如何检查textfield是否为空？

时间：2015-09-30 13:06:54

标签： javafx textfield

对于我的JavaFx应用程序我想检查TextFields是否为空，如果是，则提醒用户。 这些是TextFields：

VBox fields = new VBox();  
Text usernametext = new Text("User name");
TextField user_name = new TextField();
Text firstnametext = new Text("First name");
TextField first_name = new TextField();
Text lastnametext = new Text("Last name");
TextField last_name = new TextField();
Text ibantext = new Text("IBAN");
TextField iban = new TextField();
Text passwordtext = new Text("Password");
TextField password = new TextField();
Text confirmpasstext = new Text("Confirm password");
TextField confirmpass = new TextField();
Button createBtn = new Button("Create account");

现在我只想在一个文本字段上测试验证。这是我的验证函数，它链接到createBtn：

public void validation(){                

    if(user_name.getText().trim().isEmpty()){
        Alert fail= new Alert(AlertType.INFORMATION);
        fail.setHeaderText("failure");
        fail.setContentText("you havent typed something");
        fail.showAndWait();
    } else {
        Alert alert = new Alert(AlertType.INFORMATION);
        alert.setHeaderText("Succes");
        alert.setContentText("Account succesfully created!");
        alert.showAndWait();
    }
}

但是当我按下“创建帐户”时，我收到此错误消息。按钮：

Exception in thread "JavaFX Application Thread" 

java.lang.NullPointerException
    at opdracht1.Opdracht1.validation(Opdracht1.java:36)
    at opdracht1.Opdracht1$2$1.handle(Opdracht1.java:103)
    at opdracht1.Opdracht1$2$1.handle(Opdracht1.java:98)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:352)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$355(GlassViewEventHandler.java:388)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$149(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

提前致谢！

6 个答案:

答案 0 :(得分：8)

首先，检查user_name是否 null 。如果不是，则在代码中的某处为JavaFX组件设置 null 文本值。

  

if(user_name.getText().trim().isEmpty()){

在任何情况下，将trim()应用于 null 值都会导致您的异常。您不应该这样做（请参阅 Uluk Biy 对此答案的评论），但考虑到您创建了user_name TextField，您必须先检查getText()方法不是 null 。

这样的事情可以解决问题：

if (user_name.getText() == null || user_name.getText().trim().isEmpty()) {
     // your code here
}

答案 1 :(得分：1)

您可以使用Button disableProperty与TextField绑定。当textfield为空时，该按钮将被禁用，否则将被启用。

使用下面提到的代码

createBtn.disableProperty().bind(
    Bindings.createBooleanBinding( () -> 
        user_name.getText().trim().isEmpty(), user_name.textProperty()
    )
    // If you want to check more text field, use it as by removing comments
    //.or(  Bindings.createBooleanBinding(
    //         first_name.getText.trim().isEmpty(), first_name.textProperty()
    //     )
    //  )

);

答案 2 :(得分：1)

好吧，这就是我做到的方式而且有效。

如果上述情况均无效，请尝试以下操作：

创建一个字符串变量，让我们说String username; 接下来，尝试以下操作：

if(username.trim().isEmpty())

原始建议对我没有用，但创建了字符串，所以如果上述建议对你不起作用，请给它一个镜头。

答案 3 :(得分：0)

这可以通过

简单地检查 
if(textField.getText().trim().equals(""))
{
system.out.println("textField is empty");
}

答案 4 :(得分：0)

textField.getText（）修剪（）等于（＆＃34;＆＃34）。

上面的陈述对我来说就像是一种魅力。

答案 5 :(得分：-1)

您可以测试此代码，使用TextFeild的名称替换我的冠军姓名

if ((nom_pt.getText().toString().compareTo("") == 0) ||
    (prenom_pt.getText().toString().compareTo("") == 0) ||
    (cin_pt.getText().toString().compareTo("") == 0) ||
    (gsm_pt.getText().toString().compareTo("") == 0)) {

    JOptionPane.showMessageDialog(null, "champs vide");

} else {  JOptionPane.showMessageDialog(null, "Enregistrement a été  ajouter");  }
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