lec 07

Graphics

Animations

Location Services (GPS)

Translating Location to Address

Translating Address to Location

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Graphics resources in Android

PNG (Portable Network Graphics) is a very versatile format among the raterized formats

Make/search for PNGs with transparent backgrounds.

Raster versus Vector

Vector will render perfectly every time and scales infinitely. If you need to use buttons with fancy borders, use 9patch.

Good resource is http://openclipart.org/ From this you can get/create most any graphic element you need.

Use 9-Patch

Steps to creating 9-patch image

1/ find a good png with a transparent background.2/ open in image editor (Photoshop) and create at least a 1px tranparent margin along all sides. 3/ Issue the following command from command-line: draw9patch4/ drag/open your png into this tool. 5/ Define registration marks; left and top define the scalable area, and the bottom and right define the content area.

Android drawable directory structure.

drawable is the default directory.

drawable-mdpi (medium) is usually the corresponding directory with the same assets

drawable-ldpi (low)drawable-hdpi (high) drawable-xhdpi (extra-high)

Android's recommended percentages:

75%, 100%, 150%, 200% where medium is the baseline

When scaling your images, find the highest possible resolution and scale like this:37.5%, 50%, 75%, 100% where xhdpi is the baseline

Scaling images

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Using Location Services in Android

You must generate a debug key. See video on how to do this. ~/content/lec07/22GenerateKey.webm

Your key is dev-machine specific. If you're developing on a laptop and a desktop, you will need seperate keys for each.

Window || Preferences || Android || Build to see where the key is stored.

You don't have to, but it's easier if you externalize the key to a string.

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Using Location Services in Android

Translate from place description e.g. 'Millennium park' to location.

Translate from location to map

Overlays: extends ItemizedOverlay<OverlayItem>

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Context

In Android, Context is God. It give you direct access to application level calls such as startActivity and startService.

Many components in Android indirectly extend the Context class, including Activity and Service, but you're better off accessing the ApplicationContext because it will never be null so long as the app is in memory.

http://stackoverflow.com/questions/6854265/getapplicationcontext-getbasecontext-getapplication-getparent

http://stackoverflow.com/questions/1026973/android-whats-the-difference-between-the-various-methods-to-get-a-context