Android Resources (Resources) management

There are many things used to build an excellent Android app. In addition to coding the application, you need to focus on a variety of resources, such as you use a variety of static content, such as bitmaps, colors, layout definition, user interface strings, animation and so on. These resources are generally placed in the project's res / standalone subdirectory.

This section of the tutorial will learn how to organize your application resources, specify alternative resources, and access them in your application.

Organizational resources in eclipse

You will need to be placed in each resource under specific subdirectory of your project res / directory. For example, this is a simple file-level project:

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

res / directory contains all of the resources in various subdirectories. Here's a picture resource, two layout resources and a string resource file. The following table gives a detailed in the project res / directory support resources.

Alternative Resources

Your application needs to provide resources to support an alternative configuration for a specific device. For example, you need to provide an alternative picture of resources for different screen resolutions, providing an alternative string resources for different languages. At runtime, Android detects the current device configuration, and load the appropriate resources for an application.

To identify a set of alternative resources for specific configuration, following the steps of:

• Create a new directory res / down to <resource_name> _ <config_qualifier> are named. Here resources_name any resources mentioned in the table, such as layout and pictures. qualifier will determine what resources to use personalized configuration. You can see the official documentation for a complete list of the different types of resources qualifier.
• Saving alternative resources in response to this directory. These resource files must show the default resource file name is consistent with the following examples, however, these documents will determine the contents of the substitution. For example: While the picture's file name the same, but the screen resolution of the picture resolution will be higher.

Here is an example, to specify the default picture of the screen and high-resolution image substitution.

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, to specify the default layout language and alternative layouts 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

Access to resources

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

In the code to access resources

When the Android application is compiled to generate a class R, which contains the ID and all res / directory resources. You can use the class R, + by subclass resource name or directly use the resource ID to access resources.

Examples

Access res / drawable / myimage.png, and set it to the ImageView, you would use the following code:

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

The first line of code in here to get R.id.myimageview defined myimageview of ImageView in the layout file. The second line with R.drawable.myimage to get the image in res / drawable in a subdirectory called myimage.

Examples

Consider an example in which res / values ​​/ strings.xml defined as follows:

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

Now you can use the ID of the object msg of TextView resource ID to set the text, as follows:

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

Examples

Consider the following definition of the layout res / layout / activity_main.xml

<?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>

The application code will load the activity layout, onCreate () method as follows:

<?xml version="1.0" encoding="utf-8"?>
<resources>
   <color name="opaque_red">#f00</color>
   <string name="hello">Hello!</string>
</resources>

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"?>
<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, you can use these resources in the following layout file to set the text color and text content:

<code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;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" /&gt;
</code>

Now, if you return to the previous section to explain the "Hello World!" Instance, I can confirm you in this section all have a better understanding of the concept. Therefore, I strongly recommend to go back to look at the previous examples, and I use a different view of the basic resource usage.