gradha / icekick

Android Instance State made easy for Kotlin

IceKick

Icepick-esque Android Instance State for Kotlin, inspired by Kotter Knife.

class MyActivity : Activity() {
  // There out-of-the-box support for Serializable
  // A state that can't be null, needs a default value
  private var nonNullState: Int by serialState(0)

  // A state that can be null
  private var nullableState: Int? by serialState()

  // A state that behaves as if the variable had the 'lateinit' modifier
  private var lateinitState: String by serialLateState()

  // And for Parcelable too
  private var resourceUri: Uri by parcelState(MY_DEFAULT_URI)
  private var nullableIntentState: Intent? by parcelState()
  private val lateinitParcelState: Intent by parcelLateState()
}

These methods are available on subclasses of Activity, Fragment, the support library Fragment, and View.

If you need to save/restore an object that can't be made Serializable or Parcelable, a custom Bundler can be specified:

class MyFragment : Fragment() {
  // Your custom object
  class MyData(var value: Int)

  // Your Bundler
  class MyDataBundler : Bundler<MyData> {
    override fun save(bundle: Bundle, key: String, value: MyData?) {
      val myData = value as? MyData ?: return
      bundle.putInt(key, myData.value)
    }

    override fun load(bundle: Bundle, key: String): MyData? {
      return if (bundle.containsKey(key)) MyData(bundle.getInt(key)) ?: null
    }
  }

  // Usage
  private var myData: MyData by state(MyData(100), MyDataBundler())
  private var nullableMyData: MyData? by state(MyDataBundler())
  private var lateinitMyData: MyData by lateState(MyDataBundler())
}

Download

Currently available via JitPack.

To use it, add the jitpack maven repository to your build.gradle file:

repositories {
  ...
  maven { url "https://jitpack.io" }
  ...
}

and add the dependency:

dependencies {
  ...
  compile 'com.github.tinsukE:icekick:0.2'
  ...
}

Setup

To enable it, add these to your classes:

class MyActivity : Activity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    unfreezeInstanceState(savedInstanceState)
  }
  
  override fun onSaveInstanceState(outState: Bundle) {
    super.onSaveInstanceState(outState)
    freezeInstanceState(outState)
  }
}

class MyFragment : Fragment() {
  override fun onSaveInstanceState(outState: Bundle) {
    super.onSaveInstanceState(outState)
    freezeInstanceState(outState)
  }
  
  override fun onViewStateRestored(savedInstanceState: Bundle?) {
    super.onViewStateRestored(savedInstanceState)
    unfreezeInstanceState(savedInstanceState)
  }
}

class MyView : View {
  override fun onSaveInstanceState(): Parcelable? {
    return freezeInstanceState(super.onSaveInstanceState())
  }
  
  override fun onRestoreInstanceState(state: Parcelable) {
    super.onRestoreInstanceState(unfreezeInstanceState(state))
  }
}

License

Copyright 2016 Angelo Suzuki

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.