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7.1 graphic context

JOO — Fri, 14 Apr 2006 03:26:00 GMT

graphic context��p��Control最��层的画板，它可以��你向GUI components加入客制化的囑�Ş�Q�图片，及不同字体的文本。同样也提供事�g处理

graphic context是在GC�c�M��的，GC对象是附着于现存的Controls�?br />
要创��Z��个graphically oriented的应用程序，首先要创建graphic context�Q��ƈ��其与一个component相关联，�q�两步都可通过GC的constructor来实现。共�?个构造函敎ͼ�见下�Q?br />1. GC(Drawable)--Creates a GC and configures it for the Drawable object
2. GC(Drawable, int)--Creates and configures a GC and sets the text-display style�Q�第二个参数可以是RIGHT_TO_LEFT或LEFT_TO_RIGHT�Q�默认��|��;
�W�一个参数需要实现Drawable接口的对象，此接口包含了与graphic context.内部相联�pȝ��Ҏ��。SWT提供了三个实现Drawable接口的类�Q�Image, Device, �?Control.

Control子类虽然都能包含囑�Ş�Q�但只有一个类是特别适合GC对象的：Canvas。它不仅提供了一个Composite的containment property�Q�还可以用一�p�d��的风格来定义囑�Ş在此区域内如何显�C?br />
�C�Z��Q?/u>

package com.swtjface.Ch7;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;
public class DrawExample
{
public static void main (String [] args)
{
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Drawing Example");
Canvas canvas = new Canvas(shell, SWT.NONE);
canvas.setSize(150, 150);
canvas.setLocation(20, 20);//在shell中创建canvas
shell.open ();
shell.setSize(200,220);
GC gc = new GC(canvas);//在canvas中创�?/font>graphic context
gc.drawRectangle(10, 10, 40, 45);
gc.drawOval(65, 10, 30, 35);
gc.drawLine(130, 10, 90, 80);
gc.drawPolygon(new int[] {20, 70, 45, 90, 70, 70});
gc.drawPolyline(new int[] {10,120,70,100,100,130,130,75});
gc.dispose();//释放Color对象
while (!shell.isDisposed())
{
if (!display.readAndDispatch())
display.sleep();
}
display.dispose();
}
}
有两炚w��要注意：1.在调用shell.open()之前构徏Canvas对象�Q�然后在调用shell.open()之后创徏和��用GC对象
2.在��用完之后一定要立即释放GC object
如上例所�C�GC提供了一�p�d��在Drawable对象上画囑�Ş的方法，如下�Q?br />

但是上例中有个问题：当shell被变灰过或者最��化�q�之后，囑�Ş��׃��被擦厅R��所以我们需要解决的事，无论window怎么变化�Q�图形都保持可见。因此SWT在一�?/span>Drawable对象被刷新后让你自行控制。这个更新的�q�程��p��U�Cؓpainting�?/span>

Painting and PaintEvents

当一个GC�Ҏ��在一个Drawabel对象上画��Z��个图案，它仅执行�q�个painting�q�程一�ơ。如果用��h��变对象尺寸或是用另一个窗口去覆盖它，则图形会被消除。因此，应用�E�序能否在外界事件媄响下�l�持其外观这一点相当重要�?br />
�q�些外部事�g被称为PaintEvents�Q�接收它们的�E�序接口是PaintListener。一个Control在�Q何时候当其外观被应用�E�序或是外界�z�d��改变都会触发一个PaintEvent。这些类对于事�g和监听器的��用方式都和我们在�W�四章内提到的类伹{��由于PaintListener只有一个事件处理方法，所以不需要��用adapter�c?br />
Canvas canvas = new Canvas(shell, SWT.NONE);
canvas.setSize(150, 150);
canvas.setLocation(20, 20);
canvas.addPaintListener(new PaintListener()
{
public void paintControl(PaintEvent pe)
{
GC gc = pe.gc;//每一个PaintEvent对象都包含有其自��q��GC
gc.drawPolyline(new int[] {10,120,70,100,100,130,130,75});
}
});
shell.open();

每一个PaintEvent对象都包含有其自��q��GC�Q�主要有2个原因：1.因�ؓ�q�个GC instance是由事�g产生的，所以PaintEvent会负责释放他�?.应用�E�序可以在shell open之前创徏GC,�q�样可以使图形在一个独立的�c�M��被创建�?/font>

SWT�?/span>PaintListener接口内优�?/span>painting�q�程,SWT的开发者强烈徏�?/span>Control�?/span>painting仅对PaintEvent作出反应。如果一个应用程序因为其他原因必��L��新其囑�Ş�Q�则他们推荐使用control�?/span>redraw()�Ҏ��Q�这会在队列中加入一�?/span>paint��h��。之后，你可以调�?/span>update()�Ҏ��来处理所有的�l�定于该对象�?/span>paint��h��?br />
需要牢记的是，虽然对于Control对象推荐在一个PaintListener内painting�Q�但是由于Device和Image对象�q�不能在该接口内使用。如果你需要在一个image或device内生成图形，你必��d��独地生成一个GC对象�q�在使用�l�束后将光��毁�?/span>

JOO 2006-04-14 11:26 发表评论

6.5 Custom layouts

JOO — Wed, 12 Apr 2006 09:19:00 GMT

要客制化layout�Q�需要��承抽象类Layout�Q�需要写2个方法——computeSize() 和layout().

computeSize()

protected Point computeSize(Composite composite,
int wHint, int hHint,
boolean flushCache)
{
Point maxDimensions =
calculateMaxDimensions(composite.getChildren());
int stepsPerHemisphere =
stepsPerHemisphere(composite.getChildren().length);
int maxWidth = maxDimensions.x;
int maxHeight = maxDimensions.y;
int dimensionMultiplier = (stepsPerHemisphere + 1);
int controlWidth = maxWidth * dimensionMultiplier;
int controlHeight = maxHeight * dimensionMultiplier;
int diameter = Math.max(controlWidth, controlHeight);
Point preferredSize = new Point(diameter,
diameter);
... // code to handle case when our calculations
// are too large
return preferredSize;
}

参数�Q?br />1.composite--The object we’re going to populate. At the time this method is called, it has children, but neither the composite nor the children have been sized or positioned on the screen.

2.wHint and hHint--layout所需的最大长宽。若带有参数SWT.DEFAULT,表示此layout可以随意使用use whatever sizes it decides it needs.

3.flushCache--作�ؓflag�Q�to tell the layout whether it’s safe to use any cached values that it may be maintaining.

computeSize()的目的主要在于计��我们要layout的composite有多�?br />layout()
…�?br />

JOO 2006-04-12 17:19 发表评论

6.4 The form layout

JOO — Wed, 12 Apr 2006 04:22:00 GMT

与之前所�q�的layout不同�Q�form layout不是��Z��行和列的�Q�它是基于与其他control之间的相对位�|�的�?br />
FormLayout十分��单，你只要：1.讑֮��边距（高，宽）属性�?2.讑֮�spacing属性，��x��有control间的距离(in pixels)

同样可以使用FormData来配�|�单个的control�?br />
FormData
如果一个control没有一个FormData实例来描�q�它的话�Q�就会默认放在composite的右上角
width和height属性指定了control的尺寸，in pixels.
top, bottom, right, 和left属性，每一个都有一个FormAttachment实例�Q�这些attachments描述了control与其他control之间的关�p�R�?br />
FormAttachment
�?个��用途径�Q?br />1.通过使用percentage of the parent composite.

2.通过讑֮�一个control和另一个control之间的相对位�|��?br />《图�?br />
package com.swtjface.Ch6;
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
public class Ch6FormLayoutComposite extends Composite {
public Ch6FormLayoutComposite(Composite parent) {
super(parent, SWT.NONE);
FormLayout layout = new FormLayout();
setLayout(layout);
Text t = new Text(this, SWT.MULTI);
FormData data = new FormData();
data.top = new FormAttachment(0, 0);
data.left = new FormAttachment(0, 0);
data.right = new FormAttachment(100);
data.bottom = new FormAttachment(75);//��定text的位�|�，因�ؓ左上角是坐标原点�Q�所以right的百分数�?00�?br />t.setLayoutData(data);
Button ok = new Button(this, SWT.NONE);
ok.setText("Ok");
Button cancel = new Button(this, SWT.NONE);
cancel.setText("Cancel");
data = new FormData();
data.top = new FormAttachment(t);
data.right = new FormAttachment(cancel);//ok按钮在text下面�Q�cancel左边
ok.setLayoutData(data);
data = new FormData();
data.top = new FormAttachment(t);
data.right = new FormAttachment(100);//cancel按钮在text下面�Q�在最双��
cancel.setLayoutData(data);
}
}

JOO 2006-04-12 12:22 发表评论

6.3 The grid layout

JOO — Tue, 11 Apr 2006 08:16:00 GMT

最常用的一�U�layout.以row layout为基��?br />
package com.swtjface.Ch6;
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
public class Ch6GridLayoutComposite extends Composite {
public Ch6GridLayoutComposite(Composite parent) {
super(parent, SWT.NONE);
GridLayout layout = new GridLayout(4,false);//每一行有4个control�Q�后一个参数是a
boolean to indicate whether the columns should take up an even amount of
space. By passing false, you tell the layout to only use the minimum amount of
space needed for each column.
setLayout(layout);
for (int i = 0; i < 16; ++i) {
Button button = new Button(this, SWT.NONE);
button.setText("Cell " + i);
}
}
}

Using GridData styles
十分�c�M��于RowData对象。可通过其构造函数来讑֮�STYLE�Q�这些STYLE可分�?�c�：FILL, HORIZONTAL_ALIGN, and VERTICAL_ALIGN.
1.FILL:此cell是否fill所有的availabe的空间。可用的��D��包括FILL_HORIZONTAL�Q�水�q�x��张）,FILL_VERTICAL�Q�垂直扩张）,FILL_BOTH�?br />2.ALIGN�Q�用来指定control在cell中的什么位�|�。值包括BEGINNING, END, CENTER和FILL�?br />具体参见下表

Using GridData size attributes
与RowData不同�Q�GridData�q�有很多的public属性。其中有些是布尔值类型的�Q�一般会�Ҏ��所讄��的不同styles而自动管理，所以无需对其直接操作。还有一些是integer��|��用来��定单个cells的大��。具体�g下表�Q?br />

JOO 2006-04-11 16:16 发表评论

6.2 The row layout

JOO — Tue, 11 Apr 2006 07:58:00 GMT

可以多行/列显�C��?br />
package com.swtjface.Ch6;
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
public class Ch6RowLayoutComposite extends Composite {
public Ch6RowLayoutComposite(Composite parent) {
super(parent, SWT.NONE);
RowLayout layout = new RowLayout(SWT.HORIZONTAL);
setLayout(layout);
for (int i = 0; i < 16; ++i) {
Button button = new Button(this, SWT.NONE);
button.setText("Sample Text");
}
}
}

wrap——默认�ؓtrue,若设为false,所有的controls都在同一行�?br />pack——默认�ؓtrue.使所有的child controls都大��一栗��?br />justify——默认�ؓfalse. 若�ؓtrue,每一行的control都会以间隔相同的方式排列�?br />
RowData
可以通过setLayoutData()来设定每个control的大��，如：button.setLayoutData(new RowData(200 + 5 * i, 20 + i));

JOO 2006-04-11 15:58 发表评论

6.1 The fill layout

JOO — Tue, 11 Apr 2006 07:23:00 GMT

默认��Z��左到��x��攄��Q�根据每个control实际所需的大��来分配�I�间�Q�此composite中多于出来的�I�间�Q�再�q�x��到每个control上。随着composite的大��调��_��control的大��也会跟着调整�?br />
package com.swtjface.Ch6;
import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;
public class Ch6FillLayoutComposite extends Composite {
public Ch6FillLayoutComposite(Composite parent) {
super(parent, SWT.NONE);
FillLayout layout = new FillLayout( SWT.VERTICAL); //默认是SWT.HORIZONTAL
setLayout(layout);//为此Composite讑֮�一个layout.如果漏了此语句，会显�C�Z��出child control�?br />for (int i = 0; i < 8; ++i) {
Button button = new Button(this, SWT.NONE);
button.setText("Sample Text");
}
}
}

JOO 2006-04-11 15:23 发表评论

5.8 ProgressIndicator

JOO — Mon, 10 Apr 2006 10:07:00 GMT

同ProgressIndicator一��P��它支持工作的虚拟单位�Q�you need only initialize the ProgressIndicator with the total amount of work you expect to do and notify it as work is completed:

ProgressIndicator indicator = new ProgressIndicator(parent);
...
indicator.beginTask(10);
...
Display.getCurrent()display.asyncExec(new Runnable() {
public void run() {
//Inform the indicator that some amount of work has been done
indicator.worked(1);
}
});

正如上例所�C�，使用ProgressIndicator需�?步：
1.让indicator知道��d��有多��工作，通过使用beginTask().只有�q�个�Ҏ��被调用了之后�Q�这个control才会在屏�q�上昄��?br />2.每当有一部分工作被完成了�Q�就调用worked()。�ؓ了防止非ui的线�E�来update widgets�Q�所以��用asyncExec()来解册��个问题�?br />
ProgressIndicator也提供animated模式�Q�即��d��作量不知道的情况。在�q�种模式下，the bar continually fills and empties
until done() is called. 要��用这个模式，��p��用beginAnimatedTask()代替beginTask();�q�且不需要worked()�Ҏ��?/font>

JOO 2006-04-10 18:07 发表评论

5.7 ProgressBar

JOO — Mon, 10 Apr 2006 09:56:00 GMT

ProgressBar�Q�进度条�Q�是ProgressIndicator的简化版本。大多数情况下推荐��用ProgressIndicator。如果你军_��直接使用ProgressBar�Q�需要手动改变此bar的外观。如�?br />
//Style can be SMOOTH, HORIZONTAL, or VERTICAL
ProgressBar bar = new ProgressBar(parent, SWT.SMOOTH);
bar.setBounds(10, 10, 200, 32);
bar.setMaximum(100);
...
for(int i = 0; i < 10; i++) {
//Take care to only update the display from its
//own thread
Display.getCurrent().asyncExec(new Runnable() {
public void run() {
//Update how much of the bar should be filled in
bar.setSelection((int)(bar.getMaximum() * (i+1) / 10));
}
});
}

setSelection()causes the widget to be updated every time.This behavior is unlike that of ProgressIndicator or ProgressMonitorDialog,which will update the display only if it has changed by an amount that will be visible to the end user.

JOO 2006-04-10 17:56 发表评论

5.6 Slider

JOO — Mon, 10 Apr 2006 09:45:00 GMT

�c�M��于scrollbars。scrollbars仅限于用在可滑动的item上，如text�?br />
可通过setMinimum()和setMaximum()来设定它的范围。可通过setThumb()来设定滑块的倹{��在有些OS上，thumb的大��是常数。每按一下箭��_��所�U�d��的值称为increment.可通过setIncrement()来设定，按滑块和��头间的�I�间所滑动的��gؓpage increment�Q�可通过PageIncrement()来设定。以上这些数据可以通过void setValues( int selection, int minimum, int maximum, int thumb, int increment, int pageIncrement)来一�ơ性设定，其中selection是thumb的出发点�?br />
Slider有个属性用来设定其是水�q��是垂直的�Q�默认�ؓ水��^�?br />
package com.swtjface.Ch5;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Slider;
public class Ch5Slider extends Composite {
public Ch5Slider(Composite parent) {
super(parent, SWT.NONE);
setLayout(new FillLayout());
Slider slider = new Slider(this, SWT.HORIZONTAL);
slider.setValues(1000, 400, 1600, 200, 10, 100);
}
}

JOO 2006-04-10 17:45 发表评论

5.5 CoolBar

JOO — Mon, 10 Apr 2006 09:28:00 GMT

�c�M��于ToolBar的升�U�。他们的区别在于CoolBar上的item可以被重新配�|�，重新定大��。CoolBar的一般用途就是包含toolbars或按钮�?br />
String[] coolItemTypes = {"File", "Formatting", "Search"};
CoolBar coolBar = new CoolBar(parent, SWT.NONE);
for(int i = 0; i < coolItemTypes.length; i++)
{
CoolItem item = new CoolItem(coolBar, SWT.NONE);
ToolBar tb = new ToolBar(coolBar, SWT.FLAT);
for(int j = 0; j < 3; j++)
{
ToolItem ti = new ToolItem(tb, SWT.NONE);
ti.setText(coolItemTypes[i] + " Item #" + j);
}
}

JOO 2006-04-10 17:28 发表评论