Android Recyclerview Kotlin Library, Gencycler a Boilerplate free RecyclerView adapter. Gencycler uses annotation processing to analyze your code and generates the Recyclerview adapter for you, which means you only need to worry about your logic and not about the adapter.

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• Written in Kotlin <3, for Kotlin and Java
• Generates human readable code(plus comments, minus the human errors)
• Clean and optimized code – Generates only what is required
• Click / Long-Click listeners
• Multi view types
• Expandable items
• Swipe to delete
• Headers
• Footers
• Simple Drag and drop
• Filter
• Easily extensible
• Custom variable naming
• Parses your layout file so no more findViewById
• Comes with useful Helpers
• No runtime cost – everything happens at compile-time
• Multi flavor support
• Butterknife R2 support

Gencycler works in compile time so no runtime performance impact

Gencycler will generated a readable multi view type RecyclerView Adapter with a thread-safe accessing mechanism. It eliminates the need to write all of the boilerplate code needed for writing an adapter and leaves you with only the bare minimum needed to write your business logic.

Implement in your project

Using maven

Kotlin

 apply plugin: 'kotlin-kapt'

  repositories {
     maven { url "https://jitpack.io" }
  }
  dependencies {
        implementation 'com.github.gilgoldzweig.Gencycler:gencycler:latest_version'
        kapt 'com.github.gilgoldzweig.Gencycler:compiler:latest_version'
  }

How to use

1. Implement your model

Just create a class which implements the GencyclerModel and annotate it with @GencyclerViewHolder

Each class represents a ViewHolder & Data model. In order to associate the class with a layout we place the layout id of what the item should look like inside the annotation as shown below.

Kotlin

@GencyclerViewHolder(R.layout.item_simple)  
data class SimpleModel(val name: String, val description: String) : GencyclerModel

2. Implement your adapter

Just create a class and annotate it with @GencyclerAdapter place every model you want the adapter to use inside the annotation as shown below.

Kotlin – Single view type

@GencyclerAdapter(SimpleModel::class)
class SimpleAdapter

Kotlin – Mutli view type

@GencyclerAdapter(SimpleModel::class, AnotherModel::class) //for multiple view types just seperated each model by a comma 
class SimpleAdapter

3. Compile

Compile your project and when the compilation finishes your adapters and view holders will be generated.

The generated adapter will be named Generated + Your adapter class name and will be an abstract class with a bind function for every model you provided The ViewHolder we be Generated and implemented automatically

4. Implementing the generated adapter

Now that we have the generated code all we need to do is implement it

The generated adapter will require 3 parameters

• context: Context | Used to inflate the layout of the ViewHolder
• elements: MutableList with the type of the provided model or GencyclerModel when multiple models wer’e provided. Default: ArrayList() | Each element represents a Generated ViewHolder
• updateUi: Boolean Default: true
  • The generated adapter comes with many helper methods (add, remove, etc…) each action will update the elements in the adapter but if updateUi is True the adapter will also run a UI Thread check and call the appropriate notify method of the adapter (notifyItemInserted, notifyItemRemoved, etc…) whenever one of those function is called

And a onBind abstract function

The complete adapter will look like this

Kotlin

@GencyclerAdapter(SimpleModel::class)
class SimpleAdapter(context: Context, elements: ArrayList<SimpleModel>) : GeneratedSimpleAdapter(context, elements) {  
 
    	override fun onBindSimpleModelViewHolder(
        	simpleModelViewHolder: SimpleModelViewHolder, //Generated ViewHolder, all the views from your layout are here
        	simpleModel: SimpleModel, 
        	position: Int) { 
        	
            	//Your logic here
    }  
}

Advance/Extras

Custom naming

Gencycler provides renaming options to the adapter and the variables inside the ViewHolder

Adapter

By default the generated adapter will be named Generated + Your adapter name but you can select a custom name for your adapter by specifying it inside the @GencyclerAdapter as shown below

Kotlin

@GencyclerAdapter(SimpleModel::class, customName = "CustomNameAdapter")
class SimpleAdapter

Variables

By default the processor turns the id of every view in the xml layout to variable name and converts it to lower camel-case

You can change the names of the variables by specifying a naming adapter inside the @GencyclerViewHolder as shown below

Kotlin

@GencyclerViewHolder(R.layout.item_simple, NamingCase.NAMING_CASE_SNAKE)  
data class SimpleModel(val name: String, val description: String) : GencyclerModel

You can choose between the following

enum class NamingCase {  
    NAMING_CASE_NONE,  
    NAMING_CASE_CAMEL,  //Default
    NAMING_CASE_SNAKE  
}

Event listeners

For now Genecycler supports two listeners but if you want to create one for yourself just create and send pull request

Click / Long Click

1. Annotate your adapter with @Clickable or @LongClickable

To add listeners for item click all you need to do is annotate your adapter with @Clickable or @LongClickable (You can both at the same time) as shown below

Kotlin

@GencyclerAdapter(SimpleModel::class)
@Clickable
@LongClickable
class SimpleAdapter

2. Compile

Once the compilation completes an interface will be added to the generated adapter constructor

• OnItemClickedListener<T> for @Clickable
• OnItemLongClickedListener<T> for @LongClickable

T a generic type Your model for single type GencyclerModel for multi view types

Simple gestures(Drag and Drop, Swipe to delete)

Create a new SimpleGesturesHelper and provide it your generated adapter

Kotlin

val gesturesHelper = SimpleGesturesHelper(adapter)

gesturesHelper.setSwipeEnabled(enabled: Boolean, vararg directions: Int) //ItemTouchHelper.START or ItemTouchHelper.END
gesturesHelper.setDragAndDropEnabled(enabled: Boolean, longPressOnly: Boolean = false)

gesturesHelper.attachToRecyclerView(recyclerView)

Filter

Gencycler provides you with a way to filter your items in order to that you need to do the following

1. Annotate your adapter with @Filterable

Kotlin

@GencyclerAdapter(SimpleModel::class)
@Filterable
class SimpleAdapter

2. Compile

3. Implement the performFilter method

Kotlin

@GencyclerAdapter(SimpleModel::class)  
@Filterable  
class SimpleAdapter(context: Context, elements: ArrayList<SimpleModel>) : GeneratedSimpleAdapter(context, elements) {  
      
	//other methods
     
	override fun performFilter(constraint: CharSequence, simpleModel: SimpleModel): Boolean {  
	    //return true if the item should be retained and false if the item should be removed.
	}  
}

To filter the items, inside your Activity/Fragment call

Call this in onQueryTextSubmit() & onQueryTextChange() when using SearchView

Kotlin

adapter.filter("yourSearchTerm")

Custom view recycling

Gencycler generates functions for binding and recycling of ViewHolders

The amount of functions will be the same for binding and recycling functions

Binding function are abstract because the system does not provide a default option Recycling on the other hand do have a default option which you should edit in order to improve performance

The generated functions look as shown below

Kotlin

override fun onRecycledSimpleModelViewHolder(simpleModelViewHolder: SimpleModelViewHolder,
                                             position: Int) {
                                             
	super.onRecycledSimpleModelViewHolder(simpleModelViewHolder, position) //remove this line
	//apply your custom recycleing logic
}

Miscellaneous(Optional)

Gencycler supports number of custom options regarding customized build/flavors All of the option are inputed as shown below

android {
    //your project configuration
    defaultConfig {
        //your project default config
        
        //Add this section
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = [
                    "androidManifestFile": Providing specific file path to the manifest
                    "rClassPackage": Providing R class package - Just like when you do import but with the .R at the end (example: com.example.app.R = com.example.app)
                    "androidUseR2": true / false if you want to use Butterknife's R2 instead of R 
                    "resourcesFolder": In case you use multi flavor layouts you need to use getCurrentFlavor()
                ]
            }
        }
    }
}

This only applies if you have duplicate layouts for multi flavors here is a function to get the current flavor

Add the following function to your gradle file

def getCurrentFlavor() {

	Gradle gradle = getGradle()
	Pattern pattern;
    
	String taskRequest = gradle.getStartParameter().getTaskRequests().toString()

	if (taskRequest.contains("assemble")) {
		pattern = Pattern.compile("assemble(\\w+)(Release|Debug)")
	} else {
		pattern = Pattern.compile("generate(\\w+)(Release|Debug)")
	}

	Matcher matcher = pattern.matcher(taskRequest)

	if (matcher.find()) {
		return matcher.group(1).toLowerCase()
	} else {
		println "NO MATCH FOUND"
		return "";
	}
}

License

MIT License

Copyright (c) 2018 Gil Goldzweig Goldbaum

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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