java - 从 Java Graphics 实例中获取字符串

Question

我有一些代码片段，如下所示

:

Graphics g;      // Java Graphics class

g.drawString("text", x, y);   // x, y for coordinate info, "text" is now an image object

:

我可以从 Graphics 实例中将“文本”恢复为字符串吗？

因为我想使用字符串数据作为从表中获取一些数据的键。

Answer 1

最好的方法可能是将文本存储在一个String变量中，然后从那里获取它。

Answer 2

I solved this problem by adding two tables that each memorize the X and Y coordinate for the node instance being generated at the presentation layer and at model layer.

At runtime, node images continue to change its position and these events are all updated.

When I click on a node image on Panel instance, it gives the id of the node instance.

The reason why two tables are required is that only when the id returned by calling the X, Y position of the node image refers to the same node object is the evidence that the event is for the node object represented by the clicked node image. Now I realize I could have used multi-key table.

import java.util.ArrayList;
import java.util.List;

// * Represents node at presentation layer and its model

public class NodeObject 
{
// * node id
private int id;

// * coordinate on Panel
public double x;
public double y;

// * coordinate change
private  double dx;
private  double dy;

// * isFixed
public  boolean fixed;

// * node name
public String nodeName;

// * connected node object id list ( redundant when edge is used )
public List<Integer> connectedNodeIdList;

// * connected edge object id list
private List<Integer> connectedEdgeIdList;

// * constructor
public NodeObject()
{}

// * constructor
public NodeObject( int _id )
{
    // * initialization
    this.id = _id;

    // * default
    this.nodeName = "default";

    // * connected node id list
    this.connectedNodeIdList = new ArrayList<Integer>();
}

// * Constructor ( when node name is given )
public NodeObject( int _id, String _nodeName )
{
    // * node id
    this.id = _id;

    // * node name
    this.nodeName = _nodeName;

    // * connected node id list
    this.connectedNodeIdList = new ArrayList<Integer>();

    // * connected edge id list 
    this.connectedEdgeIdList = new ArrayList<Integer>();
}

// * set node name
public void setNodeName( String nName )
{
     this.nodeName = nName;
}

// * get node id
public int getNodeId()
{
    return this.id;
}

// * get node name
public String getNodeName()
{
    return this.nodeName;
}

// * get node name and id in String
public String getNodeNameWithID()
{
      String id = Integer.toString( this.getNodeId() );

      return ( this.nodeName + "-" +id );
}

// * store connected node
public boolean addSingleNode( int nid )
{
    if ( this.connectedNodeIdList.contains( nid ) == true )
    {
        return true;   // this node is already connected
    }
    else
    {
        // * register
        this.connectedNodeIdList.add( nid );

        // * this is the first time this node is connected
        return false;
    }
}

// * unregister a node
public boolean removeConnectedSingleNode( int nid )
{
      // * it was registered before
      if ( this.connectedNodeIdList.contains( nid ) == true )
      {
           this.connectedNodeIdList.remove( nid );

           return true; //  it had been registered and now unregistered ( only at model layer )
      }
      else
      {
           return false;   // it has not been registered before.
      }
}

// * add edge id
public boolean addSingleEdge( int eid )
{
    if ( this.connectedEdgeIdList.contains( eid ) == true )
    {
        return true;   // already registered edge
    }
    else
    {
        // * registered
        this.connectedEdgeIdList.add( eid );

        // * this is the first time this edge was connected
        return false;
    }
}

// * remove edge
public boolean removeConnectedSingleEdge( int eid )
{
      // * registered before
      if ( this.connectedEdgeIdList.contains( eid ) == true )
      {
           this.connectedEdgeIdList.remove( eid );

           return true; // now removed ( model level )
      }
      else
      {
           return false;   // it has not been registered before
      }
}

// * return edge id list
public List<Integer> getEdgeIdList()
{
    return this.connectedEdgeIdList;
}

//////// for visualization on Panel instance ///////

// * X coordinate setting
public void setNodePositionX( Double xPos )
{
     this.x = xPos;
}

// * Y coordinate setting
public void setNodePositionY( Double yPos )
{
     this.y = yPos;
}

// * change of node position
public void changeNodePosition( Double changeX, Double changeY )
{
     this.x = this.x + changeX;
     this.y = this.y + changeY;
}

// * position difference
public void changeNodePositionDifference( Double changeDX, Double changeDY )
{
     this.dx = this.dx + changeDX;
     this.dy = this.dy + changeDY;
}

// * update node position difference
public void updateNodePositionDifference( Double changeDX, Double changeDY )
{
     this.dx = changeDX;
     this.dy = changeDY;
}

// * get X pos
public double getNodePositionX()
{
     return this.x;
}

// * get Y pos
public double getNodePositionY()
{
     return this.y;
}

// * get dx
public double getNodePositionDX()
{
     return this.dx;
}

// * get dy
public double getNodePositionDY()
{
     return this.dy;
}
}

And the Graph class goes like below

public class Graph extends Panel implements Runnable, MouseListener, MouseMotionListener, ItemListener
{   

// * number of nodes
public int nnodes;

// * node generator
public NodeGenerator ndGenerator;

// * memorize the node coordinate
public Map<Integer, Integer> xCoordinateTbl;   // key : coordinate / value : node id
public Map<Integer, Integer> yCoordinateTbl;

// * node tbl
public Map<Integer, NodeObject> nodeTbl;

Once mouse click event occurs, it is handled like below

public void actionPerformed(ActionEvent event) 
{
    // * get node id of the node object being referred to at the presentation layer
    Integer nid = getNodeId( e.getPoint().x, e.getPoint().y );

    // * remove node on the presentation layer and of the model at the same time
     removeSingleNode( nid );  
}

Answer 3

不，该Graphics实例只是将屏幕上的文本或图像绘制为像素。它不记得你画的是什么文字，所以它不能告诉你。

您必须以其他方式将文本存储在程序中，以便以后可以将其取回以用于您需要的任何目的（例如从表中获取数据）。