Javafx TextField总是抛出＆＃34;空字符串＆＃34;错误

Question

以下代码应允许用户输入他们要添加到列表中的新产品的详细信息（Choicebox除外）。几乎所有的代码都可以工作，只有方法handlePrice（）。每当用户尝试输入priceText TextField时，错误＆＃34;空字符串＆＃34;被抛出并且不允许用户输入任何字符。所有变量都在代码中初始化，PartList是初始化的ObservableList。

//TextFields
@FXML
private TextField partNameText;
@FXML
private TextField brandNameText;
@FXML
private TextField itemIDText;
@FXML
private TextField materialText;
@FXML
private TextField priceText;//
@FXML
private void handlePartType() {
    partType = partTypeChoice.getValue();
}

//
@FXML
private void handlePartName() {
    partName = partNameText.getText();
}

//
@FXML
private void handleBrandName() {
    brandName = brandNameText.getText();
}

//
@FXML
private void handleItemID() {
    itemID = itemIDText.getText();
}

//
@FXML
private void handleMaterial() {
    material = materialText.getText();
}

//
@FXML
private void handlePrice() {
    String priceString = priceText.getText();
    price = Double.parseDouble(priceString);
}

//
@FXML
private void newPart() {
    //
    if((partTypeChoice.getValue().isEmpty() == false)&&(partNameText.getText().isEmpty() == false)) {
        //
        PartList.add(partListIndex, new Part(partType, partName, brandName, itemID, material, price));
        partListIndex++;

        //
        partListTable.setItems(PartList);
    }
    else {
        //Changes the text of the Required labels
        partTypeLabel.setText("*Part Type");
        partNameLabel.setText("*Part Name");

        //Changes the color of the Required Labels
        partTypeLabel.setTextFill(javafx.scene.paint.Color.RED);
        partNameLabel.setTextFill(javafx.scene.paint.Color.RED);

        //Displays the warning
        warningLabel.setVisible(true);
        dismissButton.setVisible(true);
    }
}