How to Convert Pixels to DP in Android?
Pixels are the building blocks of any modern display. They are tiny light sources that illuminate in conjunction to form the images visible on the screen. The quality of the image displayed on the screen depends on the number of pixels the display contains. A display with a higher number of pixels will display sharper images whereas a display with fewer pixels will display a clunky image.
Android devices come with displays having various sizes and pixel counts. Therefore, we cannot design an app using pixels as the measuring unit specific to one device as these measurements will render undesirable images on some other device with different screen specs. To mitigate this issue, android uses Density independent Pixels or DP values as the unit for measuring UI components. DP values don’t depend on the number of pixels that a device has. The android system scales the UI component according to the pixel counts of different devices using the DP values. Pixel values can be converted to DP by dividing the pixel value by the screen pixel density.
Overview
This article will build the following app for converting pixels to DP values.
We will write code to make a utility function that will convert pixels to DP. Using this function, we will display the screen specs in DP and will also convert inputted pixel values to DP values.
Step by Step Implementation
Step 1: Create a new Android project
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio.
Note: Select Kotlin as the programming language.
Step 2: Working with the activity_main.xml file
Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Refer to the comments added for more clarity.
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" > <!-- Linear Layout for displaying screen width specs in pixels and in dp --> < LinearLayout android:id = "@+id/screenWidthLL" android:layout_width = "0dp" android:layout_height = "wrap_content" android:layout_marginStart = "28dp" android:layout_marginTop = "60dp" android:layout_marginEnd = "28dp" android:orientation = "vertical" app:layout_constraintEnd_toEndOf = "parent" app:layout_constraintStart_toStartOf = "parent" app:layout_constraintTop_toTopOf = "parent" > < TextView android:id = "@+id/widthPixelsTv" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:textColor = "@color/black" android:textSize = "16sp" /> < TextView android:id = "@+id/widthDpTv" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:layout_marginTop = "16dp" android:textColor = "@color/black" android:textSize = "16sp" /> </ LinearLayout > <!-- Linear layout for displaying screen height specs in pixels and dp --> < LinearLayout android:id = "@+id/screenHeightLL" android:layout_width = "0dp" android:layout_height = "wrap_content" android:layout_marginStart = "28dp" android:layout_marginTop = "60dp" android:layout_marginEnd = "28dp" android:orientation = "vertical" app:layout_constraintEnd_toEndOf = "parent" app:layout_constraintStart_toStartOf = "parent" app:layout_constraintTop_toBottomOf = "@+id/screenWidthLL" > < TextView android:id = "@+id/heightPixelsTv" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:textColor = "@color/black" android:textSize = "16sp" /> < TextView android:id = "@+id/heightDpTv" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:layout_marginTop = "16dp" android:textColor = "@color/black" android:textSize = "16sp" /> </ LinearLayout > <!-- EditText for inputting the Pixel value for conversion to DP value --> < com.google.android.material.textfield.TextInputEditText android:id = "@+id/pixelInputEt" android:layout_width = "0dp" android:layout_height = "wrap_content" android:layout_marginHorizontal = "20dp" android:inputType = "numberDecimal" app:layout_constraintBottom_toBottomOf = "@id/guideline1" app:layout_constraintEnd_toEndOf = "parent" app:layout_constraintStart_toStartOf = "parent" > </ com.google.android.material.textfield.TextInputEditText > <!-- Guideline for arranging views --> < androidx.constraintlayout.widget.Guideline android:id = "@+id/guideline1" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:orientation = "horizontal" app:layout_constraintGuide_begin = "365dp" /> <!-- TextView for displaying the DP value converted from entered Pixel value --> < TextView android:id = "@+id/convertedDpValueTv" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:textColor = "@color/black" android:textSize = "20sp" android:visibility = "invisible" app:layout_constraintEnd_toEndOf = "parent" app:layout_constraintStart_toStartOf = "parent" app:layout_constraintTop_toBottomOf = "@id/guideline1" /> < Button android:id = "@+id/convertToDpButton" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:layout_marginBottom = "60dp" android:text = "Convert to DP" app:layout_constraintBottom_toBottomOf = "parent" app:layout_constraintEnd_toEndOf = "parent" app:layout_constraintStart_toStartOf = "parent" /> </ androidx.constraintlayout.widget.ConstraintLayout > |
Step 3: Working with the MainActivity.kt file
Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.
Kotlin
package com.example.gfgpixelstodp import android.content.Context import android.os.Bundle import android.view.View import android.widget.Button import android.widget.TextView import android.widget.Toast import androidx.appcompat.app.AppCompatActivity import com.google.android.material.textfield.TextInputEditText class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super .onCreate(savedInstanceState) setContentView(R.layout.activity_main) // initializing all the views val screenWidthPixelsTv: TextView = findViewById(R.id.widthPixelsTv) val screenWidthDpTv: TextView = findViewById(R.id.widthDpTv) val screenHeightPixelsTv: TextView = findViewById(R.id.heightPixelsTv) val screenHeightDpTv: TextView = findViewById(R.id.heightDpTv) val pixelInputEt: TextInputEditText = findViewById(R.id.pixelInputEt) val convertToDpButton: Button = findViewById(R.id.convertToDpButton) val convertedDpValueTv: TextView = findViewById(R.id.convertedDpValueTv) // assigning click listener to ConvertToDp button convertToDpButton.setOnClickListener { val pixels = pixelInputEt.text.toString().toFloatOrNull() if (pixels == null ) { // if input is invalid, no text is displayed convertedDpValueTv.visibility = View.INVISIBLE // show a Toast to the user Toast.makeText( this @MainActivity , "Enter valid pixel value!" , Toast.LENGTH_LONG) .show() } else { // if the input is valid, convert the pixel // value given to dp and show // in the TextView val dp = convertPixelsToDp( this @MainActivity , pixels) convertedDpValueTv.text = "Dp value: $dp" convertedDpValueTv.visibility = View.VISIBLE } } // initializing the screen specs in pixels val screenWidthInPixels = resources.displayMetrics.widthPixels val screenHeightInPixels = resources.displayMetrics.heightPixels // converting the pixel values to DP values val screenWidthInDp = convertPixelsToDp( this , screenWidthInPixels.toFloat()) val screenHeightInDp = convertPixelsToDp( this , screenHeightInPixels.toFloat()) // displaying pixel values in the respective TextViews screenWidthPixelsTv.text = "Screen Width in pixels: $screenWidthInPixels" screenHeightPixelsTv.text = "Screen Height in pixels: $screenHeightInPixels" // displaying dp values in the respective TextViews screenWidthDpTv.text = "Screen Width in DP: $screenWidthInDp" screenHeightDpTv.text = "Screen Height in DP: $screenHeightInDp" } private fun convertPixelsToDp(context: Context, pixels: Float): Float { val screenPixelDensity = context.resources.displayMetrics.density val dpValue = pixels / screenPixelDensity return dpValue } } |
Output: