在你dialog.show();后面加上

alertDialog =new AlertDialog.Builder(this, R.style.DialogTheme)

.setView(getChoiceView(2), 0, 0, 0, 0)

.create();

alertDialog.getWindow().setGravity(Gravity.BOTTOM);

alertDialog.show();

WindowManager windowManager = getWindowManager();

Display display = windowManager.getDefaultDisplay();

WindowManager.LayoutParams lp = dialog.getWindow().getAttributes();

lp.width = (int)(display.getWidth()); //设置宽度

dialog.getWindow().setAttributes(lp);