android onDateChanged，怎么用

Question

我想在我的应用程序中创建一个onDateChanged方法。 这意味着，当我点击我的editText（也是datepicker）并选择日期时， 它会立即更改textview中的数据。

然而，由于我已完成编码，当我选择日期时，文本视图中没有显示任何内容。 我想知道为什么这会发生在我的代码中。 有人可以帮助我吗？

monthDate = (EditText)findViewById(R.id.month);
        avgPrice = (TextView)findViewById(R.id.showavfPriceTV);
        exFuel = (TextView)findViewById(R.id.showexFuelTV);
        avgFC = (TextView)findViewById(R.id.showavgFCTV);
        doneButton = (Button)findViewById(R.id.doneBTN);
        exitButton = (Button)findViewById(R.id.exitBTN);

        Bundle takeBundledData = getIntent().getExtras();  
        // First we need to get the bundle data that pass from the UndergraduateListActivity

        bundleID = takeBundledData.getString("clickedID");
        bundleDate = takeBundledData.getString("clickedDate");
        bundlePrice = takeBundledData.getString("clickedPrice");
        bundlePump = takeBundledData.getString("clickedPump");
        bundleCost = takeBundledData.getString("clickedCost");
        bundleOdometer = takeBundledData.getString("clickedOdometer");
        bundlePreOdometer = takeBundledData.getString("clickedpreOdometer");
        bundleFcon = takeBundledData.getString("clickedFCon");
        Log.d("SUMMARY","bundle : "+ takeBundledData);

        monthDate.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
               // showDialog(DATE_DIALOG_ID);
                DialogFragment newFragment = new DatePickerFragment();
                newFragment.show(getFragmentManager(), "datePicker");
            }

            public void onDateChanged(DatePicker view, int year,int month, int day)
            {
                if (monthDate.getText().toString().equals(bundleDate))
                {


                    Log.d("TRYINGOUT","date : "+ bundleDate);
                    avgPrice.setText(bundlePrice);


                }
                else
                {
                     Intent intent=new Intent(getApplicationContext(),about.class);
                     startActivity(intent);
                }
            }


        });