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 and short activities that directly relate to the application in progress.

The Android API supports the following types of {@link android.app.Dialog} objects:

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 Creating a Custom Dialog below.

Showing a Dialog

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.

Note: If you decide to create a dialog outside of the onCreateDialog() method, it will not be attached to an Activity. You can, however, attach it to an Activity with {@link android.app.Dialog#setOwnerActivity(Activity)}.

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.

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.

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()}.

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 switch statement that checks the id parameter that's passed into the method. Each case 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:

Then, define the {@link android.app.Activity#onCreateDialog(int)} callback with a switch case for each ID:

Note: 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 Creating an AlertDialog, offers code suitable for this example.

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

Dismissing a Dialog

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.

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.

Using dismiss listeners

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.

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()}.

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()}.

Creating an AlertDialog

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:

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()}.

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.

Adding buttons

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

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 not cancelable (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 set...Button() 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.

Note: 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.

Adding a list

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

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.

Adding checkboxes and radio buttons

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.

Note: To save the selection when the user leaves or pauses the Activity, you must properly save and restore the setting throughout the Activity Lifecycle. To permanently save the selections, even when the Activity process is completely shutdown, you need to save the settings with one of the Data Storage techniques.

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 setItems() method with {@link android.app.AlertDialog.Builder#setSingleChoiceItems(int,int,DialogInterface.OnClickListener) setSingleChoiceItems()}:

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

Creating a ProgressDialog

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.

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:

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).

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.

Showing a progress bar

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.

Example ProgressDialog with a second thread

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.

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...");
            progressThread = new ProgressThread(handler);
            progressThread.start();
            return progressDialog;
        default:
            return null;
        }
    }

    // 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.getData().getInt("total");
            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();
                Bundle b = new Bundle();
                b.putInt("total", total);
                msg.setData(b);
                mHandler.sendMessage(msg);
                total++;
            }
        }
        
        /* sets the current state for the thread,
         * used to stop the thread */
        public void setState(int state) {
            mState = state;
        }
    }
}

Creating a Custom Dialog

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)}.

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.

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)}.

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.

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

In this document

Key classes