ButterKnife with Kotlin

Butter Knife With Kotlin (No Need)

Butter Knife

Butter knife is a little and light weight library used to inject android components using annotation processing

If you android app using Kotlin then there is no need for butter knife or findviewbyid , we can simple use view id as view object as in example below

 

Textview layout

<TextView
    android:id="@+id/textview"
    android:layout_width="match_parent"
    android:layout_height="55dp"
    android:gravity="center"
    android:text="Hello World!"
    android:textAlignment="center"
    android:textAllCaps="true"
    android:textColor="@color/colorPrimary"/> 

In the above textview we set textview as id for the textview view we can change color , settext etc,.

 //you can use this on any methods in lifecycle no need to instantiate the view

textview.setTextColor(Color.RED)
textview.text = "this text setted programatically"

Button with onclicklistener with button as id

Button Layout

<Button
    android:id="@+id/button"
    android:layout_width="match_parent"
    android:layout_height="55dp"/>

Kotlin code for onclick listener

button.setOnClickListener {
    Toast.makeText(this@MainActivity, "${button.text} clicked ", Toast.LENGTH_LONG).show()
    button.setBackgroundColor(Color.RED)
}

ImageView with set image programatically with imageview as id

Layout for ImageView

<ImageView
    android:id="match_parent"
    android:layout_width="291dp"
    android:layout_height="99dp"/>

Kotlin code for change background color and to set image drawable

imageView.setImageDrawable(ContextCompat.getDrawable(this@MainActivity, android.R.drawable.ic_menu_share))
imageView.setBackgroundColor(Color.GREEN)

Final Look of Layout

<?xml version="1.0" encoding="utf-8"?><android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.mrkotlin.mrkotlincustomtoast.MainActivity"
    tools:layout_editor_absoluteY="81dp">

    <TextView
        android:id="@+id/textview"
        android:layout_width="279dp"
        android:layout_height="55dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:gravity="center"
        android:text="Hello World!"
        android:textAlignment="center"
        android:textAllCaps="true"
        android:textColor="@color/colorPrimary"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.505"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.043" />

    <ImageView
        android:contentDescription="@string/app_name"
        android:id="@+id/imageView"
        android:layout_width="291dp"
        android:layout_height="99dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.506"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textview"
        app:layout_constraintVertical_bias="0.277"
        app:srcCompat="@mipmap/ic_launcher_round" />

    <Button
        android:id="@+id/button"
        android:layout_width="294dp"
        android:layout_height="55dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="52dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

</android.support.constraint.ConstraintLayout>

Final Look Kotlin Activity

package com.mrkotlin.mrkotlincustomtoast

import android.graphics.Color
import android.os.Bundle
import android.support.v4.content.ContextCompat
import android.support.v7.app.AppCompatActivity
import android.view.View
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        textview.setTextColor(Color.RED)
        textview.text = "this text setted programatically"

        imageView.setImageDrawable(ContextCompat.getDrawable(this@MainActivity, android.R.drawable.ic_menu_share))
        imageView.setBackgroundColor(Color.GREEN)

        button.setOnClickListener {
            Toast.makeText(this@MainActivity, "${button.text} clicked ", Toast.LENGTH_LONG).show()
            button.setBackgroundColor(Color.RED)
        }

    }
}