//dialog 居中显示
Window window = dialog.getWindow();
if (dialog != null && window != null) {
WindowManager.LayoutParams attr = window.getAttributes();
if (attr != null) {
attr.height = ViewGroup.LayoutParams.WRAP_CONTENT;
attr.width = ViewGroup.LayoutParams.WRAP_CONTENT;
attr.gravity = Gravity.CENTER;//设置dialog 在布局中的位置
}
}