1.

//设置背景图片
        String picfile= Environment.getExternalStorageDirectory() + “/pdp/pdp.png”;
        try {
            Drawable d = Drawable.createFromPath(picfile);
            linearLayout.setBackground(d);
            //Toast.makeText(getApplicationContext(),     “设置背景图片成功!”, Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            Toast.makeText(getApplicationContext(), “设置背景图片失败!”, Toast.LENGTH_SHORT).show();
        }

2.

yourlayout.setBackgroundDrawable(new BitmapDrawable(BitmapFactory.decodeFile("图片路径")));

3.

网络图片：

Bitmap bitmap=BitmapFactory.decodeStream(new Url(url).openConnection().getInputStream());
button.setBackgroundDrawable(new BitmapDrawable(bitmap));