Java中的indexOf（“ @”）方法

Question

Why does this always return -1? Does this have anything to do with '@' being the annotation symbol?

What can I do to search for the first occurrence of a substring starting with '@'?

 UserMentionEntity[] userMentionEntities = status.getUserMentionEntities();
    for (UserMentionEntity ume : userMentionEntities) {
        final String mention = ume.getText();
        int mentionStart = text.indexOf("@" + mention);
        int mentionEnd = mentionStart + mention.length();
        ss.setSpan(new ForegroundColorSpan(Color.parseColor(COLOR)), mentionStart, mentionEnd + 1, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    }

Apparently, mentionStart is -1. I am using twitter4j library.

Sample:

text: RT @Cornerstone_TMC Thank you @ukgdos at sa lahat ng nag-abang kanina kay @yengpluggedin! #SeenZoned @academyofrocksg… http://t.co/rsLqjlZJgg
mention: ukgdos

Answer 1

No. Your String doesn't contain what you think it does,

String mention = "not";
String text = "I do @not think so.";
int mentionStart = text.indexOf("@" + mention); 
System.out.printf("%d%n", mentionStart);

Prints

5

Edit

Based on your now provided text and mention

String text = "RT @Cornerstone_TMC Thank you @ukgdos "
    + "at sa lahat ng nag-abang kanina kay @yengpluggedin! "
    + "#SeenZoned @academyofrocksg… http://t.co/rsLqjlZJgg";
String mention = "ukgdos";
int mentionStart = text.indexOf("@" + mention); 
System.out.printf("%d%n", mentionStart);

Prints

30

Answer 2

I fixed the problem with my app.

    UserMentionEntity[] userMentionEntities = status.getUserMentionEntities();
    for (UserMentionEntity ume : userMentionEntities) {
        final String mention = ume.getText().toLowerCase();
        int mentionStart = text.toLowerCase().indexOf("@" + mention);
        int mentionEnd = mentionStart + mention.length();
        ss.setSpan(new ForegroundColorSpan(Color.parseColor(COLOR)), mentionStart, mentionEnd + 1, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
    }

I noticed that Twitter allows you to change cases in the mentions.

@yengPLUGGEDin can be shown as @yengpluggedin so that ume.getText() in the code there returns the proper screenname while text contains the tweet text as it is.

I am not quite sure why it also failed on my sample input there. Maybe it didn't but failed on the next before the print was executed.