从java内部访问javascript

Question

我知道有很多关于这方面的例子，但它们都感觉有点过时（甚至是太阳文档），所以我在这里要求确保我正在做的事情是最新的。我将如何从 java applet 内部与 javascript 进行对话？我正在寻找像如何调用alert()这样简单的东西。检查浏览器是否启用了 javascript 的方法的奖励积分（此小程序可以在学校环境中使用，其中确实有可能关闭 javascript）。非常感谢所有帮助，提前感谢...

代码：

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import netscape.javascript.JSObject;

public class TeamProject extends Applet implements ActionListener, MouseListener {
    char[][] charValues = new char[10][10];
    Table aTable;
    boolean allowUserInput = false;
    Button BtnStart;
    Button randomChangeBtn;
    boolean guessMode;
    JSObject jso;

    public void init() {
        //setup buttons
        BtnStart = new Button("add row/column");
        BtnStart.addActionListener((ActionListener)this);   //cast
        randomChangeBtn = new Button("change one value");
        randomChangeBtn.addActionListener((ActionListener)this);
        //add button
        this.add(BtnStart);
        //add image to Image objects
        Image imgO = getImage(getCodeBase(), "images/not.gif");
        Image imgX= getImage(getCodeBase(), "images/cross.gif");
        //setup table
        aTable = new Table(100, 100, 75, 55, 5, 5, imgX, imgO);
        //setBackground(Color.LIGHT_GRAY);
        super.resize(700, 700);
        //add mouse listener
        addMouseListener(this);
        //initially guessMode will be false
        guessMode = false;
        //to talk to javascript
        jso = JSObject.getWindow(this);
    }

    public void paint(Graphics g) {
        g.setColor(Color.black);
        aTable.draw(g);
    }

    //Mouse listener methods
    public void mousePressed (MouseEvent e) {
        if(!guessMode){
            if ((allowUserInput)) { //&&(aTable.isDrawable(e.getX(), e.getY())))
                aTable.swapSquareValue(e.getX(), e.getY());
                repaint();
            }
        } else {
            System.out.println("guessed row = " + e.getY() + " guessed col = " + e.getX());
            aTable.checkGuess(e.getX(), e.getY());
            //repaint();
        }
    }

    public void mouseClicked (MouseEvent e) {}
    public void mouseEntered (MouseEvent e) {}
    public void mouseReleased (MouseEvent e) {}
    public void mouseExited (MouseEvent e) {}

    //Button action listener
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == BtnStart) {
            aTable.addRow();
            aTable.addColumn();
            this.remove(BtnStart);
            this.add(randomChangeBtn);
            repaint();
        } else if (e.getSource() == randomChangeBtn) {
            //aTable.addRow();
            aTable.randomChangeFunc();
            repaint();
            guessMode = true;
        }
        allowUserInput = true;
        System.out.println(aTable.toString());
    }
}

和我的表类：

import java.awt.*;
import java.util.Random;

public class Table {
    private char[][]values = new char[10][10];  //probably better to use array of integer values(0 or 1)
    Image imgO;
    Image imgX;
    private int Rows;
    private int Columns;
    private int BoxWidth ;
    private int BoxHeight;
    public Point Pos = new Point();

    private int tableHeight;
    private int tableWidth;

    private int changedRow;
    private int changedCol;

    //constructor
    public Table(int x, int y, int width, int height, int col, int rows, Image X, Image O) {
        Rows = rows;
        Columns = col;
        BoxWidth = width;
        BoxHeight = height;
        Pos.x = x;
        Pos.y = y;

        imgX = X;
        imgO = O;

        tableHeight = Rows*BoxHeight;
        tableWidth = Columns*BoxWidth;
        this.setValues();
    }

    //draw table
    public void draw(Graphics g) {
        //draw vertical table lines
        for (int i = 0 ; i <= Columns ; i++)
            g.drawLine(i*BoxWidth + Pos.x, Pos.y, i*BoxWidth + Pos.x, tableHeight+Pos.y);

        //draw horizontal table line
        for(int i = 0 ; i <= Rows ; i++)
            g.drawLine(Pos.x, i*BoxHeight + Pos.y, tableWidth+Pos.x, i*BoxHeight + Pos.y);

        //draw values
        drawValues(g);
    }

    public void swapSquareValue(int x, int y) {
        if (this.isDrawable(x, y)) {
            int col = this.getColumn(x)-1;
            int row = this.getRow(y)-1;

            if(values[row][col] == 'X')
                values[row][col] = 'O';
            else if(values[row][col] == 'O')
                values[row][col] = 'X';
            else
                System.out.println("ERROR SWAPPING SQUARE VALUE");
        } else
            System.out.println("says not drawable");
    }

    public char getValue(int col, int row) {
        return values[row][col];
    }

    //return true if (x,y) is a point in the table
    public boolean isDrawable(int x, int y) {
        if((this.getRow(y)!=-1)||(this.getColumn(x)!=-1))
            return true;
        else
            return false;
    }

    public void addRow() {
        Rows++;
        tableHeight = (Rows*BoxHeight);
        int numOfXs = 0;
        for (int c=0; c < Columns; c++) {
            numOfXs = 0;
            for(int r = 0; r < Rows - 1; r++) {
                if(values[r][c] == 'X'){
                    numOfXs++;
                    System.out.println("in column " + c + "new x found at " + r + " " + c + ", numOfXs = " + numOfXs);
                }
                if(numOfXs % 2 == 0) {
                    values[Rows - 1][c] = 'O';
                } else{
                    values[Rows - 1][c] = 'X';
                }
            }//end inner for
            System.out.println("end of column " + c);
        }//end outer for
    }// end function

    public void addColumn() {
        Columns++;
        tableWidth = (Columns*BoxWidth);
        int numOfXs = 0;

        for (int r=0; r < Rows; r++) {
            numOfXs = 0;
            for(int c = 0; c < Columns - 1; c++) {
                if(values[r][c] == 'X') {
                    numOfXs++;
                    System.out.println("in row " + r + "new x found at " + r + " " + c + ", numOfXs = " + numOfXs);
                }
                if(numOfXs % 2 == 0) {
                    values[r][Columns - 1] = 'O';
                }
                else {
                    values[r][Columns - 1] = 'X';
                }
            }//end inner for
            System.out.println("end of row " + r);
        }
    }

    //does not add or remove values
    public void setColumn(int col) {
        Columns = col;
        tableWidth = (Columns*BoxWidth);
    }

    //does not add or remove values
    public void setRows(int row) {
        Rows = row;
        tableHeight = (row*BoxHeight);
    }

    public String toString() {
        String ValueString = "Displaying charValues[" + Rows + "][" + Columns + "]\n";
        for (int r=0; r < Rows; r++) {
            for (int c=0; c < Columns; c++) {
                ValueString += (char)values[r][c];
            }
            ValueString += "\n";        //next line
        }
        return ValueString;
    }

    private void drawValues(Graphics g) {
        Point drawPoint = new Point();
        for (int r=0; r < Rows; r++)
            for (int c=0; c < Columns; c++) {
                drawPoint.x = Pos.x+BoxWidth*c;
                drawPoint.y = Pos.y+BoxHeight*r;
                //g.setColor(Color.white);
                //g.fillRect(drawPoint.x+1, drawPoint.y+1, BoxWidth-1, BoxHeight-1);
                if (values[r][c] == 'X') {
                    g.drawImage(imgX,drawPoint.x+1, drawPoint.y+1, BoxWidth-1, BoxHeight-1, null);
                } else {
                    g.drawImage(imgO,drawPoint.x+1, drawPoint.y+1, BoxWidth-1, BoxHeight-1, null);
                }
                //System.out.print((char)values[r][c]);
            }
        g.setColor(Color.black);
    }

    //fills array with random values
    private void setValues() {
        for (int r=0; r < Rows; r++)
            for (int c=0; c < Columns; c++) {
                values[r][c] = this.randomChar();
            }
    }

    //randomly return 'X' or 'O'
    private char randomChar() {
        char randomValue;
        Random RandomGen = new Random();

        if (RandomGen.nextInt(2)==0)
            randomValue = 'O';
        else
            randomValue ='X';
        return randomValue;
    }

    private int getColumn(int x) {
        int offsetx=0;
        for (int i = 0 ; i < Columns ; i++) {
            offsetx = i*BoxWidth;
            if((x>Pos.x+offsetx)&& (x<Pos.x+offsetx+BoxWidth))
                return i+1;
        }
        return -1;
    }

    private int getRow(int y) {
        int offsety=0;
        for (int i = 0 ; i < Rows ; i++) {
            offsety = i*BoxHeight;
            if((y>Pos.y+offsety)&& (y<Pos.x+offsety+BoxHeight))
                return i+1;
        }
        return -1;
    }

    public void randomChangeFunc() {
        //get random row and column
        Random rand=new Random();

        int randRow = rand.nextInt(Rows);
        int randCol = rand.nextInt(Columns);

        System.out.println("randRow = " + randRow + " randCol = " + randCol);
        /*THIS SHOULD BE HANDLED BY swapSquareValue(randCol,randRow)
        /*BUT GETTING ERRORS (notDrawable). THE FOLLOWING CODE IS A WORK-AROUND
        */
        if(values[randRow][randCol] == 'X')
            values[randRow][randCol] = 'O';
        else if(values[randRow][randCol] == 'O')
            values[randRow][randCol] = 'X';
        else
            System.out.println("ERROR SWAPPING SQUARE VALUE");
        //set globals
        changedRow = randRow;
        changedCol = randCol;
    }

    public void checkGuess(int guessCol, int guessRow){
        int gCol = this.getColumn(guessCol)-1;
        int gRow = this.getRow(guessRow)-1;
        System.out.println("gCol = " + gCol + " gRow = " + gRow);
        if(gCol == changedCol && gRow == changedRow) {
            System.out.println("CORRECT!!!");
        } else
            System.out.println("incorrect :(");
    }
}

将我的 javac 命令更改为：

javac -classpath /usr/lib/Java6u1/jre/lib/plugin.jar TeamProject.java

忽略我的“表”类，并且在我提到的地方出现错误。有什么想法吗？

Answer 1

请参阅这篇文章。如果您尝试在此页面上从小程序调用 JS，它肯定可以工作，因为小程序更新操作后出现 js 异常:)

import netscape.javascript.JSObject

public void init()
{
jso = JSObject.getWindow(this);
}

 public void actionPerformed(ActionEvent e) {
     if(jso != null )
         try {
                jso.call("updateWebPage", new String[] {txt.getText()});
             }
             catch (Exception ex) {
                 ex.printStackTrace();
             }
 }

编辑：
对于类路径问题，您需要将 plugin.jar 添加到位于 %JAVA_HOME%\jre\lib\plugin.jar

EDIT2:
的类路径中
我认为你的问题是类 Table 也没有编译：

尝试 javac -classpath /usr/lib/Java6u1/jre/lib/plugin.jar TeamProject.java Table.java 或使用通配符，例如 *.java。

也许您应该考虑使用 IDE，例如 Eclipse 或 Netbeans 来编译和运行项目，而不是使用命令行工具。

Answer 2

根据要求，在嵌入的页面上调用警报的示例（在 Opera 10.01、FF 3.5.4、IE6 中测试）。

请注意小程序标记中的 MAYSCRIPT，此必须存在才能启用 java-javascript 通信。默认情况下，由于安全原因，对 JSObject 的访问被禁用。

HTML：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
  "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
  <title>Test</title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
  <applet code="HelloWWW.class" width="300px" height="100px"  MAYSCRIPT></applet>
</body>
</html>

Java（使用 javac -cp .;[pathtojre]/jre/lib/plugin.jar HelloWWW.java 编译）

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import netscape.javascript.*;

public class HelloWWW extends Applet implements ActionListener {
  Button runButton;
  public void init() {
    runButton = new Button("Run: alert(\"Hello WWW\")");
    add(runButton);
    runButton.addActionListener(this);
  }
  public void actionPerformed(ActionEvent evt) {
    if (evt.getSource() == runButton) {
      try {
        //get JSOBject
        JSObject jso = JSObject.getWindow(this);
        //call alert with parameter passed as Object array
        jso.call("alert", new Object[]{"Hello WWW"});
      } catch (JSException e) {
        e.printStackTrace();
      }
      runButton.setLabel("Did it!");
      repaint();
    }
  } 
}

另请检查 Java 到 Javascript 通信 和 Mozilla 开发人员：JSObject 了解更多信息。