To provide a widget for selecting a time, use the TimePicker
widget, which allows the user to select the hour and minute in a familiar interface.
In this tutorial, you'll create a TimePickerDialog
, which presents the
time picker in a floating dialog box at the press of a button. When the time is set by
the user, a TextView
will update with the new date.
res/layout/main.xml
file and insert the following:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="vertical"> <TextView android:id="@+id/timeDisplay" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text=""/> <Button android:id="@+id/pickTime" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Change the time"/> </LinearLayout>
This is a basic LinearLayout
with a TextView
that will display the time and a Button
that will open the TimePickerDialog
.
HelloTimePicker.java
and insert the following class members:
private TextView mTimeDisplay; private Button mPickTime; private int mHour; private int mMinute; static final int TIME_DIALOG_ID = 0;
This declares variables for the layout elements and time fields.
The TIME_DIALOG_ID
is a static integer that uniquely identifies the dialog.
onCreate()
method:
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // capture our View elements mTimeDisplay = (TextView) findViewById(R.id.timeDisplay); mPickTime = (Button) findViewById(R.id.pickTime); // add a click listener to the button mPickTime.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { showDialog(TIME_DIALOG_ID); } }); // get the current time final Calendar c = Calendar.getInstance(); mHour = c.get(Calendar.HOUR_OF_DAY); mMinute = c.get(Calendar.MINUTE); // display the current date updateDisplay(); }
First, the content is set to the main.xml
layout and then the TextView
and Button
are captured with findViewById(int)
.
Then an View.OnClickListener
is created for the Button
,
so that when clicked, it will call showDialog(int)
, passing the unique integer ID for the time picker
dialog. Using showDialog(int)
allows the Activity
to manage the life-cycle of the dialog and will call the onCreateDialog(int)
callback method to request the Dialog
that should be displayed (which you'll define later). After the on-click listener is set, a new
Calendar
is created to get the current hour and minute. Finally, the
private updateDisplay()
method is called in order to fill the TextView
with the current time.
updateDisplay()
and pad()
methods:
// updates the time we display in the TextView private void updateDisplay() { mTimeDisplay.setText( new StringBuilder() .append(pad(mHour)).append(":") .append(pad(mMinute))); } private static String pad(int c) { if (c >= 10) return String.valueOf(c); else return "0" + String.valueOf(c); }
The updateDisplay()
method uses the member fields for the time and inserts them in
the mTimeDisplay
TextView
. The pad()
method returns
the appropriate string representation of the hour or minute—it will prefix a zero to the
number if it's a single digit.
TimePickerDialog.OnTimeSetListener
that will be
called when the user sets a new time:
// the callback received when the user "sets" the time in the dialog private TimePickerDialog.OnTimeSetListener mTimeSetListener = new TimePickerDialog.OnTimeSetListener() { public void onTimeSet(TimePicker view, int hourOfDay, int minute) { mHour = hourOfDay; mMinute = minute; updateDisplay(); } };
When the user is done setting the time (clicks the "Set" button), the
onTimeSet()
method is called and it updates the member fields with
the new time and updates the layout's TextView
.
onCreateDialog(int)
callback method:
@Override protected Dialog onCreateDialog(int id) { switch (id) { case TIME_DIALOG_ID: return new TimePickerDialog(this, mTimeSetListener, mHour, mMinute, false); } return null; }
This is an Activity
callback that is passed the identifier you passed to
showDialog(int)
, in the Button
's on-click
listener. When the ID matches, this initializes the TimePickerDialog
with the
member variables initialized at the end of onCreate()
and the TimePickerDialog.OnTimeSetListener
created in the previous step.
When you press the "Change the time" button, you should see the following: