Gwt 水平对齐问题

我想在面板中央放置一些按钮，但不起作用。这是我的代码：

import com.extjs.gxt.ui.client.widget.HorizontalPanel;
import com.extjs.gxt.ui.client.widget.Label;
import com.extjs.gxt.ui.client.widget.LayoutContainer;
import com.extjs.gxt.ui.client.widget.VerticalPanel;
import com.extjs.gxt.ui.client.widget.button.Button;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.HasAlignment;
import com.google.gwt.user.client.ui.RootPanel;

private void addStartupBox() {
    VerticalPanel boxPanel = setBoxSize();      
    com.google.gwt.user.client.ui.Label title = createBoxTitle("Prüfungen");        

    // Create second panel for the content of a box     
    com.google.gwt.user.client.ui.VerticalPanel boxContent = new com.google.gwt.user.client.ui.VerticalPanel();
    boxContent.setSpacing(10);
    boxContent.setHorizontalAlignment(com.google.gwt.user.client.ui.VerticalPanel.ALIGN_CENTER);

    // Create content for the box
    Button but1 = new Button("A");
    but1.setPixelSize(280, 25);     

    Button but2 = new Button("B");
    but2.setPixelSize(280, 25);

    Button but3 = new Button("C");
    but3.setPixelSize(280, 25);

    // Add buttons to boxContent
    boxContent.add(but1);
    boxContent.add(but2);
    boxContent.add(but3);

    // Add title and boxContent to boxPanel     
    boxPanel.add(title);
    boxPanel.add(boxContent);

    RootPanel.get("boxPanelContainer").add(boxPanel);
}

结果是：

按钮是左对齐的。在那之后，我试着这样做：

boxContent.setHorizontalAlignment(HasAlignment.ALIGN_CENTER);

但是按钮仍然是左对齐的。我的最后一个想法是使用ExtGWT垂直面板：

boxContent.setHorizontalAlign(HorizontalAlignment.CENTER);

---

但不幸的是，这也不起作用。有人能告诉我，我做错了什么吗？

添加以下代码并重试

boxContent.setCellHorizontalAlignment(but1, HasHorizontalAlignment.ALIGN_CENTER);
boxContent.setCellHorizontalAlignment(but2, HasHorizontalAlignment.ALIGN_CENTER);
boxContent.setCellHorizontalAlignment(but3, HasHorizontalAlignment.ALIGN_CENTER);

---

上述代码应添加在添加到方框内容的按钮之后（在“RootPanel.get（“boxPanelContainer”）.add（boxPanel）；”这一行之前）。

添加以下代码并重试

boxContent.setCellHorizontalAlignment(but1, HasHorizontalAlignment.ALIGN_CENTER);
boxContent.setCellHorizontalAlignment(but2, HasHorizontalAlignment.ALIGN_CENTER);
boxContent.setCellHorizontalAlignment(but3, HasHorizontalAlignment.ALIGN_CENTER);

---

上面的代码应该在按钮添加到框内容之后添加（在“RootPanel.get（“boxPanelContainer”）.add（boxPanel）；”这行之前）。

问题解决了……我添加了另一个左对齐的面板。代码如下：

private void addStartupBox() {
    VerticalPanel boxPanel = setBoxSize();      
    com.google.gwt.user.client.ui.Label title = createBoxTitle("Prüfungen");        
    boxPanel.setHorizontalAlign(HorizontalAlignment.CENTER);

    // Create second panel for the content of a box     
    com.google.gwt.user.client.ui.VerticalPanel boxContent = new com.google.gwt.user.client.ui.VerticalPanel();
    boxContent.setSpacing(10);

    // Create third panel, which contains the label
    VerticalPanel labelPanel = new VerticalPanel();
    labelPanel.setHorizontalAlign(HorizontalAlignment.LEFT);        

    // Create content for the box
    Button but1 = new Button("A");
    but1.setPixelSize(280, 25);     

    Button but2 = new Button("B");
    but2.setPixelSize(280, 25);

    Button but3 = new Button("C");
    but3.setPixelSize(280, 25);

    // Add buttons to boxContent
    boxContent.add(but1);
    boxContent.add(but2);
    boxContent.add(but3);

    // Add title to third panel 
    labelPanel.add(title);      

    // Add title and boxContent to boxPanel
    boxPanel.add(labelPanel);
    boxPanel.add(boxContent);

    RootPanel.get("boxPanelContainer").add(boxPanel);
}

---

问题解决了…我添加了另一个面板，它是左对齐的。代码如下：

private void addStartupBox() {
    VerticalPanel boxPanel = setBoxSize();      
    com.google.gwt.user.client.ui.Label title = createBoxTitle("Prüfungen");        
    boxPanel.setHorizontalAlign(HorizontalAlignment.CENTER);

    // Create second panel for the content of a box     
    com.google.gwt.user.client.ui.VerticalPanel boxContent = new com.google.gwt.user.client.ui.VerticalPanel();
    boxContent.setSpacing(10);

    // Create third panel, which contains the label
    VerticalPanel labelPanel = new VerticalPanel();
    labelPanel.setHorizontalAlign(HorizontalAlignment.LEFT);        

    // Create content for the box
    Button but1 = new Button("A");
    but1.setPixelSize(280, 25);     

    Button but2 = new Button("B");
    but2.setPixelSize(280, 25);

    Button but3 = new Button("C");
    but3.setPixelSize(280, 25);

    // Add buttons to boxContent
    boxContent.add(but1);
    boxContent.add(but2);
    boxContent.add(but3);

    // Add title to third panel 
    labelPanel.add(title);      

    // Add title and boxContent to boxPanel
    boxPanel.add(labelPanel);
    boxPanel.add(boxContent);

    RootPanel.get("boxPanelContainer").add(boxPanel);
}