Question

我正在尝试使用JavaFX创建应用程序。我有个问题。当我要更新另一个场景中的标签文本时，我无法执行此操作。每当我使用setText（）更新标签文本时，它都会返回nullpointerexception。我试过创建标签实例，但这甚至无济于事。我正在发布代码段和fxml文档。请帮我该怎么办。这是我的代码。

    public void screenforward(ActionEvent event) throws IOException {

    String a = pin.getText();
    System.out.println(a);
    try {
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection con=DriverManager.getConnection(
        "jdbc:mysql://localhost:3306/mithu?autoReconnect=true&useSSL=false","root","polkadot");
        Statement stmt=con.createStatement();  
        ResultSet rs1=stmt.executeQuery("select * from banking where pin="+a);
        int bal = -1;//,id=1;
        String first = null,last = null;
        if(rs1.next()) {
            //System.out.println("Welcome "+rs.getString(5)+" "+rs.getString(6));
            first=rs1.getString(5);
            last=rs1.getString(6);
        bal=rs1.getInt(7);
        //id=rs.getInt(1);
        }
        String tex="Welcome "+first+" "+last+".";
        if(bal!=-1)
        {
            withdraw.setText("-_-");
            System.out.println(tex);
        }//
    } catch (Exception e) {
        System.out.println(e);
    }
    Parent ask = FXMLLoader.load(getClass().getResource("Sample.fxml"));
    Scene askscene = new Scene(ask);
    Stage window = (Stage)((Node)event.getSource()).getScene().getWindow();
    window.setScene(askscene);
    window.show();
}

每当我更改场景时，都会调用此函数，并且希望此函数更改场景中未发生的标签文本。下面是我的fxml文档。

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.effect.Bloom?>
<?import javafx.scene.image.Image?>
<?import javafx.scene.image.ImageView?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="319.0" prefWidth="591.0" style="-fx-background-color: #1B2D6F;" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.SampleController">
   <children>
  <ImageView fitHeight="150.0" fitWidth="200.0" layoutX="196.0" layoutY="27.0" pickOnBounds="true" preserveRatio="true">
     <image>
        <Image url="@banner.png" />
     </image>
  </ImageView>
  <Button layoutX="47.0" layoutY="120.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="93.0" text="Fund Transfer" />
  <Button layoutX="47.0" layoutY="182.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="93.0" text="Change Pin" />
  <Button layoutX="47.0" layoutY="240.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="93.0" text="Change Phone" />
  <Button fx:id="withdraw" layoutX="450.0" layoutY="120.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="100.0" text="Withdraw" />
  <Button layoutX="450.0" layoutY="182.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="100.0" text="Mini Statement" />
  <Button layoutX="450.0" layoutY="240.0" mnemonicParsing="false" onAction="#screen2" prefHeight="42.0" prefWidth="100.0" text="Check Balance" />
  <Label fx:id="name" alignment="CENTER" layoutX="215.0" layoutY="131.0" prefHeight="63.0" prefWidth="161.0" text="..Anything.." textFill="#e4eb0f">
     <effect>
        <Bloom />
     </effect>
  </Label>

JavaFX：setText（）无法更新标签文本

0 个答案: