我知道有很多答案，但它们似乎不起作用。我不知道我是不是在某种程度上使用不同版本的Java，或者applet的代码是不同的，但这是我的代码：
来自HUD课程的片段：
public void paint (Graphics g)
{
if(g instanceof Graphics2D)
{
Graphics2D g2d = (Graphics2D)g;
g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g2d.drawString("This is gona be awesome", 200, 200);
}
主类：
import java.applet.Applet; (more, they just glitched with the code block)
public class Main extends Applet implements Runnable, KeyListener {
static ArrayList<Block> all_blocks = new ArrayList<Block>();
Player player;
HUD hud;
static int amount = 0;
public void init(){
setSize(700, 500);
addKeyListener(this);
}
public void start(){
player = new Player(100, 100);
HUD hud = new HUD();
for (int i = 0; i < 75; i++){
new Grass(i*30, 400);
}
new Spikes(250, 370);
Thread thread = new Thread(this);
thread.start();
}
@Override
public void run() {
while (true){
player.update();
repaint();
camera_scroll(this.amount);
try {
Thread.sleep(17);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public void stop(){
}
public void camera_scroll(int amount){
int new_amount;
if (amount > 30){
new_amount = 30;
this.amount -= 30;
} else {
new_amount = amount;
this.amount = 0;
}
for (Block b: all_blocks){
b.x += new_amount;
b.update();
}
player.x += new_amount;
}
public void paint(Graphics g){
for (Block block: all_blocks){
block.paint(g);
}
hud.paint(g);
player.paint(g);
}
@Override
public void keyPressed(KeyEvent e) {
switch(e.getKeyCode()){
case KeyEvent.VK_LEFT:
case KeyEvent.VK_A:
player.moveLeft();
break;
case KeyEvent.VK_RIGHT:
case KeyEvent.VK_D:
player.moveRight();
break;
case KeyEvent.VK_UP:
case KeyEvent.VK_W:
player.moveUp();
break;
}
}
@Override
public void keyReleased(KeyEvent e) {
switch(e.getKeyCode()){
case KeyEvent.VK_LEFT:
case KeyEvent.VK_A:
player.stopLeft();
break;
case KeyEvent.VK_RIGHT:
case KeyEvent.VK_D:
player.stopRight();
break;
case KeyEvent.VK_UP:
case KeyEvent.VK_W:
player.stopUp();
break;
}
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}
玩家和积木的绘制工作正常，他们的绘画方法与HUD相同，但他们绘制图像。需要帮助请叫我。谢谢！
答案 0 :(得分：2)
有两个主要问题......
您要在start方法中创建对象实例，而这些对象应在init方法中创建。
start（通常在调用stop之后）以使applet继续。这不是尝试初始化基础applet状态的好地方，相反，它最好用于重新启动Thread（假设你在调用stop时也停止它）...
所以，而不是......
public void init(){
setSize(700, 500);
addKeyListener(this);
}
public void start(){
player = new Player(100, 100);
HUD hud = new HUD();
for (int i = 0; i < 75; i++){
new Grass(i*30, 400);
}
new Spikes(250, 370);
Thread thread = new Thread(this);
thread.start();
}
你应该使用像...这样的东西。
public void init(){
setSize(700, 500);
addKeyListener(this);
player = new Player(100, 100);
HUD hud = new HUD();
for (int i = 0; i < 75; i++){
new Grass(i*30, 400);
}
new Spikes(250, 370);
}
public void start(){
Thread thread = new Thread(this);
thread.start();
}
您正在创建对象的本地实例，遮蔽您的实例字段，这会导致NullPointerException（对我来说，它位于paint ...
所以而不是
public void init(){
setSize(700, 500);
addKeyListener(this);
player = new Player(100, 100);
HUD hud = new HUD();
for (int i = 0; i < 75; i++){
new Grass(i*30, 400);
}
new Spikes(250, 370);
}
你应该使用......
public void init(){
setSize(700, 500);
addKeyListener(this);
player = new Player(100, 100);
hud = new HUD();
// Notice that HUD has not been re-declared...
for (int i = 0; i < 75; i++){
new Grass(i*30, 400);
}
new Spikes(250, 370);
}
JApplet来代替...... JFrame作为核心顶级容器。JPanel之类的内容并覆盖它＃39; s paintComponent方法执行自定义绘画。推荐这是出于多种原因，包括绘画实际上非常复杂且很容易打破油漆链，顶级容器不能双重缓冲，这会导致闪烁。默认情况下，Swing组件（除顶级对应组件外）是双缓冲的。有关详细信息，请查看Painting in AWT and Swing和Performing Custom Painting KeyListener以出现与焦点相关的问题而臭名昭着。如果您转到Swing API，最好使用Key Bindings API