1
在閱讀本文之前，請明白我知道在編寫此代碼時有更好的方法。
這段代碼是很久以前發佈的，我對Java的瞭解比以前更多。儘管如此，我最近查看了代碼，並希望找出導致問題的原因，所以我知道將來會發生什麼。
更新： 我已經下載了JProfiler的實驗。事實證明，當我繪製字符串時，第158行的內存分配有一個巨大的峯值。但是，我不知道它到底意味着什麼，或者它爲什麼會導致巨大的滯後。此代碼如何導致暫停幾秒？
public void draw(Graphics g) {
if (isVisible) {
for (int i = 0; i < debugList.length - 1; i += 2) {
g.setColor(color);
g.setFont(font);
try {
g.drawString(debugList[i] + ":", xPos, yPos + (i * 15)); // Line 158
g.drawString(debugList[i + 1], xPos, yPos + 10 + (i * 15));
}
catch (NullPointerException e) {
if (!errorDisplayed) {
System.out
.println("There was a problem while displaying the debug variables. Check to make sure you added all of the variables you declared in the debug constructor");
errorDisplayed = true;
}
}
}
}
}
前陣子我正在一點點的2D平臺遊戲的遊戲，不得不修正錯誤的一個。我認爲修正錯誤的一個很好的方法是有一個調試類，它將在屏幕上顯示變量。事實證明，它效果很好！它顯示屏幕上的所有變量沒有問題！
但是，當我點擊一個鍵後，我調用changeVisible()（在代碼的最底部）方法後，它凍結了我的整個線程大約3秒鐘。
這並不重要，因爲它已經與我做的其他調試類過時了，但我仍然想知道是什麼導致未來項目的峯值。
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
public class Debug {
private String[] debugList;
private boolean errorDisplayed = false, isVisible = true;
private Color color;
private int xPos = 0, yPos = 0, currentIndex = 0;
private Font font;
/**
* This constructor will create an array that can fit (numberOfVars)
* variables
*
* @param numberOfVars
* - The amount of variables you wish to display
* @param setVisible
* - Will toggle visibility on instantiation (true):on
* (false):off
*/
public Debug(int numberOfVars, boolean setVisible) {
debugList = new String[numberOfVars * 2];
if (setVisible)
isVisible = true;
else
isVisible = false;
color = new Color(0, 0, 0);
xPos = 20;
yPos = 30;
font = new Font("SanSerif",Font.BOLD,12);
}
/**
* This constructor will create an array that can fit (numberOfVars)
* variables
*
* @param numberOfVars
* - The amount of variables you wish to display
* @param setVisible
* - Will toggle visibility on instantiation (true):on
* (false):off
* @param inputXPos
* - The location of the text on the x axis
* @param inputYPos
* - The location of the text on the y axis
*/
public Debug(int numberOfVars, boolean setVisible, int inputXPos,
int inputYPos) {
debugList = new String[numberOfVars * 2];
if (setVisible)
isVisible = true;
else
isVisible = false;
color = new Color(0, 0, 0);
xPos = inputXPos;
yPos = inputYPos;
}
/**
* This method will initialize the variable you wish to display
*
* @param objectName
* - the display name of the variable
* @param arg
* - the value of the variable you wish to display
*/
public void addDebug(String objectName, Object arg) {
if (currentIndex + 2 <= debugList.length) {
debugList[currentIndex] = objectName;
debugList[currentIndex + 1] = arg.toString();
currentIndex += 2;
}
}
/**
* This method will change the text color
*
* @param newColor
* - the color of the debug text
*/
public void changeColor(Color newColor) {
color = newColor;
}
/**
* This method will change the text font
* @param font
* - the font of the debug text
*/
public void changeFont(Font font) {
this.font = font;
}
/**
* This method will update the variable value
*
* @param objectName
* - the name of the variable you wish to display (must be the
* same name used in addDebug())
* @param arg
* - the value of the variable you wish to display
*/
public void update(String objectName, Object arg) {
for (int i = 0; i < debugList.length; i += 2) {
if (debugList[i] != null && debugList[i].equals(objectName)) {
if (i < debugList.length + 1)
debugList[i + 1] = arg.toString();
}
}
}
/**
* This method will draw the debug information
*
* @param g
* - The graphics you wish to paint on
* @param lineSpacing
* - The display space between the variables
*/
public void draw(Graphics g, int lineSpacing) {
if (isVisible) {
if (currentIndex == debugList.length) {
for (int i = 0; i < debugList.length - 1; i += 2) {
g.setColor(color);
g.setFont(font);
try {
g.drawString(debugList[i] + ":", xPos, yPos
+ (i * lineSpacing));
g.drawString(debugList[i + 1], xPos, yPos + 10
+ (i * lineSpacing));
}
catch (NullPointerException e) {
if (!errorDisplayed) {
System.out
.println("There was a problem while displaying the debug variables. Check to make sure you added all of the variables you declared in the debug constructor");
errorDisplayed = true;
}
}
}
}
}
}
/**
* This method will draw the debug information
*
* @param g
* - The graphics you wish to paint on
*/
public void draw(Graphics g) {
if (isVisible) {
for (int i = 0; i < debugList.length - 1; i += 2) {
g.setColor(color);
g.setFont(font);
try {
g.drawString(debugList[i] + ":", xPos, yPos + (i * 15));
g.drawString(debugList[i + 1], xPos, yPos + 10 + (i * 15));
}
catch (NullPointerException e) {
if (!errorDisplayed) {
System.out
.println("There was a problem while displaying the debug variables. Check to make sure you added all of the variables you declared in the debug constructor");
errorDisplayed = true;
}
}
}
}
}
/**
* Will toggle the visibility of the debug display
*/
public void changeVisible() {
isVisible = !isVisible;
}
}
主類（含調試註釋行是很重要的）：
package com.bustedearlobes.platformergame;
import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.util.*;
import javax.swing.JFrame;
public class Game extends Applet implements Runnable {
private static final long serialVersionUID = 1L;
public static int pixelSize = 3;
public static double sx = 0, sy = 0, dir = 0;
public static Dimension windowSize = new Dimension(700,560), pixels = new Dimension(windowSize.width/pixelSize,windowSize.height/pixelSize);
public static Point mousePos = new Point(0,0);
public static boolean isRunning = false,
isMoving = false,
isJumping = false,
isMouseLeft = false,
isMouseRight = false;
public static String name = "2D Game";
public static Level level;
public static Character character;
public static Inventory inventory;
public static Sky sky;
public static ArrayList<Mob> mobs = new ArrayList<Mob>();
public static ArrayList<BrokenBlocks> brokenBlocks = new ArrayList<BrokenBlocks>();
public static Spawner spawner;
public static Sound sound;
public static GameFile gameFile;
public static JFrame frame;
public static Tile tile;
public final static double GRAVITYCONSTANT = 1;
private Image screen;
public static Debug debug = new Debug(5,false); //Debug
public Game() {
setPreferredSize(windowSize);
addKeyListener(new Listening()); //Debug this is where the key listener is that calls the changeVisible() method
addMouseListener(new Listening());
addMouseMotionListener(new Listening());
addMouseWheelListener(new Listening());
}
public void start() { // Defining all the objects required
requestFocus();
tile = new Tile(); // Loading Images...
gameFile = new GameFile();
level = new Level();
character = new Character(Tile.tileSize, Tile.tileSize * 2);
isRunning = true;
sound = new Sound();
inventory = new Inventory();
sky = new Sky();
spawner = new Spawner(10);
debug.changeFont(new Font("San Serif",Font.PLAIN,10)); // Debug
debug.addDebug("Player", character); // Debug
debug.addDebug("Side X", sx); // Debug
debug.addDebug("Side Y", sy); // Debug
debug.addDebug("Sky", sky); // Debug
debug.addDebug("Level.animation", level.animation); // Debug
new Thread(this).start();
}
public void stop() {
isRunning = false;
}
public void tick() {
character.tick();
level.tick(pixels.width/Tile.tileSize + 2,pixels.height/Tile.tileSize + 2);
sky.tick();
inventory.tick();
for (int i = 0; i < mobs.toArray().length;i++)
mobs.get(i).tick();
for (int i = 0; i < brokenBlocks.toArray().length;i++)
brokenBlocks.get(i).tick();
debug.update("Player", character); // Debug
debug.update("Side X", sx); // Debug
debug.update("Side Y", sy); // Debug
debug.update("Sky", sky); // Debug
debug.update("Level.animation", level.animation); // Debug
}
public void render() {
Graphics g = screen.getGraphics();
g.setColor(new Color(100,100,255));
g.fillRect(0,0,pixels.width, pixels.height);
sky.render(g);
level.render(g,pixels.width/Tile.tileSize + 2,pixels.height/Tile.tileSize + 2);
for (int i = 0; i < brokenBlocks.toArray().length;i++)
brokenBlocks.get(i).render(g);
for (int i = 0; i < mobs.toArray().length;i++)
mobs.get(i).render(g);
character.render(g);
inventory.render(g);
debug.draw(g); // Debug
g = getGraphics();
g.drawImage(screen,0,0,windowSize.width,windowSize.height,0,0,pixels.width,pixels.height,null);
g.dispose();
}
public static void main(String[] args) {
Game game = new Game();
frame = new JFrame();
frame.add(game);
frame.setTitle(name);
frame.setResizable(false);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
game.start();
}
public void run() {
screen = createVolatileImage(pixels.width, pixels.height);
while(isRunning) {
tick();
render();
try {
Thread.sleep(5);
} catch (Exception e) {
}
}
}
}
你是怎麼使用這段代碼的？發佈您的主要課程。 – Makky
在上面發表。 – CHess
-1捕捉'NullPointerException' –