Mobile Programming Lecture 7 Dialogs, Menus, and SharedPreferences.

Mobile ProgrammingLecture 7

Dialogs, Menus, and SharedPreferences

Agenda

• Dialogs

• Menus

• SharedPreferences

Android Application Components

1. Activity

2. Broadcast Receiver

3. Content Provider

4. Service

Dialogs

• A dialog is a small window that appears in front of the current Activity

• It causes the Activity to lose focus

• Used for ProgressBars, Alerts, etc

Dialogs

• onCreateDialog() is called the first time.

• onPrepareDialog is called every time its opened.o without this, it will remain the same as the first time it

was opened

Dialogs - AlertDialog

• an AlertDialog is an extension of the 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

o a titleo a text messageo one, two, or three buttonso a list of selectable items (with optional checkboxes

or radio buttons)

Dialogs - Creating an AlertDialogpublic class MyDialogs extends Activity {

static final int DIALOG_EXIT_ID = 1;

@Override protected Dialog onCreateDialog(int id) {

Dialog dialog = null;

switch(id) { case DIALOG_EXIT_ID:

AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage("Do you want to exit?"); builder.setCancelable(true); builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { AlertDialogExample.this.finish(); } });

dialog = builder.create();break;

return dialog;}

Nothing special here, just an int I use to identify the dialog, because we can have more than one

return dialog;}

Override this method of Activity, which is called when you want to show any dialog of the Activity

return dialog;}

Switch because we can have more than one dialog, meaning we need to check the dialog id

return dialog;}

If you want an AlertDialog, you need to build one first

return dialog;}

Give the user a message

return dialog;}

If true, then the user can press the back button to dismiss the dialog. false would force the user to make an action on the dialog.

return dialog;}

Add a button, AND set a listener for when the button is pressed. This is should be the "positive" button, e.g. "Yes", "Absolutely!"

return dialog;}

This is the listener for then the "positive" button is pressed, so you should take some kind of action.

return dialog;}

The Dialog isn't created until you call create()

return dialog;}

The type of this method is Dialog, so here we return ... the Dialog!

You can add up to 3 buttons on the AlertDialog by calling

1. dialog.setPositiveButton()

o we just used this one in the previous slides

2. dialog.setNegativeButton()

o "No", "Cancel"3. dialog.setNeutralButton()

o "Remind me Later"

Dialogs - Showing a Dialog

• To show a Dialog on the screen, simply call

o showDialog(int)

from within your Activity.

• It takes as parameter the ID of the dialog.

• You can also call it from within an anonymous inner

• Make sure you override the onCreateDialog() method

in that Activity!

See AlertDialogExample

Dialogs - Dismissing a Dialog

• You don't want to show the Dialog to the user forever!

• You have to allow the user to close the dialog somehow,

even if it's not cancelable

• You can dismiss the Dialog by calling

o dismissDialog(int) from within the controlling

Activity where the argument is the Dialog ID

o dismiss() on the Dialog object

e.g. dialog.dismiss()

See DismissDialogExample

Dialogs - AlertDialog with a List

• Not only buttons!

• You can also add a list to your AlertDialog

String[] countries = new String[]{"Netherlands", "USA", "St. Martin", "Curacao"};

@Override public Dialog onCreateDialog(int id) {

Builder builder = new AlertDialog.Builder(this);

builder.setTitle("Select a Country");

builder.setItems(countries, new DialogInterface.OnClickListener() {

@Override public void onClick(DialogInterface dialog, int index) {

Toast.makeText(getApplicationContext(),

"You selected " + countries[index],

Toast.LENGTH_LONG).show(); }

return builder.create();

We will use this String array for our list

This is a method in an Activity class, as in the previous example

We're still using an AlertDialog Builder

This time we call setItems()!

First argument should be your list of items

There is more than one OnClickListener class!

If you want to use both View.OnclickListener (for buttons) and DialogInterface.OnClickListener (for Dialogs), then you need to be more specific here

When an item in the list is clicked, Android kindly provides you with the Dialog object itself, as well as the index of the clicked item

Let's not forget to create the Dialog and return it

See AlertDialogListExample

Dialogs - Date/TimePicker Dialogs

See DatePickerDialogExample

Dialogs - Custom Dialogs - SeekBar

• You can create your own Dialog if the standard Android

Dialogs are not suitable for your needs

• For example, there is no SeekBar Dialog, but you can

create your own

• See CustomDialogExample

Dialogs - DialogFragment

• creating Dialogs by using the onCreateDialog() method

of an Activity is old school

• creating Dialogs by using a DialogFragment is new

school

• DialogFragment also has an onCreateDialog() callback

method!

o i.e., both an Activity and a DialogFragment have an

onCreateDialog() callback method

DialogFragment is slightly different than the other

Fragments we've seen so far

• We don't need to add it to the XML

• Nor do we need to add it to the UI using a

FragmentTransaction

public class MyActivity extends Activity {

@Override public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button button = (Button) findViewById(R.id.button1);

button.setOnClickListener(new OnClickListener() {

@Override public void onClick(View v) {

MyDialogFragment f = new MyDialogFragment();

f.show(getFragmentManager(), "dialog");

public void doPositiveClick() {

Toast.makeText(this, "doPositiveClick()", Toast.LENGTH_LONG).show();

Let's create our Activity first ...

Let's show the Dialog when this Button is clicked!

The Button was just clicked at this point, so let's create a new instance of MyDialogFragment, which we will see in a few slides

Just call .show() on the Fragment! This time we didn't need to use the FragmentTransaction to add the Fragment

Just pass the FragmentManager and it will take care of adding and removing the Fragment for you

Second argument is the tag that you want to assign to the Fragment

We will get back to this!

Let's take a look at our DialogFragment

public class MyDialogFragment extends DialogFragment {

@Override

public Dialog onCreateDialog(Bundle savedInstanceState) {

Builder builder = new AlertDialog.Builder(getActivity());

builder.setTitle("This is a DialogFragment!");

builder.setPositiveButton("OK", new OnClickListener() {

@Override

public void onClick(DialogInterface dialog, int which) {

MyActivity act= (MyActivity) getActivity();

act.doPositiveClick();

@Override

DialogFragment!

@Override

Dialog also has an onCreateDialog(), the proof is in the @Override

@Override

This is how we get the Context from within a Fragment, remember!?

@Override

We need to return a Dialog!

@Override

You've seen this other stuff before!

@Override

The button in the Dialog has now been clicked! What do we do next?

@Override

Let's get a handle on the Activity containing this Fragment

@Override

Let's call our own custom method, doPositiveClick() on the Activity

Which takes us back here, back to our Activity.

Simply make a Toast as evidence that we were successful

• Note that we don't need to override onCreateView() or

onActivityCreated() methods of a DialogFragment

• You may choose to override onCreateView() and return

a View if you want to create some custom Dialog

without using onCreateDialog()

• I'll leave it up to the Android developer's website to

explain it if anyone is interested in doing so

See FragmentDialogExample

Menu Options

• In Android 2.3.x and below, clicking on the dedicated

Menu button allows the user to reveal menu options

• In Android 3.0 and above, the options menu is

presented by way of an action bar

o the dedicated Menu button is deprecated and some

devices just do not have one

Menu Options - Creating one <= 2.3.x

• Right click on your project > New > Other ...

• Select Android XML File

• In the Resource Type drop down list, select Menu

• Enter a File name and click Finish

• Click Add ... > Item

• Edit the id as appropriate, and enter the Title

• Repeat to add additional menu options

We will use this Menu XML file, main_menu.xml, for our

example

<?xml version="1.0" encoding="utf-8"?>

<item android:id="@+id/set_text"

android:title="@string/set_text_opt"/>

<item android:id="@+id/close"

android:title="@string/close_opt" />

</menu>

@Override

public void onCreate(Bundle savedInstanceState) {

@Override

public boolean onCreateOptionsMenu(Menu menu) {

MenuInflater inflater = getMenuInflater();

inflater.inflate(R.menu.main_menu, menu);

return true;

@Override

return true;

Override this Activity method

@Override

return true;

Similar to a LayoutInflater, but for Menus instead

@Override

return true;

Show the Menu now

@Override

return true;

This is the Menu XML file that we created previously

@Override

return true;

This is given as argument to onCreateOptionsMenu, so use it as argument to inflate the menu

@Override

return true;

Return true if you want the menu to be displayed, false if you don't

• This is enough for the Menu to be displayed on the

screen when the user presses the Menu button

• If you want to take action after an option is selected,

then you need to override the onOptionsItemSelected()

method of Activity

@Override

public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.set_text:

TextView tv = (TextView) findViewById(R.id.textView1);

tv.setText("First Option Selected!");

break;

case R.id.close:

Toast.makeText(this, "Goodbye!", Toast.LENGTH_LONG).show();

finish();

break;

return true;

@Override

case R.id.set_text:

break;

case R.id.close:

finish();

break;

return true;

We override this method of Activity

@Override

case R.id.set_text:

break;

case R.id.close:

finish();

break;

return true;

Which menu item was selected?

@Override

case R.id.set_text:

break;

case R.id.close:

finish();

break;

return true;

Here we just changed the text of a TextView when the item R.id.set_text is selected

@Override

case R.id.set_text:

break;

case R.id.close:

finish();

break;

return true;

Here we close our app when item R.id.close is selected

See MenuOptionsExample

You can change the menu options that show up at runtime

Menu Options - Creating one >= 3.0

For Android 3.0 and higher ...

http://developer.android.com/guide/topics/ui/actionbar.html

Context Menu

• A context menu is a floating menu that appears when

the user performs a long-click on an element. It

provides actions that affect the selected content.

• You can provide a context menu for any view, but they

are most often used for items in a

o ListView

o other view collections in which the user can perform

direct actions on each item.

Context Menu - Creating one

When creating a Context Menu, you can create

a Menu XML file in the same way you do for an

Options Menu

We will use the following XML file for our example

</menu>

We will use the following XML file for our example

</menu>

All of the callback methods in this example are declared within our ListActivity

As a reminder,

• a ListActivity extends Activity

• it already has a ListView, so you don't need to add one

the the Layout XML file

o you don't even need to use a Layout XML File

o which means you don't need to call

setContentView()

• You can get a handle on the ListView by simply calling

getListView().

public class ContextMenuExample extends ListActivity {

String[] entries = new String[]{"Martin","Anderson","Junior","George","Dan"};

@Override

this.setListAdapter(new ArrayAdapter<String>(this,

android.R.layout.simple_list_item_1, entries));

registerForContextMenu(getListView());

String[] entries = new String[]

{"Martin","Anderson","Junior","George","Dan"};

@Override

We will use this String array to populate our List

@Override

Populate the ListView here

@Override

Register the ListView with a Context Menu, now the menu will show up when you long press on the ListView

@Override

public void onCreateContextMenu(ContextMenu menu, View v,

ContextMenuInfo menuInfo) {

super.onCreateContextMenu(menu, v, menuInfo);

inflater.inflate(R.menu.context_menu, menu);

onCreate() from previous slide is here

@Override

Override this method. It is called when the Context Menu for View v is being built

@Override

You've seen this before

@Override

onContextItemSelected() on the next slide goes here

@Override public boolean onContextItemSelected(MenuItem item) {

AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();

TextView tv = (TextView) getListView().getAdapter().getView(info.position, null, null);

switch(item.getItemId()) {

case R.id.edit_option:

/* Edit option selected */

break;

case R.id.share_option:

/* Share option selected */

break;

case R.id.delete_option:

break;

return true;

Override this method of Activity

break;

return true;

This Object has information about the Context Menu, NOT the item in the List

break;

return true;

This Object will have information about the item pressed

break;

return true;

We can get a handle on the item in the ListView by using info.position

break;

return true;

info.position tells us which item was pressed, this is how we tell which Menu Item was pressed

break;

return true;

By combining info.position and item.getItemId(), we know the action needs to be performed on the item

See ContextMenuExample

Preferences - SharedPreferences

• SharedPreferences is 1 of the 5 methods for Data

Storage in Android

• Internal and external storage, remote server, and local database.

• http://developer.android.com/guide/topics/data/data-storage.html

• It stores primitive key-value pairs of primitive data types

o boolean, int, float, long, String

• Data persists even if your app has been fully terminated

• SharedPreferences are only available to app that

created them!

public class SharedPrefsExample extends Activity {public static final String PREFS_NAME = "MyPrefsFile";

@Override protected void onCreate(Bundle state){super.onCreate(state);

SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);boolean silent = settings.getBoolean("silentMode", false);setSilent(silent);

@Override protected void onStop(){super.onStop();

SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);SharedPreferences.Editor editor = settings.edit();editor.putBoolean("silentMode", mSilentMode);editor.commit();

The desired name of your SharedPreferences file

You can get a SharedPreferences file by name by calling this method

The second argument is the mode

If the SharedPreferences file doesn't exist at this point, it will be created for you

Try to get the boolean value "silentMode", "silentMode" is the key. You decide on the name of the key. "silentMode" is not a keyword here

If the key doesn't exist (could be because the file was just created in the previous line of code), then this will be the value returned

An imaginary method that you created to change the volume setting of the device to silent

We want data to persist even after the app has been terminated, so let's Override onStop()

Get a handle on our SharedPreferences again, which should have the "silentMode" value set at this point

If we want to modify the SharedPreferences, we need to use a SharedPreferences Editor

Let's set the value value of silentMode to the imaginary boolean value mSilentMode

Don't forget to save your changes to the file!

See SharedPrefsExample

Preferences - PreferenceActivity

If you want to provide the user with a UI for changing

preferences, you can use a PreferenceActivity in

combination with SharedPreferences

To create a PreferenceActivity, first create a Preference

XML file

• File > New > Other > Android XML File

• Resource Type: Preference

• Enter the file name, e.g. preferences.xml

• Root Element: PreferenceScreen

• Click Add to add various types of Preferences

o e.g. EditText

• Expand the Attributes on the right to edit the attributes

for your preferences

We will use this preferences.xml file for our example

<EditTextPreference android:dialogTitle="Username" android:dialogMessage="Please enter your

Username" android:summary="Username for logging in to this app" android:title="Username"

android:key="username"/>

<CheckBoxPreference android:summaryOff="I do not want your spam" android:key="spam"

android:title="Spam" android:summaryOn="Sign me up for spam"/>

</PreferenceScreen>

Creating a PreferenceActivity is easy!

public class Preferences extends PreferenceActivity {

@Override

addPreferencesFromResource(R.xml.preferences);

@Override

Extend PreferenceActivity

@Override

From the preferences.xml file we added previously

In your main Activity, you can get the Preferences without

specifying the name of the XML file

public class MainActivity extends Activity {

SharedPreferences mPrefs;

@Override

mPrefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

String username = mPrefs.getString("username","None");

@Override

This will allow you to access the preference settings, even if you have more than one preference XML file associated with a PreferenceActivity

@Override

These preferences will automatically save when the user interacts with them!

See PreferenceActivityExample

• You can also add a Listener for when a

Preference has been changed

• When a Preference is changed, you may

need to update certain values tied to these

Preferences

Preferences - PreferenceFragment

Android 3.0 and higher

PreferenceFragment

References

• The Busy Coder's Guide to Android Development - Mark Murphy

• Android Developers

• The Mobile Lab at Florida State University

Mobile Programming Lecture 7 Dialogs, Menus, and SharedPreferences.

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