如何在Android的Fragment中的onClick侦听器中使对话框工作？

Question

I am trying to build an android app and have come across a situation where I want a user to navigate between Dates by clicking Previous (Month) and Next (Month) buttons. I however do not want the user to go to a month after the current month. I would like the App to prompt a dialog letting the user know that they cant select a month after the current. Below is my code snippet - I am getting an error on two portions

01. if(formattedDate.before(currentMonth) || formattedDate.equals(currentMonth)){

On the above I am getting an error saying

The method before(Calendar) is undefined for the type String

02. new AlertDialog.Builder(HomeFragment.this)

and on the above I am getting an error saying

The constructor AlertDialog.Builder(HomeFragment) is undefined

Below is my full code for the on-click listener

NextPicker.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {

                if(formattedDate.before(currentMonth) || formattedDate.equals(currentMonth)){

                    c.add(Calendar.MONTH, 1);
                    formattedDate = df.format(c.getTime());
                    Log.v("NEXT DATE : ", formattedDate);
                    DatePicker.setText(formattedDate);
                }
                else{

                                new AlertDialog.Builder(HomeFragment.this)

                                .setTitle("Wrong Date Selection!")

                                .setMessage("The Month Selected must be before or equal to current month")

                                .setNeutralButton("Ok",

                                new DialogInterface.OnClickListener() {

                                public void onClick(DialogInterface dialog,

                                int which) {

                                }

                                }).show();
                            }


        }
    });

Answer 1

Your first problem is that formattedDate is a String. It needs to be a java.util.Date.

Your second problem comes from the fact that the AlertDialog.Builder constructor requires a Context sub-class. Fragment is not a Context sub-class, but Activity is. Try something like

new AlertDialog.Builder(HomeFragment.this.getActivity());