在ListField显示额外行 | 在ListField显示额外行

本文介绍了在ListField显示额外行的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我试图在ListField的顶部显示一个额外的行 - 所谓的添加项，它几乎工作，但在最后一行项目4的未显示我的数据

I'm trying to display an extra row at the top of a ListField - called "Add Item" and it almost works, but the very last row "Item 4" of my data is not displayed.

你会如何解决这个问题？

How would you fix this issue?

请看看我的非常简单的测试code MyList.java 如下：

Please see my very simple test code MyList.java below:

package mypackage;

import java.util.*;
import net.rim.device.api.collection.*;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.decor.*;
import net.rim.device.api.util.*;

public class MyList extends UiApplication {
    public static void main(String args[]) {
        MyList app = new MyList();
        app.enterEventDispatcher();
    }

    public MyList() {
        pushScreen(new MyScreen());
    }
}

class MyScreen extends MainScreen {

    ObjectListField myList = new ObjectListField() {
        public void drawListRow(ListField list,
                        Graphics g,
                        int index,
                        int y,
                        int width) {
            if (index == 0) {
                Font i = getFont().derive(Font.ITALIC);
                g.setFont(i);
                g.drawText("Add Item", 0, y);
            } else {
                String str = (String) get(this, index - 1);
                g.drawText(str, 0, y);
            }
        }

        protected boolean navigationClick(int status, int time) {
            int index = myList.getSelectedIndex();
            String str = (index > 0 ? (String) get(this, index - 1) :
                "Add item");
            Status.show("You have clicked: " + str);
            return true;
        }
    };

    public MyScreen() {
        setTitle("How to display an extra row?");
        myList.set(new String[]{"Item 1","Item 2","Item 3","Item 4",});
        // myList.setSize(5);
        add(myList);
    }
}

我已经尝试添加 myList.setSize（5）; ，但得到由Vector.elementAt抛出一个ArrayIndexOutOfBoundsException（4）

I've tried adding myList.setSize(5); but get an ArrayIndexOutOfBoundsException thrown by Vector.elementAt(4)

更新：

在迈克尔的建议，我已经从ObjectListField切换到KeywordFilterField（这是我在实际的程序中实际使用的），现在我可以叫 myList.setSize（5）没有任何异常被抛出。

On Michael's suggestion I've switched from ObjectListField to KeywordFilterField (which is what I actually use in my real program) and now I can call myList.setSize(5) without any exception being thrown.

但仍未显示的最后一行：

But the last row is still not displayed:

package mypackage;

import java.util.*;
import net.rim.device.api.collection.*;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.decor.*;
import net.rim.device.api.util.*;

public class MyList extends UiApplication {
    public static void main(String args[]) {
        MyList app = new MyList();
        app.enterEventDispatcher();
    }

    public MyList() {
        pushScreen(new MyScreen());
    }
}

class MyScreen extends MainScreen {
    static final int EXTRA_ROWS = 1;

    MyItemList myItems = new MyItemList();
    KeywordFilterField myList = new KeywordFilterField() {
        protected boolean navigationClick(int status, int time) {
            int index = getSelectedIndex();
            String str = (index < EXTRA_ROWS ? "Add item" :
                ((MyItem) getElementAt(index - EXTRA_ROWS)).toString());
            Status.show("You have clicked - " + str);
            return true;
        }
    };

    public MyScreen() {
        setTitle(myList.getKeywordField());
        myList.setSourceList(myItems, new MyItem.MyProvider());
        myItems.doAdd(new MyItem(1, "Eins"));
        myItems.doAdd(new MyItem(2, "Zwei"));
        myItems.doAdd(new MyItem(3, "Drei"));
        myItems.doAdd(new MyItem(4, "Vier"));

        myList.setSourceList(myItems, new MyItem.MyProvider());
        myList.setCallback(new MyListFieldCallback());
        myList.setSize(myItems.size() + EXTRA_ROWS);
        myList.updateList();
        add(myList);
    }

    private class MyListFieldCallback implements ListFieldCallback {

        public void drawListRow(ListField list, Graphics g, int index, int y, int width) {
            if (index < EXTRA_ROWS) {
                Font i = getFont().derive(Font.ITALIC);
                g.setFont(i);
                g.drawText("Add Item", 0, y);
                return;
            }

            if (index >= EXTRA_ROWS) {
                MyItem item = (MyItem) ((KeywordFilterField) list).getElementAt(index - EXTRA_ROWS);
                g.drawText(item.toString(), 0, y);
                return;
            }

            g.drawText(list.getEmptyString(), 0, y);
        }

        public Object get(ListField listField, int index) {
            return null;
        }

        public int getPreferredWidth(ListField listField) {
            return 0;
        }

        public int indexOfList(ListField listField, String prefix, int start) {
            return 0;
        }
    }
}

class MyItemList extends SortedReadableList {
    public MyItemList() {
        super(new MyItem.MyComparator());
    }

    protected void doAdd(Object obj) {
        super.doAdd(obj);
    }

    protected boolean doRemove(Object obj) {
        return super.doRemove(obj);
    }
}

class MyItem {
    int _num;
    String _name;

    public MyItem(int num, String name) {
        _num = num;
        _name = name;
    }

    public String toString() {
        return _num + ": " + _name;
    }

    static class MyComparator implements Comparator {
        public int compare(Object obj1, Object obj2) {
            MyItem item1 = (MyItem) obj1;
            MyItem item2 = (MyItem) obj2;

            return item1.toString().compareTo(item2.toString());
        }
    }

    static class MyProvider implements KeywordProvider {
        public String[] getKeywords(Object obj) {
            MyItem item = (MyItem) obj;
            return new String[]{ Integer.toString(item._num), item._name };
        }
    }
}

我有一种感觉，那的setSize（4）（而不是5）被称为插图中 - 因为我看到最后一排了一会儿，然后再次消失了。

I have a feeling, that setSize(4) (instead of 5) is called inbetween - because I see the last row for a moment and then it disappears again.

感谢您！
亚历克斯

Thank you!Alex

推荐答案

下面是我自己的解决方案 - 覆盖的setSize（）的ListField的：

Here is my own solution - override the setSize() of the ListField:

（上面的截图中有EXTRA_ROWS = 3，仍然工作正常）。

(the screenshot above has EXTRA_ROWS = 3, which still works ok).

package mypackage;

import java.util.*;
import net.rim.device.api.collection.*;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.decor.*;
import net.rim.device.api.util.*;

public class MyList extends UiApplication {
    public static void main(String args[]) {
        MyList app = new MyList();
        app.enterEventDispatcher();
    }

    public MyList() {
        pushScreen(new MyScreen());
    }
}

class MyScreen extends MainScreen {
    static final int EXTRA_ROWS = 3;

    MyItemList myItems = new MyItemList();
    KeywordFilterField myList = new KeywordFilterField() {
        protected boolean navigationClick(int status, int time) {
            int index = getSelectedIndex();
            String str = (index < EXTRA_ROWS ? "Add item" :
                ((MyItem) getElementAt(index - EXTRA_ROWS)).toString());
            Status.show("You have clicked - " + str);
            return true;
        }

        public void setSize(int count) {
            super.setSize(count + EXTRA_ROWS);
        }
    };

    public MyScreen() {
        setTitle(myList.getKeywordField());
        myList.setSourceList(myItems, new MyItem.MyProvider());
        myItems.doAdd(new MyItem(1, "Eins"));
        myItems.doAdd(new MyItem(2, "Zwei"));
        myItems.doAdd(new MyItem(3, "Drei"));
        myItems.doAdd(new MyItem(4, "Vier"));

        myList.setSourceList(myItems, new MyItem.MyProvider());
        myList.setCallback(new MyListFieldCallback());
        add(myList);
    }

    private class MyListFieldCallback implements ListFieldCallback {

        public void drawListRow(ListField list, Graphics g, int index, int y, int width) {
            if (index < EXTRA_ROWS) {
                Font i = getFont().derive(Font.ITALIC);
                g.setFont(i);
                g.drawText("Add Item", 0, y);
                return;
            }

            if (index >= EXTRA_ROWS) {
                MyItem item = (MyItem) ((KeywordFilterField) list).getElementAt(index - EXTRA_ROWS);
                g.drawText(item.toString(), 0, y);
                return;
            }

            g.drawText(list.getEmptyString(), 0, y);
        }

        public Object get(ListField listField, int index) {
            return null;
        }

        public int getPreferredWidth(ListField listField) {
            return 0;
        }

        public int indexOfList(ListField listField, String prefix, int start) {
            return 0;
        }
    }
}

class MyItemList extends SortedReadableList {
    public MyItemList() {
        super(new MyItem.MyComparator());
    }

    protected void doAdd(Object obj) {
        super.doAdd(obj);
    }

    protected boolean doRemove(Object obj) {
        return super.doRemove(obj);
    }
}

class MyItem {
    int _num;
    String _name;

    public MyItem(int num, String name) {
        _num = num;
        _name = name;
    }

    public String toString() {
        return _num + ": " + _name;
    }

    static class MyComparator implements Comparator {
        public int compare(Object obj1, Object obj2) {
            MyItem item1 = (MyItem) obj1;
            MyItem item2 = (MyItem) obj2;

            return item1.toString().compareTo(item2.toString());
        }
    }

    static class MyProvider implements KeywordProvider {
        public String[] getKeywords(Object obj) {
            MyItem item = (MyItem) obj;
            return new String[]{ Integer.toString(item._num), item._name };
        }
    }
}

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