[TabLayout] Fix TabView click listener customization

[vvinogra]

Closes #4105

Usage example:

TabLayout tabLayout = ...;

Tab firstTab = tabLayout.newTab()
    .setText("Tab 1")
    .setOnTabClickListener((tab) -> {
        if (!isSomeCheckValid) {
            // Show some error dialog.
            return;
        }

        tab.select();
     });

tabLayout.addTab(firstTab);

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[drchen]

Let's try to avoid overriding the default behavior unless there's a valid use case to do that.

[vvinogra]

@drchen Hey, thanks for the comment.

The main idea is to have an option to override a default behavior.
A usecase is described in the #4105 issue.

tl.dr.
We need to override a default behaviour to add a validation logic when user clicks on the tab before selecting it.
With the existing implementation, I tried selecting the previous tab in case the data is not valid but it doesn't look good because the tab is selected with the animation.

[drchen]

Ok cool. So I think there are several improvements I'll suggest here:

1. Let's make onTabClickListener be non-null.
2. Let OnTabClickListener .onClick() return a boolean to indicate if the click event is handled, so we can simplify the logic like:

final boolean handled = super.performClick() || tab.onTabClickListener.onClick(tab);
... rest the same

3. Refine the javadoc to make it more clear that how to override the default behavior.

[drchen]

Ok cool. So I think there are several improvements I'll suggest here:

1. Let's make onTabClickListener be non-null.
2. Let OnTabClickListener .onClick() return a boolean to indicate if the click event is handled, so we can simplify the logic like:

final boolean handled = super.performClick() || tab.onTabClickListener.onClick(tab);
... rest the same

3. Refine the javadoc to make it more clear that how to override the default behavior.

[drchen]

I think this should be part of the default onClick behavior as well.