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[英]JavaFX system MenuBar disappears when the window is being minimized on Mac
[英]Window's content disappears when minimized
我有一个简单的类,它在鼠标拖动时画一条线,或者在鼠标按下(释放)时画一个点。
当我最小化应用程序然后恢复它时,除了最后一个点(像素)之外,窗口的内容消失了。 我知道方法super.paint(g)
每次窗口更改时都会重新绘制背景,但是无论我是否使用它,结果似乎都是一样的。 两者之间的区别在于,当我不使用它时,窗口上画的不仅仅是一个像素,但不是我的全部画。 我怎样才能解决这个问题?
这是课堂。
package painting;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JFrame;
import javax.swing.JPanel;
class CustomCanvas extends Canvas{
Point oldLocation= new Point(10, 10);
Point location= new Point(10, 10);
Dimension dimension = new Dimension(2, 2);
CustomCanvas(Dimension dimension){
this.dimension = dimension;
this.init();
addListeners();
}
private void init(){
oldLocation= new Point(0, 0);
location= new Point(0, 0);
}
public void paintLine(){
if ((location.x!=oldLocation.x) || (location.y!=oldLocation.y)) {
repaint(location.x,location.y,1,1);
}
}
private void addListeners(){
addMouseListener(new MouseAdapter(){
@Override
public void mousePressed(MouseEvent me){
oldLocation = location;
location = new Point(me.getX(), me.getY());
paintLine();
}
@Override
public void mouseReleased(MouseEvent me){
oldLocation = location;
location = new Point(me.getX(), me.getY());
paintLine();
}
});
addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent me){
oldLocation = location;
location = new Point(me.getX(), me.getY());
paintLine();
}
});
}
@Override
public void paint(Graphics g){
super.paint(g);
g.setColor(Color.red);
g.drawLine(location.x, location.y, oldLocation.x, oldLocation.y);
}
@Override
public Dimension getMinimumSize() {
return dimension;
}
@Override
public Dimension getPreferredSize() {
return dimension;
}
}
class CustomFrame extends JPanel {
JPanel displayPanel = new JPanel(new BorderLayout());
CustomCanvas canvas = new CustomCanvas(new Dimension(200, 200));
public CustomFrame(String titlu) {
canvas.setBackground(Color.white);
displayPanel.add(canvas, BorderLayout.CENTER);
this.add(displayPanel);
}
}
public class CustomCanvasFrame {
public static void main(String args[]) {
CustomFrame panel = new CustomFrame("Test Paint");
JFrame f = new JFrame();
f.add(panel);
f.pack();
SwingConsole.run(f, 700, 700);
}
}
您没有存储正在绘制的点的状态。 当面板被重新绘制时,它只有它绘制的最后一个点的信息。
回复评论:
您需要有一组点,例如ArrayList<Point> location = new ArrayList<Point>();
然后,在你的听众中: location.add(new Point(me.getX(), me.getY()));
最后,在paintLine()中:
for (Point location : locations) {
repaint(location.x,location.y,1,1);
}
收集locations
通常称为显示列表。 大多数图形程序都使用它们。
回复评论:
是的,我希望如此。 我只是根据您的代码提出了一个想法,为您提供了一个起点。 完全按照我的描述去做几乎肯定是一个坏主意。
这不意味着每次按下或拖动鼠标时我都会绘制所有点(而不是一个点)吗?
是的,但是@Dave 的方法对于数千个节点来说非常令人满意,正如在GraphPanel
所见。 除此之外,请考虑享元模式,它被JTable
渲染器使用并在此处进行了说明。
附录:关注您的AWTPainting
问题,下面的变化可能说明系统触发和应用触发绘画之间的区别。 当鼠标被拖动时, repaint()
调用update()
,它调用paint()
; 这是应用程序触发的。 当您调整窗口大小时,只调用paint()
(不绘制红色数字); 这是系统触发的。 请注意,调整大小后释放鼠标时会出现闪烁。
当整个组件的背景被清除并重新绘制时,通常会发生闪烁:
4.如果组件没有重载
update()
,默认执行update()
清除组件的背景(如果它不是一个轻量级组件),并简单地调用paint()
。
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Panel;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import java.util.List;
public class AWTPainting {
public static void main(String args[]) {
CustomPanel panel = new CustomPanel();
Frame f = new Frame();
f.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.add(panel);
f.pack();
f.setVisible(true);
}
}
class CustomPanel extends Panel {
public CustomPanel() {
this.add(new CustomCanvas(new Dimension(320, 240)));
}
}
class CustomCanvas extends Canvas {
private MouseAdapter handler = new MouseHandler();
private List<Point> locations = new ArrayList<Point>();
private Point sentinel = new Point();
private Dimension dimension;
CustomCanvas(Dimension dimension) {
this.dimension = dimension;
this.setBackground(Color.white);
this.addMouseListener(handler);
this.addMouseMotionListener(handler);
this.locations.add(sentinel);
}
@Override
public void paint(Graphics g) {
g.setColor(Color.blue);
Point p1 = locations.get(0);
for (Point p2 : locations.subList(1, locations.size())) {
g.drawLine(p1.x, p1.y, p2.x, p2.y);
p1 = p2;
}
}
@Override
public void update(Graphics g) {
paint(g);
g.clearRect(0, getHeight() - 24, 50, 20); // to background
g.setColor(Color.red);
g.drawString(String.valueOf(locations.size()), 8, getHeight() - 8);
}
private class MouseHandler extends MouseAdapter {
@Override
public void mousePressed(MouseEvent e) {
if (locations.get(0) == sentinel) { // reference identity
locations.set(0, new Point(e.getX(), e.getY()));
}
}
@Override
public void mouseDragged(MouseEvent e) {
locations.add(new Point(e.getX(), e.getY()));
repaint();
}
}
@Override
public Dimension getPreferredSize() {
return dimension;
}
}
@Andrew、@Dave、@trashgod 嗨,我对此做了一些研究,最后,这就是我所得到的。 如果我错了,请纠正我。 您不能覆盖paint(),因此每次需要执行应用程序触发的绘画时都调用repaint()。 Repaint() 调用 update(),它的默认行为是调用paint()。 update() 用于增量绘制; 这解释了当paint() 完成所有工作时闪烁的屏幕,这实际上意味着它在每一步都在绘制整个图像。 但是,我的问题是,如果我在更新方法中添加“locationsAdded = 0”,这意味着每次拖动鼠标时我都会绘制整个图像(就像在绘画中一样),那么为什么它不像以前那样闪烁? 我还阅读了一些关于在 Swing 中绘画的内容,但我不明白为什么从不为 Swing 调用 update()。 你能解释一下为什么吗?
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
class CustomCanvas extends Canvas{
ArrayList<Point> locations;
int locationsAdded;
Point oldLocation;
Point location;
Dimension dimension;
CustomCanvas(Dimension dimension){
locations = new ArrayList<>();
this.dimension = dimension;
this.init();
addListeners();
}
private void init(){
oldLocation= new Point(0, 0);
location= new Point(0, 0);
}
public void paintLine(Graphics g, int x){
Point p1 = (Point)locations.get(x);
Point p2 = (Point)locations.get(x+1);
g.drawLine(p1.x, p1.y, p2.x, p2.y);
locationsAdded++;
}
@Override
public void paint(Graphics g){
locationsAdded = 0;
g.setColor(Color.red);
for(int i = locationsAdded; i < locations.size()-1; i++){
paintLine(g, i);
}
}
public void update(Graphics g) {
//locationsAdded = 0;
for (int i = locationsAdded; i < locations.size()-1; i++) {
paintLine(g, i);
}
}
private void addListeners(){
addMouseMotionListener(new MouseMotionAdapter() {
@Override
public void mouseDragged(MouseEvent me){
oldLocation = location;
location = new Point(me.getX(), me.getY());
locations.add(location);
repaint();
}
});
}
@Override
public Dimension getMinimumSize() {
return dimension;
}
@Override
public Dimension getPreferredSize() {
return dimension;
}
}
class CustomFrame extends Panel {
Panel displayPanel = new Panel(new BorderLayout());
CustomCanvas canvas = new CustomCanvas(new Dimension(700, 700));
public CustomFrame(String titlu) {
canvas.setBackground(Color.white);
displayPanel.add(canvas, BorderLayout.CENTER);
this.add(displayPanel);
}
}
public class AWTPainting {
public static void main(String args[]) {
CustomFrame panel = new CustomFrame("Test Paint");
Frame f = new Frame();
f.add(panel);
f.pack();
f.setSize(700,700);
f.show();
}
}
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