java - Why does Android draw View inside another (with width and height defined in pixels) in incorrect way? -

i wondering in way android draws views on screen inside layout views defined android:layout_width , android:layout_height values in pixels.

i using android class view extends android.view.surfaceview. mjpegview display mjpeg stream camera on android app. working code (with small changes): android ics , mjpeg using asynctask

this mjpegview class placed inside relativelayout. mjpegview object added programmatically , relativelayout has attributes defined in way:

android:layout_width="800px" android:layout_height="600px" 

this size values necessary application can't change them. application working in landscape orientation. mjpegview need set 320 x 240 pixels size inside relativelayout (800 x 600 px). application enlarges realtivelayout fill screen on current device. , problem connected streaming mjpeg. working on nexus 7 (2012 version), has 1280 x 800 resolution.

to real size of view inside layout have measured height of nexus 7 screen without action , navigation bars. have used method inside 1 activity:

@override public void onwindowfocuschanged(boolean hasfocus) {     super.onwindowfocuschanged(hasfocus);     relativelayout parentlayout = (relativelayout) findviewbyid(r.id.parent_layout);     if (parentlayout != null && islandscape) {         this.measuredactivityheight = parentlayout.getbottom();     } } 

i getting 703 value measuredactivityheight of running activity. ratio in android translates 320 x 240 px inside 800 x 600 px dp value on screen have written method:

 public int calculateforcurrentscreen(float pixelvalue) {     float ratio = pageactivity.measuredactivityheight / 600f;     int result = (int) (pixelvalue * ratio);     return result; } 

so 320 x 240 px on nexus 7 getting 374 x 281. , mjpegview in size need use method inside mjpegview class:

public void setresolution(int width, int height) {     holder.setfixedsize(width, height); } 

and size of streaming view in wanted size. view has additional black areas. in fact whole view (camera stream + black areas on bottom , right side) has 440 x 328 size.

i have checked rect object in mjpegview drawing 374 x 281 size ok. surfaceholder , canvas have size. bitmap object has 320 x 240 size, ok because bitmap object camera stream. , resized wanted size.

problem disappear (there no black areas , mjpegview in correct position , size relative other views) when have switched relativelayout 800dp x 600dp size , invoke setresolution(320, 240) mjpegview object. whole layout in moment big.

edit

thanks @mathiash comment. have uploaded screenshot nexus 7 (2012 edition) show problem.

as can see, green area relativelayout defined 800 x 600 px size. mjpeg stream http://trackfield.webcam.oregonstate.edu/. have used url: http://trackfield.webcam.oregonstate.edu/axis-cgi/mjpg/video.cgi?resolution=320x240.

for screenshot have invoked setresolution(320, 240) method. , black area has 374 x 281 , video stream 320 x 240.

for screenshot have invoked setresolution(374, 281) method. , black area bigger , video stream 374 x 281. , in case video stream has correct size black area unnecessary.

as levente kurusa suggested, using virtual pixel unit such dp may solve problem. should avoid using px diretly.