Bitmap not showing up on canvas

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I have canvas that I am drawing a bitmap on. I set the dimensions of the canvas and bitmap to variables and printed out their respective values. When I try to draw the bitmap it does not show up.

Code for SurfaceView:

protected void onDraw(Canvas canvas) {
    if (canvas != null) {
        canvas.drawColor(Color.WHITE);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setFilterBitmap(true);
        paint.setDither(true);
        int canvasWidth = canvas.getWidth();
        int canvasHeight = canvas.getHeight();
        int memoryManiaWidth = memoryMania.getWidth();
        int memoryManiaHeight = memoryMania.getHeight();
        Rect src = new Rect(0,0,memoryManiaWidth,memoryManiaHeight);
        Rect dst = new Rect(0,0,canvasWidth,canvasWidth*(memoryManiaHeight/memoryManiaWidth));
        Log.d("MM","CW"+ String.valueOf(canvasWidth));
        Log.d("MM","MMH" + String.valueOf((memoryManiaHeight)));
        Log.d("MM","MMW" + String.valueOf((memoryManiaWidth)));
        Log.d("MM",String.valueOf(canvasWidth*(memoryManiaHeight/memoryManiaWidth)));
        canvas.drawBitmap(memoryMania,src,dst,paint);
    }

}

Logcat Output:

06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ CW1080
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ MMH419
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ MMW951
06-15 21:56:07.395  22939-23030/com.delg.andrew.memorymania D/MM﹕ 0

The bitmap displays if I change the bottom parameter of the dst Rect variable to anything but its present value. For example if i changed

dst = new Rect(.....,canvasWidth*(......));

to

dst = new Rect(.....,canvasWidth));

it will display.

As you can see in the logcat output,

canvasWidth*(memoryManiaHeight/memoryManiaWidth)

is evaluated to 0. Why is this happening and what can I do to fix it?

2

There are 2 answers

0
samgak On BEST ANSWER

Change your calculation from this:

canvasWidth*(memoryManiaHeight/memoryManiaWidth)

to this:

(canvasWidth*memoryManiaHeight)/memoryManiaWidth

If you evaluate (memoryManiaHeight/memoryManiaWidth) first then it will evaluate to zero due to integer division.

0
Jack Xu On

Is there any chance that the value of memoryManiaHeight is smaller than memoryManiaWidth? They are both integers, so zero produced. Try to check values of the two variables.And this should work:

(int) ( canvasWidth * ((float)memoryManiaHeight/memoryManiaWidth) );