Android resource
- 2. Topics • Externalizing resources • Default vs. Alternative resources • Providing resources • Providing alternative resources • Accessing resources > in Code > in XML • Localization
- 4. What are Resources? • Any static data that can be externalized from code > Layouts > Images > Video and audio files > Strings > Menu definitions > Animation > etc.
- 5. Why Externalizing Resources? • Allows you to maintain them independently (from code) • Allows you to provide alternative resources that support specific device configurations such as different languages or screen sizes, which becomes increasingly important as more Android-powered devices become available with different configurations.
- 7. Default vs. Alternative Resources • For any type of resource, you can specify default and multiple alternative resources for your application • Default resources are those that should be used regardless of the device configuration or when there are no alternative resources that match the current configuration • Alternative resources are those that you've designed for use with a specific configuration.
- 8. Default vs. Alternative Resources • Two device configurations, both using default resources • Two device configurations, one using alternative resources.
- 10. Grouping Resources under /res directory • You should place each type of resource in a specific subdirectory of your project's res/ directory. For example, here's the file hierarchy for a simple project: Myproject/ src/ MyActivity.java res/ drawable/ icon.png layout/ main.xml info.xml values/ strings.xml
- 11. Resources Directories • anim/ > XML files that define tween animations • color/ • drawable/ • layout/ • menu/ • raw/ • values/ • xml/
- 13. Why Alternative Resources? • Almost every application should provide alternative resources to support specific device configurations. > For instance, you should include alternative drawable resources for different screen densities and alternative string resources for different languages. • At runtime, Android automatically detects the current device configuration and loads the appropriate resources
- 14. How to specify Alternative Resources? • Create a new directory in res/ named in the form <resources_name>-<config_qualifier> > <resources_name> is the directory name of the corresponding default resources > <config_qualifier> is a name that specifies a configuration for which these resources are to be used • Save your alternative resources in this new directory > The resource files must be named exactly the same as the default resource files.
- 15. Example: Default & Alternative Resources res/ drawable/ icon.png background.png drawable-hdpi/ icon.png background.png • The hdpi qualifier indicates that the resources in that directory are for devices with a high-density screen. • While the images in each drawable directory are sized for a specific screen density, the filenames are the same.
- 16. Alternative Resource Qualifier Names • Mobile country code (MCC) > mcc310, mcc310-mnc004 • Language and region > en, fr, en-rUS, fr-rFR, fr-rCA • Screen size > small, normal, large • Screen orientation > port, land • Screen density > ldpi, mdpi, hdpi, nodpi
- 17. How Android Finds Best-matching Resource
- 19. Resource ID • Once you provide a resource in your application (discussed in Providing Resources), you can apply it by referencing its resource ID. • All resource IDs are defined in your project's R class, which the aapt tool automatically generates. • For each type of resource, there is an R subclass (for example, R.drawable for all drawable resources) and for each resource of that type, there is a static integer (for example, R.drawable.icon). This integer is the resource ID that you can use to retrieve your resource.
- 20. Two ways to access a resource • In code: Using an static integer from a sub-class of your R class, such as: > R.string.hello (string is the resource type and hello is the resource name) • In XML: Using a special XML syntax that also corresponds to the resource ID defined in your R class, such as: > @string/hello (string is the resource type and hello is the resource name)
- 22. Accessing Resources In Code • You can use a resource in code by passing the resource ID as a method parameter. • For example, you can set an ImageView to use the res/drawable/myimage.png resource using setImageResource(): ImageView imageView = (ImageView) findViewById(R.id.myimageview); imageView.setImageResource(R.drawable.myimage);
- 23. Example: Accessing Resources in Code // Load a background for the current screen from a drawable resource getWindow().setBackgroundDrawableResource(R.drawable.my_background_image) ; // Set the Activity title by getting a string from the Resources object, because // this method requires a CharSequence rather than a resource ID getWindow().setTitle(getResources().getText(R.string.main_title)); // Load a custom layout for the current screen setContentView(R.layout.main_screen); // Set a slide in animation by getting an Animation from the Resources object mFlipper.setInAnimation(AnimationUtils.loadAnimation(this, R.anim.hyperspace_in)); // Set the text on a TextView object using a resource ID TextView msgTextView = (TextView) findViewById(R.id.msg); msgTextView.setText(R.string.hello_message);
- 24. Accessing Platform Resources • Android contains a number of standard resources, such as styles, themes, and layouts. To access these resource, qualify your resource reference with the android package name. // Android provides a layout resource you can use for list items in a ListAdapter. // In this example, simple_list_item_1 is a layout resource defined by the // platform for items in a ListView. You can use this instead of creating your // own layout for list items. setListAdapter( new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, myarray));
- 26. Accessing Resources from XML • You can define values for some XML attributes and elements using a reference to an existing resource. • You will often do this when creating layout files, to supply strings and images for your widgets. <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/submit" />
- 27. Example: Accessing Resources from XML • If you have the following resource file that includes a color resource and a string resource: <?xml version="1.0" encoding="utf-8"?> <resources> <color name="opaque_red">#f00</color> <string name="hello">Hello!</string> </resources> • You can use these resources in the following layout file to set the text color and text string: <?xml version="1.0" encoding="utf-8"?> <EditText xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:textColor="@color/opaque_red" android:text="@string/hello" />
- 28. Example: Accessing Resources from XML • To reference a system resource, you would need to include the package name. <?xml version="1.0" encoding="utf-8"?> <EditText xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:textColor="@android:color/secondary_text_dark" android:text="@string/hello" />
- 29. Thank you