CODEWITHSUNDEEP
javaandroidgenerics
Tim
Tim

Reputation: 13258

Java Generics Class as method parameter

I have a TabListener in Android defined in this way:

public static class TabListener<T extends Fragment> 
    implements ActionBar.TabListener { ... }

An I have this source code:

Tab myTab = myActionBar.
                newTab().
                setText("Home").
                setTabListener(new TabListener<MyFragment>(
                    this, 
                    "Home", 
                    MyFragment.class
                ));
...

Now I want to put this into a method:

addTab("Home", ???);

private void addTab(String text, ???) {
    Tab myTab = myActionBar.
                newTab().
                setText(text).
                setTabListener(new TabListener<???>(
                    this, 
                    text, 
                    ???.class
                ));
    ...
}

What I have to fill in instead of ????

Upvotes: 1

Views: 4112

Answers (3)

Bob Wang
Bob Wang

Reputation: 606

Your tab listener needs the type parameter to be a subclass of Fragment

public static class TabListener<T extends Fragment>

Therefore, you need to make sure it is the case in your code

addTab("Home", ???);

private <T extends Fragment> void addTab(String text, Class<T> clazz) {
    Tab myTab = myActionBar.
                newTab().
                setText(text).
                setTabListener(new TabListener<T>(
                    this, 
                    text, 
                    clazz
                ));
    ...
}

Upvotes: 5

irreputable
irreputable

Reputation: 45433

addTab("Home", MyFragment.class);

private void addTab(String text, Class<? extends Fragment> clazz) {
    Tab myTab = myActionBar.
            newTab().
            setText(text).
            setTabListener(new TabListener<>(
                this, 
                text, 
                clazz
            ));
    ...
}

Upvotes: 3

Alan Krueger
Alan Krueger

Reputation: 4786

Something like this is probably what you're looking for:

private <T> void addTab(String text, Class<T> clazz) {
    Tab myTab = myActionBar.
            newTab().
            setText(text).
            setTabListener(new TabListener<T>(
                this, 
                text, 
                clazz
            ));
    ...
}

Upvotes: 2

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