getWidth（） 在 HashMap 循环中不起作用

问：

朋友。 我正在尝试编写 JAVA 程序，该程序将根据用户提供的输入绘制图形。我有表示绘制名称图的画布的类。此类负责在条目列表更改或调整窗口大小时更新（重绘）图形。通过从文件中获取数据，将它们放入 ItemGraph 类中的 HashMap 中，然后遍历它以获取绘制图表所需的数据。我遇到了一个问题，我无法在 HashMap 循环中访问 getWidth（） 数据，尽管相同的方法在上面的代码中为我提供了正确的信息（突出显示的粗体）。此外，当我尝试添加（）一些GObjects时，它不起作用。我真的不知道那里发生了什么，问题是什么。将感谢所有的帮助。

公共类 ItemGraph 扩展了 GCanvas 实现 ItemConstants， ComponentListener {

private HashMap<String, ItemEntry> entries;

/**
 * Creates a new ItemGraph object that displays the data.
 */
public ItemGraph() {
    addComponentListener(this);
    entries = new HashMap<>();
}

/* Method: addEntry(entry) */

/**
 * Adds a new ItemEntry to the list of entries on the display.
 * Note that this method does not actually draw the graph, but
 * simply stores the entry; the graph is drawn by calling update.
 */
public void addEntry(ItemEntry entry) {
    if (entry != null) {
        entries.put(entry.getName(), entry);
    }
    update();
}


/**
 * Updates the display image by deleting all the graphical objects
 * from the canvas and then reassembling the display according to
 * the list of entries. Your application must call update after
 * calling either clear or addEntry; update is also called whenever
 * the size of the canvas changes.
 */


public void update() {

    removeAll();

    double canvasHeight = getHeight();
    double canvasWidth = getWidth();

    double columnWidth = canvasWidth / NDECADES;

    for (int i = 0; i < NDECADES; i++) {
        double x = i * columnWidth;
 **System.out.println(columnWidth); all working here**
        GLine line = new GLine(x, 0, x, canvasHeight);

        GLabel decade = new GLabel(Integer.toString(START_DECADE + i * 10),
                x + GRAPH_MARGIN_SIZE / 2, canvasHeight - GRAPH_MARGIN_SIZE / 3);
        add(line);
        add(decade);
    }

    GLine topHorizontalLine = new GLine(0, GRAPH_MARGIN_SIZE, canvasWidth,      GRAPH_MARGIN_SIZE);
    add(topHorizontalLine);

    GLine bottomHorizontalLine = new GLine(0, canvasHeight - GRAPH_MARGIN_SIZE,
            canvasWidth, canvasHeight - GRAPH_MARGIN_SIZE);
    add(bottomHorizontalLine);

    for (ItemEntry entry : entries.values()) {
        String gName = entry.getName();
**System.out.println(gName);all working here**
System.out.println(columnWidth);here i have 0**
        
        for (int i = 0; i < NDECADES; i++) {

            GOval oval = new GOval(10 * i, 10 * i, 10 * i, 10 * i);
            add(oval);

        }
    }
}


/* Implementation of the ComponentListener interface */
public void componentHidden(ComponentEvent e) {
}

public void componentMoved(ComponentEvent e) {
}

public void componentResized(ComponentEvent e) {
    update();
}

public void componentShown(ComponentEvent e) {
}

}