
Canvas c = new Canvas(bm);
c.drawText("Test", x, y, paint);

Answer Source

From the documentation:

Returns The decoded bitmap, or null if the image could not be decode.

The bytes involved in the string "test" aren't a valid bitmap, are they?

If you saved the text "test" in a file called foo.png or foo.jpg etc and tried to open it in Windows, what would you expect the result to be? It would be an error: those bytes simply aren't a valid image in any known format.

EDIT: I don't know anything about Android graphics, but your update certainly looks like a much more reasonable way to draw text onto a bitmap.

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