对于我当前的代码，它会先下载图像，然后只显示数据并导致设备滞后。
public Custom_ListField(Vector content, boolean islatest) {
this.content = content;
this.islatest = islatest;
newsid = new int[content.size()];
title = new String[content.size()];
category = new String[content.size()];
date = new String[content.size()];
imagepath = new String[content.size()];
catsid = new int[content.size()];
imagebitmap = new Bitmap[content.size()];
ischeck = new boolean[content.size()];
for (int i = 0; i < content.size(); i++) {
newslist = (List_News) content.elementAt(i);
newsid[i] = newslist.getID();
title[i] = newslist.getNtitle();
category[i] = newslist.getNewCatName();
date[i] = newslist.getNArticalD();
imagepath[i] = newslist.getImagePath();
catsid[i] = newslist.getCatID();
ischeck[i] = false;
if (!imagepath[i].toString().equals("no picture")) {
if (Config_GlobalFunction.isConnected())
imagebitmap[i] = Util_ImageLoader.loadImage(imagepath[i]);
else
imagebitmap[i] = localimage;
}
}
initCallbackListening();
}
private void initCallbackListening() {
callback = new ListCallback();
this.setCallback(callback);
this.setRowHeight(-2);
}
private class ListCallback implements ListFieldCallback {
public ListCallback() {
}
public void drawListRow(ListField listField, Graphics graphics,
final int index, int y, int width) {
currentPosition = index;
if (!imagepath[index].toString().equals("no picture")) {
float ratio = (float) ((float) localimage.getHeight() / (float) imagebitmap[index]
.getHeight());
Bitmap temp = new Bitmap(
(int) (imagebitmap[index].getWidth() * ratio),
(int) (imagebitmap[index].getHeight() * ratio));
imagebitmap[index].scaleInto(temp, Bitmap.FILTER_BILINEAR,
Bitmap.SCALE_TO_FIT);
imagebitmap[index] = temp;
graphics.drawBitmap(
Display.getWidth()
- localimage.getWidth()
- 5
+ ((localimage.getWidth() - imagebitmap[index]
.getWidth()) / 2),
y
+ (listField.getRowHeight(index) - imagebitmap[index]
.getHeight()) / 2,
imagebitmap[index].getWidth(),
imagebitmap[index].getHeight(), imagebitmap[index], 0,
0);
graphics.setColor(Color.BLACK);
text = Config_GlobalFunction
.wrap(title[index], Display.getWidth()
- imagebitmap[index].getWidth() - 15);
for (int i = 0; i < text.size(); i++) {
int liney = y + (i * Font.getDefault().getHeight());
graphics.drawText(
(String) text.elementAt(i),
5,
liney + 3,
DrawStyle.TOP | DrawStyle.LEFT | DrawStyle.ELLIPSIS,
Display.getWidth() - imagebitmap[index].getWidth()
- 10);
}
} else {
graphics.setColor(Color.BLACK);
text = Config_GlobalFunction.wrap(title[index],
Display.getWidth() - 10);
for (int i = 0; i < text.size(); i++) {
int liney = y + (i * Font.getDefault().getHeight());
graphics.drawText(
(String) text.elementAt(i),
5,
liney + 3,
DrawStyle.TOP | DrawStyle.LEFT | DrawStyle.ELLIPSIS,
Display.getWidth() - 10);
}
}
if (text.size() == 2) {
graphics.setColor(Color.GRAY);
graphics.drawText(date[index], 5, y
+ Font.getDefault().getHeight() + 3);
if (islatest) {
graphics.setColor(Color.RED);
graphics.drawText(category[index], Font.getDefault()
.getAdvance(date[index]) + 15, y
+ Font.getDefault().getHeight() + 3);
}
} else if (text.size() == 3) {
graphics.setColor(Color.GRAY);
graphics.drawText(date[index], 5, y
+ Font.getDefault().getHeight() * 2 + 3);
if (islatest) {
graphics.setColor(Color.RED);
graphics.drawText(category[index], Font.getDefault()
.getAdvance(date[index]) + 15, y
+ Font.getDefault().getHeight() * 2 + 3);
}
}
if (!imagepath[index].toString().equals("no picture"))
setRowHeight(index, imagebitmap[index].getHeight() + 10);
else {
if (text.size() == 2)
setRowHeight(index, getRowHeight() + 9);
else if (text.size() == 3) {
setRowHeight(index, getRowHeight() * 15 / 10 + 9);
}
}
graphics.setColor(Color.WHITE);
graphics.drawRect(0, y, width, listField.getRowHeight(index));
ischeck[index] = true;
}
}
我希望imagebitmap[i] = Util_ImageLoader.loadImage(imagepath[i]);在显示数据之后运行，这样就不需要卡在那里了。然而，我试图把它放在里面drawListRow，它工作但很慢，因为最初显示它会运行 0-8 次，然后当我滚动列表字段时，它会再次运行。它被下载并再次下载。
更新
public class Util_LazyLoader implements Runnable {
String url = null;
BitmapDowloadListener listener = null;
public Util_LazyLoader(String url, BitmapDowloadListener listener) {
this.url = url;
this.listener = listener;
}
public void run() {
Bitmap bmpImage = getImageFromWeb(url);
listener.ImageDownloadCompleted(bmpImage);
}
private Bitmap getImageFromWeb(String url) {
HttpConnection connection = null;
InputStream inputStream = null;
EncodedImage bitmap;
byte[] dataArray = null;
try {
connection = (HttpConnection) (new ConnectionFactory())
.getConnection(url + Database_Webservice.ht_params)
.getConnection();
int responseCode = connection.getResponseCode();
if (responseCode == HttpConnection.HTTP_OK) {
inputStream = connection.openDataInputStream();
dataArray = IOUtilities.streamToBytes(inputStream);
}
} catch (Exception ex) {
} finally {
try {
inputStream.close();
connection.close();
} catch (Exception e) {
}
}
if (dataArray != null) {
bitmap = EncodedImage.createEncodedImage(dataArray, 0,
dataArray.length);
return bitmap.getBitmap();
} else {
return null;
}
}
}
我创建了一个新类，但我不知道如何使用它。