如何在javafx-8中修复NullPointerException

Question

JavaFX在将文本设置为文本字段时会生成NullPointerexception。这段代码产生了这个异常：

public void invalidate() {
    model.getLock().lock();
    try {
        memoryDisplayTextField.setText(model.getMemory() != 0 ? "M" : "");
        mainDisplayTextField.setText(model.getDisplayText());
    } finally {
        model.getLock().unlock();
    }
}

Stacktrace如下：

java.lang.NullPointerException
at com.sun.javafx.text.TextLayout.layout(TextLayout.java:1365)
at com.sun.javafx.text.TextLayout.ensureLayout(TextLayout.java:174)
at com.sun.javafx.text.TextLayout.getBounds(TextLayout.java:197)
at javafx.scene.text.Text.getLogicalBounds(Text.java:387)
at javafx.scene.text.Text.impl_computeGeomBounds(Text.java:1182)
at javafx.scene.Node.updateGeomBounds(Node.java:3322)
at javafx.scene.Node.getGeomBounds(Node.java:3275)
at javafx.scene.Node.getLocalBounds(Node.java:3257)
at javafx.scene.Node.updateTxBounds(Node.java:3335)
at javafx.scene.Node.getTransformedBounds(Node.java:3175)
at javafx.scene.Node.updateBounds(Node.java:504)
at javafx.scene.Parent.updateBounds(Parent.java:1643)
at javafx.scene.Parent.updateBounds(Parent.java:1643)
at javafx.scene.Parent.updateBounds(Parent.java:1643)
at javafx.scene.Parent.updateBounds(Parent.java:1643)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2268)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:352)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:511)
at com.sun.javafx.tk.quantum.QuantumToolkit$12.run(QuantumToolkit.java:379)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(Unknown Source)
at com.sun.glass.ui.win.WinApplication$3$1.run(Unknown Source)
at java.lang.Thread.run(Thread.java:722)

有什么变通方法吗？或者我应该等到发布的时候？

谢谢。

Answer 1

据我所知，这个问题是由在JavaFX应用程序线程外调用setText方法引起的，所以用Platform.runLater()包装它可以解决这个问题。

 public void invalidate() {
    Platform.runLater(() -> {
        model.getLock().lock();
        try {
            memoryDisplayTextField.setText(model.getMemory() != 0 ? "M" : "");
            mainDisplayTextField.setText(model.getDisplayText());
        } finally {
            model.getLock().unlock();
        }
    });
}

PS感谢珠海的帮助。