Android How to Program Presented by Thomas Bucag, Rob Goodfellowe, Samantha Tomeï ©1992-2013 by...

Slideshow AppAndroid How to Program

Presented by Thomas Bucag, RobGoodfellowe, Samantha Tomeï

©1992-2013 by Pearson Education, Inc. All Rights Reserved.

Objectives Demo of the app/GUI design Technology Overview UML Diagrams BitmapFactory TransitionDrawable MediaPlayer Intents

Overview

Launching Intents that use built-in content providers Specifying the GUI for an AlertDialog Customizing the Layout for a ListActivity Launch an Intent that returns a result ArrayAdapter for a ListView View-Holder Pattern Notifying a ListView when its data source changes Adding data to a GUI component for use in an event

handler Playing Music with a MediaPlayer Loading Images with BitmapFactory Cross fading between images with TransitionDrawable and BitmapDrawable

Technology Overview

Class Overview

Diagrams Generated by ObjectAid UML Explorer for Eclipsehttp://www.objectaid.com

Slideshow Class


Slideshow Editor ClassClass SlideshowEditor is-a ListActivity (List View) is-an Activity


Load BitmapFactory

Class SlideshowInfo, SlideshowPlayer

SlideshowInfo is used by SlideshowStores data for a single slideshow


TransitionDrawableClass PictureTaker, MediaItem


Bitmap FactoryUsed to create bitmap objectsUsed in this app to load from the device for use as thumbnailsPackage: android.graphicsExtends: java.lang.Object.android.graphics.BitmapFactoryNested Class: BitmapFactory.Options• Used in this case to configure the bitmaps, and downsample the images to save

memory• Helps prevent out of memory errors common with bitmaps

Public Constructor: BitmapFactory()Public Methods: public static BitmapdecodeFile(String pathName)

Since: API Level 1Decode a file path into a bitmap. If the specified file name is null, or cannot be decoded into a bitmap, the function returns null.Parameters:pathName - complete path name for the file to be decoded.Returns the resulting decoded bitmap, or null if it could not be decoded.

BitmapFactory.Options() - Create a default Options object, which if left unchanged will give the same result from the decoder as if null were passed.

Source: android.developer.com retrieved 30 July 2012

TransitionDrawableextends LayerDrawableimplements Drawable.CallbackHierarchyjava.lang.Objectandroid.graphics.drawable.Drawableandroid.graphics.drawable.LayerDrawableandroid.graphics.drawable.TransitionDrawable

• An extension of LayerDrawables that is intended to cross-fade between the first and second layer. To start the transition, call startTransition(int). To display just the first layer, call resetTransition().

• It can be defined in an XML file with the <transition> element. Each Drawable in the transition is defined in a nested <item>. For more information, see the guide to Drawable Resources.


TransitionDrawablePublic Constructor:• TransitionDrawable(Drawable[] layers)• Create a new transition drawable with the specified list of layers (at least 2). Public Methods:• draw(Canvas canvas): Draw in its bounds (set via setBounds) respecting optional

effects such as alpha (set via setAlpha) and color filter (set via setColorFilter).• setCrossFadeEnabled(boolean enabled): Enables or disables the cross fade of the

drawables.• isCrossFadeEnabled(): Indicates whether the cross fade is enabled for this transition.• startTransition(int durationMillis): Begin the second layer on top of the first layer. XML Attributes• android:top, :left, :right, :bottom - coordinate of the layer’s side.• android:drawable - Drawable used to render the layer.• android:id - Identifier of the layer. This can be used to retrieve the layer from a

drawbable container.


Ability to play music and videos within an application Import android.media.MediaPlayer MediaPlayer vs SoundPool Methods associated with MediaPlayer

◦ MediaPlayer //create new object◦ setDataSource //obtain file location◦ Prepare //prepares player◦ seekTo //passes a time◦ start //starts media player◦ pause //pauses playback◦ reset //resets media player◦ release //releases resources◦ setLooping //loop playback

Developer.android.com/reference/android/media/MediaPlayer.html

MediaPlayer

Launching Intents that use built-in content providers Specify the MIME type of data

◦ Activity that shows specified type of data (Fig. 12.4a)◦ Activity-chooser dialog to select Activity to use (Fig. 12.5)

Launch an Intent that returns a result startActivity to launch Activity associated with each Intent

◦ Favorite Twitter Searches app returns from Browser◦ Address Book app automatically returns to main Activity

startActivityForResult ◦ Refresh the Slideshow Activity’s ListView after the user edits a slideshow◦ Refresh the SlideshowEditor Activity’s ListView after the user adds a new

image to the slideshow◦ Get the location of an image of music track the user added to a

slideshow

Intents


Is a ListActivityIs an Activity

Android How to Program Presented by Thomas Bucag, Rob Goodfellowe, Samantha Tomeï ©1992-2013 by...

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