Accessing Android resources

Android has a special folder called res, it makes easier to accessing android resources. Using resources you can provide different characteristics to your application without modifying your code. Different dimensions, layouts, image sizes, languages, etc…

Accessing Android resources

Resource Types

The resource folder supports some special subdirectories.

Directory	Resource Type
animator	XML files that define property animations
anim	XML files that define tween animations
color	XML files that define a static list of colors
drawable	Bitmap files (.png, .9.png, .jpg, .gif) or XML files
layout	XML files that define a user interface layout
menu	XML files that define application menus
raw	Arbitrary files to save in their raw form
values	XML files that contain simple values
xml	Arbitrary XML files that can be read at runtime

See more on the Android website

R.java

When you put a file in a resource folder, the ide will automatically add it to a special class named R (This class is auto-generated. NEVER change it). By default, it will create something like R.directory.filename (without extension), except for the files inside the folders andvaluescolor. For those, the IDE will use the tags inside this file. For example:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">ATest</string>
    <string-array name="gender">
        <item>Female</item>
        <item>Male</item>
    </string-array>
    <dimen name="app_padding">10dp</dimen>
</resources>

In this case ,the IDE creates three entries on the R file: R.string.app_name, R.array.gender and R.dimen.app_padding

Accessing

XML

For accessing resources inside your XML you can use: @<resource_type>/<resource_name>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="@dimen/app_padding">
    <ImageView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:src="@drawable/ic_launcher" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/app_name" />
</LinearLayout>

Java

For accessing resources inside your classes you can use: R.<resource_type>.<resource_name>
Some methods just expect a Resource Id to be provided, like:

setContentView(R.layout.xpto);
myTextView.setText(R.string.app_name)

Sometimes you need to get the content of your resource. Context and Activity have methods to access resources

getResources().get<resource_type>(R.<resource_type>/<resource_name>);

public class MyActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        String appName = getResources().getString(R.string.app_name);
        String[] gender = getResources().getStringArray(R.array.gender);
    }
}

For more details take a look at Android documentation page Accessing Resources or in this example app

Accessing Android resources