好的，所以我已经查看了大概 30 个不同的 SQLite 教程，甚至还有一些关于它的随机讨论。我不是一个程序员，我发现如果我能找到已经在做某事的人，并根据需要进行调整并给予信任，那么它可能比仅仅重新创建轮子更有效率。我敢肯定，我不是唯一一个有这种感觉的人。
在 Eclipse 中，我正在尝试为我的数据库管理类的上下文创建一个构造函数。这是完整的代码。它还没有完成，但在错误消失之前我无法取得进展，所以我们开始吧：
package com.bluej.movingbuddy;
import java.util.ArrayList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.SQLException;
import android.util.Log;
public class MBDatabaseManager {
//Database Version
private final static int DATABASE_VERSION = 1;
//Database Name
private final static String DATABASE_NAME = "dbMovingBuddy";
//items and weights table name
private final static String tblInW = "ItemsAndWeights";
//items and weights table columns
private final static String InWID = "ID";
private final static String InWItem = "Item";
private final static String InWDesc = "Description";
private final static String InWWeightOne = "Weight1";
private final static String InWWeightTwo = "Weight2";
private final static String InWWeightThree = "Weight3";
private final static String InWWeightAvg = "WeightAvg";
//allowances table name
private final static String tblAllowances = "Allowances";
//allowances table columns
private final static String AllowancesID = "ID";
private final static String AllowancesRank = "Rank";
private final static String AllowancesWithDep = "WithDep";
private final static String AllowancesNoDep = "NoDep";
//estimator table name
private final static String tblEstimator = "Estimator";
//estimator table columns
private final static String EstimatorID = "ID";
private final static String EstimatorRoom = "Room";
private final static String EstimatorItem = "Weight";
//inventory table name
private final static String tblInventory = "Inventory";
//inventory table column
private final static String InventoryID = "ID";
private final static String InventoryItem = "Item";
private final static String InventoryWeight = "Weight";
private final static String InventoryValue = "Value";
private final static String InventoryImage1 = "Image1";
private final static String InventoryCondition = "Condition";
private final static String InventoryImage2 = "Image2";
private final static String InventoryNotes = "Notes";
private final static String InventoryMovingInstructions = "MovingInstructions";
//stunt table name
private final static String TABLE_NAME = "database_table";
//stunt table column names
private final static String TABLE_ROW_ID = "id";
private final static String TABLE_ROW_ONE = "table_row_one";
private final static String TABLE_ROW_TWO = "table_row_two";
public MBDatabaseManager(Context context) {
// TODO Auto-generated constructor stub
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
//This string is used to create the database. It should be changed to suit your needs.
//create items and weights table
String dbCreateItemsAndWeights = "create table " +
tblInW +
" (" +
InWID + " integer primary key autoincrement not null," +
InWItem + " text," +
InWDesc + " text," +
InWWeightOne + " integer," +
InWWeightTwo + " integer," +
InWWeightThree + " integer," +
InWWeightAvg + " integer" +
");";
db.execSQL(dbCreateItemsAndWeights);
//allowances table
String dbCreateAllowances = "create table " +
tblAllowances +
" (" +
AllowancesID + " integer primary key autoincrement not null," +
AllowancesRank + " text," +
AllowancesWithDep + " integer," +
AllowancesNoDep + " integer" +
");";
db.execSQL(dbCreateAllowances);
//estimator table
String dbCreateEstimator = "create table " +
tblEstimator +
" (" +
EstimatorID + " integer primary key autoincrement not null," +
EstimatorRoom + " text," +
EstimatorItem + " integer" +
");";
db.execSQL(dbCreateEstimator);
//inventory table
String dbCreateInventory = "create table " +
tblInventory +
" (" +
InventoryID + " integer primary key autoincrement not null," +
InventoryItem + " text," +
InventoryWeight + " integer," +
InventoryValue + " integer," +
InventoryImage1 + " blob," +
InventoryCondition + " text," +
InventoryImage2 + " blob," +
InventoryNotes + " text," +
InventoryMovingInstructions + " text" +
");";
db.execSQL(dbCreateInventory);
//stunt table
String newTableQueryString = "create table " +
TABLE_NAME +
" (" +
TABLE_ROW_ID + " integer primary key autoincrement not null," +
TABLE_ROW_ONE + " text," +
TABLE_ROW_TWO + " text" +
");";
db.execSQL(newTableQueryString);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + tblInW);
db.execSQL("DROP TABLE IF EXISTS " + tblAllowances);
db.execSQL("DROP TABLE IF EXISTS " + tblEstimator);
db.execSQL("DROP TABLE IF EXISTS " + tblInventory);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
// Adding a row to the database table
public void addRow(String rowStringOne, String rowStringTwo){
SQLiteDatabase db = this.getWritableDatabase();
//this is a key value pair holder used by android's SQLite functions
ContentValues values = new ContentValues();
values.put(TABLE_ROW_ONE, rowStringOne);
values.put(TABLE_ROW_TWO, rowStringTwo);
//ask the database object to insert the new data
try {
db.insert(TABLE_NAME, null, values);
} catch (Exception e) {
// TODO Auto-generated catch block
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
}
//DELETING A ROW FROM THE DATABASE TABLE
//
// This is an example of how to delete a row from a database table
// using this class. In most cases, this method probably does not need to be rewritten.
//
// @param rowID the SQLite database identifier for the row to delete.
//
public void deleteRow(long rowID){
// ask the database object to delete the row of given rowID
try {
db.delete(TABLE_NAME, TABLE_ROW_ID + "=" + rowID, null);
} catch (Exception e) {
// TODO Auto-generated catch block
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
}
//UPDATING A ROW IN THE DATABASE TABLE
//
// This is an example of how to update a row in the database table
// using this class. You should edit this method to suit your needs.
//
// @param rowID the SQLite database identifier for the row to update.
// @param rowStringOne the new value for the row's first column
// @param rowStringTwo the new value for the row's second column
public void updateRow(long rowID, String rowStringOne, String rowStringTwo){
//this is a key value pair holder used by android's SQLite functions
ContentValues values = new ContentValues();
values.put(TABLE_ROW_ONE, rowStringOne);
values.put(TABLE_ROW_TWO, rowStringTwo);
//ask the database object to update the database row of given rowID
try {
db.update(TABLE_NAME, values, TABLE_ROW_ID + "=" + rowID, null);
} catch (Exception e) {
// TODO Auto-generated catch block
Log.e("DB Error", e.toString());
e.printStackTrace();
}
}
//RETRIEVING A ROW IN THE DATABASE TABLE
//'
// This is an example of how to retrieve a row from a database table using this class. You should edit this method to suit your needs.
//
// @param rowID the id of the row to retrieve
// @return an array containing the data from the row
public ArrayList<Object> getRowAsArray(long rowID){
//create an array list to store data from the database row.
//I would recommend creating a JavaBean compliant object
//to store this data instead. That way you can ensure data types are correct.
ArrayList<Object> rowArray = new ArrayList<Object>();
Cursor cursor;
try {
// this is a database call that creates a "cursor" object.
// the cursor object stores the information collected from the
// database and is used to iterate through the data.
cursor = db.query(
TABLE_NAME,
new String[] { TABLE_ROW_ID, TABLE_ROW_ONE, TABLE_ROW_TWO },
TABLE_ROW_ID + "=" + rowID,
null, null, null, null, null);
//move the pointer to position zero in the cursor.
cursor.moveToFirst();
// if there is data available after the cursor's pointer, add
// it to the ArrayList that will be returned by the method.
if (!cursor.isAfterLast()){
do{
rowArray.add(cursor.getLong(0));
rowArray.add(cursor.getString(1));
rowArray.add(cursor.getString(2));
} while (cursor.moveToNext());
}
//let java know that you are through with the cursor.
cursor.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
//return the ArrayList containing the given row from the database.
return rowArray;
}
//RETRIEVING ALL ROWS FROM THE DATABASE TABLE
//
//This is an example of how to retrieve all data from a database table using this class.
//You should edit this method to suit your needs.
//
// the key is automatically assigned by the database
public ArrayList<ArrayList<Object>> getAllRowsAsArrays(){
//create an ArrayList that will hold all of the data collected from the database
ArrayList<ArrayList<Object>> dataArrays = new ArrayList<ArrayList<Object>>();
//this is a database call that creates a "cursor" object.
//the cursor object stores the information collected from the database and is used to iterate through the data.
Cursor cursor;
try{
//ask the database object to create the cursor.
cursor = db.query(
TABLE_NAME,
new String[]{TABLE_ROW_ID, TABLE_ROW_ONE, TABLE_ROW_TWO},
null, null, null, null, null
);
//move the cursor's pointer to position zero.
cursor.moveToFirst();
//if there is data after the current cursor position add it to the ArrayList.
if (!cursor.isAfterLast()){
do
{
ArrayList<Object> dataList = new ArrayList<Object>();
dataList.add(cursor.getLong(0));
dataList.add(cursor.getString(1));
dataList.add(cursor.getString(2));
dataArrays.add(dataList);
}
//move the cursor's pointer up one position.
while (cursor.moveToNext());
}
}
catch (SQLException e){
Log.e("DB ERROR", e.toString());
e.printStackTrace();
}
//return the ArrayList that holds the data collected from the database.
return dataArrays;
}
}
因此，现在我再次查看它时出现了两个错误。当我制作构造函数时
public MBDatabaseManager(Context context) {
// TODO Auto-generated constructor stub
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
Eclipse 吓坏了，说“构造函数对象未定义”，当我使用 eclipse 修复它时，它删除了所有上下文内容并变成了 super();。我还没有完全理解所有内容，但我很确定这不会让我很快。
另外，当我尝试
SQLiteDatabase db = this.getWritableDatabase();
它也给了我一个错误，说“方法 getWritableDatabase() 未定义 MBDatabaseManager 类型”
我不知道我错过了什么伙计们。我敢肯定，这很明显。请协助。我需要第二或第三双眼睛。
非常感谢。