TestDialogFragment.java, fix version.

TestDialogFragment.java

package com.example.time_circle;

import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.DatePicker;
import android.widget.EditText;

public class TestDialogFragment extends DialogFragment implements DialogInterface.OnClickListener{

	private int year;
	private int month;
	private int day;

    private LayoutInflater inflater;
    private View content;

//	LayoutInflater inflater = (LayoutInflater)(getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE));
//    View content = inflater.inflate(R.layout.dialog_set,null);

    public void onClick(DialogInterface dialog, int whichButton) {

        if (whichButton == DialogInterface.BUTTON_POSITIVE){
        	DatePicker datePicker1 = (DatePicker)content.findViewById(R.id.datePicker1);
        	this.year = datePicker1.getYear();
    		this.month = datePicker1.getMonth() + 1;
    		this.day = datePicker1.getDayOfMonth();
    		EditText editText = (EditText)getActivity().findViewById(R.id.edittext2);
    		editText.setText(this.year +"/" + this.month +"/" + this.day);
        }else if (whichButton == DialogInterface.BUTTON_NEGATIVE){
        	//No Action
        }
	}

	@Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        inflater = (LayoutInflater)(getActivity().getSystemService(Add_content2.LAYOUT_INFLATER_SERVICE));
        content = inflater.inflate(R.layout.dialog_set, null);

        // Use the Builder class for convenient dialog construction
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        DialogInterface.OnClickListener MyInterface = new TestDialogFragment();

        builder.setView(content);

        //ダイアログのタイトル
        builder.setMessage("日付の選択")
                .setNegativeButton("Cancel", MyInterface)
                .setPositiveButton("OK", MyInterface);
        return builder.create();
    }
}