My question was solved ,thx ego.
But there is a new question:
when i use buffer.blit(texture, 0, 0,1256+225-(mycar_dx), 8+220+(mycar_dz), 32, 32, FrameBuffer.TRANSPARENT_BLITTING);
in device which is 1920*1080,it is ok,just in the right location.
in device which is 1280*720,it's dispear......
when i switch LANDSCAPE to PORTRAIT,it's dispear too.
I think the problem is locate the minimap was based on the pixel,is that right?
Is there a method of blit() which is not base location on pixel but base on the proportion of device's screen(1080p,720p,480P)
thanks