Android 按距离重新订购适配器

Question

我正在尝试按距离重新排序我的项目列表（使用 android getListView，而不是自定义），但我遇到了问题。

我正在使用 Maps Utils 在适配器 ( SomeAdapter ) 中获取以米为单位的球面距离（双倍）。

double distance = SphericalUtil.computeDistanceBetween(fromCoord, toCoord);

但是在我填充适配器 (AsyncTask) 之后，我需要在我的 onPostExecute 上缩短距离，但我不知道。

    @Override
    protected void onPostExecute(Boolean result) {
        try {
            SQLiteHelper dbHelper = new SQLiteHelper(getActivity());
            pds = new SomeDataSource(dbHelper.db);

            ArrayList<Raids> some = pds.getAllRaids();

            SomeAdapter listViewAdapter = new SomeAdapter(getActivity(), some);
            getListView().setAdapter(listViewAdapter);

            SharedPreferences somename = context.getSharedPreferences("SomeName", Context.MODE_PRIVATE);
            Boolean UserOrder = somename.getBoolean("UserOrder", false);
            if (UserOrder){

            }

        } catch (SQLiteException | NullPointerException s) {
            Log.d("SomeName", "SomeFrag:", s);
        }
    }

谢谢

Answer 1

只需在 Raids class -

中实现 Comparable 接口

class Raids implements Comparable<Raids> {
    private double distance;
    ...

    @Override
    public int compareTo(Raids instance2) {
        if (this.distance < instance2.distance)
            return -1;
        else if (this.distance > instance2.distance)
            return 1;
        else
            return 0;
    }
}

然后调用Collections.sort就可以了-

ArrayList<Raids> some = pds.getAllRaids();
Collections.sort(some);

并更新适配器 -

listViewAdapter.notifyDataSetChanged();

Answer 2

鉴于您的代码：

ArrayList<Raids> some = pds.getAllRaids();
SomeAdapter listViewAdapter = new SomeAdapter(getActivity(), some);

你需要：

class SomeAdapter ... {

    private ArrayList<Raids> mData;

    //TODO: now call this method instead of computeDistanceBetween directly
    private void calculateForitem(Raids item) {
        double distance = SphericalUtil.computeDistanceBetween(item.fromCoord, item.toCoord);
        item.setDistance(distance);
        Collections.sort(mData); //the list inside adapter
        notifyDataSetChanged();
    }

}

和

class Raids implements Comparable<Raids> {

    private double distance;
     ...

    @Override
    public int compareTo(Raids instance2) {
        return (this.distance < instance2.distance)? -1 : (this.distance > instance2.distance)? 1 : 0;
    }

}

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