按反向日期排列的java排序适配器ArrayList

Question

我不知道如何按日期对ArrayList适配器进行反向排序

I think my code is fine but my list don't show my array in reversed sort. I tried every way and see many question but I didn't managed to achieve my goal.

这是我的密码：

in G class :

public static ArrayList<StructureImage> images = new ArrayList<StructureImage>();

以及：

public class StructureImage implements Comparable<StructureImage> {

 public String title;
 public String tozihat;
 public String thumbnail;
 public String url;

 Date dateTime;

 public void setDateTime(Date datetime) {
    this.dateTime = datetime;
 }

 public Date getDateTime() {
    return dateTime;
 }

 @Override
 public int compareTo(StructureImage o) {
    Collections.sort(G.images, Collections.reverseOrder());
    if (getDateTime() == null || o.getDateTime() == null)
        return 0;
    return getDateTime().compareTo(o.getDateTime());
 }
}

填充方法：

public void fill(final ArrayAdapter<StructureImage> adapter, final StructureImage item, final int position) {

 txtTitle.setText(item.title);
 txtTozih.setText(item.tozihat);
 imgPreview.setClickable(true);

 String filename = item.thumbnail.replace("/thumbnail/", "");
 intent.putExtra("filename", filename);
 final File imageFile = new File(G.DIR_FINAL + "/" + filename);
 if ( !imageFile.exists()) {
     imgPreview.setImageBitmap(null);
     DownloadManager.addToDownloadList(item.thumbnail);
 }

 BitmapFactory.Options options = new BitmapFactory.Options();
//options.inSampleSize = 8;
 Bitmap bitmap = BitmapFactory.decodeFile(imageFile.getAbsolutePath(), options);
 imgPreview.setImageBitmap(bitmap);
}

我使用图像阵列：

    private void getImageListFromServer() {
    Date date = new Date(0);
    String result = Webservice.readUrl("http://192.168.1.100/file-server/service.php", null);
    if (result != null) {
        try {
            images.clear();

            JSONArray tasks = new JSONArray(result);
            for (int i = 0; i < tasks.length(); i++) {
                JSONObject object = tasks.getJSONObject(i);
                StructureImage image = new StructureImage();
                image.title = object.getString("title");
                image.tozihat = object.getString("tozihat");
                image.thumbnail = object.getString("thumbnail");
                image.url = object.getString("url");

                DownloadManager.addToDownloadList(image.thumbnail);
                images.add(image);

            }

            adapter.notifyDataSetChanged();
        }
        catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

你必须打电话：

Collections.sort(yourListOfComparablesObjects);

使订单在列表上生效

订单不是自动生成的，您必须在需要排序列表时调用订单

您的代码在G.images上调用sort，这是错误的，因为如果不是由列表上的sort调用，则永远不会调用此方法

要在反向和正常顺序之间进行更改，您必须从以下位置进行更改：

   return getDateTime().compareTo(o.getDateTime());

致：

   return o.getDateTime().compareTo(getDateTime());

您的代码：

在以下内容之后添加：

        JSONArray tasks = new JSONArray(result);
        for (int i = 0; i < tasks.length(); i++) {
            JSONObject object = tasks.getJSONObject(i);
            StructureImage image = new StructureImage();
            image.title = object.getString("title");
            image.tozihat = object.getString("tozihat");
            image.thumbnail = object.getString("thumbnail");
            image.url = object.getString("url");

            DownloadManager.addToDownloadList(image.thumbnail);
            images.add(image);

        }

做：

           Collections.sort(images);
           adapter.notifyDataSetChanged();

并删除compare方法中的SORT调用

Answer 2

。。您的代码正在做一些令人讨厌的事情，您是否打算在每个排序循环中进行排序？ 请继续并从compareTo函数中删除Collections.sort(G.images, Collections.reverseOrder());

@Override
 public int compareTo(StructureImage o) {
    if (getDateTime() == null || o == null || o.getDateTime() == null)
        return 0;
    return getDateTime().compareTo(o.getDateTime());
 }

。。然后再试一次，您可能想在另一个地方调用sortCollections.sort行