The content provider (Implement content provider)

A content provider is a component that manages access to a central repository of data. A content provider can use different ways to store its data, such as a database, files, or even over a network.

To implement a content provider in Android, you need to follow some steps, such as:

• Define a contract class that defines constants for your content provider's URI, table name, column names, and MIME types.
• Extend the Content Provider class and implement its abstract methods: on Create (), query (), insert (), update (), delete (), and get Type ()
• Register your content provider
  
  
  using the <provider> element in the Android manifest file.
• Test your content provider using a client app or the adb shell.

How to define a contract class in android

A contract class is a class that defines constants that help applications work with the content URIs, column names, intent actions, and other features of a content provider. A contract class is not included automatically with a provider, but you need to create it yourself1.

To define a contract class in Android, you need to follow some steps, such as:

• Create a new Java class file and name it as your table name followed by Contract (for example, User Contract)
• Make the class final and add a private constructor to prevent instantiation.
• Define an inner class for each table that implements the Base Columns interface.
• Define constants for the table name and each column name inside the inner class.
• Define constants for the content URI, authority, path segments, and MIME types outside the inner class.

Here is an example of a contract class for a user table:

public final class UserContract {

    // The authority of the content provider
    public static final String AUTHORITY = "com.example.provider.UserProvider";    // The content URI for the top-level user authority
    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY);    // A selection clause for ID based queries
    public static final String SELECTION_ID_BASED = BaseColumns._ID + " = ? ";    // Prevent instantiation
    private UserContract() {}    /**
     * The user table contract
     */
    public static abstract class User implements BaseColumns {        // The table name
        public static final String TABLE_NAME = "user";        // The name column
        public static final String COLUMN_NAME_NAME = "name";        // The email column
        public static final String COLUMN_NAME_EMAIL = "email";        // The password column
        public static final String COLUMN_NAME_PASSWORD = "password";        // The content URI for this table
        public static final Uri CONTENT_URI =
                Uri.withAppendedPath(UserContract.CONTENT_URI, TABLE_NAME);        /**
         * The MIME type of {@link #CONTENT_URI} providing a directory of users.
         */
        public static final String CONTENT_TYPE =
                ContentResolver.CURSOR_DIR_BASE_TYPE + "/vnd.com.example.provider.user";        /**
         * The MIME type of {@link #CONTENT_URI} providing a single user.
         */
        public static final String CONTENT_ITEM_TYPE =
                ContentResolver.CURSOR_ITEM_BASE_TYPE + "/vnd.com.example.provider.user";
        
    }
}