Copper

A content provider wrapper for reactive queries with Kotlin coroutines Flow or RxJava Observable.

contentResolver.observeQuery(uri).collect { query ->
  // ...
}

Download

// Kotlin coroutines
implementation 'app.cash.copper:copper-flow:1.0.0'

// RxJava 3
implementation 'app.cash.copper:copper-rx3:1.0.0'

// RxJava 2
implementation 'app.cash.copper:copper-rx2:1.0.0'

Snapshots of the development version are available in Sonatype's snapshots repository.

repositories {
  maven {
    url 'https://oss.sonatype.org/content/repositories/snapshots/'
  }
}
dependencies {
  testImplementation 'app.cash.copper:copper-flow:1.1.0-SNAPSHOT'
  testImplementation 'app.cash.copper:copper-rx2:1.1.0-SNAPSHOT'
  testImplementation 'app.cash.copper:copper-rx3:1.1.0-SNAPSHOT'
}

Usage

Given a ContentResolver, change your calls from query to observeQuery for a reactive version.

contentResolver.observeQuery(uri).collect { query ->
  query.run()?.use { cursor ->
    // ...
  }
}

Unlike query, observeQuery returns a Query object that you must call run() on in order to execute the underlying query for a Cursor. This ensures that intermediate operators which cache values do not leak resources and that consumers have access to the full lifetime of the cursor.

Instead of dealing with a Cursor directly, operators are provided which help convert the contained values into semantic types:

contentResolver.observeQuery(uri)
  .mapToOne { cursor ->
    Employee(cursor.getString(0), cursor.getString(1))
  }
  .collect {
    println(it)
  }

Employee(id=bob, name=Bob Bobberson)

The mapToOne operator takes a query which returns a single row and invokes the lambda to map the cursor to your desired type. If your query returns zero or one rows, the coroutine artifact has a mapToOneOrNull operator and the RxJava artifacts have a mapToOptional operator.

If your query returns a list, call mapToList with the same lambda:

contentResolver.observeQuery(uri)
  .mapToList { cursor ->
    Employee(cursor.getString(0), cursor.getString(1))
  }
  .collect {
    println(it)
  }

[Employee(id=alice, name=Alice Alison), Employee(id=bob, name=Bob Bobberson)]

License

Copyright 2015 Square, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Note: This library was forked from SQLBrite.