我正在尝试更新SWT中的部分画布,但我不明白该怎么做。
我读过我必须使用setClipping,文档确实说: “设置接收器的区域,可以通过绘制操作将其更改为参数指定的矩形区域。为矩形指定null会将接收器的剪切区域恢复为其原始值。”
所以我刚试过但没有运气,这是一个简单的例子:
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
public class SimpleCanvas {
boolean manualDraw=false;
public void run() {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Canvas Example");
createContents(shell);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
/**
* Creates the main window's contents
*
* @param shell the main window
*/
private void createContents(Shell shell) {
shell.setLayout(new FillLayout());
// Create a canvas
Canvas canvas = new Canvas(shell, SWT.NONE);
// Create a button on the canvas
Button button = new Button(shell, SWT.PUSH);
button.setBounds(10, 10, 300, 40);
button.setText("TEST");
button.addListener(SWT.Selection, new Listener() {
public void handleEvent(Event e) {
switch (e.type) {
case SWT.Selection:
manualDraw=true;
canvas.redraw();
break;
}
}
});
// Create a paint handler for the canvas
canvas.addPaintListener(new PaintListener() {
public void paintControl(PaintEvent e) {
if (manualDraw){
e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_GREEN));
e.gc.setClipping(90,90,60,60);
e.gc.drawRectangle(90,90,30,30);
return ;
}
Rectangle rect = ((Canvas) e.widget).getBounds();
e.gc.setForeground(e.display.getSystemColor(SWT.COLOR_RED));
e.gc.drawText("DRAW TEXT", 0, 0);
e.gc.dispose();
}
});
}
/**
* The application entry point
*
* @param args the command line arguments
*/
public static void main(String[] args) {
new SimpleCanvas().run();
}
}
你能帮我理解我做错了吗?
提前谢谢。
答案 0 :(得分:1)
我发现了问题。为了更新画布的一部分,我不必调用:
canvas.redraw();
并绘制了画布的一部分,但是从画布中获取GC并在那里使用setClipping,因此调用类似的东西:
public void redrawCanvas (Canvas canvas) {
GC gc = new GC(canvas);
gc.setClipping(90,90,60,60);
gc.drawRectangle(90,90,30,30);
gc.dispose();
}