book

App Inventor 2, 2nd Edition

by David Wolber, Hal Abelson, Ellen Spertus, Liz Looney

October 2014

Beginner to intermediate

360 pages

9h 3m

English

O'Reilly Media, Inc.

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A Blocks Language for Mobile PhonesWhat Can You Do with App Inventor?Why App Inventor WorksWhat Kind of Apps Can You Build?Who Can Build Apps?Conventions Used in This BookUsing Code ExamplesSafari® Books OnlineHow to Contact UsAcknowledgments
What You’ll LearnThe App Inventor EnvironmentDesigning the ComponentsMaking a LabelAdding the ButtonAdding the Meow SoundLive TestingAdding Behaviors to the ComponentsMaking the Kitty MeowAdding a PurrShaking the DeviceDownloading the App to Your Android DeviceSharing the AppVariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsCreating the Color ButtonsUsing Arrangements for Better LayoutsAdding the CanvasArranging the Bottom Buttons and the Camera ComponentAdding Behaviors to the ComponentsAdding the Touch Event to Draw a DotAdding the Drag Event That Draws a LineChanging the ColorLetting the User Take a PictureChanging the Dot SizeReferencing the dotSize Variable in DrawCircleChanging the Value of dotSizeThe Complete App: PaintPotVariationsSummary
What You’ll BuildWhat You’ll LearnGetting StartedDesigning the ComponentsPlacing the Action ComponentsPlacing the Label ComponentsAdding Behaviors to the ComponentsMoving the MoleCreating the MoveMole ProcedureCalling MoveMole When the App StartsCalling MoveMole every SecondKeeping ScoreProcedural AbstractionResetting the ScoreVibrating When the Mole Is TouchedThe Complete App: MoleMashVariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsAdding Behaviors to the ComponentsAuto-Responding to a TextEntering a Custom ResponseStoring the Custom Response PersistentlyRetrieving the Custom Response When the App OpensSpeaking the Incoming Texts AloudAdding Location Information to the ResponseSending the Location as Part of the ResponseThe Complete App: No Texting While DrivingVariationsSummary
What You’ll BuildWhat You’ll LearnDesigning the ComponentsGetting StartedPlacing the Initial ComponentsAdding Behaviors to the ComponentsMoving the LadybugDisplaying the Energy LevelStarvationAdding an AphidProgramming the Ladybug to Eat the AphidDetecting a Ladybug-Aphid CollisionThe Return of the AphidAdding a Restart ButtonAdding the FrogThe Return of the LadybugAdding Sound EffectsThe Complete App: Ladybug ChaseVariationsSummary
What You’ll LearnDesigning the ComponentsSetting the Properties of ActivityStarterAdding Behaviors to the ComponentsCreating a List of DestinationsLetting the User Choose a DestinationOpening Maps with a Search URLThe Complete App: Map Tour with Activity StarterA Virtual Tour with the Web ViewerFinding the URL for Specific MapsDefining the URLs ListModifying the ListPicker.AfterPicking BehaviorThe Complete App: Map Tour (Web Viewer)VariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsAdding Behaviors to the ComponentsDisplaying the Current LocationRecording the Current LocationDisplaying Directions to the Remembered LocationStoring the Remembered Location PersistentlyRetrieving the Remembered Location When the App LaunchesThe Complete App: Android, Where’s My Car?VariationsSummary

What You’ll LearnGetting StartedDesigning the ComponentsAdding Behaviors to the ComponentsDefining the Question and Answer ListsDefining the Index VariableDisplaying the First QuestionIterating Through the QuestionsMaking the Quiz Easy to ModifySwitching the Image for Each QuestionChecking the User’s AnswersThe Complete App: The Presidents QuizVariationsSummary
What You’ll BuildWhat You’ll LearnGetting StartedDesigning the ComponentsCreating the KeyboardCreating the First Note ButtonsAdding the Sound ComponentConnecting the Sounds to the ButtonsInstructing Android to Load the SoundsImplementing the Remaining NotesRecording and Playing Back NotesAdding the ComponentsRecording Notes and TimesPlaying Back NotesPlaying Back Notes with Proper DelaysThe Complete App: XylophoneVariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsAdding Behaviors to the ComponentsCreating Empty Question and Answer ListsRecording the User’s EntriesBlanking Out the Question and AnswerDisplaying Question-Answer Pairs on Multiple LinesCalling the displayQAs ProcedureSaving the QAs Persistently on the WebLoading Data from the DatabaseThe Complete App: MakeQuizTakeQuiz: An App for Taking the Quiz in the DatabaseHow the Blocks WorkThe Complete App: TakeQuizVariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsAdding Behaviors to the ComponentsResponding to Incoming TextsAdding Numbers to the Broadcast ListBroadcasting the MessagesBeautifying the List DisplayLogging the Broadcasted TextsStoring the BroadcastList in a DatabaseLoading the BroadcastList from a DatabaseThe Complete App: Broadcast HubVariationsSummary
What You’ll LearnGetting StartedDesigning the ComponentsNon-Visible ComponentsVisible ComponentsAdding Behaviors to the ComponentsConnecting to the NXTDisplaying the List of RobotsMaking the Bluetooth ConnectionDisconnecting from the NXTDriving the NXTUsing the Ultrasonic Sensor to Detect ObstaclesVariationsSummary
What You’ll LearnWhat is an API?Getting StartedDesigning the ComponentsProgramming the App’s BehaviorSearching by KeywordSearching by ISBNDon’t Leave Your Users HangingScanning a BookImproving the DisplayThe Complete App: Amazon at the BookstoreCustomizing the APIVariationsSummary
ComponentsBehaviorAn App as a RecipeAn App as a Set of Event HandlersEvent TypesUser-Initiated EventsInitialization EventsTimer EventsAnimation EventsExternal EventsEvent Handlers Can Ask QuestionsEvent Handlers Can Repeat BlocksEvent Handlers Can Remember ThingsEvent Handlers Can Interact with the WebSummary
Software Engineering PrinciplesSolve Real ProblemsBuild a Prototype and Show UsersIncremental DevelopmentDesign Before CodingComment Your CodeDivide, Layer, and ConquerUnderstand Your Language: Tracking with Pen and PaperDebugging an AppWatching VariablesTesting Individual BlocksIncremental Development with Do ItDisabling BlocksSummary
Named Memory SlotsPropertiesDefining VariablesSetting and Getting a VariableSetting a Variable to an ExpressionIncrementing a VariableBuilding Complex ExpressionsDisplaying VariablesLocal VariablesSummary
Adding a Canvas Component to Your AppThe Canvas Coordinate SystemAnimating Objects with Timer EventsCreating MovementSpeedCollision DetectionEdgeReachedCollidingWith and NoLongerCollidingWithInteractive AnimationSpecifying Sprite Animation Without a Clock TimerSummary
Testing Conditions with if and else if BlocksProgramming an Either/Or DecisionProgramming Conditions Within ConditionsProgramming Complex ConditionsSummary
Creating a List VariableSelecting an Item in a ListUsing an Index to Traverse a ListExample: Traversing a List of Paint ColorsCreating Input Forms and Dynamic DataDefining a Dynamic ListAdding an ItemDisplaying a ListRemoving an Item from a ListLists of ListsSummary
Controlling an App’s Execution: Branching and LoopingIterating Functions on a List with for eachA Closer Look at LoopingWriting Maintainable CodeUsing for each to Display a ListThe while-do BlockUsing while-do to Compute a FormulaSummary
Eliminating RedundancyDefining a ProcedureCalling a ProcedureThe Program CounterAdding Parameters to Your ProcedureReturning Values from a ProcedureReusing Blocks Among AppsThe distanceBetweenPoints ProcedureSummary
Storing Persistent Data in TinyDBRetrieving Data from TinyDBShared Data and TinyWebDBStoring Data by Using TinyWebDBRequesting and Processing Data with TinyWebDBGetValue-GotValue in ActionA More Complex GetValue/GotValue ExampleRequesting Data with Various TagsSetting Up a Web DatabaseSummary
Creating Location-Aware AppsThe Global Positioning SystemSensing Location with App InventorChecking BoundariesLocation Information Providers: GPS, WiFi, and Cell IDUsing the Orientation SensorUsing the Roll Parameter to Move an ObjectMoving in Any Direction by Using Heading and MagnitudeUsing the Phone As a CompassUsing the AccelerometerResponding to the Device ShakingUsing the AccelerometerSensor’s ReadingsDetecting Free FallSummary
The WebViewer ComponentThe Web ComponentStock Market SampleTinyWebDB and TinyWebDB-Compliant APIsSummary

Content preview from App Inventor 2, 2nd Edition

Preface

You’re on your regular running route, just jogging along, and an idea for the next killer mobile app hits you. All the way home, you don’t even care what your time is, all you can think about is getting your idea out there. But how exactly do you do that? You’re no programmer, and that would take years, and time is money, and...well, someone has probably done it already anyway. Just like that, your idea is dead in the water.

Now imagine a different world, where creating apps doesn’t require years of programming experience, where artists, scientists, humanitarians, health-care workers, attorneys, firefighters, marathon runners, football coaches, and people from all walks of life can create apps. Imagine a world where you can transform ideas into prototypes without hiring programmers, where you can make apps that work specifically for you, where you can adapt mobile computing to fit your personal needs.

This is the world of App Inventor, a visual programming tool for building mobile apps. Based on a visual “blocks” programming method that’s proven successful even with kids, App Inventor dramatically lowers the barriers to creating apps for Android phones and devices. How about a video game where the characters look like you and your friends? Or a “did you pick up the milk?” app that reminds you if it’s after 3 p.m. and you’re near the grocery store? Or a quiz app you give your significant other that’s in fact a surprise marriage proposal? “Question 4: Will you marry me? ...