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过去两天我一直在努力解决这个问题。我试图创建一个从数据库查询填充的列表视图（看起来很简单）。由于我将管理多个表，我创建了一个数据库辅助类来管理插入和删除操作。但它并不一致（或迟到）。从Android SQLite数据库返回一个或多个表的空数据记录
当我试图查询一个表，使用其中一个定义的函数时，db返回具有XX个记录但不包含空列数据的游标。实际上，多行（我看到行分隔符），但每行都是空白的。
我有点难住这个问题，并希望得到任何帮助。以下是DB助手类。
数据库助手类
package org.data.agroassistant;
import static android.provider.BaseColumns._ID;
import static org.data.agroassistant.Constants.*;
import java.net.URL;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class AgroAssistantDB extends SQLiteOpenHelper {
private static final String CREATE_TABLE_FARMERS = "create table " + FARMERS_TABLE + " ("
+ _ID + " integer primary key autoincrement, "
+ FARMER_ID + " int not null, "
+ FARMER_FNAME + " text not null, "
+ FARMER_LNAME + " text not null, "
+ FARMER_SIZE + " text not null);";
private static final String CREATE_TABLE_FARMS = "create table " + FARMS_TABLE + " ("
+ _ID + " integer primary key autoincrement, "
+ FARM_ID + " integer not null, "
+ FARM_FARMER_ID + " integer not null, "
+ FARM_SIZE + " text not null, "
+ FARM_PARISH + " text not null, "
+ FARM_EXTENSION + " text not null, "
+ FARM_DISTRICT + " text not null, "
+ FARM_LAT + " long not null, "
+ FARM_LONG + " long not null);";
private static final int DATABASE_VERSION = 1;
private SQLiteDatabase db;
public AgroAssistantDB(Context ctx) {
super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase dbl) {
try {
dbl.execSQL(CREATE_TABLE_FARMERS);
Log.d("AgroAssistant", "Create Farmers table: " + CREATE_TABLE_FARMERS);
//dbl.execSQL(CREATE_TABLE_FARMS);
//Log.d("AgroAssistant", "Create Farms table: " + CREATE_TABLE_FARMS);
} catch (RuntimeException e) {
Log.d("AgroAssistant", "Unable to create tables: " + CREATE_TABLE_FARMERS + CREATE_TABLE_FARMS);
}
}
@Override
public void onUpgrade(SQLiteDatabase dbl, int oldVersion, int newVersion) {
Log.w("AgroAssistant", "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
dbl.execSQL("DROP TABLE IF EXISTS " + FARMERS_TABLE);
dbl.execSQL("DROP TABLE IF EXISTS " + FARMS_TABLE);
Log.d("AgroAssistant", "Upgrade step: " + "DROP TABLE IF EXISTS " + FARMERS_TABLE + FARMS_TABLE);
onCreate(dbl);
}
/*
* Userdefined function used to run rawQueries again specific tables
*/
public Cursor rawQuery(String tableName, String tableColumns, String queryParams) {
db = this.getReadableDatabase();
Log.d("AgroAssistant", "Raw Query Insertion: SELECT "+ tableColumns + " FROM " + tableName + " WHERE " + queryParams);
Cursor cursor = db.rawQuery("SELECT "+ tableColumns + " FROM " + tableName +" WHERE " + queryParams, null);
Log.d("AgroAssistant", "Raw Query Result: Returned " + cursor.getCount() + " record(s)");
return cursor;
}
public Cursor getFarmers() {
db = this.getReadableDatabase();
//Cursor cursor = db.query(FARMERS_TABLE, FROM_FARMERS, null, null, null, null, null);
Cursor cursor = db.query(FARMERS_TABLE, new String[] {"*"}, null, null, null, null, null);
return cursor;
}
public boolean insertFarmer(int id, String firstname, String lastname, String farmersize) {
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(FARMER_ID, id);
values.put(FARMER_FNAME, firstname);
values.put(FARMER_LNAME, lastname);
values.put(FARMER_SIZE, farmersize);
try {
db.insertOrThrow(FARMERS_TABLE, null, values);
Log.d("AgroAssistant", "Insert Farmer: " + id + " " + firstname + " " + lastname + " " + farmersize);
//db.close();
return true;
}
catch (RuntimeException e) {
//db.close();
Log.e("AgroAssistant","Farmer Insertion Exception: "+e.toString());
return false;
}
}
public boolean deleteFarmer(Long farmerId) {
db = this.getWritableDatabase();
if (db.delete(FARMERS_TABLE, _ID + '=' + farmerId.toString(), null) > 0) {
db.close();
return true;
} else {
db.close();
return false;
}
}
public boolean insertFarm(int fid, int pid, int p_size, int latitude, int longtitude, String p_parish, String p_extension, String p_district) {
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(FARM_ID, pid);
values.put(FARM_FARMER_ID, fid);
values.put(FARM_SIZE, p_size);
values.put(FARM_LAT, latitude);
values.put(FARM_LONG, longtitude);
values.put(FARM_PARISH, p_parish);
values.put(FARM_EXTENSION, p_extension);
values.put(FARM_DISTRICT, p_district);
try {
db.insertOrThrow(FARMS_TABLE, null, values);
Log.d("AgroAssistant", "Insert Farm: " + fid + " " + pid + " " + p_size + " " + latitude + " " + longtitude + " " + p_extension + " " + p_district);
db.close();
return true;
}
catch (RuntimeException e) {
db.close();
Log.e("AgroAssistant","Farm Insertion Exception: "+e.toString());
return false;
}
}
public Cursor getFarms() {
db = this.getReadableDatabase();
Cursor cursor = db.query(FARMS_TABLE, FROM_FARMS, null, null, null, null, null);
return cursor;
}
public boolean deleteFarm(Long farmId) {
db = this.getWritableDatabase();
if (db.delete(FARMS_TABLE, _ID + '=' + farmId.toString(), null) > 0) {
db.close();
return true;
} else {
db.close();
return false;
}
}
}
所有我在DB类使用常量都在这里定义：
package org.data.agroassistant;
import android.provider.BaseColumns;
public interface Constants extends BaseColumns {
public static final int FARMER_SEARCH = 0;
public static final int FARM_SEARCH = 1;
public static final int CROP_SEARCH = 2;
public static final int PRICE_SEARCH = 3;
/*====DATABASE CONSTANTS======================
* Constants used by the database adapter class
*/
public static final String DATABASE_NAME = "agroassistant";
public static final String FARMERS_TABLE= "farmers";
public static final String FARMS_TABLE= "farms";
//Columns in the Farmers table
public static final String FARMER_ID = "farmerid";
public static final String FARMER_FNAME = "firstname";
public static final String FARMER_LNAME = "lastname";
public static final String FARMER_SIZE = "farmersize";
//Columns in the Farms table
public static final String FARM_ID = "farmid";
public static final String FARM_FARMER_ID = "farmerid";
public static final String FARM_SIZE = "propertysize";
public static final String FARM_PARISH = "parish";
public static final String FARM_EXTENSION = "extension";
public static final String FARM_DISTRICT = "district";
public static final String FARM_LAT = "xcoord";
public static final String FARM_LONG = "ycoord";
public static final String[] FROM_FARMERS = {_ID, FARMER_ID, FARMER_FNAME, FARMER_LNAME, FARMER_SIZE};
public static final String[] FROM_FARMS = {_ID, FARM_ID, FARM_FARMER_ID, FARM_SIZE, FARM_PARISH, FARM_EXTENSION, FARM_DISTRICT, FARM_LAT, FARM_LONG};
public static final String FROM_S_FARMERS = _ID + ", " + FARMER_ID + ", " + FARMER_FNAME + ", " + FARMER_LNAME + ", " + FARMER_SIZE;
public static final String FROM_S_FARMS = _ID + ", " + FARM_ID + ", " + FARM_FARMER_ID + ", " + FARM_SIZE + ", " + FARM_PARISH + ", " + FARM_EXTENSION + ", " + FARM_DISTRICT + ", " + FARM_LAT + ", " + FARM_LONG;
}
下面是attemps使用DB辅助对象的listactivity。
package org.data.agroassistant;
import static org.data.agroassistant.Constants.*;
import java.util.Arrays;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class ResultView extends ListActivity {
private AgroAssistantDB agroDB;
private Cursor resultsCursor;
private int searchType;
private String searchParams;
private static final int[] FARMER_TO = {R.id.txt_farmer_id, R.id.txt_farmer_fname, R.id.txt_farmer_lname};
/*
* @see android.app.Activity#onCreate(android.os.Bundle)
* @Intent Params:
* (int) searchType Type of search performed {Farmer,Farm,Crop,Price}
* (String) searchParams String of WHERE clause for query
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.result_search);
Bundle b = getIntent().getExtras();
agroDB = new AgroAssistantDB(this);
//searchType = b.getInt("searchType");
//final String searchResponse = b.getString("searchResponse");
//final String searchParams = b.getString("searchParams");
/*
* Need
* Cursor
* CursorAdapter
* SQL query (params)
* SQL (from)
*/
searchType = FARMER_SEARCH;
searchParams = FARMER_ID + "=1102018039";
try {
switch(searchType) {
case(FARMER_SEARCH):
//resultsCursor = agroDB.rawQuery(FARMERS_TABLE, FROM_S_FARMERS, searchParams);
break;
case (FARM_SEARCH):
resultsCursor = agroDB.rawQuery(FARMS_TABLE, FROM_S_FARMS, searchParams);
break;
case (CROP_SEARCH):
resultsCursor = agroDB.rawQuery(CROPS_TABLE, "FROM_S_CROPS", searchParams);
break;
case (PRICE_SEARCH):
resultsCursor = agroDB.rawQuery(PRICES_TABLE, "FROM_PRICES", searchParams);
break;
default:
break;
}
resultsCursor = agroDB.getFarmers();
startManagingCursor(resultsCursor);
showResults(resultsCursor);
} finally {
//agroDB.close();
}
}
private void showResults(Cursor cursor){
SimpleCursorAdapter results = null;
switch(searchType) {
case(FARMER_SEARCH):
ListView list = getListView();
Cursor cursorSelect = (Cursor) list.getItemAtPosition(0);
cursor.getColumnNames();
Log.d("AgroAssistant", "showResults: Cusor contains " + cursor.getCount() + " record(s)");
Log.d("AgroAssistant", "showResults: Cusor contains " + cursor.getColumnCount() + " column(s)");
Log.d("AgroAssistant", "showResults: Cusor contains " + Arrays.toString(cursor.getColumnNames()));
/*
Log.d("AgroAssistant", "ID " + cursorSelect.getString(cursor.getColumnIndex(_ID)));
Log.d("AgroAssistant", "FID " + cursorSelect.getString(cursor.getColumnIndex("farmerid")));
Log.d("AgroAssistant", "FNAME " + cursorSelect.getString(cursor.getColumnIndex("fname")));
Log.d("AgroAssistant", "LNAME " + cursorSelect.getString(cursor.getColumnIndex(FARMER_LNAME)));
*/
results = new SimpleCursorAdapter(this, R.layout.farmer_row, cursor, new String[] {FARMER_ID, FARMER_FNAME, FARMER_LNAME}, FARMER_TO);
break;
case (FARM_SEARCH):
//results = new SimpleCursorAdapter(this, R.layout.farm_row, cursor, new String[] {FEED_TITLE}, TO);
break;
case (CROP_SEARCH):
//results = new SimpleCursorAdapter(this, R.layout.crop_row, cursor, new String[] {FEED_TITLE}, TO);
break;
case (PRICE_SEARCH):
//results = new SimpleCursorAdapter(this, R.layout.price_row, cursor, new String[] {FEED_TITLE}, TO);
break;
default:
break;
}
setListAdapter(results);
}
任何想法或援助将非常感激。
*编辑：我将sqlite db从电话中拿出来，并在sqlite浏览器中打开它。所有记录都在那里。而且，查询在浏览器视图中编写时可以工作。
是你在最后的switch语句中的结果行注释掉了吗？ – Pikaling