任务中的Java FX新模式窗口

Question

My problem is that I can not start a new modal window in Task, it just does not go out. I do not understand how it is possible to derive not just an allert, but any modal window from Task. Translated by Google =)

Task<Void> task = new Task<Void>() {
            @Override 
            public Void call() throws ApiException,ClientException,InterruptedException {
                 int i = 0;
                 for ( i = 0; i < bufferLenght; i++){
                    try {
                    ...some code
                    }catch(ApiCaptchaException e) {
                       ...get capcha
                       captchaSid = e.getSid();
                       captchaImg = e.getImage();
                       System.out.println( captchaSid);
}

                    System.out.println(captchaSid);
                    if (captchaSid != null) {
                        System.out.println("gg");
                        Alert alert = new Alert(AlertType.INFORMATION);
                        alert.setTitle("Test Connection");
                        //here he is stuck
                        alert.setHeaderText("Results:");
                        alert.setContentText("Connect to the database successfully!");
                        alert.showAndWait();

                        System.out.println("gg3");  
                    if(i<bufferLenght-1) {
                    Thread.sleep(2000);
                    }
                }
                return null;
            }
        };

        new Thread(task).start();

Answer 1

You must create and show new windows on the FX Application Thread. You can schedule code to execute on the FX Application Thread by submitting it to Platform.runLater(...) . If you need your background thread to wait for the user to dismiss the Alert , you can use a CompletableFuture , as in this question :

Task<Void> task = new Task<Void>() {

    @Override
    protected Void call() throws Exception {

        // ...

        CompletableFuture.runAsync(() -> {
            Alert alert = new Alert(AlertType.INFORMATION);
            alert.setTitle("Test Connection");
            alert.setHeaderText("Results:");
            alert.setContentText("Connect to the database successfully!");
            alert.showAndWait();
        }, Platform::runLater).join();

        // ...
    }
};

If your alert is returning a value which you need, use supplyAsync(...) instead and return the value from the lambda expression. You can then assign that value to the result of join() :

Task<Void> task = new Task<Void>() {

    @Override
    protected Void call() throws Exception {

        // ...

        String result = CompletableFuture.supplyAsync(() -> {
            Alert alert = new Alert(AlertType.INFORMATION);
            alert.setTitle("Test Connection");
            alert.setHeaderText("Results:");
            alert.setContentText("Connect to the database successfully!");
            alert.showAndWait();
            // presumably here you want to return a string
            // depending on the alert...
            return "" ;
        }, Platform::runLater).join();

        // ...
    }
};