从SQLite数据库获取数据时出错
从SQLite数据库获取数据时出错
提问于 2016-11-06 15:40:14
我编写了一个应用程序，并将数据存储到数据库中。
问题是，当我试图从数据库中获取数据时，我会得到一个空列表。
有什么问题吗？我将张贴我的代码，如果有人有想法，请告诉我:)
这是我的数据库助手：
public class DatabaseHelpher extends SQLiteOpenHelper {
Context context;
private static final String DATABASE_NAME="TODO.DB";
private static final int DATABASE_VERSION = 1;
private static final String Todo_id= "Todo_id";
private static final String COLMN_TODO_TITLE = "TODO_TITLE";
private static final String COLUMN_Priority = "priority";
private static final String TODO_TABLE = "TODO";
private static final String createTodoTable = "CREATE TABLE " +TODO_TABLE +
"(" +Todo_id+ " INTEGER PRIMARY KEY AUTOINCREMENT, " +COLMN_TODO_TITLE+
" VARCHAR, " +COLUMN_Priority+
" VARCHAR);";
public DatabaseHelpher(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(createTodoTable);}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public void insertIntoDB(String Title,String Priority){
Log.d("insert", "before insert");
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLMN_TODO_TITLE, Title);
values.put(COLUMN_Priority, Priority);
db.insert(TODO_TABLE, null, values);
db.close();
}
public List<Data> getDataFromDB(){
List<Data> modelList = new ArrayList<Data>();
String query = "select * from "+ TODO_TABLE;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query,null);
if (cursor.moveToFirst()){
do {
Data model = new Data();
String Title = cursor.getString(cursor.getColumnIndex(COLMN_TODO_TITLE));
String Description = cursor.getString(cursor.getColumnIndex(COLUMN_Priority));
model.setTODO_TITLE(Title);
model.setPriority(Description);
modelList.add(model);
}while (cursor.moveToNext());
}
return modelList;
}
}我就是这样插入和获取数据的：
public void getLocalData ()
{
helpher = new DatabaseHelpher(this);
dbList= new ArrayList<Data>();
dbList.addAll(helpher.getDataFromDB());
}
private void insert(String Title, String prority ) {
db.insertIntoDB(Title, prority);
}Data.class
public class Data {
String TODO_TITLE ;
String priority;
public String getTODO_TITLE() {
return TODO_TITLE;
}
public void setTODO_TITLE(String TODO_TITLE) {
this.TODO_TITLE = TODO_TITLE;
}
public String getPriority() {
return priority;
}
public void setPriority(String priority) {
this.priority = priority;
}回答 1
Stack Overflow用户
回答已采纳
发布于 2016-11-06 16:02:44
我可以从insert、delete和数据库获得完整的代码。
package com.mssinfotech.dropjourney;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.util.ArrayList;
public class DBHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "MyDBName.db";
public static final String TABLE_NAME = "login";
public DBHelper(Context context)
{
super(context, DATABASE_NAME , null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(
"CREATE TABLE IF NOT EXISTS " + TABLE_NAME +
"(id integer PRIMARY KEY AUTOINCREMENT, phone text, avatar text, name text)"
);
Log.d("create", "table ceated");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
Log.d("create", "table droped");
}
public boolean insertUser (Integer id, String phone, String avatar,String name)
{
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
ContentValues contentValues = new ContentValues();
contentValues.put("id", id);
contentValues.put("phone", phone);
contentValues.put("avatar", avatar);
contentValues.put("name", name);
db.insert(TABLE_NAME, null, contentValues);
Log.d("Inserted", "Record Inserted");
return true;
}
public Cursor getUserData(int id){
SQLiteDatabase db = this.getReadableDatabase();
onCreate(db);
Cursor res = db.rawQuery( "select * from "+TABLE_NAME+" where id="+id+"", null );
return res;
}
public int numberOfRows(){
SQLiteDatabase db = this.getReadableDatabase();
onCreate(db);
int numRows = (int) DatabaseUtils.queryNumEntries(db, TABLE_NAME);
return numRows;
}
public boolean updateUser (Integer id, String phone, String avatar, String name)
{
SQLiteDatabase db = this.getWritableDatabase();
onCreate(db);
ContentValues contentValues = new ContentValues();
contentValues.put("phone", phone);
contentValues.put("avatar", avatar);
contentValues.put("name", name);
db.update(TABLE_NAME, contentValues, "id = ? ", new String[] { Integer.toString(id) } );
return true;
}
public void deleteAllUser(){
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
public Integer deleteUser (Integer id)
{
SQLiteDatabase db = this.getWritableDatabase();
return db.delete(TABLE_NAME,
"id = ? ",
new String[] { Integer.toString(id) });
}
public ArrayList<String> getAllUser()
{
ArrayList<String> array_list = new ArrayList<String>();
//hp = new HashMap();
SQLiteDatabase db = this.getReadableDatabase();
Cursor res = db.rawQuery( "select * from "+TABLE_NAME, null );
res.moveToFirst();
while(res.isAfterLast() == false){
array_list.add(res.getString(res.getColumnIndex("phone")));
res.moveToNext();
}
return array_list;
}
}现在该如何插入
DBHelper mydb = new DBHelper(this);
String avatar = "ImageURL";
String name = "name";
String mobileno = "mEmail";
Integer id=1;
mydb.insertUser(id, mobileno, avatar, name);如何取
DBHelper mydb = new DBHelper(this);
Integer c=mydb.numberOfRows();
if(c>0){
// do your code
}如何删除
DBHelper mydb = new DBHelper(this);
mydb.deleteAllUser();页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/40451165
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