Dart

Additional

Language
Java
Version
dart-parent-2.0.1 (Aug 4, 2016)
Created
Jan 10, 2014
Updated
Feb 16, 2017
Owner
f2prateek
Contributors
f2prateek
Anton Malinskiy (Malinskiy)
孙善明 (yaming116)
johncarl81
Iain Connor (iainconnor)
Macarse
Stéphane Nicolas (stephanenicolas)
intrications
Alessandro Facciorusso (alexfacciorusso)
bryant1410
aurae
stkent
dlemures
aardouin
gabrieloshiro
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Dart

Extra "injection" 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.inject(this);
    // TODO Use "injected" extras...
  }
}

Simply call one of the inject() methods, which will delegate to generated code. You can inject 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 injection, 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 "injection"-free code.

@InjectExtra String title = "Default Title";

This value will be overridden after you call inject(). Remember to use the @Nullable annotation, if this injection 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"
    }
}

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 injected 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.inject(this);
    // TODO Use "injected" 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 **$$ExtraInjector { *; }
-keepclasseswithmembernames class * {
    @com.f2prateek.dart.* <fields>;
}
#for dart 2.0 only
-keep class **Henson { *; }
-keep class **$$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>

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.