[移动图书馆]在手持设备上一步一步实现Table(1)
J2ME,J2EE,移动开发,移动企业开发,图书馆 在我开发移动图书馆过程中，由于要用到桌面程序中的表格UI，J2ME 高级界面API没有，就只好用低级API实现了，现在该Table的功能已经比较完善，我将通过几篇Blog，一步一步地把这个手持设备上使用的Table的源码共享给大家，希望对大家能有所用处。
我是借鉴Swing MVC的思想来实现这个Table组件的，包括一个TableModel接口和Table类。很明显，TableModel接口是Table数据模型，容纳Table要显示的数据，和与这些数据相关的getter方法供Table类使用。了解Swing Table的实现机制的朋友理解我的Table组件的思想应该没有任何问题，这里我也不想多做什么解释了，看代码吧，思想全都在里面。
下面代码一共有3个文件，一个主Midlet文件，推荐大家在NetBeans IDE中建工程，非常好用。
/*
* TableModel.java
*
* Created on 2006年7月2日, 下午3:53
*
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
*/
package cn.edu.uestc.table;
/**
* <P>Returns the number of rows the model contains.
*/
public int getRowCount();
/**
* <P>Returns the text for the column header.
*/
public String getColumnHeaderText(int col);
/**
* <P>Returns whether column headers are displayed.
*/
public boolean hasColumnHeaders();
/**
* <P>Returns the value for the specified cell.
*/
public String getValueAt(int row,int col);
}
/*
* Table.java
*
* Created on 2006年7月2日, 下午3:55
*
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
*/
package cn.edu.uestc.table;
import javax.microedition.lcdui.*;
/**
*
* @author pandaxiaoxi
*/
public class Table extends Canvas {
public static final int ORIENT_VERTICAL = 0;
public static final int ORIENT_HORIZONTAL = 1;
private TableModel model = null;
private Font font = Font.getDefaultFont();
private int columnWidth = 85;
private int orientation = ORIENT_VERTICAL; //每列竖直显示
private boolean separatorLines = true;
/**
* <P>Creates an instance with the associated model.
*/
public Table(TableModel model) {
if(null == model) {
throw new IllegalArgumentException("Cannot pass a null model to a table");
}
this.model = model;
}
public Table(){
}
public void setTableModel(TableModel model){
if(null == model) {
throw new IllegalArgumentException("Cannot pass a null model to a table");
}
this.model = model;
}
/**
* <P>Sets the column width
*/
public void setColumnWidth(int width) {
if(0 < width) {
columnWidth = width;
}
}
/**
* <P>Returns the column width.
*/
public int getColumnWidth() {
return columnWidth;
}
/**
* <P>Sets the table orientation.
*
* @param orient either <CODE>ORIENT_VERTICAL</CODE> or <CODE>ORIENT_HORIZONTAL</CODE>
*/
public void setOrientation(int orient) {
switch(orient) {
case ORIENT_VERTICAL:
case ORIENT_HORIZONTAL:
orientation = orient;
break;
default:
System.out.println("Invalid orientation!");
break;
}
}
/**
* <P>Returns the table orientation.
*/
public int getOrientation() {
return orientation;
}
/**
* <P>Toggles whether separator lines are used between rows and between columns.
*/
public void setSeparatorLines(boolean sep) {
separatorLines = sep;
}
/**
* <P>Returns whether separator lines are used.
*/
public boolean getSeparatorLines() {
return separatorLines;
}
public void paint(Graphics g) {
int width = getFullWidth(), height = getFullHeight();
// clear the background
g.setColor(255,255,255);
g.fillRect(0,0,width,height);
g.setColor(0,0,0);
// draw the border for the table
g.drawRect(0,0,width,height);
if(separatorLines) {
int vbars = 0;
int hbars = 0;
// determine how many vertical and horizontal bars to draw
switch(orientation) {
case ORIENT_VERTICAL:
vbars = model.getColumnCount();
hbars = model.getRowCount();
if(model.hasColumnHeaders()) hbars++;
break;
case ORIENT_HORIZONTAL:
vbars = model.getRowCount();
hbars = model.getColumnCount();
if(model.hasColumnHeaders()) vbars++;
break;
}
boolean flag = false;
// draw horizontal row with different color
for(int index = 0;index < hbars;index++) {
int y = index * getVerticalSpacing();
if(index == 0){
g.setColor(152, 152, 152);
g.fillRect(0,y, width-1,getVerticalSpacing());
continue;
}
if(flag){
g.setColor(215,215,215);
flag = false;
}else{
g.setColor(255,255,255);
flag = true;
}
g.fillRect(0,y, width-1,getVerticalSpacing());
}
g.setColor(70,95,182);
g.setColor(0,0,0);
// draw horizontal bars
for(int index = 0;index < hbars;index++) {
int y = index * getVerticalSpacing();
g.drawLine(0,y,width - 1,y);
}
// draw vertical bars
for(int index = 0;index < vbars;index++) {
//int x = index * getHorizontalSpacing();
int x = index * columnWidth;
g.drawLine(x,0,x,height - 1);
}
}
int rowOffset = 0; // used to flag whether headers are displayed
// if using column headers, let's show them first
if(model.hasColumnHeaders()) {
for(int col = 0;col < model.getColumnCount();col++) {
// the row should be -1 for this call
drawTableCell(g,0,col,model.getColumnHeaderText(col));
}
// set the row offset
rowOffset = 1;
}
// now draw each element of the table
for(int row = 0;row < model.getRowCount();row++) {
for(int col = 0;col < model.getColumnCount();col++) {
String value = model.getValueAt(row,col);
// now use the rowOffset to adjust if column headers were used
drawTableCell(g,row + rowOffset,col,value);
}
}
}
private void drawTableCell(Graphics g,int row,int col,String value) {
int valueSize = columnWidth - 4; // to make sure it fits in a column space
if(0 < valueSize) {
while(valueSize < font.stringWidth(value)) {
value = value.substring(0,value.length() - 1);
// if the string is now empty, just exit... we can't display it...
if(0 == value.length()) {
return;
}
}
int x = getXFor(row,col) + 1;
int y = getYFor(row,col) + 2;
g.drawString(value,x,y,Graphics.LEFT | Graphics.TOP);
}
}
private int getXFor(int row,int col) {
if(ORIENT_VERTICAL == orientation) {
return col * getHorizontalSpacing();
} else {
return row * getHorizontalSpacing();
}
}
private int getYFor(int row,int col) {
if(ORIENT_VERTICAL == orientation) {
return row * getVerticalSpacing();
} else {
return col * getVerticalSpacing();
}
}
private int getVerticalSpacing() {
return font.getHeight() + 3; // font height + 1 line above + 1 line below + 1 line for separator
}
private int getHorizontalSpacing() {
int rightBorder = getFullWidth() - 1;
if(ORIENT_VERTICAL == orientation) {
return rightBorder / model.getColumnCount();
} else {
return rightBorder / model.getRowCount();
}
}
// Scrollable interface
public int getFullWidth() {
int count = 0;
if(ORIENT_VERTICAL == orientation) {
count = model.getColumnCount();
} else {
count = model.getRowCount();
if(model.hasColumnHeaders()) count++;
}
return (count * columnWidth) + 1;
}
public int getFullHeight() {
int count = 0;
if(ORIENT_VERTICAL == orientation) {
count = model.getRowCount();
if(model.hasColumnHeaders()) count++;
} else {
count = model.getColumnCount();
}
return (getVerticalSpacing() * count) + 1;
}
public int getVerticalScrollAmount() {
return getVerticalSpacing();
}
public int getHorizontalScrollAmount() {
return getHorizontalSpacing();
}
public void render(Graphics g) {
paint(g);
}
}
/*
* TableDemo.java
*
* Created on 2006年7月2日, 下午3:59
*/
package cn.edu.uestc.table;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
/**
*
* @author pandaxiaoxi
* @version
*/
public class TableDemo extends MIDlet {
private Display display = null;
public void startApp() {
display = Display.getDisplay(this);
Table table = new Table(new TableModel(){
public int getColumnCount(){return 3;}
public int getRowCount(){return 5;}
public String getColumnHeaderText(int col){return Integer.toString(col)+"列";}
public boolean hasColumnHeaders(){return true;}
public String getValueAt(int row,int col){return Integer.toString(row)+"."+Integer.toString(col);}
});
display.setCurrent(table);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
}
/**
*
* @author pandaxiaoxi
*/
public interface TableModel {
/**
* <P>Returns the number of columns the model contains.
*/
public int getColumnCount();
