6286501: JTabbedPane throws NPE from its stateChanged listener in particular case

[prsadhuk]

JTabbedPane throws NPE from its stateChanged listener as it tries to access uninstantiated TabbedPane.
Fix is to use the tabPane passed to stateChangeListener so that correct tabPane is accessed.

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Issue

• JDK-6286501: JTabbedPane throws NPE from its stateChanged listener in particular case

Reviewers

• Jayathirth D V (@jayathirthrao - Reviewer)

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[mlbridge]

Webrevs

• 00: Full (f88c2c5f)

[jayathirthrao]

I see BasicTabbedPaneUI.tabPane object getting used in other listeners in this Handler class. Is there a reason why only when we hit stateChanged() function we are seeing NPE?

Is this NPE for tabPane object itself or Layout not being initialized?

[prsadhuk]

Basically, when a tab index is selected via tbp.setSelectedIndex() in testcase, it fires a state change event (via DefaultSingleSelectionModel#setSelectedIndex) which is caught by the application and in this case, state change listener in the testcase calls JTabbedPane.updateUI() which calls JComponent.setUI() which first uninstalls UI (which made tabPane null in BasicTabbedPaneUI#uninstallUI) and then install new UI instance but when it goes to JDK's stateChange listener BasicTabbedPaneUI.stateChanged() it passes the new instance but scrollableTabLayoutEnabled() still uses old UI instance in which tabPane is already made null so NPE happens, so it is better to use the tabPane instance passed to UI's stateChange listener..

[jayathirthrao]

When we install new UI instance will we not call BasicTabbedPaneUI.installUI() to update current tabPane object? or is it happening at later stage(like after BasicTabbedPaneUI.stateChanged() is called)?

[prsadhuk]

installUI is called for new UI instance with current tabpane object but scrollableTabLayoutEnabled was using the old UI instance whose tabpane object is already reset to null.

[openjdk]

@prsadhuk This change now passes all automated pre-integration checks.

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6286501: JTabbedPane throws NPE from its stateChanged listener in particular case

Reviewed-by: jdv

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At the time when this comment was updated there had been 173 new commits pushed to the master branch:

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• ... and 163 more: https://git.openjdk.org/jdk/compare/bd674dc55e87940f442cb140841f95424b6d42fd...master

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[prsadhuk]

/integrate

[openjdk]

Going to push as commit ab7f58a.
Since your change was applied there have been 199 commits pushed to the master branch:

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• ... and 189 more: https://git.openjdk.org/jdk/compare/bd674dc55e87940f442cb140841f95424b6d42fd...master

Your commit was automatically rebased without conflicts.

[openjdk]

@prsadhuk Pushed as commit ab7f58a.

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