Android Time Picker

To provide a way for the user to select a time, you can use TimePicker. Android apps typically use TimePicker with TimePickerDialog for selecting a time value – this helps to ensure a consistent interface across devices and applications. TimePicker allows users to select the time of day in either 24-hour or 12-hour AM/PM mode. TimePickerDialog is a helper class that encapsulates the TimePicker in a dialog.

Overview

Modern Android applications display the TimePickerDialog in a DialogFragment. This makes it possible for an application to display the TimePicker as a popup dialog or embed it in an Activity. In addition, the DialogFragment manages the lifecycle and display of the dialog, reducing the amount of code that must be implemented.

This guide demonstrates how to use the TimePickerDialog, wrapped in a DialogFragment. The sample application displays the TimePickerDialog as a modal dialog when the user clicks a button on an Activity. When the time is set by the user, the dialog exits and a handler updates a TextView on the Activity screen with the time that was selected.

Requirements

The sample application for this guide targets Android 4.1 (API level 16) or higher, but is can be used with Android 3.0 (API level 11 or higher). It is possible to support older versions of Android with the addition of the Android Support Library v4 to the project and some code changes.

Using the TimePicker

This example extends DialogFragment; the subclass implementation of DialogFragment (called TimePickerFragment below) hosts and displays a TimePickerDialog. When the sample app is first launched, it displays a PICK TIME button above a TextView that will be used to display the selected time:

When you click the PICK TIME button, the example app launches the TimePickerDialog as seen in this screenshot:

In the TimePickerDialog, selecting a time and clicking the OK button causes the TimePickerDialog to invoke the method IOnTimeSetListener.OnTimeSet. This interface is implemented by the hosting DialogFragment (TimePickerFragment, described below). Clicking the Cancel button causes the fragment and dialog to be dismissed.

DialogFragment returns the selected time to the hosting Activity in one of three ways:

1. Invoking a method or setting a property – The Activity can provide a property or method specifically for setting this value.

2. Raising an event – The DialogFragment can define an event that will be raised when OnTimeSet is invoked.

3. Using an Action – The DialogFragment can invoke an Action<DateTime> to display the time in the Activity. The Activity will provide the Action<DateTime when instantiating the DialogFragment.

This sample will use the third technique, which requires that the Activity supply an Action<DateTime> handler to the DialogFragment.

Start an App Project

Start a new Android project called TimePickerDemo (if you are not familiar with creating Xamarin.Android projects, see Hello, Android to learn how to create a new project).

Edit Resources/layout/Main.axml and replace its contents with the following XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_gravity="center_horizontal"
    android:padding="16dp">
    <Button
        android:id="@+id/select_button"
        android:paddingLeft="24dp"
        android:paddingRight="24dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="PICK TIME"
        android:textSize="20dp" />
    <TextView
        android:id="@+id/time_display"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:paddingTop="22dp"
        android:text="Picked time will be displayed here"
        android:textSize="24dp" />
</LinearLayout>

This is a basic LinearLayout with a TextView that displays the time and a Button that opens the TimePickerDialog. Note that this layout uses hard-coded strings and dimensions to make the app simpler and easier to understand – a production app normally uses resources for these values (as can be seen in the DatePicker code example).

Edit MainActivity.cs and replace its contents with the following code:

using Android.App;
using Android.Widget;
using Android.OS;
using System;
using Android.Util;
using Android.Text.Format;

namespace TimePickerDemo
{
    [Activity(Label = "TimePickerDemo", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        TextView timeDisplay;
        Button timeSelectButton;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);
            timeDisplay = FindViewById<TextView>(Resource.Id.time_display);
            timeSelectButton = FindViewById<Button>(Resource.Id.select_button);
        }
    }
}

When you build and run this example, you should see an initial screen similar to the following screen shot:

Clicking the PICK TIME button does nothing because the DialogFragment has not yet been implemented to display the TimePicker. The next step is to create this DialogFragment.

Extending DialogFragment

To extend DialogFragment for use with TimePicker, it is necessary to create a subclass that is derived from DialogFragment and implements TimePickerDialog.IOnTimeSetListener. Add the following class to MainActivity.cs:

public class TimePickerFragment : DialogFragment, TimePickerDialog.IOnTimeSetListener
{
    public static readonly string TAG = "MyTimePickerFragment";
    Action<DateTime> timeSelectedHandler = delegate { };

    public static TimePickerFragment NewInstance(Action<DateTime> onTimeSelected)
    {
        TimePickerFragment frag = new TimePickerFragment();
        frag.timeSelectedHandler = onTimeSelected;
        return frag;
    }

    public override Dialog OnCreateDialog (Bundle savedInstanceState)
    {
        DateTime currentTime = DateTime.Now;
        bool is24HourFormat = DateFormat.Is24HourFormat(Activity);
        TimePickerDialog dialog = new TimePickerDialog
            (Activity, this, currentTime.Hour, currentTime.Minute, is24HourFormat);
        return dialog;
    }

    public void OnTimeSet(TimePicker view, int hourOfDay, int minute)
    {
        DateTime currentTime = DateTime.Now;
        DateTime selectedTime = new DateTime(currentTime.Year, currentTime.Month, currentTime.Day, hourOfDay, minute, 0);
        Log.Debug(TAG, selectedTime.ToLongTimeString());
        timeSelectedHandler (selectedTime);
    }
}

This TimePickerFragment class is broken down into smaller pieces and explained in the next section.

DialogFragment Implementation

TimePickerFragment implements several methods: a factory method, a Dialog instantiation method, and the OnTimeSet handler method required by TimePickerDialog.IOnTimeSetListener.

• TimePickerFragment is a subclass of DialogFragment. It also implements the TimePickerDialog.IOnTimeSetListener interface (that is, it supplies the required OnTimeSet method):

  public class TimePickerFragment : DialogFragment, TimePickerDialog.IOnTimeSetListener
  

• TAG is initialized for logging purposes (MyTimePickerFragment can be changed to whatever string you want to use). The timeSelectedHandler Action is initialized to an empty delegate to prevent null reference exceptions:

  public static readonly string TAG = "MyTimePickerFragment";
  Action<DateTime> timeSelectedHandler = delegate { };
  

• The NewInstance factory method is called to instantiate a new TimePickerFragment. This method takes an Action<DateTime> handler that is invoked when the user clicks the OK button in the TimePickerDialog:

  public static TimePickerFragment NewInstance(Action<DateTime> onTimeSelected)
  {
      TimePickerFragment frag = new TimePickerFragment();
      frag.timeSelectedHandler = onTimeSelected;
      return frag;
  }
  

• When the fragment is to be displayed, Android calls the DialogFragment method OnCreateDialog. This method creates a new TimePickerDialog object and initializes it with the Activity, the callback object (which is the current instance of the TimePickerFragment), and the current time:

  public override Dialog OnCreateDialog (Bundle savedInstanceState)
  {
      DateTime currentTime = DateTime.Now;
      bool is24HourFormat = DateFormat.Is24HourFormat(Activity);
      TimePickerDialog dialog = new TimePickerDialog
          (Activity, this, currentTime.Hour, currentTime.Minute, is24HourFormat);
      return dialog;
  }
  

• When the user changes the time setting in the TimePicker dialog, the OnTimeSet method is invoked. OnTimeSet creates a DateTime object using the current date and merges in the time (hour and minute) selected by the user:

  public void OnTimeSet(TimePicker view, int hourOfDay, int minute)
  {
      DateTime currentTime = DateTime.Now;
      DateTime selectedTime = new DateTime(currentTime.Year, currentTime.Month, currentTime.Day, hourOfDay, minute, 0);
  

• This DateTime object is passed to the timeSelectedHandler that is registered with the TimePickerFragment object at creation time. OnTimeSet invokes this handler to update the Activity's time display to the selected time (this handler is implemented in the next section):

  timeSelectedHandler (selectedTime);
  

Displaying the TimePickerFragment

Now that the DialogFragment has been implemented, it is time to instantiate the DialogFragment using the NewInstance factory method and display it by invoking DialogFragment.Show:

Add the following method to MainActivity:

void TimeSelectOnClick (object sender, EventArgs eventArgs)
{
    TimePickerFragment frag = TimePickerFragment.NewInstance (
        delegate (DateTime time)
        {
            timeDisplay.Text = time.ToShortTimeString();
        });

    frag.Show(FragmentManager, TimePickerFragment.TAG);
}

After TimeSelectOnClick instantiates a TimePickerFragment, it creates and passes in a delegate for an anonymous method that updates the Activity's time display with the passed-in time value. Finally, it launches the TimePicker dialog fragment (via DialogFragment.Show) to display the TimePicker to the user.

At the end of the OnCreate method, add the following line to attach the event handler to the PICK TIME button that launches the dialog:

timeSelectButton.Click += TimeSelectOnClick;

When the PICK TIME button is clicked, TimeSelectOnClick will be invoked to display the TimePicker dialog fragment to the user.

Try It!

Build and run the app. When you click the PICK TIME button, the TimePickerDialog is displayed in the default time format for the Activity (in this case, 12-hour AM/PM mode):

When you click OK in the TimePicker dialog, the handler updates the Activity's TextView with the chosen time and then exits:

Next, add the following line of code to OnCreateDialog immediately after is24HourFormat is declared and initialized:

is24HourFormat = true;

This change forces the flag passed to the TimePickerDialog constructor to be true so that 24-hour mode is used instead of the time format of the hosting Activity. When you build and run the app again, click the PICK TIME button, the TimePicker dialog is now displayed in 24 hour format:

Because the handler calls DateTime.ToShortTimeString to print the time to the Activity's TextView, the time is still printed in the default 12-hour AM/PM format.

Summary

This article explained how to display a TimePicker widget as a popup modal dialog from an Android Activity. It provided a sample DialogFragment implementation and discussed the IOnTimeSetListener interface. This sample also demonstrated how the DialogFragment can interact with the host Activity to display the selected time.

Related Links

• DialogFragment
• TimePicker
• TimePickerDialog
• TimePickerDialog.IOnTimeSetListener