The key must be an application-specific resource id

Question

The reason you're not able to use setTag(int, Object) is because android require a pre-compiled unique id in the 'int' argument.

Try creating two unique entry in String.xml xml say, "firstname" & "secondname" & use them as below

imageView.setTag(R.string.firstname, "Abhishek");
imageView.setTag(R.string.lastname, "Gondalia");

I'm a little late to the party but I stumbled on this problem myself today and thought I'd give an answer as well. This answer will be a bit of a compilation of the other answers, but with a twist. First of all, the id, as has been pointed out by others, can NOT be a constant defined in your code (such as private static final int MYID = 123) or any other int that you define as a field somewhere.

The id has to be a precompiled unique id, just like the ones you get for strings that you put in values/strings.xml (ie R.string.mystring). Refer to http://developer.android.com/guide/topics/resources/available-resources.html and http://developer.android.com/guide/topics/resources/more-resources.html for more information.

My suggestion is that you create a new file called values/tags.xml and write:

    <resources xmlns:android="http://schemas.android.com/apk/res/android">
      <item name="TAG_ONLINE_ID" type="id"/>
    </resources>

I think it's better to create a separate file instead of putting it in strings.xml as EtienneSky suggested.

THIS WILL DO THE JOB...

If you just have 1 setTag in your class, you could use any int, maybe static final declared in the top.

The problem comes when you had 2 or more setTag's with different keys. I mean:

public static final int KEY_1 = 1;
public static final int KEY_2 = 2;
...
setTag(KEY_1, VALUE_1)
setTag(KEY_2, VALUE_2)
...

That scenario is wrong. You then need to add a value file called maybe ids.xml with the following:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item type="id" name="resourceDrawable" />
    <item type="id" name="imageURI" />
</resources>

Then, in your class, call:

 ...
 setTag(R.id.resourceDrawable, VALUE_1)
 setTag(R.id.imageURI, VALUE_2)
 ...

The tag id must be unique so it wants it to be an id created in a resources file to guarantee uniqueness.

If the view will only contain one tag though you can just do

setTag(objContact.onlineid);

private static final int TAG_ONLINE_ID = 1 + 2 << 24;

should work. More info from ceph3us:

The specified key should be an id declared in the resources of the application to ensure it is unique Keys identified as belonging to the Android framework or not associated with any package will cause an IllegalArgumentException to be thrown.

from source:

public void setTag(int key, final Object tag) {
    // If the package id is 0x00 or 0x01, it's either an undefined package
    // or a framework id
    if ((key >>> 24) < 2) {
        throw new IllegalArgumentException("The key must be an application-specific "
                + "resource id.");
    }

    setKeyedTag(key, tag);
}

I've used viewHolder.itemTitleTextView.getId(). But you can also declare in your resources: <item type="id" name="conversation_thread_id"/>