Skip to content

Dart & Henson v2

Jump to bottom Edit New page
Stéphane Nicolas edited this page Jan 6, 2018 · 1 revision

Dart & Henson V2 README

Version 3 is gonna be released soon. This page is the old README of version 2+.

Dart Maven Central Android ArsenalBuild Status

Extra "binding" library for Android which uses annotation processing to generate code that does direct field assignment of your extras.

Dart is inspired by ButterKnife.

class ExampleActivity extends Activity {
  @InjectExtra String extra1;
  @InjectExtra int extra2;
  @InjectExtra User extra3; // User implements Parcelable

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    Dart.bind(this);
    // TODO Use "bound" extras...
  }
}

Simply call one of the bind() methods, which will delegate to generated code. You can bind from an Activity (which uses its intent extras), Fragment (which uses its arguments) or directly from a Bundle.

The key used for the extra will be the field name by default. However, it can be set manually as a parameter in the annotation: @InjectExtra("key")

Optional Injection

By default all @InjectExtra fields are required. An exception will be thrown if the target extra cannot be found.

To suppress this behavior and create an optional binding, add the @Nullable annotation to the field or method. Any annotation with the class name Nullable is respected, including ones from the support library annotations and ButterKnife.

@Nullable @InjectExtra String title;

Default Values

You can assign any values to your fields to be used as default values, just as you would in regular "binding"-free code.

@InjectExtra String title = "Default Title";

This value will be overridden after you call bind(). Remember to use the @Nullable annotation, if this binding is optional.

Bonus

Also included is a get() method that simplifies code to retrieve extras from a Bundle. It uses generics to infer return type and automatically perform the cast.

Bundle bundle = getIntent().getExtras(); // getArguments() for a Fragment
User user = Dart.get(bundle, "key"); // User implements Parcelable

Henson

In Dart 2.0, we added an annotation processor that helps you to navigate between activities. The new module is called Henson (after Matthew Henson, the African-American Arctic explorer that first reached the North Pole) :

For the sample activity mentioned above, Henson will offer a DSL to navigate to it easily :

Intent intent = Henson.with(this)
        .gotoExampleActivity()
        .extra1("defaultKeyExtra")
        .extra2(2)
        .extra3(new User())
        .build();

startActivity(intent);

Of course, you can add any additional extra to the intent before using it.

The DSL will be generated for all classes which contain @InjectExtra fields. If you want to extend it to other classes, use the @HensonNavigable annotation.

@HensonNavigable
class AnotherActivity extends Activity {
  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
  }
}

The Henson annotation processor will generate the Henson navigator class (used above) in a package that is :

  • either the package specified by the dart.henson.package annotation processor option
  • or if no such option is used, in the common package of all annotated activities. See the Javadoc of HensonExtraProcessor for more details.

If your activites and fragment are in different packages, you will need to specify a package via the dart.henson.package annotation processor option. If you're using gradle, simply add this to your build.gradle

apt {
    arguments {
        "dart.henson.package" "your.package.name"
    }
}

If you're using the newest version of Android gradle plugin, it's now possible to use a built-in annotationProcessor scope instead of apt. In this case, you can pass arguments to the annotation processors using :

defaultConfig {
    javaCompileOptions {
        annotationProcessorOptions {
            arguments = [ 'dart.henson.package' : 'your.package.name' ]
        }
    }
}

Bonus

As you can see from the examples above, using both Dart & Henson not only provides a very structured generated navigation layer and convenient DSLs; it also allows to wrap/unwrap parcelables automatically.

Parceler

Dart 2.0 offers a built-in support for Parceler. Using Parceler with Dart 2 is optional.

If you use Parceler, Dart will automatically detect @Parcel annotated beans (pojos), or collections of them, and wrap them using the Henson DSL and unwrap them when they are bound via Dart.

@Parcel
public class ParcelExample {
    ...
}
class OneMoreActivityActivity extends Activity {
  @InjectExtra ParcelExample extra;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    Dart.bind(this);
    // TODO Use "bound" extras...
  }
}
Intent intent = Henson.with(this)
        .gotoOneMoreActivityActivity()
        .extra(new ParcelExample())
        .build();

startActivity(intent);

Parceler usage is optional and will take place only when Parceler is present in the classpath.

When available, Parceler will be used to parcelize collections instead of serializing them, in order to gain speed.

ProGuard

If ProGuard is enabled be sure to add these rules to your configuration:

-dontwarn com.f2prateek.dart.internal.**
-keep class **__ExtraBinder { *; }
-keepclasseswithmembernames class * {
    @com.f2prateek.dart.* <fields>;
}
#for dart 2.0 only
-keep class **Henson { *; }
-keep class **__IntentBuilder { *; }


#if you use it
#see Parceler's github page
#for specific proguard instructions

Download

For Dart 2.x : Gradle:

compile 'com.f2prateek.dart:dart:(insert latest version)'
provided 'com.f2prateek.dart:dart-processor:(insert latest version)'

or maven

<dependency>
  <groupId>com.f2prateek.dart</groupId>
  <artifactId>dart</artifactId>
  <version>(insert latest version)</version>
</dependency>
<dependency>
  <groupId>com.f2prateek.dart</groupId>
  <artifactId>dart-processor</artifactId>
  <version>(insert latest version)</version>
  <scope>provided</scope>
</dependency>

And for using Henson : Gradle:

compile 'com.f2prateek.dart:henson:(insert latest version)'
provided 'com.f2prateek.dart:henson-processor:(insert latest version)'

When using Henson, as Android Studio doesn't call live annotation processors when editing a file, you might prefer using the apt Android Studio plugin. It will allow you to use the Henson generated DSL right away when you edit your code.

The Henson annotation processor dependency would then have to be declared within the apt scope instead of provided.

or maven

<dependency>
  <groupId>com.f2prateek.dart</groupId>
  <artifactId>henson</artifactId>
  <version>(insert latest version)</version>
</dependency>
<dependency>
  <groupId>com.f2prateek.dart</groupId>
  <artifactId>henson-processor</artifactId>
  <version>(insert latest version)</version>
  <scope>provided</scope>
</dependency>

For Dart 1.x : Gradle:

compile 'com.f2prateek.dart:dart:(insert latest version)'

Maven:

<dependency>
  <groupId>com.f2prateek.dart</groupId>
  <artifactId>dart</artifactId>
  <version>(insert latest version)</version>
</dependency>

Kotlin

For all Kotlin enthusiasts, you may wonder how to use this library to configure your intents. This is perfectly compatible, with a bit of understanding of how Kotlin works, especially when it comes to annotation processing.

Assuming that your project is already configured with Kotlin, update your build.gradle file :

apply plugin: 'kotlin-kapt'

dependencies {
  implementation 'com.f2prateek.dart:henson:(insert latest version)'
  kapt 'com.f2prateek.dart:henson-processor:(insert latest version)'
}

Now you can use @InjectExtra annotation to generate either non-null or nullables properties :

class ExampleActivity : Activity() {
  @InjectExtra
  lateinit var title: String

  @InjectExtra
  var titleDefaultValue: String = "Default Title"

  @Nullable
  @JvmField
  @InjectExtra
  var titleNullable: String? = null

  override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.simple_activity)
      Dart.inject(this)
      // TODO Use "injected" extras...
  }
}

Note that you still need to use the Java @Nullable annotation otherwise Henson won't interpret your property as nullable and will generate a builder with a mandatory field (even though you declared your property as nullable with the "?" Kotlin marker). Finally, you have to add the @JvmField annotation or your compiler will complain about not having a backing field.

You may need to add an argument to your build.gradle file if your activities and fragments are located in different packages as mentioned above. The Kotlin syntax with kapt is :

kapt {
    arguments {
        arg("dart.henson.package", "your.package.name")
    }
}

Finally, if you are using Parceler that comes built-in with this library, the syntax does not change from Java, except when dealing with data classes. Because Parceler requires a default constructor with no argument, here is how you need to declare your data class :

@Parcel(Parcel.Serialization.BEAN)
data class ParcelExample @ParcelConstructor constructor(
        val id: Int,
        val name: String,
        ...
}

Talks & Slides

License

Copyright 2013 Jake Wharton
Copyright 2014 Prateek Srivastava (@f2prateek)

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.
Add a custom footer

Home

DH3 Overview

DH3 Migration guide

DH3 design document

Dart & Henson v2 (deprecated)

Clone this wiki locally