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Dec 26 '11

Android Custom Hyperlinked TextView

This Post is Contributed by Y. Ramesh Rao

(http://stackoverflow.com/users/92039/y-ramesh-rao)
Finding Links in Android is very simple you might have heard of Linkify which is a great class in which there are many static methods for getting a simple job done but the problem is that in Linkify you cannot specify the behavior that you require on clicking the links at the Most what Linkify does is that it simply finds the links based on the “Pattern” you provide and adds a “Scheme” string to complete the URL and created a Android Intent for Launching the Browser. The Linkify behavior cannot be overridden as all the methods in Linkify class are static final.

This was the issue that inspired me to create a Custom TextView Widget the one which collects the links in my scenario I also programmed it to collect the the Strings starting with “@” and “#” but this things can be changed by simply changing the Patterns that you require and giving the proper Regular Expression for them.

The LinkEnableTextView class is like this:

import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import android.content.Context;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.style.ClickableSpan;
import android.util.AttributeSet;
import android.view.View;
import android.widget.TextView;


public class LinkEnabledTextView  extends TextView
{
// The String Containing the Text that we have to gather links from private SpannableString linkableText;
// Populating and gathering all the links that are present in the Text
private ArrayList<Hyperlink> listOfLinks; 

// A Listener Class for generally sending the Clicks to the one which requires it
TextLinkClickListener mListener;

// Pattern for gathering @usernames from the Text
Pattern screenNamePattern = Pattern.compile("(@[a-zA-Z0-9_]+)");

// Pattern for gathering #hasttags from the Text
Pattern hashTagsPattern = Pattern.compile("(#[a-zA-Z0-9_-]+)");

// Pattern for gathering http:// links from the Text
Pattern hyperLinksPattern = Pattern.compile("([Hh][tT][tT][pP][sS]?:\\/\\/[^ ,'\">\\]\\)]*[^\\. ,'\">\\]\\)])");

public LinkEnabledTextView(Context context, AttributeSet attrs)
{
    super(context, attrs);
    listOfLinks = new ArrayList<Hyperlink>();

}

public void gatherLinksForText(String text)
{
    linkableText = new SpannableString(text);
    /*
     *  gatherLinks basically collects the Links depending upon the Pattern that we supply
     *  and add the links to the ArrayList of the links
     */
    gatherLinks(listOfLinks, linkableText, screenNamePattern);
    gatherLinks(listOfLinks, linkableText, hashTagsPattern);
    gatherLinks(listOfLinks, linkableText, hyperLinksPattern);

    for(int i = 0; i< listOfLinks.size(); i++)
    {
        Hyperlink linkSpec = listOfLinks.get(i);
        android.util.Log.v("listOfLinks :: " + linkSpec.textSpan, "listOfLinks :: " + linkSpec.textSpan);
        /*
         * this process here makes the Clickable Links from the text
         */
        linkableText.setSpan(linkSpec.span, linkSpec.start, linkSpec.end, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    }

    /*
     * sets the text for the TextView with enabled links
     */
    setText(linkableText);
}

/*
 * sets the Listener for later click propagation purpose
 */
public void setOnTextLinkClickListener(TextLinkClickListener newListener)
{
    mListener = newListener;
}

/*
 * The Method mainly performs the Regex Comparison for the Pattern and adds them to
 * listOfLinks array list
 */

private final void gatherLinks(ArrayList<Hyperlink> links,
                               Spannable s, Pattern pattern)
{
    // Matcher matching the pattern
    Matcher m = pattern.matcher(s);

    while (m.find())
    {
        int start = m.start();
        int end = m.end();

        /*
         *  Hyperlink is basically used like a structure for storing the information about
         *  where the link was found.
         */
        Hyperlink spec = new Hyperlink();

        spec.textSpan = s.subSequence(start, end);
        spec.span = new InternalURLSpan(spec.textSpan.toString());
        spec.start = start;
        spec.end = end;

        links.add(spec);
    }
}

/*
 * This is class which gives us the clicks on the links which we then can use.
 */
public class InternalURLSpan extends ClickableSpan
{
    private String clickedSpan;

    public InternalURLSpan (String clickedString)
    {
        clickedSpan = clickedString;
    }

    @Override
    public void onClick(View textView)
    {
        mListener.onTextLinkClick(textView, clickedSpan);
    }
}

/*
 * Class for storing the information about the Link Location
 */

class Hyperlink
{
    CharSequence textSpan;
    InternalURLSpan span;
    int start;
    int end;
}

Now, having this you require just another interface for propagating the clicks to the place you require to handle them in my case I implemented the interface in my Activity and simple wrote a Log Command there.

The TextLinkClickListener interface is like this:

import android.view.View;

public interface TextLinkClickListener
{

 /*
  *  This method is called when the TextLink is clicked from LinkEnabledTextView
  */
public void onTextLinkClick(View textView, String clickedString)
}

After doing all this you just require to create an Activity using the Custom LinkEnabledTextView and check the things out yourself. There are a few things that you must do while creating a object of the Custom LinkEnabledTextView those are mentioned and described in the Code of the Activity below:


import android.text.method.MovementMethod;
import com.umundoinc.Tvider.Component.LinkEnabledTextView.LinkEnabledTextView;
import com.umundoinc.Tvider.Component.LinkEnabledTextView.TextLinkClickListener;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.text.method.LinkMovementMethod;
import android.view.View;

/*
 * Here the Activity is implementing the TextLinkClickListener the one we have created
 * the Clicks over the Links are forwarded over here from the LinkEnabledTextView
 */
public class TextViewActivity  extends Activity  implements TextLinkClickListener 
{
private LinkEnabledTextView check;
protected void onCreate(Bundle savedInstance)
{
    super.onCreate(savedInstance);

    String text  =  "This is a #test of regular expressions with http://example.com links as used in @twitter
                     for performing various operations based on the links this handles multiple links like
                     http://this_is_fun.com and #Awesomess and @Cool";

    check = new LinkEnabledTextView(this, null);
    check.setOnTextLinkClickListener(this);
    check.gatherLinksForText(text);
    check.setTextColor(Color.WHITE);
    check.setLinkTextColor(Color.GREEN);

    MovementMethod m = check.getMovementMethod();
    if ((m == null) || !(m instanceof LinkMovementMethod)) {
        if (check.getLinksClickable()) {
            check.setMovementMethod(LinkMovementMethod.getInstance());
        }
    }

    setContentView(check);
}

public void onTextLinkClick(View textView, String clickedString)
{
    android.util.Log.v("Hyperlink clicked is :: " + clickedString, "Hyperlink clicked is :: " + clickedString);
}

Here, is the Screenshot describing the output in my Listener method I programmed it to display a Toast but anything can be achieved in same method.

image

Now that’s pretty much all that you’ll need that makes the Custom LinkEnabledTextView working, try it out and share your views and reviews over it.

6 notes View comments Tags: Programming android code samples software

  1. orangeappletemp posted this
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