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[TabLayout] Fix TabView click listener customization #4107

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29 changes: 28 additions & 1 deletion lib/java/com/google/android/material/tabs/TabLayout.java
Original file line number Diff line number Diff line change
Expand Up @@ -2173,6 +2173,8 @@ public static class Tab {
@NonNull public TabView view;
private int id = NO_ID;

private OnTabClickListener onTabClickListener = new DefaultOnTabClickListener();

// TODO(b/76413401): make package private constructor after the widget migration is finished
public Tab() {
// Private constructor
Expand Down Expand Up @@ -2219,6 +2221,17 @@ public int getId() {
return id;
}

/**
* Register a callback to be invoked when the tab is clicked.
* <p>
* Note: By default, tab is selected on click.
*/
public Tab setOnTabClickListener(@Nullable OnTabClickListener onTabClickListener) {
this.onTabClickListener = onTabClickListener;

return this;
}

/**
* Returns the custom view used for this tab.
*
Expand Down Expand Up @@ -2529,6 +2542,18 @@ void reset() {
contentDesc = null;
position = INVALID_POSITION;
customView = null;
onTabClickListener = new DefaultOnTabClickListener();
}

private static class DefaultOnTabClickListener implements OnTabClickListener {
@Override
public void onClick(@NonNull Tab tab) {
tab.select();
}
}

interface OnTabClickListener {
void onClick(@NonNull Tab tab);
}
}

Expand Down Expand Up @@ -2644,7 +2669,9 @@ public boolean performClick() {
if (!handled) {
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I think this should be part of the default onClick behavior as well.

playSoundEffect(SoundEffectConstants.CLICK);
}
tab.select();
if (tab.onTabClickListener != null) {
tab.onTabClickListener.onClick(tab);
}
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Let's try to avoid overriding the default behavior unless there's a valid use case to do that.

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@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.

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

return true;
} else {
return handled;
Expand Down