我遇到这个问题,当我执行 repaint()时,没有调用类中的 paint()或 update()方法。这是代码:
public class BufferedDisplay extends Canvas implements Runnable {
// Contains all the images in order, ordered from background to foreground
private ArrayList<ImageStruct> images;
// Tracks the last insert ID of the last image for a particular layer
private TreeMap<Integer, Integer> insertIDs;
// Image that holds the buffered Image
private Image offscreen;
public BufferedDisplay() {
images = new ArrayList<ImageStruct>();
insertIDs = new TreeMap<Integer, Integer>();
}
public void addImageStruct(ImageStruct is) {
int layer = is.getLayer();
// Index to insert the image at
int index = -1;
if(insertIDs.containsKey(layer)) {
index = insertIDs.get(layer)+1;
insertIDs.put(layer, index);
}
else {
index = images.size();
insertIDs.put(layer, index);
}
if(index>-1) {
images.add(index, is);
}
}
public void run() {
try
{
while(true)
{
System.out.print("\nSleeping... ");
System.out.print("ArraySize:"+images.size()+" ");
Thread.sleep(1000);
System.out.print("Slept. ");
repaint();
}
}
catch(Exception e)
{
System.out.println("Display Error: ");
e.printStackTrace();
System.exit(-1);
}
}
// Overrides method so the background isn't automatically cleared
public void update( Graphics g )
{
System.out.print("Updating... ");
paint(g);
}
public void paint( Graphics g )
{
System.out.print("Painting... ");
if(offscreen == null)
offscreen = createImage(getSize().width, getSize().height);
Graphics buffer = offscreen.getGraphics();
buffer.setClip(0,0,getSize().width, getSize().height);
g.setColor(Color.white);
paintImages(buffer);
g.drawImage(offscreen, 0, 0, null);
buffer.dispose();
}
public void paintImages( Graphics window )
{
for(ImageStruct i : images) {
i.draw(window);
}
}
}
此课程在以下实施:
public class Game extends JPanel{
// A reference to the C4Game class
private C4Game game;
// A reference to the BufferedDisplay class
private BufferedDisplay display;
// The Image used to initialize the game board
private Image tile;
private int tileSize = 75;
private int tileLayer = 5;
// Thread that controls animation for the BufferedDisplay
Thread animation;
public Game(C4Game game) {
this.game = game;
display = new BufferedDisplay();
try {
tile = ImageIO.read(new File("img\\tile.png"));
} catch (IOException e) {
System.out.println("ERROR: ");
e.printStackTrace();
}
((Component)display).setFocusable(true);
add(display);
animation = new Thread(display);
animation.start();
initBoard();
}
public void initBoard() {
for(int x = 0; x<game.numRows()*tileSize; x+=tileSize) {
for(int y = 0; y<game.numCols()*tileSize; y+=tileSize) {
System.out.println("Placing " +x +" " +y +"...");
display.addImageStruct(new ImageStruct(tile, tileLayer, x, y, tileSize, tileSize));
}
}
}
}
...然后在JFrame中实现。
public class TetraConnect extends JFrame{
public TetraConnect() {
super("TetraConnect", 800, 600);
try {
setIconImage(Toolkit.getDefaultToolkit().createImage("img/icon.png"));
ms = new MainScreen(this);
add(ms);
ms.updateUI();
C4Game c4g = new C4Game(5,6);
Game g = new Game(c4g);
add(g);
g.updateUI();
}
catch(Exception e) {
System.out.println("Init. Error: ");
e.printStackTrace();
System.exit(-1);
}
}
运行时的输出是:
Slept.
Sleeping... Slept.
Sleeping... Slept.
Sleeping... Slept.
等等。我也无法在画布上看到任何图像(我假设它们从未被绘制过)。它似乎完全跳过了重绘方法;调试语句“正在更新...”和“重绘......”永远不会出现。然而,重绘似乎也在执行;循环重复没有问题。为什么重绘方法不调用paint()或update()方法?
答案 0 :(得分:2)
正如@camickr在评论中指出的那样,你正在使用重量级的AWT画布。你应该真正使用轻量级Swing组件。而不是:
public class BufferedDisplay extends Canvas implements Runnable {
我建议:
public class BufferedDisplay extends JPanel implements Runnable {
鉴于这一小变化,我会做以下事情:
当覆盖组件的默认痛苦时,您应该覆盖paintComponent()方法。
所以,而不是:
public void paint( Graphics g )
{
应该是:
protected void paintComponent( Graphics g )
{
这可能会解决您的问题。
此外,您不必覆盖update()
方法。相反,只需在paint组件方法中忽略对super.paintCompenent(g)
的调用。这应该会导致背景默认保持不变。
答案 1 :(得分:1)
确保已将BufferedDisplay
对象添加到容器(例如Frame
),并且容器本身可见。如果组件未显示,则调用repaint()
不会导致update()
被调用。
这只是一般性建议。如果您发布可以编译并运行的self-contained example,则可能更容易找出错误。