Android Boot Camp for Developers Using Java, Comprehensive: A Guide to Creating Your First - PowerPoint Presentation

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Android Boot Camp for Developers Using Java, Comprehensive: A Guide to Creating Your First Android AppsChapter 5: Investigate! Android Lists, Arrays, and Web Browsers

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ObjectivesIn this chapter, you learn to:Create an Android project using a listDevelop a user interface that uses ListViewExtend the ListActivity classUse an array to create a listCode a setListAdapter to display an arrayDesign a custom ListView layout with XML code

Display an image with the ListView controlChange the default title bar text

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Objectives (continued)Code a custom setListAdapter for a custom layoutCall the onListItemClick method when a list item is selectedWrite code using the Switch decision structureCall an intent to work with an outside appOpen an Android Web browserLaunch a Web site through the use of a URI using an Android browserTest an application with multiple

decisions

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Creating a ListLists are one of the most common designs in mobile appsScrollableSelectableProgrammable to bring up thenext Activity (screen)

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Creating a List5Android Boot Camp for Developers Using Java, 2nd Ed.Slide6

Creating a List (continued)Steps to complete the app:Create a list using a ListView control.Define an array to establish the items of the list.

Add the images used in the project.Define an XML file to design the custom list with a leading image.

Code a switch decision structure to handle the selection of items.

Open an Android Web browser to display a specified Uniform Resource Identifier (URI).

Create multiple classes and XML layout files to display pictures of attractions.

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Creating a List (continued)Opening screen contains a vertical list of attractionsList is automatically scrollable if it exceeds the window sizeListView is better than TableLayout View because each row can be selected for further actionSelecting an item opens up a related Web page or an image of the attraction

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Creating a List (continued)8Android Boot Camp for Developers Using Java, 2nd Ed.

Extending a ListActivity

A

ListActivity

class is needed to

display

a list of

items

An ExpandedlistView can be

used to provide a two-level

listSlide9

Creating a List (continued)9Android Boot Camp for Developers Using Java, 2nd Ed.Slide10

Creating a List (continued)Creating an ArrayArray variables can store more than one valueDifferent from other data types that can hold only one valueEach individual item in an array is called an elementRefer to each element using an index in the array

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Creating a List (continued)Declaring an ArraySquare brackets [ ] are used to define an arrayCurley braces { } contain the list of items in the array

String[] attraction={"Alcatraz Island", "Ferry Marketplace", "

Golden Gate Bridge", "Cable Car Trolley", "Fisherman's Wharf

"};

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Creating a List (continued)Using a setListAdapter and Array AdapterAn adapter provides a model for the layout and converts the data into a listThe setListAdapter

connects the list items to the images or Web pages they representAn array adapter supplies the array data to the ListView

setListAdapter(new

ArrayAdapter <

String

> (this,android.R.layout.simple_list_item_1

, attraction));

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Creating a List (continued)Adding the Images to the Resources FolderImages must be locatedin the drawable-hdpi folderRemember that images

may be subject to copyright laws

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Creating a List (continued)Changing the Title Bar TextCustom titles can appear in the title bar at the top of the window

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Creating a List (continued)Creating a Custom XML Layout for ListView

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Creating a List (continued)Creating a Custom XML Layout for ListView (Continued)

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Creating a List (continued)Coding a setListAdapter with a Custom XML LayoutBuilt-in layout is called simple_list_item_1

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Creating a List (continued)Using the onListItemClick methodonListItemClick() is called when an item from the list is selectedThe item’s position in the list is captured so the app knows which of the items was selected

The position represents the number of the item in the list

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Creating a List (continued)Using the onListItemClick method (Continued)

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Creating a List (continued)Decision Structure – Switch StatementIf statements are also decision structuresThe switch statement is used when there are many list items to be evaluatedCan only evaluate integers or single characters

The keyword case is used to test each itemThe keyword break

is used to exit the switch decision structure

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Creating a List (continued)Decision Structure – Switch Statement (Continued)

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Creating a List (continued)Android IntentsAndroid intents send and receive activities and services including:Opening a Web pageCalling a phone numberLocating a GPS position on a mapPosting notes to a note-taking program

Opening your contacts listPosting to a social network

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Creating a List (continued)Launching the Browser from an Android DeviceThe intent sends the browser a URI (Uniform Resource Identifier)URI is similar to URL (Uniform Resource Locator)

URI has additional information necessary for gaining access to the resources required for posting the pageThe action called ACTION_VIEW

(must be in

caps

) is what actually displays the page in the browser

ACTION_VIEW is the most common action performed on data

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Creating a List (continued)24Android Boot Camp for Developers Using Java, 2nd Ed.Slide25

Designing XML Layout FilesXML layout files must be designed to display an ImageView control with an image source file 25

Android Boot Camp for Developers Using Java, 2nd Ed.Creating a List

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Designing XML Layout Files (Continued)26Android Boot Camp for Developers Using Java, 2nd Ed.

Creating a List (continued)Slide27

Designing XML Layout Files (Continued)27Android Boot Camp for Developers Using Java, 2nd Ed.

Creating a List (continued)Slide28

Adding Multiple Class FilesA new class is needed to display each imageClasses must be referenced in the Android Manifest FileCode for Wharf.java class (Bridge and trolley already created)

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Creating a List

(continued)Slide29

Adding Multiple Class Files (Continued)29Android Boot Camp for Developers Using Java, 2nd Ed.

Creating a List

(continued)Slide30

Opening the Class FilesstartActivity opens the next Activity which launches the appropriate XML layoutRunning and testingthe ApplicationBe sure to test every optionShould handle

all clicks

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Creating a List

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SummaryThe Java View class creates a list and makes it scrollable; use a ListView control to select each row for further actionExtend the ListActivity class in Main.java to display a ListView controlDeclare list items in an array variableThe index provides access to each element in the list (the list begins with 0)To declare an array, specify the data type followed by the values

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Summary (continued)Use an adapter to display the values in the arrayA ListView control is a container for the list items and the adapter binds the elements of the array to the ListView layout statements if the condition is falseDrag controls from the palette to the emulator for a simple designAdd code to the main.xml file to get a custom layout

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Summary (continued)App names are displayed in the app title bar – can be customizedsetListAdapter has 3 parameters:this classThe layout used to display the listThe array containing the list valuesCode the onListItemClick method to respond to the event of the user’s selection

Use the switch decision structure with a list or menu

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Summary (continued)Android intents send and receive activities and servicesTest every possible combination of clicks, including incorrect user entries before publishing the app

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