我尝试制作一个带有 20 个按钮和一个处理程序的简单计算器。在 java 中,我可以在 ActionPerformed 中使用带有 event.getSource() 的“if”语句来检查按下了哪个按钮,但它不适用于 javafx 中的处理程序。在 javafx 中是否有可能所有按钮都有一个处理程序? (我不想使用 java 8 Lambdas。)
上次我尝试使用 setId/getId 但它同样不起作用(对我来说)。
public class Calculator extends Application {
public Button b0, b1;
@Override
public void start(Stage primaryStage) {
GridPane grid = new GridPane();
b0 = new Button("0");
b0.setId("0");
b0.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
grid.add(b0, 0, 1);
b0.setOnAction(myHandler);
b1 = new Button("1");
b1.setId("1");
b1.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
grid.add(b1, 0, 0);
b1.setOnAction(myHandler);
Scene scene = new Scene(grid, 365, 300);
scene.getStylesheets().add
(Calculator.class.getResource("calculator.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.setResizable(false);
primaryStage.show();
}
final EventHandler<ActionEvent> myHandler = new EventHandler<ActionEvent>(){
@Override
public void handle(final ActionEvent event) {
Button x = (Button) event.getSource();
if (x.getId().equals(b0.getId()))
System.out.println("0");
else if(x.getId().equals(b1.getId()))
System.out.println("1");
}
};
public static void main(String[] args) {
launch(args);
}
}
最佳答案
我测试了你的代码,它似乎工作得很好。
不过,没有真正的理由来测试按钮的 id。如果您真的想使用相同的处理程序(我不建议这样做),只需测试每个按钮和事件源之间的相等性:
final EventHandler<ActionEvent> myHandler = new EventHandler<ActionEvent>(){
@Override
public void handle(final ActionEvent event) {
if (event.getSource() == b0)
System.out.println("0");
else if(event.getSource() == b1)
System.out.println("1");
}
};
但是(几乎?)为每个 Action 使用不同的处理程序总是更好。它使代码免于所有
if/else
结构,这两者都使其在性能方面更清洁和更好。在这里,由于您的按钮几乎做同样的事情,您可以使用单个实现但多个对象。这是一个完整的例子:
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Priority;
import javafx.stage.Stage;
public class Calculator extends Application {
private final IntegerProperty value = new SimpleIntegerProperty();
class NumberButtonHandler implements EventHandler<ActionEvent> {
private final int number ;
NumberButtonHandler(int number) {
this.number = number ;
}
@Override
public void handle(ActionEvent event) {
value.set(value.get() * 10 + number);
}
}
@Override
public void start(Stage primaryStage) {
GridPane grid = createGrid();
for (int n = 1; n<10; n++) {
Button button = createNumberButton(n);
int row = (n-1) / 3;
int col = (n-1) % 3 ;
grid.add(button, col, 2 - row);
}
Button zeroButton = createNumberButton(0);
grid.add(zeroButton, 1, 3);
Button clearButton = createButton("C");
// without lambdas:
// clearButton.setOnAction(
// new EventHandler<ActionEvent>() {
// @Override
// public void handle(ActionEvent event) {
// value.set(0);
// }
// }
// );
// with lambdas:
clearButton.setOnAction(event -> value.set(0));
grid.add(clearButton, 2, 3);
TextField displayField = createDisplayField();
BorderPane root = new BorderPane();
root.setPadding(new Insets(10));
root.setTop(displayField);
root.setCenter(grid);
Scene scene = new Scene(root, 365, 300);
primaryStage.setScene(scene);
primaryStage.setResizable(false);
primaryStage.show();
}
private Button createNumberButton(int number) {
Button button = createButton(Integer.toString(number));
button.setOnAction(new NumberButtonHandler(number));
return button ;
}
private Button createButton(String text) {
Button button = new Button(text);
button.setMaxSize(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY);
GridPane.setFillHeight(button, true);
GridPane.setFillWidth(button, true);
GridPane.setHgrow(button, Priority.ALWAYS);
GridPane.setVgrow(button, Priority.ALWAYS);
return button ;
}
private GridPane createGrid() {
GridPane grid = new GridPane();
grid.setAlignment(Pos.CENTER);
grid.setHgap(5);
grid.setVgap(5);
grid.setPadding(new Insets(10));
return grid;
}
private TextField createDisplayField() {
TextField displayField = new TextField();
displayField.textProperty().bind(Bindings.format("%d", value));
displayField.setEditable(false);
displayField.setAlignment(Pos.CENTER_RIGHT);
return displayField;
}
public static void main(String[] args) {
launch(args);
}
}
关于button - javafx 多个按钮到同一个处理程序,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25409044/