SWT(JFace)体验之GridLayout布局

GridLayout布局

GridLayout 布局的功能非常强大，也是笔者常用的一种布局方式。GridLayout是网格式布局，它把父组件分成一个表格，默认情况下每个子组件占据一个单元格的空间，每个子组件按添加到父组件的顺序排列在表格中。GridLayout提供了很多的属性，可以灵活设置网格的信息。另外，GridLayout 布局提供了GridData类，子组件可以设置相应的GridData，例如 “dogPhoto.setLayoutData(gridData)”，GridData可以设置每个组件当做单元格的信息。

GridLayout的风格

GridLayout类提供了GridLayout 布局中划分网格的信息，主要通过以下几个参数进行设置。

NumColumns：通过“gridLayout.numColumns”属性可以设置父组件中分几列显示子组件。

MakeColumnsEqualWidth：通过“gridLayout. makeColumnsEqualWidth”属性可以设置父组件中子组件是否有相同的列宽，当MakeColumnsEqualWidth为true时表示每列的列宽相等。
MarginLeft：表示当前组件距离父组件左边距的像素点个数。
MarginRight：表示当前组件距离父组件右边距的像素点个数。
MarginTop：表示当前组件距离父组件上边距的像素点个数。
MarginBottom：表示当前组件距离父组件下边距的像素点个数。
HorizontalSpacing：表示子组件的水平间距。
VerticalSpacing：表示子组件的垂直间距。

GridData的相关属性

GridLayout布局的灵活之处在于它利用网格布局数据GridData。通过GridData可以设置子组件在网格中的填充方式、大小边距等信息，用户可以通过子组件的setLayoutData方法设置网格布局数据。

GridData可以控制子组件在网格中的位置大小等相关显示信息。GridData可以设置如下的一些属性。

HorizontalAlignment：表示水平对齐方式。

VerticalAlignment：表示子组件的垂直对齐方式，值和水平方式一样。
HorizontalIndent：表示子组件水平偏移多少像素。此属性和“horizontalAlignment = GridData.BEGINNING”属性一起使用。

HorizontalSpan：表示组件水平占据几个网格。

GrabExcessHorizontalSpace：表示当父组件大小改变时，子组件是否以水平方向抢占空间。
GrabExcessVerticalSpace：表示当父组件大小改变时，子组件是否以垂直方向抢占空间。
WidthHint：表示子组件的宽度为多少像素（前提是未设置其他相关属性）。
HeightHint：表示子组件的高度为多少像素（前提是未设置其他相关属性）。

另外，GridData可以通过构造函数指定相应的属性值，有兴趣的读者可以参考GridData类的构造函数。

测试代码:

GridLayoutSample.java


代码如下:

package swt_jface.demo2;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;
public class GridLayoutSample {

Display display = new Display();
Shell shell = new Shell(display);
public GridLayoutSample() {

GridLayout gridLayout = new GridLayout();
gridLayout.numColumns = 2;
gridLayout.makeColumnsEqualWidth = true;
shell.setLayout(gridLayout);
Button button1 = new Button(shell, SWT.PUSH);
button1.setText("button1");
button1.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_BEGINNING));

List list = new List(shell, SWT.BORDER);
list.add("item 1");
list.add("item 2");
list.add("item 3");
list.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_CENTER));

Button button2 = new Button(shell, SWT.PUSH);
button2.setText("button #2");
GridData gridData = new GridData(GridData.VERTICAL_ALIGN_END);
gridData.horizontalIndent = 5;
button2.setLayoutData(gridData);

Button button3 = new Button(shell, SWT.PUSH);
button3.setText("3");
button3.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_FILL));

shell.pack();
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
public static void main(String[] args) {
new GridLayoutSample();
}
}

GridLayoutSampleGrabSpace.java


代码如下:

package swt_jface.demo2;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
public class GridLayoutSampleGrabSpace {
public GridLayoutSampleGrabSpace() {

Display display = new Display();
Shell shell = new Shell(display);

GridLayout gridLayout = new GridLayout();
gridLayout.numColumns = 3;
shell.setLayout(gridLayout);

Label label = new Label(shell, SWT.BORDER);
label.setText("label");

GridData gridData3 = new GridData();
gridData3.widthHint = 60;
gridData3.heightHint = 20;

label.setLayoutData(gridData3);

Text text = new Text(shell, SWT.SINGLE | SWT.BORDER);
text.setText("text");

GridData gridData = new GridData();
gridData.grabExcessHorizontalSpace = true;
gridData.grabExcessVerticalSpace = true;
gridData.horizontalAlignment = GridData.FILL;
gridData.verticalAlignment = GridData.FILL;
text.setLayoutData(gridData);

Button button = new Button(shell, SWT.PUSH);
button.setText("button");

GridData gridData2 = new GridData();
gridData2.grabExcessVerticalSpace = true;
gridData2.grabExcessHorizontalSpace = true;
gridData2.verticalAlignment = GridData.FILL;
gridData2.horizontalAlignment = GridData.FILL;

button.setLayoutData(gridData2);

shell.setSize(300, 80);
//shell.pack();
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
public static void main(String[] args) {
new GridLayoutSampleGrabSpace();
}
}

GridLayoutSampleSpan.java


代码如下:

package swt_jface.demo2;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.List;
import org.eclipse.swt.widgets.Shell;
public class GridLayoutSampleSpan {

Display display = new Display();
Shell shell = new Shell(display);
public GridLayoutSampleSpan() {

GridLayout gridLayout = new GridLayout();
gridLayout.numColumns = 2;
gridLayout.makeColumnsEqualWidth = true;
shell.setLayout(gridLayout);
Button button1 = new Button(shell, SWT.PUSH);
button1.setText("button1");
button1.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_BEGINNING));

List list = new List(shell, SWT.BORDER);
list.add("item 1");
list.add("item 2");
list.add("item 3");
list.setLayoutData(new GridData(GridData.VERTICAL_ALIGN_CENTER));

Button button2 = new Button(shell, SWT.PUSH);
button2.setText("button #2");
GridData gridData = new GridData(GridData.VERTICAL_ALIGN_END);
gridData.horizontalSpan = 2;
gridData.horizontalAlignment = GridData.FILL;
button2.setLayoutData(gridData);

Button button3 = new Button(shell, SWT.PUSH);
button3.setText("3");
GridData gridData2 = new GridData(GridData.VERTICAL_ALIGN_END);
gridData2.verticalSpan = 3;
button3.setLayoutData(gridData2);

shell.pack();
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
public static void main(String[] args) {
new GridLayoutSampleSpan();
}
}

下面这个例子布局稍微复杂一点:


代码如下:

package swt_jface.demo2;
import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.CLabel;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
public class Sample {

Display display = new Display();
Shell shell = new Shell(display);
public Sample() {
shell.setText("Book Entry Demo");
GridLayout gridLayout = new GridLayout(4, false);
gridLayout.verticalSpacing = 8;
shell.setLayout(gridLayout);
Label label = new Label(shell, SWT.NULL);
label.setText("Title: ");
Text title = new Text(shell, SWT.SINGLE | SWT.BORDER);
GridData gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL);
gridData.horizontalSpan = 3;
title.setLayoutData(gridData);
label = new Label(shell, SWT.NULL);
label.setText("Author(s): ");
Text authors = new Text(shell, SWT.SINGLE | SWT.BORDER);
gridData = new GridData(GridData.HORIZONTAL_ALIGN_FILL);
gridData.horizontalSpan = 3;
authors.setLayoutData(gridData);
label = new Label(shell, SWT.NULL);
label.setText("Cover: ");
gridData = new GridData();
gridData.verticalSpan = 3;
label.setLayoutData(gridData);
CLabel cover = new CLabel(shell, SWT.NULL);
gridData = new GridData(GridData.FILL_HORIZONTAL);
gridData.horizontalSpan = 1;
gridData.verticalSpan = 3;
gridData.heightHint = 100;
gridData.widthHint = 100;
cover.setLayoutData(gridData);
label = new Label(shell, SWT.NULL);
label.setText("Pages");
Text pages = new Text(shell, SWT.SINGLE | SWT.BORDER);
pages.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));
label = new Label(shell, SWT.NULL);
label.setText("Publisher");
Text pubisher = new Text(shell, SWT.SINGLE | SWT.BORDER);
pubisher.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));
label = new Label(shell, SWT.NULL);
label.setText("Rating");
Combo rating = new Combo(shell, SWT.READ_ONLY);
rating.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_FILL));
rating.add("5");
rating.add("4");
rating.add("3");
rating.add("2");
rating.add("1");
label = new Label(shell, SWT.NULL);
label.setText("Abstract:");
Text bookAbstract =
new Text(
shell,
SWT.WRAP
| SWT.MULTI
| SWT.BORDER
| SWT.H_SCROLL
| SWT.V_SCROLL);
gridData =
new GridData(
GridData.HORIZONTAL_ALIGN_FILL | GridData.VERTICAL_ALIGN_FILL);
gridData.horizontalSpan = 3;
gridData.grabExcessVerticalSpace = true;
bookAbstract.setLayoutData(gridData);
Button enter = new Button(shell, SWT.PUSH);
enter.setText("Enter");
gridData = new GridData();
gridData.horizontalSpan = 4;
gridData.horizontalAlignment = GridData.END;
enter.setLayoutData(gridData);
title.setText("Professional Java Interfaces with SWT/JFace");
authors.setText("Jack Li Guojie");
pages.setText("500pp");
pubisher.setText("John Wiley & Sons");
cover.setBackground(new Image(display, "C:/eclipse32.gif"));
bookAbstract.setText(
"This book provides a comprehensive guide for \n"
+ "you to create Java user interfaces with SWT/JFace. ");
shell.pack();
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
public static void main(String[] args) {
new Sample();
}
}

GridLayout 布局的功能非常强大，也是笔者常用的一种布局方式。GridLayout是网格式布局，它把父组件分成一个表格，默认情况下每个子组件占据一个单元格的空间，每个子组件按添加到父组件的顺序排列在表格中。

GridLayout提供了很多的属性，可以灵活设置网格的信息。另外，GridLayout 布局提供了GridData类，子组件可以设置相应的GridData，例如“dogPhoto.setLayoutData(gridData)”，GridData可以设置每个组件当做单元格的信息。

14.11.1 GridLayout的风格

GridLayout类提供了GridLayout 布局中划分网格的信息，主要通过以下几个参数进行设置。

NumColumns：通过“gridLayout.numColumns”属性可以设置父组件中分几列显示子组件，如表14-4所示。

表14-4  NumColumns效果

列    数	显 示 效 果
numColumns = 1	498)this.style.width=498;" border=0>
numColumns = 2	498)this.style.width=498;" border=0>
numColumns = 3	498)this.style.width=498;" border=0>

MakeColumnsEqualWidth：通过“gridLayout. makeColumnsEqualWidth”属性可以设置父组件中子组件是否有相同的列宽，当MakeColumnsEqualWidth为true时表示每列的列宽相等。

MarginLeft：表示当前组件距离父组件左边距的像素点个数。

MarginRight：表示当前组件距离父组件右边距的像素点个数。

MarginTop：表示当前组件距离父组件上边距的像素点个数。

MarginBottom：表示当前组件距离父组件下边距的像素点个数。

HorizontalSpacing：表示子组件的水平间距。

VerticalSpacing：表示子组件的垂直间距。