3.9.1. Organize resources in eclipse ¶

You need to place each resource in the project res/ A specific subdirectory of the directory. For example, this is the file level of a simple project:

MyProject/
    src/
        MyActivity.java
    res/
        drawable/
            icon.png
        layout/
            activity_main.xml
            info.xml
        values/
            strings.xml

res/ The directory contains all the resources in various subdirectories. There is a picture resource, two layout resources and a string resource file. The following table shows in detail in the project res/ Resources supported in the directory.

3.9.2. Alternative resources ¶

Your application needs to provide alternative resource support for specific device configurations. For example, you need to provide alternative image resources for different screen resolutions and alternative string resources for different languages. At run time, Android detects the current device configuration and loads the appropriate resources for the application.

To identify a series of alternative resources for a specific configuration, follow these steps:

• In res/ Create a new directory under to <resource_name>_<config_qualifier> The way it is named. Here resources_name Is any of the resources mentioned in the above table, such as layouts, pictures, etc. qualifier It will determine which resources are used in the configuration of personality. You can check the official documentation for a complete picture of different types of resources. qualifier List.

• Save alternative resources for responses in this directory. These resource files must match the default resource file names shown in the following example, but these files will replace what is determined. For example, although the file name of the picture is the same, the resolution of the picture will also be high on a high-resolution screen.

Here is an example that specifies a default screen image and a high-resolution alternative image.

MyProject/
   src/
    main/
    java/
       MyActivity.java
       res/
          drawable/
            icon.png
            background.png
        drawable-hdpi/
            icon.png
            background.png
        layout/
            activity_main.xml
            info.xml
        values/
            strings.xml

Here is another example that specifies the layout of the default language and the alternative layout of the Arabic language.

MyProject/
   src/
    main/
    java/
       MyActivity.java
      res/
         drawable/
            icon.png
            background.png
        drawable-hdpi/
            icon.png
            background.png
        layout/
            activity_main.xml
            info.xml
        layout-ar/
            main.xml
        values/
            strings.xml

3.9.3. Access to resources ¶

In application development, you need to access defined resources, either through code or through XML files. The following sections describe how to access resources in each of these two scenarios.

3.9.4. Access resources in code ¶

When the Android application is compiled, an R class is generated that contains all of the res/ The ID of the resources under the directory. You can use the R class to access the resource through the subclass + resource name or directly using the resource ID.

3.9.5. Example ¶

Visit res/drawable/myimage.png And set it to ImageView You will use the following code:

ImageView imageView = (ImageView) findViewById(R.id.myimageview);
imageView.setImageResource(R.drawable.myimage);

The first line of code here uses R.id.myimageview To get in the layout file defined as myimageview Of ImageView . The second line is used R.drawable.myimage To get access to the res/ Of drawable Under the subdirectory named myimage It’s a picture.

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string  name="hello">Hello, World!</string>
</resources>

TextView msgTextView = (TextView) findViewById(R.id.msg);
msgTextView.setText(R.string.hello);

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:orientation="vertical" >

   <TextView android:id="@+id/text"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Hello, I am a TextView" />

   <Button android:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Hello, I am a Button" />

</LinearLayout>

public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main_activity);
}

3.9.6. Access in XML ¶

Consider the following XML resource file res/values/strings.xml Which contains 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>

Now, you can use these resources to set the text color and text content in the following layout file:

<?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" />

Now, if you go back to the “Hello World!” example explained in the previous chapter, I can be sure that you have a better understanding of all the concepts in this section. Therefore, I strongly recommend going back to the previous example and looking at the basic usage of my different resources.