comparison of two Strings doesn't work in android

Question

here's my code, Eclipse doesn't show any errors, program's working fine, but it simply doesn't do exactly what i want:)

    View image_view_danger_rate = (ImageView) findViewById(R.id.origin);
    View image_view_origin = (ImageView) findViewById(R.id.danger_rate);

    String entry_tag = (String) descriptionResultView.findViewById(resID).getTag();

    String dangerous = "dangerous";
    String not_dangerous = "not_dangerous";

    if ( entry_tag == dangerous) {
        image_view_danger_rate.setBackgroundResource(R.drawable.attention);
    }else if ( entry_tag == not_dangerous) {
        image_view_danger_rate.setBackgroundResource(R.drawable.its_ok);
        image_view_origin.setBackgroundResource(R.drawable.artificial);
    }

The application should choose between two images to pop-up on the screen, depending on a tag stored in the xml file. So, if the tag says "dangerous", then should be shown the "attention"-image. If the tag says "not_dangerous", there should be the "its_ok"-image.

Now, displaying the images without an if-comparison works perfectly.

If i print out the tags as a string, it works, it prints correctly "dangerous" or "not_dangerous", depending on the tag.

But if there's a if-comparison as shown above, nothing happens, no image is shown.

Please anyone help!!=)

This question has been asked on this site more times than I care to find. Please use the search function. — Woot4Moo, Jul 25 '11 at 17:29
@Woot4Moo Duplication is not necesarilly bad. http://blog.stackoverflow.com/2010/11/dr-strangedupe-or-how-i-learned-to-stop-worrying-and-love-duplication/ — Marcelo, Jul 25 '11 at 17:34
@Woot4Moo Your link to the supposedly duplicate question does not even have to do with this question too. — Marcelo, Jul 25 '11 at 17:37
@Marcelo even still how is this subtly different than any of the other examples on this site about people not knowing how to do string comparison in java? — Woot4Moo, Jul 25 '11 at 17:37
well too late now to change my vote to close because of no new edit: http://stackoverflow.com/questions/995918/java-string-comparison — Woot4Moo, Jul 25 '11 at 17:38

score 45 · Answer 1 · answered Jul 25 '11 at 16:53

45

Use string1.equalsIgnoreCase("something) or .equals("Something");

With == (for strings) in java you are comparing they are of same reference. Like you did is the test if both of them are strings objects.

answered Jul 25 '11 at 16:53

Nikola Despotoski

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I just learned something very important! =D it worked for me...thank you for this quick answer! – Silvan Jul 25 '11 at 17:00

score 13 · Answer 2 · answered Jul 25 '11 at 16:56

13

In java, a==b is used to compare 2 references, not the objects themselves.

so if you have 2 strings that you want to compare, use the equals() method on String. for eg

boolean resultOfComparison=stringA.equals(stringB);

answered Jul 25 '11 at 16:56

Archit

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thanks to all of you, that was the solution! – Silvan Jul 25 '11 at 17:08

score 5 · Answer 3 · answered Jul 25 '11 at 16:53

5

Use

entry_tag.equals(dangerous)

you're comparing actual String objects, not their content. In Java, operators are not overloaded so == can't be used to compare strings.

answered Jul 25 '11 at 16:53

diciu

29,133
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thanks to all of you, that was the solution! – Silvan Jul 25 '11 at 17:00

score 2 · Answer 4 · answered Jul 25 '11 at 16:53

2

In Java, if you want to compare Strings, you need to use equals():

if (entry_tag.equals(dangerous)) {
}

answered Jul 25 '11 at 16:53

Erich Douglass

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comparison of two Strings doesn't work in android

4 Answers4

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