我有一个包含多个项目的列表字段。我想从列表中选择一个项目并拖放到列表中的另一个项目。将项目放在另一个项目上后，项目的位置应该互换。 （示例： - 如果我从列表中选择第一项并将此项拖放到列表中的第4项 之后，两个项目的项目位置应该改变第4个位置的第1个项目和第1个位置的第4个项目）
我不知道该怎么做。请帮我完成这项任务。
public class ListScreen extends MainScreen implements ListFieldCallback {
// private ObjectChoiceField choices;
private int x, y;
int start = 0 , end=0;
private int startPos;
// private int pos;
private ObjectListField list;
private Object[] listData = new Object[] { "Ram", "Sunny", "Ramit",
"Vishal","Ravinder","Manoj","Ravi","Vikas","Santosh","Ravi","Deepak","Sharma","Nvn" };
public ListScreen() {
init();
}
private void init() {
list = new ObjectListField(FOCUSABLE);
list.setRowHeight(45);
list.setCallback(this);
list.set(listData);
add(list);
}
public void drawListRow(ListField listField, Graphics graphics, int index,
int y, int width) {
graphics.drawText(listData[index].toString(), 25, y + 10);
}
public Object get(ListField listField, int index) {
return listData[index];
}
public int getPreferredWidth(ListField listField) {
return getPreferredWidth();
}
public int indexOfList(ListField listField, String prefix, int start) {
// TODO Auto-generated method stub
return 0;
}
// protected boolean navigationMovement(int dx, int dy, int status, int
// time) {
//
// return super.navigationMovement(dx, dy, status, time);
// }
protected boolean touchEvent(TouchEvent message) {
int eventCode = message.getEvent();
// Get the screen coordinates of the touch event
int touchX = message.getX(1);
int touchY = message.getY(1);
if (eventCode == TouchEvent.CLICK) {
calculateStart(touchY);
// Dialog.alert("You clicked at (" + touchX + "," + touchY + ")");
}
if (eventCode == TouchEvent.MOVE) {
x = touchX;
y = touchY;
invalidate();
}
if (eventCode == TouchEvent.UNCLICK) {
int unClickx = message.getX(1);
int unClicky = message.getY(1);
System.out.println("unclick at:" + unClickx + "::::" + unClicky);
calculatePosition(unClicky);
}
return true;
}
private void calculatePosition(int dy) {
if (dy != 0) {
end = dy / 45;
System.out.println(start + ":::" + end);
Object temp = listData[start];
listData[start] = listData[end];
listData[end] = temp;
invalidate();
}
}
private void calculateStart(int dy){
if(dy!=0)
start = dy/45;
}
}
答案 0 :(得分：3)
[ 更新了触摸和非触摸设备 ]：尝试以下代码;我在Torch（9800），Storm（9550），Bold（9700）上测试过：
import net.rim.device.api.system.Characters;
import net.rim.device.api.ui.Graphics;
import net.rim.device.api.ui.TouchEvent;
import net.rim.device.api.ui.component.LabelField;
import net.rim.device.api.ui.component.ListField;
import net.rim.device.api.ui.component.ListFieldCallback;
import net.rim.device.api.ui.component.ObjectListField;
import net.rim.device.api.ui.container.MainScreen;
import net.rim.device.api.ui.container.VerticalFieldManager;
import net.rim.device.api.ui.decor.BackgroundFactory;
public class ListTestScreen extends MainScreen {
private VerticalFieldManager mainManager = new VerticalFieldManager();
public ListTestScreen() {
mainManager.add(new LabelField("My Title"));
mainManager.add(new LabelField("My List:"));
mainManager.add(new MyList());
mainManager.add(new LabelField("Something else"));
add(mainManager);
}
}
class MyList extends VerticalFieldManager implements ListFieldCallback {
private int mouseDownY, mouseUpY;
private static int rowHeight = 45;
private int mouseDownRowIndex, mouseUpRowIndex;
int firstSelectedRow=-1, secondSelectedRow=-1;
private int touchX;
private int touchY;
private boolean showShadow = false;
private ObjectListField list;
private Object[] listData = new Object[] { "Ram", "Sunny", "Ramit",
"Vishal","Ravinder","Manoj","Ravi","Vikas","Santosh","Ravi","Deepak","Sharma","Nvn" };
public MyList() {
init();
setBackground(BackgroundFactory.createLinearGradientBackground(0x0FCFC0, 0x0CCCC0, 0x09C9C0, 0x01C1C0));
}
private void init() {
list = new ObjectListField(FOCUSABLE);
list.setRowHeight(rowHeight);
list.setCallback(this);
list.set(listData);
add(list);
}
private void interchangeRows(int r1, int r2) {
Object temp = listData[r1];
listData[r1] = listData[r2];
listData[r2] = temp;
invalidate();
}
public void drawListRow(ListField listField, Graphics graphics, int index,
int y, int width) {
graphics.drawText(listData[index].toString(), 25, y + 10);
}
public Object get(ListField listField, int index) {
return listData[index];
}
public int getPreferredWidth(ListField listField) {
return getPreferredWidth();
}
public int indexOfList(ListField listField, String prefix, int start) {
// TODO Auto-generated method stub
return 0;
}
public int indexOfRowAt(int posY) {
int index =(int) Math.floor(posY / rowHeight * 1.0);
return index;
}
protected boolean keyChar(char ch, int status, int time) {
if(ch==Characters.SPACE) {
if(firstSelectedRow ==-1) {
firstSelectedRow = list.getSelectedIndex();
return true;
} else {
secondSelectedRow = list.getSelectedIndex();
if(firstSelectedRow == secondSelectedRow) {
firstSelectedRow = secondSelectedRow = -1;
invalidate();
return true;
} else {
interchangeRows(firstSelectedRow, secondSelectedRow);
firstSelectedRow = secondSelectedRow = -1;
return true;
}
}
}
return super.keyChar(ch, status, time);
}
protected void paint(Graphics graphics) {
if(firstSelectedRow!=-1) {
int x = 0, y = firstSelectedRow*rowHeight;
int savedColor = graphics.getColor();
int preAlpha = graphics.getGlobalAlpha();
graphics.setGlobalAlpha(90) ;
graphics.setColor(0xFF22FF);
graphics.fillRect(0, y, getWidth(), rowHeight);
graphics.setColor(savedColor);
graphics.setGlobalAlpha(preAlpha) ;
}
super.paint(graphics);
if(showShadow && mouseDownRowIndex != -1) {
int preAlpha = graphics.getGlobalAlpha();
graphics.setGlobalAlpha(100) ;
graphics.drawText(listData[mouseDownRowIndex].toString(), 25, touchY);
graphics.setGlobalAlpha(preAlpha) ;
}
}
protected boolean touchEvent(TouchEvent message) {
int eventCode = message.getEvent();
// Get the screen coordinates of the touch event
touchX = message.getX(1);
touchY = message.getY(1);
if(eventCode == TouchEvent.DOWN) {
mouseDownY = touchY;
mouseDownRowIndex = indexOfRowAt(mouseDownY);
showShadow = true;
invalidate();
return true;
}
else if(eventCode == TouchEvent.UP) {
showShadow = false;
mouseUpY = touchY;
mouseUpRowIndex = indexOfRowAt(mouseUpY);
if(mouseDownRowIndex != mouseUpRowIndex) {
interchangeRows(mouseDownRowIndex, mouseUpRowIndex);
mouseDownRowIndex = mouseUpRowIndex = -1;
return true;
}
mouseDownRowIndex = mouseUpRowIndex = -1;
invalidate();
} else if(eventCode == TouchEvent.MOVE) {
invalidate();
return true;
}
return super.touchEvent(message);
}
}
[<强>编辑：
对于支持触控的设备：第一个选定项目的文字阴影会随光标一起移动。
对于非触控设备：我使用空格键来选择要互换的项目。选择一个项目，按空格键，选择第二个项目，再次按空格键，项目互换!!在已选择的项目上按空格键将取消选择该项目。
让我知道它是否有效。
列表字段自定义的进一步增强已发布在中 这StackOverflow Answer。