如何在自定义布局中在 BaseAdapter 中显示来自 SQLite 的所有数据？

Question

这段代码向我显示了一些来自数据库的意外数据，但不完全是一个一个，有时显示相同的数据 10 次，有什么办法可以解决这个问题？

    listItem = new ArrayList<>();
    customAdapter customAdapter = new customAdapter();
    userlist = v.findViewById(R.id.lisview); 
    userlist.setDivider(null);
    userlist.setAdapter(customAdapter); 

我的自定义适配器

class customAdapter extends BaseAdapter {

    @Override
    public int getCount() {
        int cursor = databaseHelper.getAllServiceAll().getCount();
        return cursor;
    }

    @Override
    public Object getItem(int position) {
            return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = getLayoutInflater().inflate(R.layout.customlayout, null);
        TextView showprice = view.findViewById(R.id.showprice);
        TextView showliters = view.findViewById(R.id.showLiters);
        TextView showdata = view.findViewById(R.id.showdata);
        TextView showvalute = view.findViewById(R.id.showvalute);
        Cursor cursor = databaseHelper.getAllServiceAll();
        cursor.moveToFirst();
        cursor.moveToNext();
        String formula4S = new DecimalFormat("#0.00").format(Float.parseFloat(cursor.getString(2)));
            showprice.setText(formula4S); // Price
            showdata.setText(cursor.getString(3) ); // data
            showvalute.setText("" + databaseHelper.getValute ()); // Valute
            showliters.setText(cursor.getString(1) ); // Liters

        return view;
    }
}

DatabaseHelper.java：

public Cursor getAllServiceAll (){
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res = db.rawQuery("SELECT * FROM servis ORDER BY id DESC LIMIT 10", null);
    return res;
}

Answer 1

通常，您会在 Activity 中获取项目的 ArrayList 并将其传递给您的适配器。以下是 Activity 中的代码示例：

private DataBaseHelper myDbHelper;
private ListView mLocationList;
private TextView mEmptyList;
static  ArrayList<LocationAddress> locationList = new ArrayList<LocationAddress>();
private LocationsListAdapter adapter;

....

    thisContext = this;

    myDbHelper = new DataBaseHelper(thisContext);

    mLocationList = (ListView) findViewById(R.id.list_browse);

    mLocationList.setOnItemClickListener(new LocationClickListener());

// at this point locationList is empty      
    adapter = new LocationsListAdapter(thisContext, locationList);
    mLocationList.setAdapter(adapter);

// now, get the locationList by calling a background Async Task 
    new GetLocations().execute(""); 


   private class GetLocations extends AsyncTask<String, Void, String> {
    ProgressDialog dialog;    

    @Override     
    protected void onPreExecute() {   

        dialog = new ProgressDialog(thisContext);         
        dialog.setMessage("Loading, please wait...");         
        dialog.setIndeterminate(true);         
        dialog.setCancelable(false);         
        dialog.show();     

        }

    protected String doInBackground(String... urls) {

            String results = "";
            locationList = new ArrayList<LocationAddress>();

            try {

                myDbHelper.openDataBase();

            }catch(SQLException sqle){
                results = "Error Opening Database";

                throw sqle;

            }

            Cursor c = null;

            try{

                c = myDbHelper.getLocations();

                if (c != null) { 
                    if (c.moveToFirst())
                    {

                        do { 

                            LocationAddress location = new LocationAddress();

                            location.setID(c.getInt(0));
                            location.setName(c.getString(1));
                            location.setAddress(c.getString(2));
                            location.setLatitude(c.getDouble(3));
                            location.setLongitude(c.getDouble(4));
                            location.setType(c.getString(5));
                            location.setSortOrder(c.getInt(6));

                            locationList.add(location);

                        } while (c.moveToNext());
                    }
                }

                if (c != null) { 
                    if (!c.isClosed()) {
                        c.close();  
                    }
                }

            } catch (Throwable t){
                if (c != null) { 
                    if (!c.isClosed()) {
                        c.close();  
                    }
                }
            }

            try {

                myDbHelper.close();

            }catch(SQLException sqle){
                results = "SQL Error";
                throw sqle;

            }

            return results;
    }

    protected void onPostExecute(String results) {
        dialog.dismiss(); 

        if (results != null) {
            if (results.length() > 0) {
                alertMessage("Get Locations", results);
            } else {

            // This refreshes the adapter with a full list of items
                adapter = new LocationsListAdapter(thisContext, locationList);
                mLocationList.setAdapter(adapter);
            }
        }

    }
} // private Class

适配器类看起来像这样：

public class LocationsListAdapter extends BaseAdapter {

private Context context;
private ArrayList<LocationAddress> locationItems;

public LocationsListAdapter(Context context, ArrayList<LocationAddress> locationItems){
    this.context = context;
    this.locationItems = locationItems;
}

@Override
public int getCount() {
    return locationItems.size();
}

@Override
public Object getItem(int position) {       
    return locationItems.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@SuppressLint("InflateParams")
@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if (convertView == null) {
        LayoutInflater mInflater = (LayoutInflater)
                context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        convertView = mInflater.inflate(R.layout.location_list_item, null);
    }
    LinearLayout topLayout = (LinearLayout) convertView.findViewById(R.id.location_top_layout);
    TextView txtSectionTitle = (TextView) convertView.findViewById(R.id.location_section_title);
    TextView txtTitle = (TextView) convertView.findViewById(R.id.location_title);
    TextView txtAddress = (TextView) convertView.findViewById(R.id.location_address);

    String previous_section_title = "";
    String section_title = "";

    if (position > 0) {
        previous_section_title = locationItems.get(position - 1).getType();
    }

    section_title = locationItems.get(position).getType();
    String location_title = locationItems.get(position).getName();
    String location_address = locationItems.get(position).getAddress();

    txtSectionTitle.setText(section_title);

    if (section_title.contentEquals(previous_section_title)) {
        topLayout.setVisibility(View.GONE);
    } else {
        topLayout.setVisibility(View.VISIBLE);
    }

    txtTitle.setText(location_title);
    txtAddress.setText(location_address);


    return convertView;
}

}