MainActivity.kt
package com.example.jetpack
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.core.graphics.scale
import kotlinx.android.synthetic.main.activity_main.*
import kotlin.math.roundToInt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// image source
//https://pixabay.com/photos/flower-flowers-quince-bush-spring-4853422/
// get bitmap from drawable resource
val bitmap = BitmapFactory.decodeResource(resources,R.drawable.flower)
button.setOnClickListener {
imageView2.setImageBitmap(bitmap.scaleByWidth(700))
}
button2.setOnClickListener {
imageView2.setImageBitmap(bitmap.scaleByHeight(700))
}
}
}
fun Bitmap.scaleByWidth(newWidth:Int):Bitmap{
val ratio:Float = this.width.toFloat() / this.height.toFloat()
val newHeight = (newWidth/ratio).roundToInt()
return this.scale(newWidth,newHeight,false)
}
fun Bitmap.scaleByHeight(newHeight:Int):Bitmap{
val ratio:Float = this.height.toFloat() / this.width.toFloat()
val newWidth= (newHeight/ratio).roundToInt()
return this.scale(newWidth,newHeight,false)
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">
<ImageView
android:id="@+id/imageView"
android:layout_width="0dp"
android:layout_height="250dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:scaleType="fitCenter"
android:src="@drawable/flower"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:srcCompat="@tools:sample/avatars[4]" />
<ImageView
android:id="@+id/imageView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.501"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button"
tools:srcCompat="@tools:sample/avatars[13]" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="4dp"
android:text="Scale By Width 700px"
android:backgroundTint="#4B3621"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/imageView" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="4dp"
android:text="By Height 700px"
android:backgroundTint="#4B3621"
app:layout_constraintStart_toEndOf="@+id/button"
app:layout_constraintTop_toBottomOf="@+id/imageView" />
</androidx.constraintlayout.widget.ConstraintLayout>
build.gradle dependencies[add]
// android ktx
implementation 'androidx.core:core-ktx:1.2.0'
build.gradle [add]
android {
kotlinOptions {
jvmTarget = JavaVersion.VERSION_1_8.toString()
}
}


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- kotlin - ConstraintLayout set constraint programmatically
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- kotlin - ConstraintLayout set margin programmatically
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