Java Tutorial/SWT/Canvas
Содержание
Add Controls to Canvas
<source lang="java">
import org.eclipse.swt.SWT; import org.eclipse.swt.events.PaintEvent; import org.eclipse.swt.events.PaintListener; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.layout.FillLayout; import org.eclipse.swt.widgets.Button; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; public class CanvasControlAdd {
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Canvas Example");
shell.setLayout(new FillLayout());
Canvas canvas = new Canvas(shell, SWT.NONE);
Button button = new Button(canvas, SWT.PUSH);
button.setBounds(10, 10, 300, 40);
button.setText("You can place widgets on a canvas");
canvas.addPaintListener(new PaintListener() {
public void paintControl(PaintEvent e) {
Rectangle rect = ((Canvas) e.widget).getBounds();
e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_RED));
e.gc.drawFocus(5, 5, rect.width - 10, rect.height - 10);
e.gc.drawText("You can draw text directly on a canvas", 60, 60);
}
});
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
}</source>
Add KeyEvent to Canvas
<source lang="java">
import org.eclipse.swt.SWT; import org.eclipse.swt.events.KeyEvent; import org.eclipse.swt.events.KeyListener; import org.eclipse.swt.graphics.Font; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.layout.RowLayout; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; public class CanvasKeyEvent {
public static void main(String[] args) {
final Display display = new Display();
Shell shell = new Shell(display);
shell.setLayout(new RowLayout());
final Canvas canvas = new Canvas(shell, SWT.NULL);
canvas.setSize(500, 500);
canvas.setBackground(display.getSystemColor(SWT.COLOR_YELLOW));
canvas.addKeyListener(new KeyListener() {
public void keyPressed(KeyEvent e) {
GC gc = new GC(canvas);
Rectangle rect = canvas.getClientArea();
gc.fillRectangle(rect.x, rect.y, rect.width, rect.height);
Font font = new Font(display, "Arial", 32, SWT.BOLD );
gc.setFont(font);
gc.drawString("" + e.character, 15, 10);
gc.dispose();
font.dispose();
}
public void keyReleased(KeyEvent e) {
}
});
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
}
}</source>
Add Traverse event to Canvas
<source lang="java">
import org.eclipse.swt.SWT; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Event; import org.eclipse.swt.widgets.Listener; import org.eclipse.swt.widgets.Shell; import org.eclipse.swt.widgets.Text; public class CanvasTranverseEvent {
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
final Canvas c = new Canvas(shell, SWT.BORDER);
c.setBounds(10, 50, 100, 32);
c.addListener(SWT.Traverse, new Listener() {
public void handleEvent(Event e) {
switch (e.detail) {
/* Do tab group traversal */
case SWT.TRAVERSE_ESCAPE:
System.out.println("SWT.TRAVERSE_ESCAPE");
break;
case SWT.TRAVERSE_RETURN:
case SWT.TRAVERSE_TAB_NEXT:
System.out.println("SWT.TRAVERSE_TAB_NEXT");
break;
case SWT.TRAVERSE_TAB_PREVIOUS:
case SWT.TRAVERSE_PAGE_NEXT:
case SWT.TRAVERSE_PAGE_PREVIOUS:
e.doit = true;
break;
}
}
});
Text t = new Text(shell, SWT.SINGLE | SWT.BORDER);
t.setBounds(10, 85, 100, 32);
c.setFocus();
shell.setSize(200, 200);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch())
display.sleep();
}
display.dispose();
}
}</source>
Canvas: scroll an image (flicker free, no double buffering)
<source lang="java">
/*******************************************************************************
* Copyright (c) 2000, 2004 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/
/*
* Canvas example snippet: scroll an image (flicker free, no double buffering) * * For a list of all SWT example snippets see * http://www.eclipse.org/swt/snippets/ */
import org.eclipse.swt.SWT; import org.eclipse.swt.graphics.GC; import org.eclipse.swt.graphics.Image; import org.eclipse.swt.graphics.Point; import org.eclipse.swt.graphics.Rectangle; import org.eclipse.swt.layout.FillLayout; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Event; import org.eclipse.swt.widgets.FileDialog; import org.eclipse.swt.widgets.Listener; import org.eclipse.swt.widgets.ScrollBar; import org.eclipse.swt.widgets.Shell; public class ImageScrollFlickerFree {
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
shell.setLayout(new FillLayout());
Image originalImage = null;
FileDialog dialog = new FileDialog(shell, SWT.OPEN);
dialog.setText("Open an image file or cancel");
String string = dialog.open();
if (string != null) {
originalImage = new Image(display, string);
}
if (originalImage == null) {
int width = 150, height = 200;
originalImage = new Image(display, width, height);
GC gc = new GC(originalImage);
gc.fillRectangle(0, 0, width, height);
gc.drawLine(0, 0, width, height);
gc.drawLine(0, height, width, 0);
gc.drawText("Default Image", 10, 10);
gc.dispose();
}
final Image image = originalImage;
final Point origin = new Point(0, 0);
final Canvas canvas = new Canvas(shell, SWT.NO_BACKGROUND | SWT.NO_REDRAW_RESIZE | SWT.V_SCROLL
| SWT.H_SCROLL);
final ScrollBar hBar = canvas.getHorizontalBar();
hBar.addListener(SWT.Selection, new Listener() {
public void handleEvent(Event e) {
int hSelection = hBar.getSelection();
int destX = -hSelection - origin.x;
Rectangle rect = image.getBounds();
canvas.scroll(destX, 0, 0, 0, rect.width, rect.height, false);
origin.x = -hSelection;
}
});
final ScrollBar vBar = canvas.getVerticalBar();
vBar.addListener(SWT.Selection, new Listener() {
public void handleEvent(Event e) {
int vSelection = vBar.getSelection();
int destY = -vSelection - origin.y;
Rectangle rect = image.getBounds();
canvas.scroll(0, destY, 0, 0, rect.width, rect.height, false);
origin.y = -vSelection;
}
});
canvas.addListener(SWT.Resize, new Listener() {
public void handleEvent(Event e) {
Rectangle rect = image.getBounds();
Rectangle client = canvas.getClientArea();
hBar.setMaximum(rect.width);
vBar.setMaximum(rect.height);
hBar.setThumb(Math.min(rect.width, client.width));
vBar.setThumb(Math.min(rect.height, client.height));
int hPage = rect.width - client.width;
int vPage = rect.height - client.height;
int hSelection = hBar.getSelection();
int vSelection = vBar.getSelection();
if (hSelection >= hPage) {
if (hPage <= 0)
hSelection = 0;
origin.x = -hSelection;
}
if (vSelection >= vPage) {
if (vPage <= 0)
vSelection = 0;
origin.y = -vSelection;
}
canvas.redraw();
}
});
canvas.addListener(SWT.Paint, new Listener() {
public void handleEvent(Event e) {
GC gc = e.gc;
gc.drawImage(image, origin.x, origin.y);
Rectangle rect = image.getBounds();
Rectangle client = canvas.getClientArea();
int marginWidth = client.width - rect.width;
if (marginWidth > 0) {
gc.fillRectangle(rect.width, 0, marginWidth, client.height);
}
int marginHeight = client.height - rect.height;
if (marginHeight > 0) {
gc.fillRectangle(0, rect.height, client.width, marginHeight);
}
}
});
shell.setSize(200, 150);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch())
display.sleep();
}
originalImage.dispose();
display.dispose();
}
}</source>
Repaint Canvas
<source lang="java">
import org.eclipse.swt.SWT; import org.eclipse.swt.events.PaintEvent; import org.eclipse.swt.events.PaintListener; import org.eclipse.swt.layout.FillLayout; import org.eclipse.swt.widgets.Canvas; import org.eclipse.swt.widgets.Display; import org.eclipse.swt.widgets.Shell; public class CanvasRepaint {
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Canvas Example");
shell.setLayout(new FillLayout());
Canvas canvas = new Canvas(shell, SWT.NONE);
canvas.addPaintListener(new PaintListener() {
public void paintControl(PaintEvent e) {
e.gc.drawRoundRectangle(10, 10, 200, 200, 30, 30);
}
});
canvas.redraw();
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
}</source>
