为什么构造函数不能在下面的代码中工作？

Question

在这里,我想使用构造函数动态分配表中的行数.datamodel是类,datamodel(int count)方法指定no.of行.

import javax.swing.table.AbstractTableModel;

@SuppressWarnings("serial")
public class datamodel extends AbstractTableModel{
    int row1;
    datamodel(int count){

        row1 = count;
        count = 0;
    }

    private String[] columnNames = {"Sl No","Material Code", "Material Name", "Select", "Received QTY", "Unit", "To Be Delivered", "PO No", "PO Sl"};//new String[9];
    //table has 100 rows and 9 columns
    private Object[][] data = new Object[row1][9]; 


    public int getColumnCount() { return columnNames.length; }
    public int getRowCount() { return data.length;}
    public String getColumnName(int col) {
        // TODO Auto-generated method stub
        return columnNames[col];
    }

    public Object getValueAt(int row, int col) {
        // TODO Auto-generated method stub
        return data[row][col];
    }

    @Override
    public void setValueAt(Object aValue, int row, int col) {
        // TODO Auto-generated method stub
        data[row][col] = aValue;
        fireTableCellUpdated(row, col);
    }

    public boolean isCellEditable(int rowIndex, int columnIndex) {
        // TODO Auto-generated method stub
        return true;
    }

    public Class getColumnClass(int col) {
        if((col == 4) || (col == 6))
            return Double.class;
            //return getValueAt(0, c).getClass();
        else if(col == 3)
            return Boolean.class;
        else
            return String.class;
    }
}

这是一个abstracttablemodel,我想将行数传递给datamodel.

Answer 1

int row1;
datamodel(int count){   
    row1 = count;
    count = 0;
}

您将局部变量 count设置为零.这对该领域没有影响row1.

现在,仔细看看你的代码.强烈建议:缩进代码,坚持命名约定,收集文件顶部的所有字段声明.然后我们更容易理解代码..

int row1;
private Object[][] data = new Object[row1][9];

datamodel(int count) {
    row1 = count;
    count = 0;
}

你想做什么:用构造函数传递值,以便初始化数组.您的方法将无法工作,因为数组是在构造函数方法执行之前创建的.所以你总是有一个Object [0] [9],不管你用构造函数传递什么.

您应该创建阵列内部的构造方法来代替:

int row1;
private Object[][] data;

datamodel(int count) {
    row1 = count;
    data = new Object[count][9];
}