Draw text on canvas and make it visible on screen

This code was supposed to convert text to image

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Paint paint = new Paint();
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.RED);
 开发者_开发技巧       paint.setTextSize(16);
        paint.setAntiAlias(true);
        paint.setTypeface(Typeface.MONOSPACE);

        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);
}

Is this code ok? If yes, how can I make this new bitmap visible on screen? I tried this code which produced an error

setContentView(c); //<- ERROR!

I am confused with the element Canvas as there is not such element in XML which I can use in the code.

setContentView(View) takes a View and Canvas is not a View.

I am not sure that you want to create a Canvas on your own. There are ways to get a Canvas passed to you from the Android Framework though. One way you can do this is by creating a custom View. To do this, you will need to create a new class that extends View.

When overriding a View class, you will have the ability to override the onDraw(Canvas) method. This is probably where you want to do what you are attempting to do in your onCreate() method in the code you posted.

This link gives a good overview of what is required to create your own custom view.

First: If you draw your text at the x and y position you specified, you draw it at the lower right corner, starting with exactly that pixel. Nothing will be drawn on your canvas. Try bm.getWidth()/2, for height the same for test drawing. You can optimize that later.

Second: Canvas is not a View (does not extend the View class). You can only set Views via set ContentView(). What I recommend here is writing a XML layout containing only a single ImageView and set that via setContentView(R.layout.mylayout).

After that, you can use findViewById() to grab that ImageView and use ImageView.setImageBitmap(bm) to show your bitmap on it. You dont have to do anything with the canvas, once you created it with your bitmap. Everything you draw inside the canvas from that point on is found in the Bitmap immediately. Therefore you can't specify the Canvas in XML. It's just an "Editor" to edit pictures, so to speak and not an actual UI element.