How to draw full 800 by 480 images on Android_问答_开发者

I've got an image that is 800 by 300, which I know is the width of my test platform's resolution (HTC Desire at 800x480). When I try to draw this image to the screen it scales oddly. It spills over the left hand side of the screen and fills almost all the vertical.

I'm using code like this:

canvas.drawBitmap( screen[1], new Rect(0,0,800,300), new Rect(0,0,800,300), null);

For some reason

width_x = canvas.getWidth();

width_y = canvas.getHeight();

reports my resolution as 533 by 320. Now I assume this is for the expletive-deleted fascinating scaling system Android uses so apps appear the same size on all phones but I want to ignore this. I'm writing a game, so want to handle scaling and positioning myself - for instance using more screen estate if it becomes available. Best Android practice may be suitable for an icon based application, but I would like to draw to absolute pixel positions, and get absolute resolution information for the screen.

Therefore my question is this - is this absolutely impossible? If it is completely contraindicated because Android has a simple and effective system in place to do this then I would be interested to know what it is. Dpi is not relevant to my game design (just like if this was a pc game, it would be irrelevant)

Perhaps my screen actually 533 by 320 unless I specify a resolution somehow? I tried using the scaling values from width and height and the image was the correct size on screen, roughly, but had jagged edges because some sort of scaling had occurred. I therefore did no开发者_如何学Got have access to all the pixels my screen is capable of displaying.

To scale it I used something like

canvas.drawBitmap( screen[1], new Rect(0,0,800,300), new Rect((int)(0.0f),(int)(0.0f),(int)(533.0f),(int)(187.5f)), null); // numbers

Just whacked in for testing - ratio equivalent to reported screen resolution. Looks horrid.

Android is not doing anything to mess with your perceived resolution - you are working with 800x480 pixels on that Desire.

Are you working in a fullscreen, custom View and overriding onDraw? Are you working with a SurfaceView? We need to know these things before we can help you with your problem.

Assuming you are doing the above, you should be able to draw your bitmap to the screen without any scaling using Canvas.drawBitmap(Bitmap bitmap, float left, float top, Paint paint). In your case, that would look something like canvas.drawBitmap( screen[1], 0.0f, 0.0f, null); to put it in the upper left corner of your canvas.

In performance-sensitive apps (like games), you don't want to use the source/destination Rect version of drawBitmap() during your draw loop, since it will do the scaling during every iteration of the loop. Instead, draw a scaled/cropped version of your original bitmap to another member bitmap, and draw that one in the loop, using the x/y offset version of drawBitmap linked above.

If you want to know the amount of screen real estate you're working with (and you definitely should, if you're doing any custom drawing), you'll want to override either onSizeChanged() or surfaceChanged(), depending on implementation.

You should really check out the API demos, there are some great examples of how to do exactly what you're trying to do in there.

Good luck!

I fixed one of my problems - in the manifest file the OS I was targeting was set up incorrectly - switching it to 4 (i.e. 1.6) seemed to fix the values I was getting for height and width, at least for the HTC. Emulator is more problematic, but at least its a major step in the right direction. For your info, I'm working in full screen, landscape mode (fixed), with overridden functions for pretty much everything. (Including onDraw, surfaceChanged, and so forth)

If I can get the absolute width and height I can write my own code for loading the correct assets and using the correct scaling for screen positioning - DPI isn't an issue so hopefully that won't stray too far from suggested guidelines.