将applet转换为应用程序。请帮忙 [英] Conversion of applet into application. Please help

问题描述

我正在尝试将applet转换为java app。但除了一个空框架，我什么都没得到。如果有人能帮我解决这个问题，我将不胜感激。 Pleaseeee！



我这里修改过的代码：

I am trying to convert an applet into java app. But I m getting nothing except an empty frame. I would be grateful if anyone could help me through this. Pleaseeee!

My modified code here:

import java.awt.event.WindowEvent;
import java.util.*;
import java.awt.*;
import java.awt.event.WindowListener;

/** A BST node */

class node {

  int  key;			// element key
  node left;			// left child
  node right;			// right child
  node parent;			// parent
  float x, y;			// (x,y) location in window
  float incx, incy;		// increment in (x,y) with each move
  boolean highlight_node;	// true if node is to be highlighted
  Color highlight_colour;
  boolean hide_edge;		// true if parent edge is to be hidden (i.e. not drawn)
}


/** A Binary Search Tree */

 public class try2 extends Frame{

  node root;			// root of tree
  node rotation_node;		// node to rotate about
  int num_edges;		// edges to draw
  float edges[][] = new float[100][4];
  rotate rotate_thread;		// thread to handle rotations
  search search_thread;		// thread to handle searches
  boolean only_root_children;	// true if only the root's children may be rotated
  boolean alternate_nodes;	// true if we alternately rotate two nodes only
  boolean allow_rotation;	// true if we can do rotations
  boolean allow_search;		// true if we can do searches
  final int MAX_ROTATABLE_NODES = 100;
  int rotatable_nodes[] = new int[MAX_ROTATABLE_NODES]; // nodes that we may rotate
  int num_rotatable_nodes = 0;	// (num_rotable_nodes = 0 means all nodes may be rotated)
  TextField search_field;	// UI component to capture user's search request
  int search_key;		// the key to search for

  // Things having to do with appearance:

  Font f = new Font( "TimesRoman", Font.PLAIN, 14 );
  FontMetrics fm = getFontMetrics( f );

  final Color LineColor      = Color.black;
  final Color HighlightColor = Color.orange;
  final Color NodeColor      = Color.cyan;

  final int NODE_WIDTH = 40;	// width of a node
  final int NODE_HEIGHT = 30;	// height of a node

  public static void main(String[] args)
  {
    try2 app=new try2();
    app.setSize(400,400);
    app.setVisible(true);
    app.setLayout(new FlowLayout());
  }
   //

  /**
   * Init the applet.  Just insert elements into the tree and
   * compute the tree's initial position.
   */

   try2() {

    // Get the applet parameters

    // Determine initial tree position
    position_tree( root, 0, 0 );

    // Set up UI components
    if (allow_search) {
      setLayout( new FlowLayout(FlowLayout.LEFT) );
      search_field = new TextField( 4 );
      search_field.setEditable( true );
      add( new Label( "Enter search key:", Label.RIGHT ) );
      add( search_field );
    }
  }


  /**
   * Upon starting, start any threads that were previously stopped
   */

  public void start() {

    if (rotate_thread != null && rotate_thread.isAlive())
      rotate_thread.resume();

    if (search_thread != null && search_thread.isAlive())
      search_thread.resume();
  }

  /**
   * Upon stopping, stop all active threads
   */

  public void stop() {

    if (rotate_thread != null && rotate_thread.isAlive())
      rotate_thread.suspend();

    if (search_thread != null && search_thread.isAlive())
      search_thread.suspend();
  }

  /**
   * Upon a `paint', just redraw the tree.
   */


  public void paintComponent( Graphics g ) {

    // Draw any stored edges
    if (num_edges > 0) {
      g.setColor( LineColor );
      for (int i=0; i<num_edges; i++)
	g.drawLine( (int) edges[i][0], (int) edges[i][1],
                    (int) edges[i][2], (int) edges[i][3] );
    }

    // Draw the rest of the tree
    draw_tree( root, g );
  }

  /**
   * Use update() to do double buffering.
   */

  Image     buffer_image;
  Graphics  buffer_graphics;
  Dimension buffer_size;

  public synchronized void update( Graphics g ) {

    if (buffer_image == null) {
      buffer_size     = size();
      buffer_image    = createImage( buffer_size.width, buffer_size.height );
      buffer_graphics = buffer_image.getGraphics();
      buffer_graphics.setFont( getFont() );
    }

    buffer_graphics.setColor( Color.white );
    buffer_graphics.fillRect( 0, 0, buffer_size.width, buffer_size.height );

    paint( buffer_graphics );

    g.drawImage( buffer_image, 0, 0, null );
  }

  /**
   * Upon a mouseDown, colour the two nodes involved, but
   * don't rotate.
   */

    @Override
  public boolean mouseDown( Event evt, int x, int y ) {

    // Ignore mouse if rotations are not allowed
    if (! allow_rotation)
      return false;

    // Ignore mouse if still rotating
    if (rotate_thread != null && rotate_thread.isAlive())
      return false;

    // Find node closest to mouse
    rotation_node = find_closest_node( root, x, y );

    if (rotation_node == root)
      rotation_node = null;	// Ignore root, since it can't be rotated

    else if (only_root_children && rotation_node.parent != root)
      rotation_node = null;	// Restrict to children of root if flag is set

    else if (alternate_nodes && rotatable_nodes[0] != rotation_node.key)
      rotation_node = null;	// Restrict rotations to two nodes alternately

    else if (num_rotatable_nodes != 0) { // Restrict to `rotatable nodes' if supplied
      int i;
      for (i=0; i<num_rotatable_nodes; i++)
	if (rotatable_nodes[i] == rotation_node.key)
	  break;
      if (i == num_rotatable_nodes)
	rotation_node = null;
    }

    if (alternate_nodes && rotation_node != null) {
      int temp = rotatable_nodes[0];
      rotatable_nodes[0] = rotatable_nodes[1];
      rotatable_nodes[1] = temp;
    }

    // Highlight rotation node and its parent

    if (rotation_node != null) {
      rotation_node.highlight_node = true;
      rotation_node.parent.highlight_node = true;
      repaint();
    }

    return true;
  }

  /**
   * Upon a mouseUp, rotate the two nodes.  This involves spawning
   * a thread that will slowly move the nodes.
   */

    @Override
  public boolean mouseUp( Event evt, int x, int y ) {

    // Ignore mouse if still rotating
    if (rotate_thread != null && rotate_thread.isAlive())
      return false;

    // Ignore mouse no node selected for rotation
    if (rotation_node == null)
      return true;

    // Start rotating
    rotation_node.highlight_node = false;
    rotation_node.parent.highlight_node = false;

    rotate_thread = new rotate(this);
    rotate_thread.start();

    return true;
  }

  /**
   * Handle an action from one of the UI components.
   */

    @Override
  public boolean action( Event evt, Object arg ) {

    // Ignore if searches not allowed
    if (! allow_search)
      return false;

    // Ignore if still performing the search
    if (search_thread != null && search_thread.isAlive())
      return false;

    // Handle the event
    if (evt.target instanceof TextField) {
      try{
	search_key = Integer.parseInt( search_field.getText() ); }
      catch (NumberFormatException e) {
	System.out.println( "ERROR in BST applet: `" + search_field.getText() + "' is not an integer" );
	return true;
      }
      //search_thread = new search(this);
      //search_thread.start();

    } else
      System.out.println( "ERROR in BST applet: Unrecognized UI event" );

    return true;
  }

  /**
   * Parse the parameters supplied with the applet.  These are listed at the
   * top of this file.
   */

  void parse_parameters() {

    String keys;

    // Read keys
    keys = getParameter( "keys" );
    if (keys != null) {
      StringTokenizer t = new StringTokenizer( keys );
      while (t.hasMoreTokens())
	insert( Integer.parseInt(t.nextToken()) );
    }

    // Read allowable actions
    keys = getParameter( "action" );
    if (keys != null) {
      StringTokenizer t = new StringTokenizer( keys );
      while (t.hasMoreTokens()) {
	String s = t.nextToken();
	if (s.equals("rotate"))
	  allow_rotation = true;
	else if (s.equals("search"))
	  allow_search = true;
	else
	  System.out.println( "Error in BST applet: unrecognized action `" + s + "' in param list." );
      }
    }

    // Read rotatable nodes
    only_root_children = (getParameter( "only_root_children" ) != null);

    keys = getParameter( "alternate_nodes" );
    if (keys != null) {
      alternate_nodes = true;
      StringTokenizer t = new StringTokenizer( keys );
      while (t.hasMoreTokens()) {
	int i = Integer.parseInt(t.nextToken());
	if (num_rotatable_nodes < MAX_ROTATABLE_NODES)
	  rotatable_nodes[ num_rotatable_nodes++ ] = i;
      }
      if (num_rotatable_nodes != 2)
	System.out.println( "Error in BST applet: expected 2 keys for `alternate_nodes' param, but got " + num_rotatable_nodes );
    }

    keys = getParameter( "rotatable_nodes" );
    if (keys != null) {
      StringTokenizer t = new StringTokenizer( keys );
      while (t.hasMoreTokens()) {
	int i = Integer.parseInt(t.nextToken());
	if (num_rotatable_nodes < MAX_ROTATABLE_NODES)
	  rotatable_nodes[ num_rotatable_nodes++ ] = i;
      }
    }
  }

  /**
   * Find the closest tree node to a mouse click.
   */

  node find_closest_node( node root, int x, int y ) {

    node l_closest, r_closest;
    int  l_dist, r_dist, root_dist;

    if (root == null)
      return null;

    l_closest = find_closest_node( root.left, x, y );
    r_closest = find_closest_node( root.right, x, y );

    l_dist = dist_to_node( l_closest, x, y );
    r_dist = dist_to_node( r_closest, x, y );
    root_dist = dist_to_node( root, x, y );

    if (l_dist <= r_dist && l_dist <= root_dist)
      return l_closest;

    if (r_dist <= l_dist && r_dist <= root_dist)
      return r_closest;

    return root;
  }

  /**
   * Return the L1 distance from (x,y) to node n.
   */

  int dist_to_node( node n, int x, int y ) {

    if (n == null)
      return Integer.MAX_VALUE;

    return Math.abs( x - (int) n.x ) + Math.abs( y - (int) n.y );
  }


  /**
   * Determine the (x,y) locations of each node of the tree.  This
   * positions the subtree at `root' in a box whose upper-left corner
   * is defined by `upper' and `left' pixel locations.  This returns
   * the width of the box, in pixels.
   */

  int position_tree( node root, int upper, int left ) {

    int l_width, r_width;

    if (root == null)
      return 0;

    l_width = position_tree( root.left, upper + NODE_HEIGHT, left );

    root.x = left + l_width + NODE_WIDTH/2;
    root.y = upper + NODE_HEIGHT/2;

    r_width = position_tree( root.right, upper + NODE_HEIGHT,
			     left + l_width + NODE_WIDTH );

    return l_width + NODE_WIDTH + r_width;
  }

  /**
   * Draw the tree: For each node, draw its subtrees, then
   * draw its parent link (if any), then draw the node itself.
   */

  void draw_tree( node root, Graphics g ) {

    if (root == null)
      return;

    draw_tree( root.left, g );
    draw_tree( root.right, g );

    if (root.parent != null)
      draw_parent_edge( root, g );

    draw_node( root, g );
  }

  /**
   * Draw the parent edge of this node.
   */

  void draw_parent_edge( node n, Graphics g ) {

    if (! n.hide_edge) {
      g.setColor( LineColor );
      g.drawLine( (int) n.x, (int) n.y, (int) n.parent.x, (int) n.parent.y );
    }
  }

  /**
   * Draw this node.
   */

  void draw_node( node n, Graphics g ) {

    String key = Integer.toString( n.key );
    int width  = fm.stringWidth( key );
    int height = fm.getAscent(); // just numbers, so Descent = 0

    // Fill in node's circle
    if (n.highlight_node)
      if (n.highlight_colour == null)
	g.setColor( HighlightColor );
      else
	g.setColor( n.highlight_colour );
    else
      g.setColor( NodeColor );

    g.fillOval( (int) n.x - NODE_WIDTH/2, (int) n.y - NODE_HEIGHT/2,
		NODE_WIDTH, NODE_HEIGHT );

    // Outline the circle and draw the key
    g.setColor( LineColor );

    g.drawOval( (int) n.x - NODE_WIDTH/2, (int) n.y - NODE_HEIGHT/2,
		NODE_WIDTH, NODE_HEIGHT );
    g.drawString( key, (int) n.x - width/2, (int) n.y - height/2 + fm.getAscent() - 1 );
  }

  /**
   * Insert a node into the BST
   */

  void insert( int k ) {

    node x, y, new_node;

    y = null;
    x = root;

    // y follows x down the tree until x is null
    while (x != null) {
      y = x;
      if (k == x.key)
	return;
      else if (k < x.key)
	x = x.left;
      else
	x = x.right;
    }

    // allocate a new node
    new_node = new node();

    new_node.key    = k;
    new_node.parent = y;
    new_node.left   = null;
    new_node.right  = null;

    // point tree node to new node
    if (y == null)
      root = new_node;
    else
      if (k < y.key)
	y.left = new_node;
      else
	y.right = new_node;
  }

  /**
   * Perform a rotation
   */

  void rotate( node c ) {

    node p = c.parent;		// parent of c
    node gp = p.parent;		// grandparent of c (might be null)

    // Update the lower edge which switches sides
    if (c == p.left) {
      p.left = c.right;
      if (p.left != null)
	p.left.parent = p;
      c.right = p;
      p.parent = c;
    } else {
      p.right = c.left;
      if (p.right != null)
	p.right.parent = p;
      c.left = p;
      p.parent = c;
    }

    // Update the upper edge which switches sides
    if (gp == null)
      root = c;
    else if (p == gp.left)
      gp.left = c;
    else
      gp.right = c;

    c.parent = gp;
  }

    private String getParameter(String string) {
       throw new UnsupportedOperationException("Not yet implemented");
    }
}


/* A Thread to animate rotating nodes */


class rotate extends Thread implements Runnable {

  final int ROTATE_TIME = 1000;	// total rotate time, in milliseconds

  try2 tree;			// tree in which rotation occurs

  rotate( try2 t ) {
    tree = t;
  }

  public void run() {

    node c, p, gc, gp;		// rotate about edge c-p

    c = tree.rotation_node;	// find c (= child)
    p = c.parent;		// find p (= parent)
    gp = p.parent;		// find gp (= grandparent)
    if (c == p.right)		// find gc (= grandchild, might be null)
      gc = c.left;
    else
      gc = c.right;

    // Phase I: move the nodes
    c.highlight_node = true;
    p.highlight_node = true;

    for (int i=0; i<tree.NODE_HEIGHT; i++) {

      c.y --;
      if (c == p.left)
	shift_up( c.left );
      else
	shift_up( c.right );

      p.y ++;
      if (c == p.right)
	shift_down( p.left );
      else
	shift_down( p.right );

      tree.repaint();

      try{			// delay 1/3 of ROTATE_TIME for ALL of Phase I
	Thread.sleep( ROTATE_TIME/3/tree.NODE_HEIGHT );}
      catch (InterruptedException e) {}
    }

    c.highlight_node = false;
    p.highlight_node = false;

    // Phase II: swap the lower edge (= parent edge of gc) from c to p
    tree.num_edges = 0;

    if (gc != null) {

      tree.num_edges = 1;
      gc.highlight_node = true;
      gc.hide_edge = true;

      tree.edges[0][0] = gc.x;
      tree.edges[0][1] = gc.y;
      tree.edges[0][2] = c.x;
      tree.edges[0][3] = c.y + tree.NODE_HEIGHT/2;

      float dx = p.x - tree.edges[0][2];
      float dy = p.y - tree.edges[0][3];

      float loops = (Math.abs(dx) > Math.abs(dy) ? Math.abs(dx) : Math.abs(dy)) / 2;

      int sleep_time = (int) (ROTATE_TIME/3/loops);
      if (sleep_time < 5)
	sleep_time = 5;

      dx = dx/loops;
      dy = dy/loops;

      tree.repaint();

      for (int i=0; i < loops; i++) {

	tree.edges[0][2] += dx;
	tree.edges[0][3] += dy;

	tree.repaint();

	try		{	// delay 1/3 of ROTATE_TIME for ALL of Phase II
	  Thread.sleep( sleep_time );}
	catch (InterruptedException e) {}
      }

      gc.highlight_node = false;
    }

    // Phase III: swap the upper edge
    if (gp != null) {

      tree.num_edges ++;
      gp.highlight_node = true;
      p.hide_edge = true;

      tree.edges[tree.num_edges-1][0] = gp.x;
      tree.edges[tree.num_edges-1][1] = gp.y;
      tree.edges[tree.num_edges-1][2] = p.x;
      tree.edges[tree.num_edges-1][3] = p.y - tree.NODE_HEIGHT/2;

      float dx = c.x - tree.edges[tree.num_edges-1][2];
      float dy = c.y - tree.edges[tree.num_edges-1][3];

      float loops = (Math.abs(dx) > Math.abs(dy) ? Math.abs(dx) : Math.abs(dy)) / 2;

      int sleep_time = (int) (ROTATE_TIME/3/loops);
      if (sleep_time < 5)
	sleep_time = 5;

      dx = dx/loops;
      dy = dy/loops;

      tree.repaint();

      for (int i=0; i < loops; i++) {

	tree.edges[tree.num_edges-1][2] += dx;
	tree.edges[tree.num_edges-1][3] += dy;

	tree.repaint();

	try		{	// delay 1/3 of ROTATE_TIME for ALL of Phase II
	  Thread.sleep( sleep_time ); }
	catch (InterruptedException e) {}
      }

      p.hide_edge = false;
      gp.highlight_node = false;
    }

    if (gc != null)
      gc.hide_edge = false;

    tree.num_edges = 0;

    tree.rotate( c );

    tree.repaint();
  }

  void shift_up( node n ) {
    if (n == null)
      return;
    shift_up( n.left );
    shift_up( n.right );
    n.y --;
  }

  void shift_down( node n ) {
    if (n == null)
      return;
    shift_down( n.left );
    shift_down( n.right );
    n.y ++;
  }

}


/* A Thread to animate BST search */
class search extends Thread implements Runnable {

  final int SEARCH_TIME = 800;	// search time per node, in milliseconds

  try2 tree;			// tree in which search occurs

  search( try2 t ) {
    tree = t;
  }


  public void run() {
    node n, pn;

    // Clear old highlights
    if (tree.root != null  /*tree.root.highlight_node*/) {
      clear_highlights( (node) tree.root);
      tree.repaint();
      try{
	Thread.sleep( SEARCH_TIME );}
      catch (InterruptedException e) {}
    }

    // Search
    pn = null;
    n = (node) tree.root;

    while (n != null && n.key != tree.search_key) {

      // Pause on the node

      n.highlight_node = true;
      tree.repaint();
      try{
	Thread.sleep( SEARCH_TIME );}
      catch (InterruptedException e) {}

      // Move downward
      pn = n;

      if (tree.search_key < n.key)
	n = n.left;
      else
	n = n.right;
    }

    if (n != null) {
      n.highlight_node = true;
      tree.repaint();
      try {
	Thread.sleep( SEARCH_TIME ); }
      catch (InterruptedException e) {}
      n.highlight_colour = Color.green;
    } else if (pn != null) {
      pn.highlight_node = true;
      pn.highlight_colour = Color.red;
    }

    tree.repaint();
  }

  void clear_highlights( node n ) {

    if (n == null)
      return;

    clear_highlights( n.left );
    clear_highlights( n.right );

    n.highlight_node = false;
    n.highlight_colour = null;
  }

    public class try2 extends Frame implements WindowListener{
      private int search_key;
      private Object root;

    public void windowClosing(WindowEvent e)
    {
      dispose();
      System.exit(0);// normal exit of program
      this.addWindowListener(this);
    }

    public void windowOpened(WindowEvent e) {
      //throw new UnsupportedOperationException("Not supported yet.");
    }

    /*public void windowClosing(WindowEvent e) {
      //throw new UnsupportedOperationException("Not supported yet.");
    }*/

    public void windowClosed(WindowEvent e) {

    }

    public void windowIconified(WindowEvent e) {
      // throw new UnsupportedOperationException("Not supported yet.");
    }

    public void windowDeiconified(WindowEvent e) {
      // throw new UnsupportedOperationException("Not supported yet.");
    }

    public void windowActivated(WindowEvent e) {
      //throw new UnsupportedOperationException("Not supported yet.");
    }

    public void windowDeactivated(WindowEvent e) {
      // throw new UnsupportedOperationException("Not supported yet.");
    }
  }
}

推荐答案

In the constructor for try2 you only add controls to the Frame if allow_search is true, but it’s never initialized so it will have the default value of false, hence nothing is added and you only get a white frame.

Changing the value of allow_search to true should make some controls visible in the frame.



Also, in the constructor <code>root is null so the position_tree method has little to work with.



If I may give you a tip; try creating it from scratch again. Start with a Frame and add a few controls to it. When you’ve got that working, start copying functionality from the applet code into your new code.



Hope this helps,

Fredrik

In the constructor for try2 you only add controls to the Frame if allow_search is true, but it's never initialized so it will have the default value of false, hence nothing is added and you only get a white frame.
Changing the value of allow_search to true should make some controls visible in the frame.

Also, in the constructor <code>root is null so the position_tree method has little to work with.

If I may give you a tip; try creating it from scratch again. Start with a Frame and add a few controls to it. When you've got that working, start copying functionality from the applet code into your new code.

Hope this helps,
Fredrik

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