What I want to do...
I have a webview in my android app. I get a huge html content from the server as a string and a search string from the application user(the android phone user). Now I break the search string and create a regex out of it. I want all the html content that matches my regex to be highlighted when I display it into my WebView.
What I tried...
Since it is html, I just want to wrap the regex matched words into a pair of tags with yellow background.
- Simple regex and replaceAll on the html Content that i get. Very wrong because it screws and replaces even what is inside the '<' and '>'.
- I tried using Matcher and Pattern combo. It is difficult to omit what is inside the tags.
- I used JSOUP Parser and it worked!
I traverse the html using NodeTraversor class. I used Matcher and Pattern classes to find and replace matched words with tags as i wanted to do.
But it is very slow. And I basically want to use it on Android and the size of it is like 284kB. I removed some unwanted classes and it is now 201kB but it is still too much for an android device. Additionally, the html content can be really large. I looked into JSoup source as well. It kind of iterates over every single character when it parses. I do not know whether all the parsers do the same but it is definitely slow for large html documents.
Here is my code -
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Highlighter {
private String regex;
private String htmlContent;
Pattern pat;
Matcher mat;
public Highlighter(String searchString, String htmlString) {
regex = buildRegexFromQuery(searchString);
htmlContent = htmlString;
pat = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);
}
public String getHighlightedHtml() {
Document doc = Jsoup.parse(htmlContent);
final List<TextNode> nodesToChange = new ArrayList<TextNode>();
NodeTraversor nd = new NodeTraversor(new NodeVisitor() {
@Override
public void tail(Node node, int depth) {
if (node instanceof TextNode) {
TextNode textNode = (TextNode) node;
String text = textNode.getWholeText();
mat = pat.matcher(text);
if(mat.find()) {
nodesToChange.add(textNode);
}
}
}
@Override
public void head(Node node, int depth) {
}
});
nd.traverse(doc.body());
for (TextNode textNode : nodesToChange) {
Node newNode = buildElementForText(textNode);
textNode.replaceWith(newNode);
}
return doc.toString();
}
private static String buildRegexFromQuery(String queryString) {
String regex = "";
String queryToConvert = queryString;
/* Clean up query */
queryToConvert = queryToConvert.replaceAll("[\\p{Punct}]*", " ");
queryToConvert = queryToConvert.replaceAll("[\\s]*", " ");
String[] regexArray = queryString.split(" ");
regex = "(";
for(int i = 0; i < regexArray.length - 1; i++) {
String item = regexArray[i];
regex += "(\\b)" + item + "(\\b)|";
}
regex += "(\\b)" + regexArray[regexArray.length - 1] + "[a-zA-Z0-9]*?(\\b))";
return regex;
}
private Node buildElementForText(TextNode textNode) {
String text = textNode.getWholeText().trim();
ArrayList<MatchedWord> matchedWordSet = new ArrayList<MatchedWord>();
mat = pat.matcher(text);
while(mat.find()) {
matchedWordSet.add(new MatchedWord(mat.start(), mat.end()));
}
StringBuffer newText = new StringBuffer(text);
for(int i = matchedWordSet.size() - 1; i >= 0; i-- ) {
String wordToReplace = newText.substring(matchedWordSet.get(i).start, matchedWordSet.get(i).end);
wordToReplace = "<b>" + wordToReplace+ "</b>";
newText = newText.replace(matchedWordSet.get(i).start, matchedWordSet.get(i).end, wordToReplace);
}
return new DataNode(newText.toString(), textNode.baseUri());
}
class MatchedWord {
public int start;
public int end;
public MatchedWord(int start, int end) {
this.start = start;
this.end = end;
}
}
}
Here is how I call it -
htmlString = getHtmlFromServer();
Highlighter hl = new Highlighter("Hello World!", htmlString);
new htmlString = hl.getHighlightedHTML();
I am sure what i'm doing is not the most optimal way. But I can't seem to think of anything else.
I want to - reduce the time it takes to highlight it. - reduce the size of library
Any suggestions?
