Thread: Components?

Hi, Gravity games here, and I was trying to add an object to my JPanel. However, for some reason it says I need to specify a component. Whats a component and how do I use it to add my object?

(Sorry if this is a n00by question, I'm still learning Java...)

Component is a class in the standard Java API. It's the basis of all AWT and Swing gui elements. See: Java Component Javadoc.

What the compiler is telling you is that you need to add an object which is or inherits the Component class. Basically, anything which is compatible with the AWT or Swing GUI toolkits.

Even when I extend component, the object won't get spawned by the JPanel. What should I do?

Please post the full text of the error message and the code that is causing it.
BTW The class is named: Component not component.

The line that throws an error:

add(GroundTileATop(spx,spy));

Error Eclipse gives in the console:

at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectio nPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation problem:
The method GroundTileATop(int, int) is undefined for the type MainJPanel

The method GroundTileATop(int, int) is undefined for the type MainJPanel

The compiler can not find a definition for the GroundTileATop() method.
Check the spelling and the arguments.
Is it a method that returns an object that extends the Component class?

No, GroundTileATop IS the object. Should I try returning the object instead?

Can you post the definitional statement(s) for GroundTileATop?
I'm not sure what you mean when you say it is the object. The statement with the error is coded like a method call. Method calls use the (..) syntax after the name.

Alright, here's the code of GroundTileATop:

package scorpioengine.main;
 
import java.awt.*;
 
public class GroundTileATop extends Tile{
    int width = 32;
    int height = 32;
	public GroundTileATop(int x, int y) {
		super(x, y);
    }
 
    void draw(Graphics g) {
        g.setColor(Color.RED);
        g.fillRect(getX(), getY(), width, height);
    }
}

...and for Tile...

package scorpioengine.main;
 
import java.awt.Component;
import java.awt.Graphics;
 
public abstract class Tile extends Component{
    private int x, y;
 
    public Tile(int x, int y){
        this.x = x;
        this.y = y;
    }
 
    public int getX() {
        return x;
    }
 
    public int getY() {
        return y;
    }
 
    abstract void draw(Graphics g); 
}

Originally Posted by Gravity Games

No, GroundTileATop IS the object. Should I try returning the object instead?

GroundTileATop is a class, not an object (nor a method...the code you posted shows it being used as one would call a method). It seems you are trying to create an instance of that class. Thus, you must create it using the new operator See Creating Objects (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

eg
add(new GroundTileATop(spx,spy));

...although, I'm not sure why you are extending Component, when you don't use or override any of its methods.

Wow, I can't believe I made such a dumb mistake...now it doesn't crash, but I can't get the object to show up properly. What now?

EDIT: Duplicate post for some reason, I guess I must have double clicked submit or something.

Well, here's the full JPanel Code:

package scorpioengine.main;
 
import java.awt.*;
import java.awt.event.*;
import java.io.File;
import java.util.*;
 
import javax.swing.*;
//These import lines assure that all needed Java files are imported into the game.
//The "*"s tell the game to import the entire package of files.
 
import scorpioengine.main.intro.IntroJpanel;
 
public class MainJPanel extends JPanel implements ActionListener, Runnable{
 
	public static GroundTileATop GroundATop;
	public static int objectsSpawned=0;
 
	private int OW;
	private int character=1;
	private int characters=2;
	private int cutscene;
	private int forcedcharacter;
	private boolean downpressed=false;
	public boolean running=true;
	private int keyDown=KeyEvent.VK_DOWN;
	private int keyLeft=KeyEvent.VK_LEFT;
	private int keyRight=KeyEvent.VK_RIGHT;
	private boolean uppressed=false;
	private int keyUp=KeyEvent.VK_UP;
	public boolean selectpressed=false;
	public int keySelect=KeyEvent.VK_Z;
	private int objectId;
	private int spx;
	private int spy;
	private Image A,B,C,D,E,F,G,H,I,K,L,M,N,O,P,Q,R,S,T,U,V,Y,Point,ChompTilesBG,PointerL,PointerR,ChompPortrait,chomppointer,eggplantpointer;
	public int menuoption=1;
	public int optionsoption=1;
	public int quikplay=0;
	public int gamestate=1;
	public String GroundTileATop = "GroundTileATop";
 
	private Map m;
	private MapPointer mp;
	private Level l;
	private Collection<Tile> elements = new ArrayList<Tile>();
	private Scanner s;
	private String currenttile;
	public Thread game;
 
	public MainJPanel(){
		//game controls
		l = new Level();
		m = new Map();
		mp = new MapPointer();
 
		File();
		game = new Thread(this);
		game.start();
 
		addKeyListener(new KeyAdapter(){
 
			public void keyPressed(KeyEvent e){
				int keycode=e.getKeyCode();
 
				if(keycode==keyDown){
					if(gamestate==1){
					if (menuoption<4){
						downpressed=true;
						menuoption+=1;
					}
					else{
						menuoption=1;
						downpressed=true;
					}
					}
					if(gamestate==7){
						if(m.getMap(mp.getTileX(),mp.getTileY()+1).equals("1")){
						mp.movement(0, 1);
						}
					}
				}
				if(keycode==keyUp){
					if(gamestate==1){
					if (menuoption>1){
					    uppressed=true;
						menuoption-=1;
					}
					else{
						menuoption=4;
						uppressed=true;
					}
					}
					if(gamestate==7){
						if(m.getMap(mp.getTileX(),mp.getTileY()-1).equals("1")){
						mp.movement(0, -1);
						}
					}
				}
				if(keycode==keyLeft){
					if(gamestate==2){
						if (character>=1){
							character-=1;
						}
						if (character<1){
							character=characters;
						}
					}
					if(gamestate==7){
						if(m.getMap(mp.getTileX()-1,mp.getTileY()).equals("1")){
						mp.movement(-1, 0);
						}
					}
				}
	if(keycode==keyRight){
		if(gamestate==2){
			if (character<=characters){
				character+=1;
			}
			if (character>characters){
				character=1;
			}
		}
		if(gamestate==7){
			if(m.getMap(mp.getTileX()+1,mp.getTileY()).equals("1") || m.getMap(mp.getTileX()+1,mp.getTileY()).equals("2")){
			mp.movement(1, 0);
			}
		}
				}
				if(keycode==keySelect && !selectpressed){
	if(gamestate==1){
					if(menuoption==1){
						selectpressed=true;
					gamestate=2;
					}
					if(menuoption==2){
						selectpressed=true;
						gamestate=3;
					}
					if(menuoption==3){
						selectpressed=true;
						gamestate=4;
					}
					if(menuoption==4){
						selectpressed=true;
						gamestate=5;
					}
				}
	if(gamestate==2 && !selectpressed){
		selectpressed=true;
		cutscene=0;
		gamestate=6;
				}
if(gamestate==6 && !selectpressed){
	gamestate=7;
	selectpressed=true;
}
if(gamestate==7 && !selectpressed){
	if(m.getMap(mp.getTileX(),mp.getTileY()).equals("1")){   //this controls which tiles act as stage tiles so the game will switch to level mode
		gamestate=8;
		selectpressed=true;
}
}
 
		}
			}
			public void keyReleased(KeyEvent e){
	if(e.getKeyCode()==keyDown){
					downpressed=false;
				}
				if(e.getKeyCode()==keyUp){
					uppressed=false;
				}
				if(e.getKeyCode()==keySelect){
					selectpressed=false;
				}
			}
 
			public void keyTyped(KeyEvent e){
				int keycode=e.getKeyCode();
 
			}
 
			});
 
 
		setFocusable(true);
 
		ImageIcon img = new ImageIcon("C://CWWGFX//8x8ALarge.PNG");    //Filepath to the "A" of the main font
		A=img.getImage();
		img = new ImageIcon("C://CWWGFX//8x8BLarge.PNG");    //Filepath to the "B" of the main font
		B=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8CLarge.PNG");    //Filepath to the "C" of the main font
		C=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8DLarge.PNG");    //Filepath to the "D" of the main font
		D=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8ELarge.PNG");    //Filepath to the "E" of the main font
		E=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8FLarge.PNG");    //Filepath to the "F" of the main font
		F=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8GLarge.PNG");    //Filepath to the "F" of the main font
		G=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8HLarge.PNG");    //Filepath to the "H" of the main font
		H=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8ILarge.PNG");    //Filepath to the "I" of the main font
		I=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8KLarge.PNG");    //Filepath to the "K" of the main font
		K=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8LLarge.PNG");    //Filepath to the "L" of the main font
		L=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8MLarge.PNG");    //Filepath to the "M" of the main font
		M=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8NLarge.PNG");    //Filepath to the "N" of the main font
		N=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8OLarge.PNG");    //Filepath to the "O" of the main font
		O=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8PLarge.PNG");    //Filepath to the "P" of the main font
		P=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8QLarge.PNG");    //Filepath to the "Q" of the main font
		Q=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8RLarge.PNG");    //Filepath to the "R" of the main font
		R=img.getImage();
		img = new ImageIcon("C://CWWGFX//8x8SLarge.PNG");    //Filepath to the "S" of the main font
		S=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8TLarge.PNG");    //Filepath to the "T" of the main font
		T=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8ULarge.PNG");    //Filepath to the "U" of the main font
		U=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8VLarge.PNG");    //Filepath to the "V" of the main font
		V=img.getImage();
		img=new ImageIcon("C://CWWGFX//8x8YLarge.PNG");    //Filepath to the "Y" of the main font
		Y=img.getImage();
		img=new ImageIcon("C://CWWGFX//OptionTriangleLarge.PNG");    //Filepath to the option triangle of the main menu
		Point=img.getImage();
		img=new ImageIcon("C://CWWGFX//ChompTilesBG.PNG");    //Filepath to the Chomp portrait of the character select
		ChompTilesBG=img.getImage();
		img=new ImageIcon("C://CWWGFX//Pointertriangleleft.PNG");    //Filepath to the left arrow of the character select
		PointerL=img.getImage();
		img=new ImageIcon("C://CWWGFX//Pointertriangleright.PNG");    //Filepath to the right arrow of the character select
		PointerR=img.getImage();
		img=new ImageIcon("C://CWWGFX//ChompPortraitLarge.PNG");    //Filepath to the Chomp portrait of the character select
		ChompPortrait=img.getImage();
		img = new ImageIcon("C://CWWGFX//ChompPointerLarge.png");
		chomppointer=img.getImage();
		img = new ImageIcon("C://CWWGFX//EggplantPointerLarge.png");
		eggplantpointer=img.getImage();
 
	}
 
	public void actionPerformed(ActionEvent e) {
		repaint();
	}
 
	public void paint(Graphics g){ //this is the graphics subroutine
		super.paint(g);
		if(gamestate==1){
		if(menuoption==1){
		g.drawImage(Point,14,32,null);
		}
		if(menuoption==2){
			g.drawImage(Point,14,64,null);
		}
		if(menuoption==3){
			g.drawImage(Point,14,96,null);
		}
		if(menuoption==4){
			g.drawImage(Point,14,128,null);
		}
 
		g.drawImage(S,32,32,null);
		g.drawImage(T,48,32,null);
		g.drawImage(A,64,32,null);
		g.drawImage(R,80,32,null);
		g.drawImage(T,96,32,null);
 
		g.drawImage(L,32,64,null);
		g.drawImage(O,48,64,null);
		g.drawImage(A,64,64,null);
		g.drawImage(D,80,64,null);
 
		g.drawImage(O,32,96,null);
		g.drawImage(P,48,96,null);
		g.drawImage(T,64,96,null);
		g.drawImage(I,80,96,null);
		g.drawImage(O,96,96,null);
		g.drawImage(N,112,96,null);
		g.drawImage(S,128,96,null);
 
		g.drawImage(E,32,128,null);
		g.drawImage(D,48,128,null);
		g.drawImage(I,64,128,null);
		g.drawImage(T,80,128,null);
		g.drawImage(O,96,128,null);
		g.drawImage(R,112,128,null);
		}
		if (gamestate==2){
			g.drawImage(PointerL,132,224,null);
			g.drawImage(PointerR,398,224,null);
			if(character==1){
			g.drawImage(ChompPortrait,220,150,null);
			g.drawImage(C,246,280,null);
			g.drawImage(H,262,280,null);
			g.drawImage(O,278,280,null);
			g.drawImage(M,294,280,null);
			g.drawImage(P,310,280,null);
			}		
			if(character==2){
				g.drawImage(M,220,150,null);
				g.drawImage(N,246,280,null);
				g.drawImage(O,262,280,null);
				g.drawImage(L,278,280,null);
				g.drawImage(L,294,280,null);
				g.drawImage(L,310,280,null);
				}		
		}
		if (gamestate==4){
			g.drawImage(ChompTilesBG,0,0,null);
			if (optionsoption==1){
			g.drawImage(Point,14,32,null);
			}
			g.drawImage(Q,32,32,null);
			g.drawImage(U,48,32,null);
			g.drawImage(I,64,32,null);
			g.drawImage(K,80,32,null);
			g.drawImage(P,112,32,null);
			g.drawImage(L,128,32,null);
			g.drawImage(A,144,32,null);
			g.drawImage(Y,160,32,null);
			if (quikplay==0){
				g.drawImage(O,192,32,null);
				g.drawImage(F,208,32,null);
				g.drawImage(F,224,32,null);
			}
			if (quikplay==1){
				g.drawImage(O,192,32,null);
				g.drawImage(N,208,32,null);
			}
			g.drawImage(K,32,64,null);
			g.drawImage(E,48,64,null);
			g.drawImage(Y,64,64,null);
			g.drawImage(C,96,64,null);
			g.drawImage(O,112,64,null);
			g.drawImage(N,128,64,null);
			g.drawImage(F,144,64,null);
			g.drawImage(I,160,64,null);
			g.drawImage(G,176,64,null);
 
			g.drawImage(L,32,96,null);
			g.drawImage(I,48,96,null);
			g.drawImage(V,64,96,null);
			g.drawImage(E,80,96,null);
			g.drawImage(S,96,96,null);
 
			g.drawImage(B,32,128,null);
			g.drawImage(O,48,128,null);
			g.drawImage(S,64,128,null);
			g.drawImage(S,80,128,null);
			g.drawImage(I,112,128,null);
			g.drawImage(N,128,128,null);
			g.drawImage(T,144,128,null);
			g.drawImage(R,160,128,null);
			g.drawImage(O,176,128,null);
		}
		if (gamestate==6){
			g.drawImage(L,310,280,null);
		}
		if (gamestate==7){
			for(int y = 0; y < (m.getmapsizey()); y++){
				for(int x = 0; x < m.getmapsizex(); x++){
					if(m.getMap(x,y).equals("g")){
						g.drawImage(m.getGrassEK(),x*32,y*32,null);
					}
					if(m.getMap(x,y).equals("t")){
						g.drawImage(m.getGrassEKTop(),x*32,y*32,null);
					}
					if(m.getMap(x,y).equals("w")){
						g.drawImage(m.getWaterEK(),x*32,y*32,null);
					}
				}
			}
			for(int y = (m.getmapsizey()+1); y < (m.getmapsizey()*2); y++){
				for(int x = 0; x < m.getmapsizex(); x++){
					if(m.getMap(x,y).equals("1")){
						g.drawImage(m.getPath1(),x*32,(y-14)*32,null);
					}
					if(m.getMap(x,y).equals("2")){
						g.drawImage(m.getPath2(),x*32,(y-14)*32,null);
					}
				}
			}
			if (character==1){
			g.drawImage(chomppointer,mp.getTileX()*32,(mp.getTileY()-15)*32,null);
			}
			if (character==2){
				g.drawImage(eggplantpointer,mp.getTileX()*32,(mp.getTileY()-15)*32,null);
				}
		}
		if (gamestate==8){
			add(new GroundTileATop(spx,spy));
		}
	}
 
public void File(){
 
		try{
		s = new Scanner(new File("C://CWWLEVELS//world1stage1.txt"));
		while(s.hasNextLine()){
			addElements(s.nextLine());
		}
		s.close();
		}catch(Exception e){
			System.out.println("error loading map2");
		}
 
	}
public void fpsSetter() {
	try{game.sleep(16);
	} catch(Exception e){
		e.printStackTrace();
	}
}
 
public void run() {
	while (running){
	fpsSetter();
	repaint();
	}
}
public void addElements(String line) {
	Scanner scanner = new Scanner(line);
	objectId = scanner.nextInt();
	spx = scanner.nextInt();
	spy = scanner.nextInt();
	System.out.println("Object: " + objectId + " At: " + spx + "," + spy);
}
}

Yeah it gets into state 8, and I'm not using a timer because at one point it worked fine and then at another randomly threw an error. Also, I only want to draw the objects once, and I'll use a seperate method once I get the add object to actually work.

How should I call the draw method then? Just use GroundTileATop.g.draw?

How should I call the draw method then? Just use GroundTileATop.g.draw?

You need to study how to call a method and pass it an argument. What you have coded is NOT a method call. See the tutorial:
Passing Information to a Method or a Constructor (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

I thought classes and objects were interchangable...well I guess that's the kind of thing a bad tutorial can do to you...well I'm making the object part of the JPanel class for simplicity, but I can only draw one (i'm assuming because the spx and spy variables change too quickly for all the integers to be registered. How would I get all the objects to show? I can only get the last one in the list to show.

spx and spy variables change too quickly for all the integers to be registered.

What does "registered" mean? How does that relate to the values of the two variables?

I can only get the last one in the list to show.

There are many ways that can happen.
One is that all the references in the list point to the same object. Check that you make new objects each time you add one to the list.

Try debugging the code by printing out each item as you take it from the list to show to see if they are different.


Otherwise you will have to post the code so it can be tested to see the problem.

I already have printlines showing each variable, and each one shows, but I think the problem is that the first integer is replaced a frame later. I don't want to use arrays since they're stuck at the initial size you set them at, would arraylists work?

ArrayLists would work for most places that you would use an array.

...and of course ANOTHER problem comes up. Now I can't get the game to read a certain line of an ArrayList...

What am I doing wrong here?

g.fillRect(Integer.parseInt(xarray[a]), Integer.parseInt(yarray[a]), 32, 32);