PopupWindow中点击Spinner 显示Unable to add window android.view.ViewRoot is not valid is your activity running

在MainActivity中有一个按钮事件，点击会弹出PopupWindow

send_data.setOnClickListener(new Popup_Window());

class Popup_Window implements View.OnClickListener{
   public void onClick(View v){
        popupwindow_view = getLayoutInflater().inflate(R.layout.pop, null,false);

//R.layout.pop 是一个自定义的xml

        popup_window=new PopupWindow(popupwindow_view,LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT,true);

            popupwindow_view.setOnTouchListener(new View.OnTouchListener() {
                public boolean onTouch(View v, MotionEvent event) {
                    if(popup_window!=null && popup_window.isShowing()){
                        popup_window.dismiss();
                        popup_window=null;
                    }
                    return false;
                }
            });

            Spinner spinner = (Spinner) popupwindow_view.findViewById(R.id.language);
            ArrayAdapter<CharSequence> adapter=ArrayAdapter.createFromResource(getApplicationContext(),
                    R.array.language, android.R.layout.simple_spinner_item);
            adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(adapter);


            ColorDrawable dw = new ColorDrawable(Color.parseColor("#99000000"));
            popup_window.setBackgroundDrawable(dw);
            popup_window.showAtLocation(v, Gravity.CENTER, 0, 0);
        }
    }

界面出现后一点击，这个Spinner 下拉菜单，应用就会崩溃，，，，
catlog: Unable to add window is your activity running?