GUI thread exception handler

[vasso123]

Hi guys,

I'm having a problem regarding the exception handler on the TextGUIThread.

As I understand it, setting the exception handler using the setExceptionHandler method, all unhandled exceptions in the "user" code are trapped and handled with that handler.

However, I can't get it to work, example:

package hr.vkeglevic.doomsdayterminal;

import com.googlecode.lanterna.gui2.BasicWindow;
import com.googlecode.lanterna.gui2.Button;
import com.googlecode.lanterna.gui2.MultiWindowTextGUI;
import com.googlecode.lanterna.gui2.TextGUIThread;
import com.googlecode.lanterna.screen.TerminalScreen;
import com.googlecode.lanterna.terminal.DefaultTerminalFactory;
import com.googlecode.lanterna.terminal.Terminal;
import java.io.IOException;

public class TestExceptionHandler {

    private static DefaultTerminalFactory terminalFactory;
    private static Terminal terminal;
    private static TerminalScreen screen;
    private static MultiWindowTextGUI textGUI;
    private static BasicWindow window;

    public static void main(String[] args) throws IOException {
        terminalFactory = new DefaultTerminalFactory();
        terminal = terminalFactory.createTerminal();
        screen = new TerminalScreen(terminal);
        screen.startScreen();
        textGUI = new MultiWindowTextGUI(screen);
        setExceptionHandler();
        window = new BasicWindow();

        Button button = new Button("test");
        button.addListener((b) -> {
            setExceptionHandler();
            throw new RuntimeException("This should be caught in the uncaght exception handler!");
        });
        window.setComponent(button);

        textGUI.addWindowAndWait(window);
        screen.stopScreen();
    }

    private static void setExceptionHandler() {
        textGUI.getGUIThread().setExceptionHandler(new TextGUIThread.ExceptionHandler() {

            private boolean handleException(Exception e) {
                System.err.println("### Caught!");
                e.printStackTrace();
                return false;
            }

            @Override
            public boolean onIOException(IOException e) {
                return handleException(e);
            }

            @Override
            public boolean onRuntimeException(RuntimeException e) {
                return handleException(e);
            }
        });
    }

}

When pressing the button, the string "### Caught!" should be printed on the standard output, but it doesn't.

Any ideas?

Thanks

[Martin Berglund]

Hello,

I don't have the code open right now, did you try to step through with a debugger and see what happened to the exception? The code should be pretty clear if you download the sources from Maven central from your IDE.

Regards,

Martin

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[vasso123]

Hi,

tried just now, here's the stack trace:

at hr.vkeglevic.test.TestExceptionHandler.lambda$main$0(TestExceptionHandler.java:32)
at com.googlecode.lanterna.gui2.Button.triggerActions(Button.java:101)
at com.googlecode.lanterna.gui2.Button.handleKeyStroke(Button.java:93)
at com.googlecode.lanterna.gui2.AbstractInteractableComponent.handleInput(AbstractInteractableComponent.java:142)
at com.googlecode.lanterna.gui2.AbstractBasePane.doHandleInput(AbstractBasePane.java:126)
at com.googlecode.lanterna.gui2.AbstractBasePane.handleInput(AbstractBasePane.java:97)
at com.googlecode.lanterna.gui2.AbstractWindow.handleInput(AbstractWindow.java:133)
at com.googlecode.lanterna.gui2.MultiWindowTextGUI.handleInput(MultiWindowTextGUI.java:333)
at com.googlecode.lanterna.gui2.AbstractTextGUI.processInput(AbstractTextGUI.java:94)
at com.googlecode.lanterna.gui2.AbstractTextGUIThread.processEventsAndUpdate(AbstractTextGUIThread.java:75)
at com.googlecode.lanterna.gui2.MultiWindowTextGUI.waitForWindowToClose(MultiWindowTextGUI.java:406)
at com.googlecode.lanterna.gui2.AbstractWindow.waitUntilClosed(AbstractWindow.java:269)
at com.googlecode.lanterna.gui2.MultiWindowTextGUI.addWindowAndWait(MultiWindowTextGUI.java:370)
at hr.vkeglevic.test.TestExceptionHandler.main(TestExceptionHandler.java:36)

Exception went uncaught through the lanterna code.

Using lanterna 3.0.0.

[Pordi Erstaquel]

Why are you setting the exception handler each button click? Probably not a solution, but this looks to me error-prone.

[vasso123]

Just to prove that it doesn't matter when you set the exception handler (before or after starting running the gui thread).