xref: /frameworks/base/docs/html/guide/topics/ui/dialogs.jd

page.title=Dialogs
parent.title=User Interface
parent.link=index.html
@jd:body

<div id="qv-wrapper">
  <div id="qv">
    <h2>In this document</h2>
    <ol>
      <li><a href="#ShowingADialog">Showing a Dialog</a></li>
      <li><a href="#DismissingADialog">Dismissing a Dialog</a></li>
      <li><a href="#AlertDialog">Creating an AlertDialog</a>
        <ol>
          <li><a href="#AddingButtons">Adding buttons</a></li>
          <li><a href="#AddingAList">Adding a list</a></li>
        </ol>
      </li>
      <li><a href="#ProgressDialog">Creating a ProgressDialog</a>
        <ol>
          <li><a href="#ShowingAProgressBar">Showing a progress bar</a></li>
        </ol>
      </li>
      <li><a href="#CustomDialog">Creating a Custom Dialog</a></li>
    </ol>

    <h2>Key classes</h2>
    <ol>
      <li>{@link android.app.Dialog}</li>
      <li>{@link android.app.AlertDialog}</li>
      <li>{@link android.app.DialogFragment}</li>
    </ol>

    <h2>Related tutorials</h2>
    <ol>
      <li><a href="{@docRoot}resources/tutorials/views/hello-datepicker.html">Hello
DatePicker</a></li>
      <li><a href="{@docRoot}resources/tutorials/views/hello-timepicker.html">Hello
TimePicker</a></li>
    </ol>
    
    <h2>See also</h2>
    <ol>
      <li><a href="{@docRoot}design/building-blocks/dialogs.html">Android Design: Dialogs</a></li>
    </ol>
  </div>
</div>

<p>A dialog is usually a small window that appears in front of the current Activity.
The underlying Activity loses focus and the dialog accepts all user interaction. Dialogs are
normally used for notifications that should interupt the user and to perform short tasks that
directly relate to the application in progress (such as a progress bar or a login prompt).</p>

<p>The {@link android.app.Dialog} class is the base class for creating dialogs. However, you
typically should not instantiate a {@link android.app.Dialog} directly. Instead, you should use one
of the following subclasses:</p>
<dl>
  <dt>{@link android.app.AlertDialog}</dt>
  <dd>A dialog that can manage zero, one, two, or three buttons, and/or a list of
    selectable items that can include checkboxes or radio buttons. The AlertDialog 
    is capable of constructing most dialog user interfaces and is the suggested dialog type.
    See <a href="#AlertDialog">Creating an AlertDialog</a> below.</dd>
  <dt>{@link android.app.ProgressDialog}</dt>
  <dd>A dialog that displays a progress wheel or progress bar. Because it's an extension of
    the AlertDialog, it also supports buttons.
    See <a href="#ProgressDialog">Creating a ProgressDialog</a> below.</dd>
  <dt>{@link android.app.DatePickerDialog}</dt>
  <dd>A dialog that allows the user to select a date. See the 
    <a href="{@docRoot}resources/tutorials/views/hello-datepicker.html">Hello DatePicker</a> tutorial.</dd>
  <dt>{@link android.app.TimePickerDialog}</dt>
  <dd>A dialog that allows the user to select a time. See the 
    <a href="{@docRoot}resources/tutorials/views/hello-timepicker.html">Hello TimePicker</a> tutorial.</dd>
</dl>

<p>If you would like to customize your own dialog, you can extend the
base {@link android.app.Dialog} object or any of the subclasses listed above and define a new layout.
See the section on <a href="#CustomDialog">Creating a Custom Dialog</a> below.</p>

<div class="note design">
<p><strong>Dialog Design</strong></p>
  <p>For design guidelines, read Android Design's <a
href="{@docRoot}design/building-blocks/dialogs.html">Dialogs</a> guide.</p>
</div>



<h2 id="ShowingADialog">Showing a Dialog</h2>

<p>A dialog is always created and displayed as a part of an {@link android.app.Activity}. 
You should normally create dialogs from within your Activity's
{@link android.app.Activity#onCreateDialog(int)} callback method. 
When you use this callback, the Android system automatically manages the state of 
each dialog and hooks them to the Activity, effectively making it the "owner" of each dialog.
As such, each dialog inherits certain properties from the Activity. For example, when a dialog
is open, the Menu key reveals the options menu defined for the Activity and the volume
keys modify the audio stream used by the Activity.</p>

<p class="note"><strong>Note:</strong> If you decide to create a dialog outside of the 
<code>onCreateDialog()</code> method, it will not be attached to an Activity. You can, however,
attach it to an Activity with {@link android.app.Dialog#setOwnerActivity(Activity)}.</p>

<p>When you want to show a dialog, call 
{@link android.app.Activity#showDialog(int)} and pass it an integer that uniquely identifies the 
dialog that you want to display.</p>

<p>When a dialog is requested for the first time, Android calls 
{@link android.app.Activity#onCreateDialog(int)} from your Activity, which is
where you should instantiate the {@link android.app.Dialog}. This callback method
is passed the same ID that you passed to {@link android.app.Activity#showDialog(int)}. 
After you create the Dialog, return the object at the end of the method.</p>

<p>Before the dialog is displayed, Android also calls the optional callback method
{@link android.app.Activity#onPrepareDialog(int,Dialog)}. Define this method if you want to change
any properties of the dialog each time it is opened. This method is called
every time a dialog is opened, whereas {@link android.app.Activity#onCreateDialog(int)} is only
called the very first time a dialog is opened. If you don't define 
{@link android.app.Activity#onPrepareDialog(int,Dialog) onPrepareDialog()}, then the dialog will 
remain the same as it was the previous time it was opened. This method is also passed the dialog's
ID, along with the Dialog object you created in {@link android.app.Activity#onCreateDialog(int)
onCreateDialog()}.</p>

<p>The best way to define the {@link android.app.Activity#onCreateDialog(int)} and 
{@link android.app.Activity#onPrepareDialog(int,Dialog)} callback methods is with a 
<em>switch</em> statement that checks the <var>id</var> parameter that's passed into the method. 
Each <em>case</em> should check for a unique dialog ID and then create and define the respective Dialog.
For example, imagine a game that uses two different dialogs: one to indicate that the game
has paused and another to indicate that the game is over. First, define an integer ID for
each dialog:</p>
<pre>
static final int DIALOG_PAUSED_ID = 0;
static final int DIALOG_GAMEOVER_ID = 1;
</pre>

<p>Then, define the {@link android.app.Activity#onCreateDialog(int)} callback with a 
switch case for each ID:</p>
<pre>
protected Dialog onCreateDialog(int id) {
    Dialog dialog;
    switch(id) {
    case DIALOG_PAUSED_ID:
        // do the work to define the pause Dialog
        break;
    case DIALOG_GAMEOVER_ID:
        // do the work to define the game over Dialog
        break;
    default:
        dialog = null;
    }
    return dialog;
}
</pre>

<p class="note"><strong>Note:</strong> In this example, there's no code inside
the case statements because the procedure for defining your Dialog is outside the scope
of this section. See the section below about <a href="#AlertDialog">Creating an AlertDialog</a>,
offers code suitable for this example.</p>

<p>When it's time to show one of the dialogs, call {@link android.app.Activity#showDialog(int)}
with the ID of a dialog:</p>
<pre>
showDialog(DIALOG_PAUSED_ID);
</pre>


<h2 id="DismissingADialog">Dismissing a Dialog</h2>

<p>When you're ready to close your dialog, you can dismiss it by calling
{@link android.app.Dialog#dismiss()} on the Dialog object.
If necessary, you can also call {@link android.app.Activity#dismissDialog(int)} from the
Activity, which effectively calls {@link android.app.Dialog#dismiss()} on the 
Dialog for you.</p>

<p>If you are using {@link android.app.Activity#onCreateDialog(int)} to manage the state
of your dialogs (as discussed in the previous section), then every time your dialog is
dismissed, the state of the Dialog
object is retained by the Activity. If you decide that you will no longer need this object or 
it's important that the state is cleared, then you should call
{@link android.app.Activity#removeDialog(int)}. This will remove any internal references
to the object and if the dialog is showing, it will dismiss it.</p>

<h3>Using dismiss listeners</h3>

<p>If you'd like your application to perform some procedures the moment that a dialog is dismissed, 
then you should attach an on-dismiss listener to your Dialog.</p>

<p>First define the {@link android.content.DialogInterface.OnDismissListener} interface.
This interface has just one method,
{@link android.content.DialogInterface.OnDismissListener#onDismiss(DialogInterface)}, which
will be called when the dialog is dismissed.
Then simply pass your OnDismissListener implementation to 
{@link android.app.Dialog#setOnDismissListener(DialogInterface.OnDismissListener)
setOnDismissListener()}.</p>

<p>However, note that dialogs can also be "cancelled." This is a special case that indicates
the dialog was explicitly cancelled by the user. This will occur if the user presses the 
"back" button to close the dialog, or if the dialog explicitly calls {@link android.app.Dialog#cancel()}
(perhaps from a "Cancel" button in the dialog). When a dialog is cancelled,
the OnDismissListener will still be notified, but if you'd like to be informed that the dialog
was explicitly cancelled (and not dismissed normally), then you should register 
an {@link android.content.DialogInterface.OnCancelListener} with
{@link android.app.Dialog#setOnCancelListener(DialogInterface.OnCancelListener)
setOnCancelListener()}.</p>


<h2 id="AlertDialog">Creating an AlertDialog</h2>

<p>An {@link android.app.AlertDialog} is an extension of the {@link android.app.Dialog}
class. It is capable of constructing most dialog user interfaces and is the suggested dialog type.
You should use it for dialogs that use any of the following features:</p>
<ul>
  <li>A title</li>
  <li>A text message</li>
  <li>One, two, or three buttons</li>
  <li>A list of selectable items (with optional checkboxes or radio buttons)</li>
</ul>

<p>To create an AlertDialog, use the {@link android.app.AlertDialog.Builder} subclass.
Get a Builder with {@link android.app.AlertDialog.Builder#AlertDialog.Builder(Context)} and
then use the class's public methods to define all of the
AlertDialog properties. After you're done with the Builder, retrieve the 
AlertDialog object with {@link android.app.AlertDialog.Builder#create()}.</p>

<p>The following topics show how to define various properties of the AlertDialog using the
AlertDialog.Builder class. If you use any of the following sample code inside your 
{@link android.app.Activity#onCreateDialog(int) onCreateDialog()} callback method, 
you can return the resulting Dialog object to display the dialog.</p>


<h3 id="AddingButtons">Adding buttons</h3>

<img src="{@docRoot}images/dialog_buttons.png" alt="" style="float:right" />

<p>To create an AlertDialog with side-by-side buttons like the one shown in the screenshot to the right,
use the <code>set...Button()</code> methods:</p>

<pre>
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
       .setCancelable(false)
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                MyActivity.this.finish();
           }
       })
       .setNegativeButton("No", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                dialog.cancel();
           }
       });
AlertDialog alert = builder.create();
</pre>

<p>First, add a message for the dialog with 
{@link android.app.AlertDialog.Builder#setMessage(CharSequence)}. Then, begin
method-chaining and set the dialog
to be <em>not cancelable</em> (so the user cannot close the dialog with the back button)
with {@link android.app.AlertDialog.Builder#setCancelable(boolean)}. For each button, 
use one of the <code>set...Button()</code> methods, such as
{@link android.app.AlertDialog.Builder#setPositiveButton(CharSequence,DialogInterface.OnClickListener)
setPositiveButton()}, that accepts the name for the button and a 
{@link android.content.DialogInterface.OnClickListener} that defines the action to take 
when the user selects the button.</p>

<p class="note"><strong>Note:</strong> You can only add one of each button type to the
AlertDialog. That is, you cannot have more than one "positive" button. This limits the number
of possible buttons to three: positive, neutral, and negative. These names are technically irrelevant to the
actual functionality of your buttons, but should help you keep track of which one does what.</p>


<h3 id="AddingAList">Adding a list</h3>

<img src="{@docRoot}images/dialog_list.png" alt="" style="float:right" />

<p>To create an AlertDialog with a list of selectable items like the one shown to the right, 
use the <code>setItems()</code> method:</p>

<pre>
final CharSequence[] items = {"Red", "Green", "Blue"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Pick a color");
builder.setItems(items, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
});
AlertDialog alert = builder.create();
</pre>

<p>First, add a title to the dialog with 
{@link android.app.AlertDialog.Builder#setTitle(CharSequence)}. 
Then, add a list of selectable items with
{@link android.app.AlertDialog.Builder#setItems(CharSequence[],DialogInterface.OnClickListener)
setItems()}, which accepts the array of items to display and a 
{@link android.content.DialogInterface.OnClickListener} that defines the action to take 
when the user selects an item.</p>


<h4>Adding checkboxes and radio buttons</h4>

<img src="{@docRoot}images/dialog_singlechoicelist.png" alt="" style="float:right" />

<p>To create a list of multiple-choice items (checkboxes) or 
single-choice items (radio buttons) inside the dialog, use the
{@link android.app.AlertDialog.Builder#setMultiChoiceItems(Cursor,String,String,
DialogInterface.OnMultiChoiceClickListener) setMultiChoiceItems()} and 
{@link android.app.AlertDialog.Builder#setSingleChoiceItems(int,int,DialogInterface.OnClickListener) 
setSingleChoiceItems()} methods, respectively.
If you create one of these selectable lists in the
{@link android.app.Activity#onCreateDialog(int) onCreateDialog()} callback method,
Android manages the state of the list for you. As long as the Activity is active, 
the dialog remembers the items that were previously selected, but when the user exits the
Activity, the selection is lost.

<p class="note"><strong>Note:</strong> To save the selection when the user leaves or
pauses the Activity, you must properly save and restore the setting throughout
the <a href="{@docRoot}guide/components/activities.html#Lifecycle">activity lifecycle</a>. 
To permanently save the selections, even when the Activity process is completely shutdown, 
you need to save the settings
with one of the <a href="{@docRoot}guide/topics/data/data-storage.html">Data
Storage</a> techniques.</p>

<p>To create an AlertDialog with a list of single-choice items like the one shown to the right,
use the same code from the previous example, but replace the <code>setItems()</code> method with
{@link android.app.AlertDialog.Builder#setSingleChoiceItems(int,int,DialogInterface.OnClickListener) 
setSingleChoiceItems()}:</p>

<pre>
final CharSequence[] items = {"Red", "Green", "Blue"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Pick a color");
builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
});
AlertDialog alert = builder.create();
</pre>

<p>The second parameter in the
{@link android.app.AlertDialog.Builder#setSingleChoiceItems(CharSequence[],int,DialogInterface.OnClickListener)
setSingleChoiceItems()} method is an integer value for the <var>checkedItem</var>, which indicates the 
zero-based list position of the default selected item. Use "-1" to indicate that no item should be 
selected by default.</p>


<h2 id="ProgressDialog">Creating a ProgressDialog</h2>

<img src="{@docRoot}images/dialog_progress_spinning.png" alt="" style="float:right" />

<p>A {@link android.app.ProgressDialog} is an extension of the {@link android.app.AlertDialog}
class that can display a progress animation in the form of a spinning wheel, for a task with
progress that's undefined, or a progress bar, for a task that has a defined progression.
The dialog can also provide buttons, such as one to cancel a download.</p>

<p>Opening a progress dialog can be as simple as calling 
{@link android.app.ProgressDialog#show(Context,CharSequence,CharSequence)
ProgressDialog.show()}. For example, the progress dialog shown to the right can be 
easily achieved without managing the dialog through the 
{@link android.app.Activity#onCreateDialog(int)} callback,
as shown here:</p>

<pre>
ProgressDialog dialog = ProgressDialog.show(MyActivity.this, "", 
                        "Loading. Please wait...", true);
</pre>

<p>The first parameter is the application {@link android.content.Context}, 
the second is a title for the dialog (left empty), the third is the message, 
and the last parameter is whether the progress
is indeterminate (this is only relevant when creating a progress bar, which is
discussed in the next section).
</p>

<p>The default style of a progress dialog is the spinning wheel.
If you want to create a progress bar that shows the loading progress with granularity,
some more code is required, as discussed in the next section.</p>


<h3 id="ShowingAProgressBar">Showing a progress bar</h3>

<img src="/images/dialog_progress_bar.png" alt="" style="float:right" />

<p>To show the progression with an animated progress bar:</p>

<ol>
  <li>Initialize the 
    ProgressDialog with the class constructor, 
    {@link android.app.ProgressDialog#ProgressDialog(Context)}.</li>
  <li>Set the progress style to "STYLE_HORIZONTAL" with 
    {@link android.app.ProgressDialog#setProgressStyle(int)} and 
    set any other properties, such as the message.</li>
  <li>When you're ready to show the dialog, call 
    {@link android.app.Dialog#show()} or return the ProgressDialog from the  
    {@link android.app.Activity#onCreateDialog(int)} callback.</li>
  <li>You can increment the amount of progress displayed
    in the bar by calling either {@link android.app.ProgressDialog#setProgress(int)} with a value for 
    the total percentage completed so far or {@link android.app.ProgressDialog#incrementProgressBy(int)}
    with an incremental value to add to the total percentage completed so far.</li>
</ol>

<p>For example, your setup might look like this:</p>
<pre>
ProgressDialog progressDialog;
progressDialog = new ProgressDialog(mContext);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading...");
progressDialog.setCancelable(false);
</pre>

<p>The setup is simple. Most of the code needed to create a progress dialog is actually 
involved in the process that updates it. You might find that it's
necessary to create a second thread in your application for this work and then report the progress
back to the Activity's UI thread with a {@link android.os.Handler} object. 
If you're not familiar with using additional 
threads with a Handler, see the example Activity below that uses a second thread to
increment a progress dialog managed by the Activity.</p>

<script type="text/javascript">
function toggleDiv(link) {
  var toggleable = $(link).parent();
  if (toggleable.hasClass("closed")) {
    $(".toggleme", toggleable).slideDown("fast");
    toggleable.removeClass("closed");
    toggleable.addClass("open");
    $(".toggle-img", toggleable).attr("title", "hide").attr("src", "/assets/images/triangle-opened.png");
  } else {
    $(".toggleme", toggleable).slideUp("fast");
    toggleable.removeClass("open");
    toggleable.addClass("closed");
    $(".toggle-img", toggleable).attr("title", "show").attr("src", "/assets/images/triangle-closed.png");
  }
  return false;
}
</script>
<style>
.toggleme {
  padding:0 0 1px 0;
}
.toggleable a {
  text-decoration:none;
}
.toggleable.closed .toggleme {
  display:none;
}
#jd-content .toggle-img {
  margin:0;
}
</style>

<div class="toggleable closed">
  <a href="#" onclick="return toggleDiv(this)">
        <img src="/assets/images/triangle-closed.png" class="toggle-img" />
        <strong>Example ProgressDialog with a second thread</strong></a>
  <div class="toggleme">
        <p>This example uses a second thread to track the progress of a process (which actually just
counts up to 100). The thread sends a {@link android.os.Message} back to the main
Activity through a {@link android.os.Handler} each time progress is made. The main Activity then updates the 
ProgressDialog.</p>

<pre>
package com.example.progressdialog;

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class NotificationTest extends Activity {
    static final int PROGRESS_DIALOG = 0;
    Button button;
    ProgressThread progressThread;
    ProgressDialog progressDialog;
   
    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Setup the button that starts the progress dialog
        button = (Button) findViewById(R.id.progressDialog);
        button.setOnClickListener(new OnClickListener(){
            public void onClick(View v) {
                showDialog(PROGRESS_DIALOG);
            }
        }); 
    }
   
    protected Dialog onCreateDialog(int id) {
        switch(id) {
        case PROGRESS_DIALOG:
            progressDialog = new ProgressDialog(NotificationTest.this);
            progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            progressDialog.setMessage("Loading...");
            return progressDialog;
        default:
            return null;
        }
    }

    &#64;Override
    protected void onPrepareDialog(int id, Dialog dialog) {
        switch(id) {
        case PROGRESS_DIALOG:
            progressDialog.setProgress(0);
            progressThread = new ProgressThread(handler);
            progressThread.start();
    }

    // Define the Handler that receives messages from the thread and update the progress
    final Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            int total = msg.arg1;
            progressDialog.setProgress(total);
            if (total >= 100){
                dismissDialog(PROGRESS_DIALOG);
                progressThread.setState(ProgressThread.STATE_DONE);
            }
        }
    };

    /** Nested class that performs progress calculations (counting) */
    private class ProgressThread extends Thread {
        Handler mHandler;
        final static int STATE_DONE = 0;
        final static int STATE_RUNNING = 1;
        int mState;
        int total;
       
        ProgressThread(Handler h) {
            mHandler = h;
        }
       
        public void run() {
            mState = STATE_RUNNING;   
            total = 0;
            while (mState == STATE_RUNNING) {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    Log.e("ERROR", "Thread Interrupted");
                }
                Message msg = mHandler.obtainMessage();
                msg.arg1 = total;
                mHandler.sendMessage(msg);
                total++;
            }
        }
        
        /* sets the current state for the thread,
         * used to stop the thread */
        public void setState(int state) {
            mState = state;
        }
    }
}
</pre>
  </div> <!-- end toggleme -->
</div> <!-- end toggleable -->



<h2 id="CustomDialog">Creating a Custom Dialog</h2>

<img src="{@docRoot}images/dialog_custom.png" alt="" style="float:right" />

<p>If you want a customized design for a dialog, you can create your own layout
for the dialog window with layout and widget elements.
After you've defined your layout, pass the root View object or
layout resource ID to {@link android.app.Dialog#setContentView(View)}.</p>

<p>For example, to create the dialog shown to the right:</p>

<ol>
  <li>Create an XML layout saved as <code>custom_dialog.xml</code>:
<pre>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/layout_root"
              android:orientation="horizontal"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:padding="10dp"
              >
    &lt;ImageView android:id="@+id/image"
               android:layout_width="wrap_content"
               android:layout_height="fill_parent"
               android:layout_marginRight="10dp"
               />
    &lt;TextView android:id="@+id/text"
              android:layout_width="wrap_content"
              android:layout_height="fill_parent"
              android:textColor="#FFF"
              />
&lt;/LinearLayout>
</pre>

    <p>This XML defines an {@link android.widget.ImageView} and a {@link android.widget.TextView}
    inside a {@link android.widget.LinearLayout}.</p>
  <li>Set the above layout as the dialog's content view and define the content 
    for the ImageView and TextView elements:</p>
<pre>
Context mContext = getApplicationContext();
Dialog dialog = new Dialog(mContext);

dialog.setContentView(R.layout.custom_dialog);
dialog.setTitle("Custom Dialog");

TextView text = (TextView) dialog.findViewById(R.id.text);
text.setText("Hello, this is a custom dialog!");
ImageView image = (ImageView) dialog.findViewById(R.id.image);
image.setImageResource(R.drawable.android);
</pre>

    <p>After you instantiate the Dialog, set your custom layout as the dialog's content view with 
    {@link android.app.Dialog#setContentView(int)}, passing it the layout resource ID.
    Now that the Dialog has a defined layout, you can capture View objects from the layout with
    {@link android.app.Dialog#findViewById(int)} and modify their content.</p>
  </li>

  <li>That's it. You can now show the dialog as described in 
    <a href="#ShowingADialog">Showing A Dialog</a>.</li>
</ol>

<p>A dialog made with the base Dialog class must have a title. If you don't call
{@link android.app.Dialog#setTitle(CharSequence) setTitle()}, then the space used for the title
remains empty, but still visible. If you don't want
a title at all, then you should create your custom dialog using the
{@link android.app.AlertDialog} class. However, because an AlertDialog is created easiest with 
the {@link android.app.AlertDialog.Builder} class, you do not have access to the 
{@link android.app.Dialog#setContentView(int)} method used above. Instead, you must use 
{@link android.app.AlertDialog.Builder#setView(View)}. This method accepts a {@link android.view.View} object,
so you need to inflate the layout's root View object from
XML.</p>

<p>To inflate the XML layout, retrieve the {@link android.view.LayoutInflater} with 
{@link android.app.Activity#getLayoutInflater()} 
(or {@link android.content.Context#getSystemService(String) getSystemService()}),
and then call
{@link android.view.LayoutInflater#inflate(int, ViewGroup)}, where the first parameter
is the layout resource ID and the second is the ID of the root View. At this point, you can use
the inflated layout to find View objects in the layout and define the content for the
ImageView and TextView elements. Then instantiate the AlertDialog.Builder and set the
inflated layout for the dialog with {@link android.app.AlertDialog.Builder#setView(View)}.</p>

<p>Here's an example, creating a custom layout in an AlertDialog:</p>

<pre>
AlertDialog.Builder builder;
AlertDialog alertDialog;

Context mContext = getApplicationContext();
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.custom_dialog,
                               (ViewGroup) findViewById(R.id.layout_root));

TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("Hello, this is a custom dialog!");
ImageView image = (ImageView) layout.findViewById(R.id.image);
image.setImageResource(R.drawable.android);

builder = new AlertDialog.Builder(mContext);
builder.setView(layout);
alertDialog = builder.create();
</pre>

<p>Using an AlertDialog for your custom layout lets you
take advantage of built-in AlertDialog features like managed buttons,
selectable lists, a title, an icon and so on.</p>

<p>For more information, refer to the reference documentation for the 
{@link android.app.Dialog} and {@link android.app.AlertDialog.Builder} 
classes.</p>