SWT(JFace)体验之GridLayout布局

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本文详细介绍了GridLayout布局的特点和使用方法，包括如何设置网格数量、列宽、边距等，并通过多个示例展示了子组件如何通过GridData类调整其在网格中的位置和大小。

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

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

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

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:

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(); } }

参考资料：http://book.51cto.com/art/200711/59447.htm