Javafx 2 如何布局按钮，使其填满可用空间

我需要在2x2网格中布置4个按钮。所有按钮必须具有相同的大小，并在窗口更改其大小时进行更改

我现在使用以下FXML，但按钮的大小不会改变

<GridPane xmlns:fx="http://javafx.com/fxml">
    <Button fx:id="btnLogin" text="Login" GridPane.rowIndex="0" GridPane.columnIndex="0"/>
    <Button fx:id="btnLibrary" text="Library" GridPane.rowIndex="0" GridPane.columnIndex="1"/>
    <Button fx:id="btnRegister" text="Register" GridPane.rowIndex="1" GridPane.columnIndex="0"/>
    <Button fx:id="btnHelp" text="Help" GridPane.rowIndex="1" GridPane.columnIndex="1"/>
</GridPane>

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我就是这样做到的

<GridPane xmlns:fx="http://javafx.com/fxml">
    <columnConstraints>
        <ColumnConstraints percentWidth="50"/>
        <ColumnConstraints percentWidth="50"/>
    </columnConstraints>
    <rowConstraints>
        <RowConstraints percentHeight="50"/>
        <RowConstraints percentHeight="50"/>
    </rowConstraints>
    <Button fx:id="btnLogin" text="Login" GridPane.rowIndex="0" GridPane.columnIndex="0" maxWidth="10000" maxHeight="10000"/>
    <Button fx:id="btnLibrary" text="Library" GridPane.rowIndex="0" GridPane.columnIndex="1" maxWidth="10000" maxHeight="10000"/>
    <Button fx:id="btnRegister" text="Register" GridPane.rowIndex="1" GridPane.columnIndex="0" maxWidth="10000" maxHeight="10000"/>
    <Button fx:id="btnHelp" text="Help" GridPane.rowIndex="1" GridPane.columnIndex="1" maxWidth="10000" maxHeight="10000"/>
</GridPane>

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我在组合框上遇到了同样的问题，并通过以下方式解决了它：

<ComboBox hgrow="ALWAYS" maxWidth="Infinity" />