# Android : Content Provider Implementation

Basic about [Content Provider](https://rommansabbir.com/android-content-provider).

Creating our own Content Provider is a powerful way to share data stored in our app with other apps securely. In this section, we'll create a custom `Content Provider` that uses `SharedPreferences` as a data storage mechanism and demonstrate how to access this data from other apps.

### Step 1: Define the Custom Content Provider

First, create a new Kotlin class for your custom `Content Provider`. In this example, let's call it `MyContentProvider`. Our custom Content Provider class should extend the `ContentProvider` class and override essential methods like `onCreate()`, `query()`, `insert()`, `update()`, and `delete()`.

```kotlin
class MyContentProvider : ContentProvider() {

    private lateinit var sharedPreferences: SharedPreferences

    override fun onCreate(): Boolean {
        context?.let {
            sharedPreferences = it.getSharedPreferences("my_prefs", Context.MODE_PRIVATE)
        }
        return true
    }

    override fun query(
        uri: Uri,
        projection: Array<String>?,
        selection: String?,
        selectionArgs: Array<String>?,
        sortOrder: String?
    ): Cursor? {
        // Implement query logic to retrieve data from SharedPreferences
        // We can use the uri and projection to determine what data to fetch
        // and return the results as a Cursor
        // ...
        return null
    }

    override fun insert(uri: Uri, values: ContentValues?): Uri? {
        // Implement insert logic to store data in SharedPreferences
        // We can use the uri and values to determine where to store the data
        // ...
        return null
    }

    override fun update(
        uri: Uri,
        values: ContentValues?,
        selection: String?,
        selectionArgs: Array<String>?
    ): Int {
        // Implement update logic to modify data in SharedPreferences
        // We can use the uri and values to determine what to update
        // ...
        return 0
    }

    override fun delete(uri: Uri, selection: String?, selectionArgs: Array<String>?): Int {
        // Implement delete logic to remove data from SharedPreferences
        // We can use the uri to determine what to delete
        // ...
        return 0
    }

    override fun getType(uri: Uri): String? {
        // Return the MIME type for the data associated with the given URI
        // ...
        return null
    }
}
```

### Step 2: Declare the Content Provider in AndroidManifest.xml

To make our custom `Content Provider` accessible to other apps, we need to declare it in our app's `AndroidManifest.xml` file. Add the following lines inside the `<application>` element:

```xml
<provider
    android:name=".MyContentProvider"
    android:authorities="com.rommansabbir.cpexample.package.mycontentprovider"
    android:exported="true">
</provider>
```

Replace `com.rommansabbir.cpexample.package` with our app's actual package name.

### Step 3: Accessing the Custom Content Provider from Another App

Now, let's see how another app can access data from our custom `Content Provider`.

```kotlin
val uri = Uri.parse("content://com.rommansabbir.cpexample.package.mycontentprovider/some_data")
val projection = arrayOf("key1", "key2")

val cursor = contentResolver.query(uri, projection, null, null, null)

if (cursor != null && cursor.moveToFirst()) {
    val key1Value = cursor.getString(cursor.getColumnIndex("key1"))
    val key2Value = cursor.getInt(cursor.getColumnIndex("key2"))
    // Use the retrieved data in the other app
    cursor.close()
}
```

In this example, we access data from our custom `Content Provider` using a `URI` with the authority we specified in the `AndroidManifest.xml` file and the desired path (`"some_data"` in this case). The projection array specifies which data columns to retrieve.

### Step 4: Storing Data in the Custom Content Provider

To store data in our custom `Content Provider` from another app, we can use the `insert()` method. Here's an example:

```kotlin
val uri = Uri.parse("content://com.your.app.package.mycontentprovider/some_data")
val values = ContentValues().apply {
    put("key1", "Some value")
    put("key2", 42)
}

val insertedUri = contentResolver.insert(uri, values)
```

This code inserts data into our custom `Content Provider` under the specified `URI` (`"some_data"` in this case).

With these steps, we've created a custom `Content Provider` that uses `SharedPreferences` for data storage and demonstrated how to access and modify that data from other apps. Remember to handle data storage and retrieval logic within the `Content Provider`'s `query()`, `insert()`, `update()`, and `delete()` methods according to our app's requirements.

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That's it for today. Happy Coding...