从TimePicker将TextView设置为时间-Android

Question

I have been using this tutorial here to create a time picker. I can select the time fine, but I can't get the time selected to show up in my TextView. Java is not my preferred language so that is probably where I am falling down.

Here is my java code:

import android.app.Activity;
import android.app.Dialog;
import android.app.DialogFragment;
import android.app.TimePickerDialog;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.TimePicker;

import java.util.Calendar;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    //code from: http://developer.android.com/guide/topics/ui/controls/pickers.html
    public void showTimePicker(View v) {
        DialogFragment newFragment = new TimePickerFragment();
        newFragment.show(getFragmentManager(), "timePicker");
    }

    public static class TimePickerFragment extends DialogFragment
            implements TimePickerDialog.OnTimeSetListener {

        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {

            // Use the current time as the default values for the picker
            final Calendar c = Calendar.getInstance();
            int hour = c.get(Calendar.HOUR_OF_DAY);
            int minute = c.get(Calendar.MINUTE);

            // Create a new instance of TimePickerDialog and return it
            return new TimePickerDialog(getActivity(), this, hour, minute,
                    DateFormat.is24HourFormat(getActivity()));
        }

        public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
            // Do something with the time chosen by the user - how!?
        }
    }
}

In my XML I have the Choose Time button run the showTimePicker method on click like so:

android:onClick="showTimePicker"

I have tried just setting the text field inside the onTimeSet method but I get a nullpointerexception. Then I thought I should initialize it in onCreateDialog but there I don't know how to use findViewById to find the actual text view. I'm sure this is probably simple but I have searched up and down without much luck. Thanks for your help!

Answer 1

you can do it like that:

1) Solution 1 ( better ):

public class MainActivity extends Activity {

        TextView resultText;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            resultText = (TextView)findViewById(R.id./*YOUR TEXT VIEW ID*/);
        }

        //code from: http://developer.android.com/guide/topics/ui/controls/pickers.html
        public void showTimePicker(View v) {
            DialogFragment newFragment = new TimePickerFragment(resultText);
            newFragment.show(getFragmentManager(), "timePicker");
        }

        public class TimePickerFragment extends DialogFragment
                implements TimePickerDialog.OnTimeSetListener {

             TextView mResultText;

             public TimePickerFragment(TextView textView) {
                mResultText = textView;
            }

            @Override
            public Dialog onCreateDialog(Bundle savedInstanceState) {

                // Use the current time as the default values for the picker
                final Calendar c = Calendar.getInstance();
                int hour = c.get(Calendar.HOUR_OF_DAY);
                int minute = c.get(Calendar.MINUTE);

                // Create a new instance of TimePickerDialog and return it
                return new TimePickerDialog(getActivity(), this, hour, minute,
                        DateFormat.is24HourFormat(getActivity()));
            }

            public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
                String time = /*CONVERT YOUR TIME FROM hourOfDay and minute*/;
                mResultText.setText(time);
            }
        }
    }

2) Solution 2 :

public class MainActivity extends Activity {
    public TextView mResultText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mResultText = (TextView)findViewById(R.id./*YOUR TEXT VIEW ID*/);
    }

    //code from: http://developer.android.com/guide/topics/ui/controls/pickers.html
    public void showTimePicker(View v) {
        DialogFragment newFragment = new TimePickerFragment();
        newFragment.show(getFragmentManager(), "timePicker");
    }

    public class TimePickerFragment extends DialogFragment
            implements TimePickerDialog.OnTimeSetListener {

        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {

            // Use the current time as the default values for the picker
            final Calendar c = Calendar.getInstance();
            int hour = c.get(Calendar.HOUR_OF_DAY);
            int minute = c.get(Calendar.MINUTE);

            // Create a new instance of TimePickerDialog and return it
            return new TimePickerDialog(getActivity(), this, hour, minute,
                    DateFormat.is24HourFormat(getActivity()));
        }

        public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
            String time = /*CONVERT YOUR TIME FROM hourOfDay and minute*/;
            mResultText.setText(time);
        }
    }
}

Answer 2

You can actually use findViewById , as with getActivity() your fragment gets access to the activity it is running in and thus to the views inside the activity.

public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
    TextView textView = (TextView) getActivity().findViewById(R.id.my_text_view);
    textView.setText(String.format("%02d", hourOfDay), String.format("%02d", minute);
}

This simple solution should be preferred over passing a reference to the TextView to the fragment, as this reference will be lost on reinstantiation of the fragment (see comment ).