How to Display HTML in Textview along with Images in Android?

There are some situations when one needs to display rich formatted text in the app, like for a blog app or an app like Quora but Android’s inbuilt function doesn’t allow to display inline images by default, moreover they show the ugly blue line to the left of anything inside blockquote tag. Here is the simple solution to show HTML in TextView along with images in Android. Note that we are going to implement this project using Kotlin language in Android. Below is a demo screenshot of the app.

demo

Prerequisites

Approach

Step 1: Create a new Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language.

Step 2: Project setup before coding

  • Add some colors in the colors.xml file. The Colors here are for the blockquote Styling. You are free to choose different colors.

colors.xml

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<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#0F9D58</color>
    <color name="colorPrimaryDark">#0F9D58</color>
    <color name="colorAccent">#03DAC5</color>
    <color name="Grey">#878585</color>
</resources>

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// Picasso library to downlowding images  



implementation ‘com.squareup.picasso:picasso:2.71828’

// Coroutines dependency to put the downloading process in background thread

implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9’

Step 3: Working with activity_main.xml file

In the following activity_main.xml file we have added the following widgets:

  • EditText where the user will input the HTML text,
  • Button to trigger an event to display HTML text,
  • ScrollView for smooth scrolling,
  • TextView to display the HTML after processing the input.

activity_main.xml

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<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    tools:context=".MainActivity">
  
  
    <!-- Edittext to take input for this sample app,
          for real app you will not need this -->
    <EditText
        android:id="@+id/editor"
        android:layout_width="0dp"
        android:layout_height="40dp"
        app:layout_constraintEnd_toStartOf="@+id/display_html"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
  
    <!-- Button to trigger an event to display html/Rich text-->
    <Button
        android:id="@+id/display_html"
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:text="Display Html"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
  
    <!-- Scroll View for smooth scrolling -->
    <ScrollView
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginTop="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editor">
  
        <!-- Text View in which you will display the html after 
             processing the input-->
        <TextView
            android:id="@+id/html_viewer"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </TextView>
          
    </ScrollView>
  
</androidx.constraintlayout.widget.ConstraintLayout>

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Output UI:

Step 4: Create a Kotlin class ImageGetter.kt

Create a class that will download images contained in the img tag. Below is the complete ImageGetter.kt file. Understand the complete code by referring to the corresponding comments inside the code. 



ImageGetter.kt

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import android.content.res.Resources
import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.drawable.BitmapDrawable
import android.graphics.drawable.Drawable
import android.text.Html
import android.widget.TextView
import com.squareup.picasso.Picasso
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
  
// Class to download Images which extends [Html.ImageGetter]
class ImageGetter(
    private val res: Resources,
    private val htmlTextView: TextView
) : Html.ImageGetter {
  
    // Function needs to overridden when extending [Html.ImageGetter] ,
    // which will download the image
    override fun getDrawable(url: String): Drawable {
        val holder = BitmapDrawablePlaceHolder(res, null)
  
        // Coroutine Scope to download image in Background
        GlobalScope.launch(Dispatchers.IO) {
            runCatching {
  
                // downloading image in bitmap format using [Picasso] Library
                val bitmap = Picasso.get().load(url).get()
                val drawable = BitmapDrawable(res, bitmap)
  
                // To make sure Images don't go out of screen , Setting width less
                // than screen width, You can change image size if you want
                val width = getScreenWidth() - 150
  
                // Images may stretch out if you will only resize width,
                // hence resize height to according to aspect ratio
                val aspectRatio: Float =
                    (drawable.intrinsicWidth.toFloat()) / (drawable.intrinsicHeight.toFloat())
                val height = width / aspectRatio
                drawable.setBounds(10, 20, width, height.toInt())
                holder.setDrawable(drawable)
                holder.setBounds(10, 20, width, height.toInt())
                withContext(Dispatchers.Main) {
                    htmlTextView.text = htmlTextView.text
                }
            }
        }
        return holder
    }
  
    // Actually Putting images
    internal class BitmapDrawablePlaceHolder(res: Resources, bitmap: Bitmap?) :
        BitmapDrawable(res, bitmap) {
        private var drawable: Drawable? = null
  
        override fun draw(canvas: Canvas) {
            drawable?.run { draw(canvas) }
        }
  
        fun setDrawable(drawable: Drawable) {
            this.drawable = drawable
        }
    }
  
    // Function to get screenWidth used above
    fun getScreenWidth() =
        Resources.getSystem().displayMetrics.widthPixels
}

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Note: One can change the height and the width of the image according to your will in the getDrawable() function.

Step 5: Working with MainActivity.kt file

  • Create a click-Listener for the button inside the onCreate() method.

MainActivity.kt

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class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Click Listener to listner button click events.
        // display_html is button id from activity_main.xml 
        // You don't need to get reference to it because koltin 
        // provides synthetic import and 
        // We are gonna use for the same for rest of Views
        display_html.setOnClickListener {
            if (editor.text.isNotEmpty()) {
                displayHtml(editor.text.toString())
            }
        }
    }
}

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  • Create a function displayHtml() which you just called inside click listener.

Note: Kotlin has Synthetic import ,so there was no need of storing reference to views in a variable and we are going to do the same for all other views.

Kotlin

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private fun displayHtml(html: String) {
    
      // Creating object of ImageGetter class you just created
      val imageGetter = ImageGetter(resources, html_viewer)
       
      // Using Html framework to parse html
      val styledText=HtmlCompat.fromHtml(html, 
                                         HtmlCompat.FROM_HTML_MODE_LEGACY,
                                         imageGetter,null)
         
      // to enable image/link clicking
      html_viewer.movementMethod = LinkMovementMethod.getInstance()
        
      // setting the text after formatting html and downloadig and setting images
      html_viewer.text = styledText
  }

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  • So now the Image work is done, now it should load the images. Below is the complete code for the MainActivity.kt file.

Kotlin

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import android.os.Bundle
import android.text.method.LinkMovementMethod
import androidx.appcompat.app.AppCompatActivity
import androidx.core.text.HtmlCompat
import kotlinx.android.synthetic.main.activity_main.*
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Click Listener to listner button click events.
        // display_html is button id from activity_main.xml 
        // You don't need to get reference to it 
        // because koltin provides synthetic import and 
        // We are gonna use for the same for rest of Views
        display_html.setOnClickListener {
            if (editor.text.isNotEmpty()) {
                displayHtml(editor.text.toString())
            }
        }
    }
  
    private fun displayHtml(html: String) {
        // Creating object of ImageGetter class you just created
        val imageGetter = ImageGetter(resources, html_viewer)
  
        // Using Html framework to parse html
        val styledText =
            HtmlCompat.fromHtml(html, HtmlCompat.FROM_HTML_MODE_LEGACY, imageGetter,null)
  
        // to enable image/link clicking
        html_viewer.movementMethod = LinkMovementMethod.getInstance()
  
        // setting the text after formatting html and downloadig and setting images
        html_viewer.text = styledText
    }
}

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  • Let’s see how it’s working now. Use HTML of another webpage. Here we have used the following webpage of the GFG article. Get the HTML string file from here.

Note: Remember that input the HTML text inside the EditText and then click on the “DISPLAY HTML” Button

Output

ouput screen

The images are now loading but you can see, for the blockquote part, there is the plain ugly blue line. We are now gonna fix that. 

Step 6: Create a Kotlin class QuoteSpanClass.kt

Create a Kotlin Class named QuoteSpanClass and add this following code to this file.



QuoteSpanClass.kt

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import android.graphics.Canvas
import android.graphics.Paint
import android.text.Layout
import android.text.style.LeadingMarginSpan
import android.text.style.LineBackgroundSpan
  
class QuoteSpanClass(
    private val backgroundColor: Int,
    private val stripeColor: Int,
    private val stripeWidth: Float,
    private val gap: Float
) : LeadingMarginSpan, LineBackgroundSpan {
      
    // Margin for the block quote tag
    override fun getLeadingMargin(first: Boolean): Int {
        return (stripeWidth + gap).toInt()
    }
  
    // this function draws the margin.
    override fun drawLeadingMargin(
        c: Canvas,
        p: Paint,
        x: Int,
        dir: Int,
        top: Int,
        baseline: Int,
        bottom: Int,
        text: CharSequence,
        start: Int,
        end: Int,
        first: Boolean,
        layout: Layout
    ) {
  
        val style = p.style
        val paintColor = p.color
        p.style = Paint.Style.FILL
        p.color = stripeColor
  
        // Creating margin according to color and stripewidth it recieves
        // Press CTRL+Q on function name to read more
        c.drawRect(x.toFloat(), top.toFloat(), x + dir * stripeWidth, bottom.toFloat(), p)
        p.style = style
        p.color = paintColor
    }
  
    override fun drawBackground(
        c: Canvas,
        p: Paint,
        left: Int,
        right: Int,
        top: Int,
        baseline: Int,
        bottom: Int,
        text: CharSequence,
        start: Int,
        end: Int,
        lnum: Int
    ) {
        val paintColor = p.color
        p.color = backgroundColor
  
        // It draws the background on which blockquote text is written
        c.drawRect(left.toFloat(), top.toFloat(), right.toFloat(), bottom.toFloat(), p)
        p.color = paintColor
    }
}

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Step 7: Working with MainActivity.kt file

  • Since the QuoteSpanClass is created, it’s time to use this class in MainActivity.kt, but before you need to create a function to parse blockquote tags and draw the margin and background using the QuoteSpanClass.

MainActivity.kt

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private fun replaceQuoteSpans(spannable: Spannable) 
{
  val quoteSpans: Array<QuoteSpan> = 
      spannable.getSpans(0, spannable.length - 1, QuoteSpan::class.java)
  
  for (quoteSpan in quoteSpans) 
  {
    val start: Int = spannable.getSpanStart(quoteSpan)
    val end: Int = spannable.getSpanEnd(quoteSpan)
    val flags: Int = spannable.getSpanFlags(quoteSpan)
    spannable.removeSpan(quoteSpan)
       spannable.setSpan(
               QuoteSpanClass(
                    // background color
                    ContextCompat.getColor(this, R.color.colorPrimary),  
                    // strip color
                    ContextCompat.getColor(this, R.color.colorAccent),
                    // strip width
                    10F, 50F
                ),
                start, end, flags
            )
        }   
  }

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  • And finally, call this function from displayHtml() function before setting the text for html_viewer. Below is the complete code for the MainActivity.kt file.

Kotlin

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import android.os.Bundle
import android.text.Spannable
import android.text.method.LinkMovementMethod
import android.text.style.QuoteSpan
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat
import androidx.core.text.HtmlCompat
import kotlinx.android.synthetic.main.activity_main.*
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Click Listener to listner button click events.
        // display_html is button id from activity_main.xml 
        // You don't need to get reference to it
        // because koltin provides synthetic import and
        // We are gonna use for the same for rest of Views
        display_html.setOnClickListener {
            if (editor.text.isNotEmpty()) {
                displayHtml(editor.text.toString())
            }
        }
    }
  
    private fun displayHtml(html: String) {
        // Creating object of ImageGetter class you just created
        val imageGetter = ImageGetter(resources, html_viewer)
  
        // Using Html framework to parse html
        val styledText =
            HtmlCompat.fromHtml(html, HtmlCompat.FROM_HTML_MODE_LEGACY, imageGetter,null)
  
        replaceQuoteSpans(styledText as Spannable)
  
        // setting the text after formatting html and downloadig and setting images
        html_viewer.text = styledText
  
        // to enable image/link clicking
        html_viewer.movementMethod = LinkMovementMethod.getInstance()
  
    }
  
    private fun replaceQuoteSpans(spannable: Spannable)
    {
        val quoteSpans: Array<QuoteSpan> =
            spannable.getSpans(0, spannable.length - 1, QuoteSpan::class.java)
  
        for (quoteSpan in quoteSpans)
        {
            val start: Int = spannable.getSpanStart(quoteSpan)
            val end: Int = spannable.getSpanEnd(quoteSpan)
            val flags: Int = spannable.getSpanFlags(quoteSpan)
            spannable.removeSpan(quoteSpan)
            spannable.setSpan(
                QuoteSpanClass(
                    // background color
                    ContextCompat.getColor(this, R.color.colorPrimary),
                    // strip color
                    ContextCompat.getColor(this, R.color.colorAccent),
                    // strip width
                    10F, 50F
                ),
                start, end, flags
            )
        }
    }
}

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Output

Now let’s see the changes in the output screen.

output screen

Note: One can change strip Color, background color, strip width of your choice in replaceQuoteSpans function, and beautify it.

Step 8: Cretae a method ImageClick() in the MainActivity.kt file

  • But there is still one problem. What if you click an image? Nothing happens as of now. You need to add a few more lines to handle that.

Kotlin

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// Function to parse image tags and enable click events
fun ImageClick(html: Spannable) 
{
  for (span in html.getSpans(0, html.length, ImageSpan::class.java))
  {
    val flags = html.getSpanFlags(span)
    val start = html.getSpanStart(span)
    val end = html.getSpanEnd(span)
    html.setSpan(object : URLSpan(span.source) {
         override fun onClick(v: View) {
                Log.d(TAG, "onClick: url is ${span.source}")
            }
  }, start, end, flags)
}

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  • And then call this function from displayHtml() Function before setting the text for html_viewer. Below is the complete code for the MainActivity.kt file. 

Kotlin

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import android.os.Bundle
import android.text.Spannable
import android.text.method.LinkMovementMethod
import android.text.style.ImageSpan
import android.text.style.QuoteSpan
import android.text.style.URLSpan
import android.util.Log
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat
import androidx.core.text.HtmlCompat
import kotlinx.android.synthetic.main.activity_main.*
  
private const val TAG="MainActivity"
  
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Click Listener to listner button click events.
        // display_html is button id from activity_main.xml 
        // You don't need to get reference to it
        // because koltin provides synthetic import and
        // We are gonna use for the same for rest of Views
        display_html.setOnClickListener {
            if (editor.text.isNotEmpty()) {
                displayHtml(editor.text.toString())
            }
        }
    }
  
    private fun displayHtml(html: String) {
        // Creating object of ImageGetter class you just created
        val imageGetter = ImageGetter(resources, html_viewer)
  
        // Using Html framework to parse html
        val styledText =
            HtmlCompat.fromHtml(html, HtmlCompat.FROM_HTML_MODE_LEGACY, imageGetter, null)
  
        replaceQuoteSpans(styledText as Spannable)
        ImageClick(styledText as Spannable)
  
        // setting the text after formatting html and downloadig and setting images
        html_viewer.text = styledText
  
        // to enable image/link clicking
        html_viewer.movementMethod = LinkMovementMethod.getInstance()
  
    }
  
    private fun replaceQuoteSpans(spannable: Spannable) {
        val quoteSpans: Array<QuoteSpan> =
            spannable.getSpans(0, spannable.length - 1, QuoteSpan::class.java)
  
        for (quoteSpan in quoteSpans) {
            val start: Int = spannable.getSpanStart(quoteSpan)
            val end: Int = spannable.getSpanEnd(quoteSpan)
            val flags: Int = spannable.getSpanFlags(quoteSpan)
            spannable.removeSpan(quoteSpan)
            spannable.setSpan(
                QuoteSpanClass(
                    // background color
                    ContextCompat.getColor(this, R.color.colorPrimary),
                    // strip color
                    ContextCompat.getColor(this, R.color.colorAccent),
                    // strip width
                    10F, 50F
                ),
                start, end, flags
            )
        }
    }
  
    // Function to parse image tags and enable click events
    fun ImageClick(html: Spannable) {
        for (span in html.getSpans(0, html.length, ImageSpan::class.java)) {
            val flags = html.getSpanFlags(span)
            val start = html.getSpanStart(span)
            val end = html.getSpanEnd(span)
            html.setSpan(object : URLSpan(span.source) {
                override fun onClick(v: View) {
                    Log.d(TAG, "onClick: url is ${span.source}")
                }
            }, start, end, flags)
        }
    }
}

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  • Now if you click on any Image and check Logcat you will see the URL of the image is being logged. From there you can trigger some function with that URL.

Output: Run on Emulator

Resource: Get the complete project file here.




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