Kotlin for Android

Helps not to write boilerplate code with instantiating abstract or interfaces instances. The purpose of the library is to save time of writing code using Android SDK wrapping as much as possible common functionality.

The library uses one of the coolest feature of the Kotlin language inline almost everywhere, that prevents overhead code.

Warning

This project is not relative to JetBrains company or their products. Use this project as is, no author nor anybody else is responsible for any damage.

Linking to Android project

1. Create regular or use existing Android project in IDEA
2. Select File from menu and click on Project Structure...
3. Select Libraries section and add new Java library
4. Choose the source src folder of kotlinAndroidLib and click Ok
5. Choose category sources and click Ok
6. Select and name the library kotlinAndroidLib
7. Add new file to the library ^N and choose classes.jar of kotlinAndroidLib
8. Add import to your kotlin files in the android project import com.vlad.android.kotlin.*

Usage

Small example of usage most of the functions and also some examples like how to create Parcelable. See Sample Activity

• findViewById replacement for Activity and View:

    val myButton = findView<Button>(R.id.my_button) 

• setOnClickListener for Views:

    myView?.setOnClickListener {
   /* code here */ 
  }
  
  myView?.setOnClickListener {
   view -> /* code here with view: View? argument */ 
  }
  
  val onClickListener = OnClickListener {
   view -> /* code here */ 
  }
  
   myView?.setOnTouchListener {
   view, event -> false /* with view: View? and event: MotionEvent? */ 
  }
  
  val onTouchListener = OnTouchListener {
   view, event -> false 
  }
   

• runOnUiThread for Activities:

  It can be used without the library:

    runOnUiThread(runnable {
   /* action */
  }
  ) 

  Library just remove runnable call and can be used as:

    runOnUiThread {
   /* action */ 
  }
   

• Short definition of BroadcastReceiver:

  Library just wraps onReceive call:

    val myBroadcastReceiver = BroadcastReceiver {
   context, intent ->
  
   /* handle intent here */
  
  }
   

• setPositiveButton and setNegativeButton for AlertDialog.Builder:

    AlertDialog.Builder(this).setTitle("Hello")
  
   ?.setMessage("Want to say hello to world?")
  
   ?.setPositiveButton("Yes", {
   dialog, which -> /* hello */ 
  }
  )
  
   ?.setNegativeButton("No", {
   dialog, which -> /* no hello now */ 
  }
  )
  
   ?.create()
   val positiveButton = dialogOnClickListener {
   dialog, which -> 
  }
   

• Short definition of OnEditorActionListener:

  Library just wraps onEditorAction call:

    val myEditorActionListener = OnEditorActionListener {
   v, actionId, event ->
  
   /* handle actionId and/or event */
  
   false
  
  }
  
   myEditText?.setOnEditorActionListener /* OnEditorActionListener */ {
   v, actionId, event ->
  
   false
  
  }
   

• getSystemService with or without casting for known services:

  Library allows call with casting for specific name of the service or call directly for known services:

    val inputMethodManager = getSystemServiceAs<InputMethodManager>(Context.INPUT_METHOD_SERVICE)
  val inputMethodManager = getInputMethodService() 

• AdapterView<out Adapter?>.setOnItemClickListener and AdapterView<out Adapter?>.setOnItemLongClickListener:

    listView.setOnItemClickListener {
   parent, view, position, id -> 
  }
  
  listView.setOnItemLongClickListener {
   parent, view, position, id -> false 
  }
   

• Wrap calls without runnable() for Handler:

    val handler = Handler()
  handler.post {
   /* code here */ 
  }
  
  handler.postDelayed(100) {
   /* code here */ 
  }
  
  handler.postAtFrontOfQueue {
   /* code here */ 
  }
  
  handler.postAtTime(System.currentTimeMillis() + 100) {
   /* code here */ 
  }
   

  Also easy to create handler with callback to handle messages:

    val handler = Handler {
   message ->
  
   when (message.what) {
  
    1 -> handleMessage1(message.getData())
  
    else -> false
  
   
  }
  
  }
   

• Wrap SQLiteDatabase functionality:

  • Wrap pattern: beginTransaction -> setTransactionSuccessful -> endTransaction with try and finally:

      sqliteDatabase.transaction {
    
     // call any method of SQLiteDatabase without . or ?.
    
     execSQL("ALTER TABLE table_1 RENAME TO table_2")
    
    }
     

  • Wrap pattern: cursor not null -> moveToFirst -> moveToNext in do-while loop -> close with try and finally:

      // query call with same arguments + last argument is a body in the loop
    val collection /* of String */ = sqliteDatabase.query<String>("people", array("first_name"), null, null, null, null, null, null) {
    
     /* Cursor namespace */
    
     getString(getColumnIndexOrThrow("first_name"))
    
    }
     

    Support also queryWithFactory, rawQuery and rawQueryWithFactory.

  • Wrap ContentValues for insert and update:

      sqliteDatabase?.insert("table_name", null) {
    
     // ContentValues namespace
    
     put("column_text", "Hello")
    
     put("column_int", 12.toInt())
    
     put("column_float", 13.toFloat())
    
    }
    
     sqliteDatabase?.update("table_name", "ID = ?", array("3")) {
    
     // ContentValues namespace
    
     put("column_text", "Hello World")
    
    }
     

• Wrap Cursor pattern moveToFirst -> moveToNext in do-while loop:

  Possible to call all functions on Cursor?, if Cursor? == null, returns empty collection

    try {
  
   val collection /* Of String? */ = cursor.map {
  
    getString(getColumnIndexOrThrow("first_name"))
  
   
  }
  
  }
   finally {
  
   cursor?.close()
  
  }
   

  or

    val collection = LinkedList<String?>()
  try {
  
   cursor.mapTo(collection) {
  
    getString(getColumnIndexOrThrow("first_name"))
  
   
  }
  
  }
   finally {
  
   cursor?.close()
  
  }
   

  or

    val collection /* Of String? */ = cursor.mapAndClose {
  
   getString(getColumnIndexOrThrow("first_name"))
  
  }
   

• ExecutorService:

    executorService.execute {
   /* code here */ 
  }
  
  val future = executorService.submit<Any?> {
   /* code here and no result */ 
  }
  
  val future = executorService.submit<String?> {
   /* code here */ "Result" 
  }
  
  val future = executorService.submit<String?>("Result") {
   /* code here and result */ 
  }
   

• Wrap Intent, now easy to create new Intent without defining new variable:

    sendBroadcast(Intent() {
   setAction(Intent.ACTION_DEFAULT) 
  }
  )
  startActivity(Intent(Intent.ACTION_VIEW) {
   setDataAndType(Uri.parse("http://example.com/audio.mp3"), "audio/mpeg") 
  }
  ) 

  or make it even nicer if you have an action and it's a String value:

    "my.application.intent.action.ACTION_MINE" toIntent {
  
   /* namespace of Intent */
  
  }
   

  or just convert String to Intent:

    "my.application.intent.action.ACTION_MINE".toIntent() 

• Wrap IntentFilter, now easy to create new IntentFilter without defining new variable:

    registerReceiver(broadcastReceiver, IntentFilter {
  
   addAction(ACTION_HELLO)
  
  }
  ) 

• Wrap Bundle, now easy to create new Bundle without defining new variable:

    Bundle {
   putString("result", "Some result!") 
  }
   

• Short definition of ResultReceiver:

  Library just wraps onReceiveResult call:

    val myResultReceiver = ResultReceiver(Hanlder()) {
   code, data ->
  
   /* handle result here */
  
  }
   

  or automatically create new Hanlder

    val myResultReceiver = ResultReceiver {
   code, data ->
  
   /* handle result here */
  
  }
   

• Wrap 'CREATOR' for Parcelable. Example of usage:

  WARNING: It might wrong or not supported yet!

    class MyParcelable(val number: Int, val text: String?) : Parcelable {
  
    public override fun writeToParcel(p0: Parcel?, p1: Int) = if (p0 != null) {
  
    p0.writeInt(number)
  
    p0.writeString(text)
  
   
  }
  
    public override fun describeContents(): Int = 0
  
    class object {
  
  val CREATOR = CreateParcelable<MyParcelable> {
   MyParcelable(it.readInt(), it.readString()) 
  }
  
   
  }
  
  }
   

• Wrap Thread, run and call start method:

    async {
  
   // some code here
  
  }