Figure 1. A dialog with a message and two action buttons.
A dialog is a small window that prompts the user to make a decision or enter additional information. A dialog does not fill the screen and is normally used for modal events that require users to take an action before they can proceed.
Dialog Design
For information about how to design your dialogs, including recommendations for language, read the Dialogs design guide.
The {@link android.app.Dialog} class is the base class for dialogs, but you should avoid instantiating {@link android.app.Dialog} directly. Instead, use one of the following subclasses:
Android includes another dialog class called {@link android.app.ProgressDialog} that shows a dialog with a progress bar. However, if you need to indicate loading or indeterminate progress, you should instead follow the design guidelines for Progress & Activity and use a {@link android.widget.ProgressBar} in your layout.
These classes define the style and structure for your dialog, but you should use a {@link android.support.v4.app.DialogFragment} as a container for your dialog. The {@link android.support.v4.app.DialogFragment} class provides all the controls you need to create your dialog and manage its appearance, instead of calling methods on the {@link android.app.Dialog} object.
Using {@link android.support.v4.app.DialogFragment} to manage the dialog ensures that it correctly handles lifecycle events such as when the user presses the Back button or rotates the screen. The {@link android.support.v4.app.DialogFragment} class also allows you to reuse the dialog's UI as an embeddable component in a larger UI, just like a traditional {@link android.support.v4.app.Fragment} (such as when you want the dialog UI to appear differently on large and small screens).
The following sections in this guide describe how to use a {@link android.support.v4.app.DialogFragment} in combination with an {@link android.app.AlertDialog} object. If you'd like to create a date or time picker, you should instead read the Pickers guide.
Note:
Because the {@link android.app.DialogFragment} class was originally added with
Android 3.0 (API level 11), this document describes how to use the {@link
android.support.v4.app.DialogFragment} class that's provided with the Support Library. By adding this library
to your app, you can use {@link android.support.v4.app.DialogFragment} and a variety of other
APIs on devices running Android 1.6 or higher. If the minimum version your app supports
is API level 11 or higher, then you can use the framework version of {@link
android.app.DialogFragment}, but be aware that the links in this document are for the support
library APIs. When using the support library,
be sure that you import android.support.v4.app.DialogFragment
class and not android.app.DialogFragment.
You can accomplish a wide variety of dialog designs—including custom layouts and those described in the Dialogs design guide—by extending {@link android.support.v4.app.DialogFragment} and creating a {@link android.app.AlertDialog} in the {@link android.support.v4.app.DialogFragment#onCreateDialog onCreateDialog()} callback method.
For example, here's a basic {@link android.app.AlertDialog} that's managed within a {@link android.support.v4.app.DialogFragment}:
public class FireMissilesDialogFragment extends DialogFragment {
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the Builder class for convenient dialog construction
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setMessage(R.string.dialog_fire_missiles)
.setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// FIRE ZE MISSILES!
}
})
.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User cancelled the dialog
}
});
// Create the AlertDialog object and return it
return builder.create();
}
}
Figure 1. A dialog with a message and two action buttons.
Now, when you create an instance of this class and call {@link android.support.v4.app.DialogFragment#show show()} on that object, the dialog appears as shown in figure 1.
The next section describes more about using the {@link android.app.AlertDialog.Builder} APIs to create the dialog.
Depending on how complex your dialog is, you can implement a variety of other callback methods in the {@link android.support.v4.app.DialogFragment}, including all the basic fragment lifecycle methods.
The {@link android.app.AlertDialog} class allows you to build a variety of dialog designs and is often the only dialog class you'll need. As shown in figure 2, there are three regions of an alert dialog:
Figure 2. The layout of a dialog.
This is optional and should be used only when the content area is occupied by a detailed message, a list, or custom layout. If you need to state a simple message or question (such as the dialog in figure 1), you don't need a title.
This can display a message, a list, or other custom layout.
There should be no more than three action buttons in a dialog.
The {@link android.app.AlertDialog.Builder} class provides APIs that allow you to create an {@link android.app.AlertDialog} with these kinds of content, including a custom layout.
To build an {@link android.app.AlertDialog}:
// 1. Instantiate an {@link android.app.AlertDialog.Builder} with its constructor
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
// 2. Chain together various setter methods to set the dialog characteristics
builder.setMessage(R.string.dialog_message)
.setTitle(R.string.dialog_title);
// 3. Get the {@link android.app.AlertDialog} from {@link android.app.AlertDialog.Builder#create()}
AlertDialog dialog = builder.create();
The following topics show how to define various dialog attributes using the {@link android.app.AlertDialog.Builder} class.
To add action buttons like those in figure 2, call the {@link android.app.AlertDialog.Builder#setPositiveButton setPositiveButton()} and {@link android.app.AlertDialog.Builder#setNegativeButton setNegativeButton()} methods:
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
// Add the buttons
builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User clicked OK button
}
});
builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User cancelled the dialog
}
});
// Set other dialog properties
...
// Create the AlertDialog
AlertDialog dialog = builder.create();
The set...Button() methods require a title for the button (supplied
by a string resource) and a
{@link android.content.DialogInterface.OnClickListener} that defines the action to take
when the user presses the button.
There are three different action buttons you can add:
You can add only one of each button type to an {@link android.app.AlertDialog}. That is, you cannot have more than one "positive" button.
Figure 3. A dialog with a title and list.
There are three kinds of lists available with the {@link android.app.AlertDialog} APIs:
To create a single-choice list like the one in figure 3, use the {@link android.app.AlertDialog.Builder#setItems setItems()} method:
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle(R.string.pick_color)
.setItems(R.array.colors_array, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// The 'which' argument contains the index position
// of the selected item
}
});
return builder.create();
}
Because the list appears in the dialog's content area, the dialog cannot show both a message and a list and you should set a title for the dialog with {@link android.app.AlertDialog.Builder#setTitle setTitle()}. To specify the items for the list, call {@link android.app.AlertDialog.Builder#setItems setItems()}, passing an array. Alternatively, you can specify a list using {@link android.app.AlertDialog.Builder#setAdapter setAdapter()}. This allows you to back the list with dynamic data (such as from a database) using a {@link android.widget.ListAdapter}.
If you choose to back your list with a {@link android.widget.ListAdapter}, always use a {@link android.support.v4.content.Loader} so that the content loads asynchronously. This is described further in Building Layouts with an Adapter and the Loaders guide.
Note: By default, touching a list item dismisses the dialog, unless you're using one of the following persistent choice lists.
Figure 4. A list of multiple-choice items.
To add a list of multiple-choice items (checkboxes) or single-choice items (radio buttons), use the {@link android.app.AlertDialog.Builder#setMultiChoiceItems(Cursor,String,String, DialogInterface.OnMultiChoiceClickListener) setMultiChoiceItems()} or {@link android.app.AlertDialog.Builder#setSingleChoiceItems(int,int,DialogInterface.OnClickListener) setSingleChoiceItems()} methods, respectively.
For example, here's how you can create a multiple-choice list like the one shown in figure 4 that saves the selected items in an {@link java.util.ArrayList}:
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
mSelectedItems = new ArrayList(); // Where we track the selected items
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
// Set the dialog title
builder.setTitle(R.string.pick_toppings)
// Specify the list array, the items to be selected by default (null for none),
// and the listener through which to receive callbacks when items are selected
.setMultiChoiceItems(R.array.toppings, null,
new DialogInterface.OnMultiChoiceClickListener() {
@Override
public void onClick(DialogInterface dialog, int which,
boolean isChecked) {
if (isChecked) {
// If the user checked the item, add it to the selected items
mSelectedItems.add(which);
} else if (mSelectedItems.contains(which)) {
// Else, if the item is already in the array, remove it
mSelectedItems.remove(Integer.valueOf(which));
}
}
})
// Set the action buttons
.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
// User clicked OK, so save the mSelectedItems results somewhere
// or return them to the component that opened the dialog
...
}
})
.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
...
}
});
return builder.create();
}
Although both a traditional list and a list with radio buttons provide a "single choice" action, you should use {@link android.app.AlertDialog.Builder#setSingleChoiceItems(int,int,DialogInterface.OnClickListener) setSingleChoiceItems()} if you want to persist the user's choice. That is, if opening the dialog again later should indicate what the user's current choice is, then you create a list with radio buttons.
Figure 5. A custom dialog layout.
If you want a custom layout in a dialog, create a layout and add it to an {@link android.app.AlertDialog} by calling {@link android.app.AlertDialog.Builder#setView setView()} on your {@link android.app.AlertDialog.Builder} object.
By default, the custom layout fills the dialog window, but you can still use {@link android.app.AlertDialog.Builder} methods to add buttons and a title.
For example, here's the layout file for the dialog in Figure 5:
res/layout/dialog_signin.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView
android:src="@drawable/header_logo"
android:layout_width="match_parent"
android:layout_height="64dp"
android:scaleType="center"
android:background="#FFFFBB33"
android:contentDescription="@string/app_name" />
<EditText
android:id="@+id/username"
android:inputType="textEmailAddress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:layout_marginLeft="4dp"
android:layout_marginRight="4dp"
android:layout_marginBottom="4dp"
android:hint="@string/username" />
<EditText
android:id="@+id/password"
android:inputType="textPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:layout_marginLeft="4dp"
android:layout_marginRight="4dp"
android:layout_marginBottom="16dp"
android:fontFamily="sans-serif"
android:hint="@string/password"/>
</LinearLayout>
Tip: By default, when you set an {@link android.widget.EditText} element to use the {@code "textPassword"} input type, the font family is set to monospace, so you should change its font family to {@code "sans-serif"} so that both text fields use a matching font style.
To inflate the layout in your {@link android.support.v4.app.DialogFragment}, get a {@link android.view.LayoutInflater} with {@link android.app.Activity#getLayoutInflater()} and call {@link android.view.LayoutInflater#inflate inflate()}, where the first parameter is the layout resource ID and the second parameter is a parent view for the layout. You can then call {@link android.app.AlertDialog#setView setView()} to place the layout in the dialog.
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
// Get the layout inflater
LayoutInflater inflater = getActivity().getLayoutInflater();
// Inflate and set the layout for the dialog
// Pass null as the parent view because its going in the dialog layout
builder.setView(inflater.inflate(R.layout.dialog_signin, null))
// Add action buttons
.setPositiveButton(R.string.signin, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int id) {
// sign in the user ...
}
})
.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
LoginDialogFragment.this.getDialog().cancel();
}
});
return builder.create();
}
Tip: If you want a custom dialog,
you can instead display an {@link android.app.Activity} as a dialog
instead of using the {@link android.app.Dialog} APIs. Simply create an activity and set its theme to
{@link android.R.style#Theme_Holo_Dialog Theme.Holo.Dialog}
in the {@code
<activity android:theme="@android:style/Theme.Holo.Dialog" >
That's it. The activity now displays in a dialog window instead of fullscreen.
When the user touches one of the dialog's action buttons or selects an item from its list, your {@link android.support.v4.app.DialogFragment} might perform the necessary action itself, but often you'll want to deliver the event to the activity or fragment that opened the dialog. To do this, define an interface with a method for each type of click event. Then implement that interface in the host component that will receive the action events from the dialog.
For example, here's a {@link android.support.v4.app.DialogFragment} that defines an interface through which it delivers the events back to the host activity:
public class NoticeDialogFragment extends DialogFragment {
/* The activity that creates an instance of this dialog fragment must
* implement this interface in order to receive event callbacks.
* Each method passes the DialogFragment in case the host needs to query it. */
public interface NoticeDialogListener {
public void onDialogPositiveClick(DialogFragment dialog);
public void onDialogNegativeClick(DialogFragment dialog);
}
// Use this instance of the interface to deliver action events
NoticeDialogListener mListener;
// Override the Fragment.onAttach() method to instantiate the NoticeDialogListener
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// Verify that the host activity implements the callback interface
try {
// Instantiate the NoticeDialogListener so we can send events to the host
mListener = (NoticeDialogListener) activity;
} catch (ClassCastException e) {
// The activity doesn't implement the interface, throw exception
throw new ClassCastException(activity.toString()
+ " must implement NoticeDialogListener");
}
}
...
}
The activity hosting the dialog creates an instance of the dialog with the dialog fragment's constructor and receives the dialog's events through an implementation of the {@code NoticeDialogListener} interface:
public class MainActivity extends FragmentActivity
implements NoticeDialogFragment.NoticeDialogListener{
...
public void showNoticeDialog() {
// Create an instance of the dialog fragment and show it
DialogFragment dialog = new NoticeDialogFragment();
dialog.show(getSupportFragmentManager(), "NoticeDialogFragment");
}
// The dialog fragment receives a reference to this Activity through the
// Fragment.onAttach() callback, which it uses to call the following methods
// defined by the NoticeDialogFragment.NoticeDialogListener interface
@Override
public void onDialogPositiveClick(DialogFragment dialog) {
// User touched the dialog's positive button
...
}
@Override
public void onDialogNegativeClick(DialogFragment dialog) {
// User touched the dialog's negative button
...
}
}
Because the host activity implements the {@code NoticeDialogListener}—which is enforced by the {@link android.support.v4.app.Fragment#onAttach onAttach()} callback method shown above—the dialog fragment can use the interface callback methods to deliver click events to the activity:
public class NoticeDialogFragment extends DialogFragment {
...
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Build the dialog and set up the button click handlers
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setMessage(R.string.dialog_fire_missiles)
.setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// Send the positive button event back to the host activity
mListener.onDialogPositiveClick(NoticeDialogFragment.this);
}
})
.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// Send the negative button event back to the host activity
mListener.onDialogNegativeClick(NoticeDialogFragment.this);
}
});
return builder.create();
}
}
When you want to show your dialog, create an instance of your {@link android.support.v4.app.DialogFragment} and call {@link android.support.v4.app.DialogFragment#show show()}, passing the {@link android.support.v4.app.FragmentManager} and a tag name for the dialog fragment.
You can get the {@link android.support.v4.app.FragmentManager} by calling {@link android.support.v4.app.FragmentActivity#getSupportFragmentManager()} from the {@link android.support.v4.app.FragmentActivity} or {@link android.support.v4.app.Fragment#getFragmentManager()} from a {@link android.support.v4.app.Fragment}. For example:
public void confirmFireMissiles() {
DialogFragment newFragment = new FireMissilesDialogFragment();
newFragment.show(getSupportFragmentManager(), "missiles");
}
The second argument, {@code "missiles"}, is a unique tag name that the system uses to save and restore the fragment state when necessary. The tag also allows you to get a handle to the fragment by calling {@link android.support.v4.app.FragmentManager#findFragmentByTag findFragmentByTag()}.
You might have a UI design in which you want a piece of the UI to appear as a dialog in some situations, but as a full screen or embedded fragment in others (perhaps depending on whether the device is a large screen or small screen). The {@link android.support.v4.app.DialogFragment} class offers you this flexibility because it can still behave as an embeddable {@link android.support.v4.app.Fragment}.
However, you cannot use {@link android.app.AlertDialog.Builder AlertDialog.Builder} or other {@link android.app.Dialog} objects to build the dialog in this case. If you want the {@link android.support.v4.app.DialogFragment} to be embeddable, you must define the dialog's UI in a layout, then load the layout in the {@link android.support.v4.app.Fragment#onCreateView onCreateView()} callback.
Here's an example {@link android.support.v4.app.DialogFragment} that can appear as either a
dialog or an embeddable fragment (using a layout named purchase_items.xml):
public class CustomDialogFragment extends DialogFragment {
/** The system calls this to get the DialogFragment's layout, regardless
of whether it's being displayed as a dialog or an embedded fragment. */
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout to use as dialog or embedded fragment
return inflater.inflate(R.layout.purchase_items, container, false);
}
/** The system calls this only when creating the layout in a dialog. */
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// The only reason you might override this method when using onCreateView() is
// to modify any dialog characteristics. For example, the dialog includes a
// title by default, but your custom layout might not need it. So here you can
// remove the dialog title, but you must call the superclass to get the Dialog.
Dialog dialog = super.onCreateDialog(savedInstanceState);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
return dialog;
}
}
And here's some code that decides whether to show the fragment as a dialog or a fullscreen UI, based on the screen size:
public void showDialog() {
FragmentManager fragmentManager = getSupportFragmentManager();
CustomDialogFragment newFragment = new CustomDialogFragment();
if (mIsLargeLayout) {
// The device is using a large layout, so show the fragment as a dialog
newFragment.show(fragmentManager, "dialog");
} else {
// The device is smaller, so show the fragment fullscreen
FragmentTransaction transaction = fragmentManager.beginTransaction();
// For a little polish, specify a transition animation
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
// To make it fullscreen, use the 'content' root view as the container
// for the fragment, which is always the root view for the activity
transaction.add(android.R.id.content, newFragment)
.addToBackStack(null).commit();
}
}
For more information about performing fragment transactions, see the Fragments guide.
In this example, the mIsLargeLayout boolean specifies whether the current device
should use the app's large layout design (and thus show this fragment as a dialog, rather
than fullscreen). The best way to set this kind of boolean is to declare a
bool resource value
with an alternative resource value for different screen sizes. For example, here are two
versions of the bool resource for different screen sizes:
res/values/bools.xml
<!-- Default boolean values -->
<resources>
<bool name="large_layout">false</bool>
</resources>
res/values-large/bools.xml
<!-- Large screen boolean values -->
<resources>
<bool name="large_layout">true</bool>
</resources>
Then you can initialize the {@code mIsLargeLayout} value during the activity's {@link android.app.Activity#onCreate onCreate()} method:
boolean mIsLargeLayout;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mIsLargeLayout = getResources().getBoolean(R.bool.large_layout);
}
Instead of showing a dialog as a fullscreen UI when on small screens, you can accomplish the same result by showing an {@link android.app.Activity} as a dialog when on large screens. Which approach you choose depends on your app design, but showing an activity as a dialog is often useful when your app is already designed for small screens and you'd like to improve the experience on tablets by showing a short-lived activity as a dialog.
To show an activity as a dialog only when on large screens,
apply the {@link android.R.style#Theme_Holo_DialogWhenLarge Theme.Holo.DialogWhenLarge}
theme to the {@code
<activity android:theme="@android:style/Theme.Holo.DialogWhenLarge" >
For more information about styling your activities with themes, see the Styles and Themes guide.
When the user touches any of the action buttons created with an {@link android.app.AlertDialog.Builder}, the system dismisses the dialog for you.
The system also dismisses the dialog when the user touches an item in a dialog list, except when the list uses radio buttons or checkboxes. Otherwise, you can manually dismiss your dialog by calling {@link android.support.v4.app.DialogFragment#dismiss()} on your {@link android.support.v4.app.DialogFragment}.
In case you need to perform certain actions when the dialog goes away, you can implement the {@link android.support.v4.app.DialogFragment#onDismiss onDismiss()} method in your {@link android.support.v4.app.DialogFragment}.
You can also cancel a dialog. This is a special event that indicates the user explicitly left the dialog without completing the task. This occurs if the user presses the Back button, touches the screen outside the dialog area, or if you explicitly call {@link android.app.Dialog#cancel()} on the {@link android.app.Dialog} (such as in response to a "Cancel" button in the dialog).
As shown in the example above, you can respond to the cancel event by implementing {@link android.support.v4.app.DialogFragment#onCancel onCancel()} in your {@link android.support.v4.app.DialogFragment} class.
Note: The system calls {@link android.support.v4.app.DialogFragment#onDismiss onDismiss()} upon each event that invokes the {@link android.support.v4.app.DialogFragment#onCancel onCancel()} callback. However, if you call {@link android.app.Dialog#dismiss Dialog.dismiss()} or {@link android.support.v4.app.DialogFragment#dismiss DialogFragment.dismiss()}, the system calls {@link android.support.v4.app.DialogFragment#onDismiss onDismiss()} but not {@link android.support.v4.app.DialogFragment#onCancel onCancel()}. So you should generally call {@link android.support.v4.app.DialogFragment#dismiss dismiss()} when the user presses the positive button in your dialog in order to remove the dialog from view.