不触发setOnAction

Question

我需要在单击按钮时显示一些文本。已将按钮arraylist添加到vbox，在Platform.runLater（）方法中调用vbox到gridpane和setOnAction，如图所示。 代码：

  private ArrayList<Button> btnar;
  private VBox vb;
  private Button downloadbtn;
@FXML
  private ScrollPane displayscroll;
   private GridPane gridpane;

 public HomeUI_2Controller() {
    Platform.runLater(new Runnable() {

        @Override
        public void run() {
         gridpane = new GridPane();
         displayscroll.setContent(gridpane);

         btnar = new ArrayList<>();
            for (int i = 0; i < filelist2.size(); i++) {
                downloadbtn = new Button("Download");
                btnar.add(downloadbtn);
            }
            int imageCol = 0;
            int imageRow = 0;

            for (int i = 0; i < filelist2.size(); i++) {
                System.out.println(filelist2.get(i).getName());

                image = new Image(filelist2.get(i).toURI().toString());

                pic = new ImageView();
                pic.setFitWidth(130);
                pic.setFitHeight(130);

                pic.setImage(image);
                vb = new VBox();
                vb.getChildren().addAll(pic, (Button) btnar.get(i));

                gridpane.add(vb, imageCol, imageRow);
                GridPane.setMargin(pic, new Insets(2, 2, 2, 2));
                imageCol++;

                // To check if all the 3 images of a row are completed
                if (imageCol > 2) {
                    // Reset Column
                    imageCol = 0;
                    // Next Row
                    imageRow++;
                }

            }
             downloadbtn.setOnAction(new EventHandler<ActionEvent>() {
                @Override
                public void handle(ActionEvent arg0) {
                    System.out.println("sssss");
                }
            });

    }
    });

}

Answer 1

• 只有你的上一个＆＃34;下载＆＃34;按钮应该被触发。因为您只是将onAction事件处理程序添加到最后一个。

• 您在这里不需要Paltform.runLater()。

• 如果只能循环一次，则不应构建相同的多循环。

• 尽量保持变量的范围尽可能窄。换句话说，不要定义全局变量，并将其作为占位符使用。这使得代码更容易出错并且难以维护。

测试这个重构的代码：

private ArrayList<Button> btnar;
private VBox vb;
@FXML
private ScrollPane displayscroll;
private GridPane gridpane;

public HomeUI_2Controller() {

    gridpane = new GridPane();
    displayscroll.setContent(gridpane);

    btnar = new ArrayList<>();
    int imageCol = 0;
    int imageRow = 0;

    for (int i = 0; i < filelist2.size(); i++) {
        Button downloadbtn = new Button("Download");
        downloadbtn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent arg0) {
                System.out.println("You are requested to download the file " + filelist2.get(i).getName());
            }
        });
        btnar.add(downloadbtn);

        System.out.println(filelist2.get(i).getName());
        image = new Image(filelist2.get(i).toURI().toString());

        ImageView pic = new ImageView();
        pic.setFitWidth(130);
        pic.setFitHeight(130);

        pic.setImage(image);
        vb = new VBox();
        vb.getChildren().addAll(pic, downloadbtn);

        gridpane.add(vb, imageCol, imageRow);
        GridPane.setMargin(pic, new Insets(2, 2, 2, 2));
        imageCol++;

        // To check if all the 3 images of a row are completed
        if (imageCol > 2) {
            // Reset Column
            imageCol = 0;
            // Next Row
            imageRow++;
        }
    }
}