android dialog对话框设置宽高

AlertDialog.Builder builder = new Builder(MainActivity.this);
AlertDialog dialog = builder.create();
View contentView = View.inflate(MainActivity.this,
R.layout.dialog_update_cart, null);                            
dialog.setView(contentView);
dialog.show();
//-------------设置弹出框宽高-----------------
WindowManager windowManager = getWindowManager();
Display display = windowManager.getDefaultDisplay();
WindowManager.LayoutParams lp = dialog.getWindow().getAttributes();
lp.width = (int)(display.getWidth()*0.8);   //设置宽度
lp.height = (int)(display.getWidth()*0.7); //设置高度
System.out.println("宽"+display.getWidth()*0.8);
System.out.println("高"+display.getHeight()*0.8);
dialog.getWindow().setAttributes(lp);