For more complex resources such as entire layouts or drawables, the identifier is the filename (without the file extension): for example R.layout.activity_main refers to the root element of the layout/activity_main.xml file. This allows you to use dot notation to refer to each resource based on its type (e.g., R.eeting)-similar to the syntax used to refer to nested JSON objects!įor most resources, the identifier is defined as an element attribute ( name attribute for values like Strings id for specific View elements in layouts). Public static final String greeting = "Hello Android!" Public static final String app_name = "My Application" Style and theming information should be defined as resourcesĪs introduced in Lecture 1, there are a number of different resource types used in Android, and which can be found in the res/ folder of a default Android project, including:.Any user-facing strings should be defined as resources.Any graphic images (drawables) should be defined as resources.UI controls (buttons, etc) should mostly be defined as resources (they are part of layouts), though behavior will be defined programmatically in Java.Layouts should always be defined as resources.You can choose to show different images based on device screen resolution, or pick different Strings based on the language of the device (internationalization!)-the behavior of the app is the same, but the “content” is different! Similarly, keeping resources separate allows you to choose what resources to include dynamically. Theoretically you could have a Graphic Designer create these resources, which can then be integrated into the code without the designer needing to do a lick of Java. Resources represent components that are separate from the app’s behavior, so are kept separate from the Java code to support the Principle of Separation of Concernsīy defining resources in XML, they can be developed (worked on) without coding tools (e.g., with systems like the graphical “design” tab in Android Studio). You can think of them as “media content”: often images, but also things like text clippings (or short String constants), usually defined in XML files. Resources can be found in the res/ folder, and represent elements or data that are “external” to the code. 7.1 Intents for Another Activity (Explicit).
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