在android项目中尝试使用数据库时没有此类表错误
我正在为我的android项目创建数据库表,下面是helper类。在这里,我可以创建数据库,当我尝试从getSettings()方法获取数据时,它显示一个错误,表示没有这样的表“设置”。但是我用onCreate方法创建了表。之后,我调试并发现OnCreate方法没有调用。你们能看一下下面的代码并给我提个建议吗在android项目中尝试使用数据库时没有此类表错误,android,android-sqlite,Android,Android Sqlite,我正在为我的android项目创建数据库表,下面是helper类。在这里,我可以创建数据库,当我尝试从getSettings()方法获取数据时,它显示一个错误,表示没有这样的表“设置”。但是我用onCreate方法创建了表。之后,我调试并发现OnCreate方法没有调用。你们能看一下下面的代码并给我提个建议吗 public class DataBaseHelper extends SQLiteOpenHelper { private static String TAG = "DataBase
public class DataBaseHelper extends SQLiteOpenHelper
{
private static String TAG = "DataBaseHelper"; // Tag just for the LogCat window
//destination path (location) of our database on device
private static String DB_PATH = "";
private static String DB_NAME ="testDatabase";// Database name
private SQLiteDatabase mDataBase;
private final Context mContext;
private final String SETTINGS_TABLE = "settings";
private final String SETTINGS_COLUMN_ID = "_id";
private final String SETTINGS_COLUMN_PROFILE_ID = "profileId";
private final String SETTINGS_TABLE_CREATE = "create table " + SETTINGS_TABLE
+ "(" + SETTINGS_COLUMN_ID + " integer primary key autoincrement, "
+ SETTINGS_COLUMN_PROFILE_ID + " varchar(100), );";
private final int SETTINGS_ID = 1;
public DataBaseHelper(Context context)
{
super(context, DB_NAME, null, 1);// 1? its Database Version
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
}
public void createDataBase() throws IOException
{
//If database not exists copy it from the assets
boolean mDataBaseExist = checkDataBase();
if(!mDataBaseExist)
{
this.getWritableDatabase();
this.close();
try
{
//Copy the database from assests
copyDataBase();
Log.e(TAG, "createDatabase database created");
}
catch (IOException mIOException)
{
throw new Error("ErrorCopyingDataBase");
}
}
}
//Check that the database exists here: /data/data/your package/databases/Da Name
private boolean checkDataBase()
{
File dbFile = new File(DB_PATH + DB_NAME);
//Log.v("dbFile", dbFile + " "+ dbFile.exists());
return dbFile.exists();
}
//Copy the database from assets
private void copyDataBase() throws IOException
{
InputStream mInput = mContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream mOutput = new FileOutputStream(outFileName);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer))>0)
{
mOutput.write(mBuffer, 0, mLength);
}
mOutput.flush();
mOutput.close();
mInput.close();
}
//Open the database, so we can query it
public boolean openDataBase() throws SQLException
{
String mPath = DB_PATH + DB_NAME;
mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
mDataBase = getWritableDatabase();
return mDataBase != null;
}
@Override
public synchronized void close()
{
if(mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
mDataBase = db;
System.out.println("Oncreate table");
try {
db.execSQL(SETTINGS_TABLE_CREATE);
InsertSettingsData();
Log.d(TAG, "onCreate Success create SETTINGS_TABLE_CREATE");
} catch (Exception e) {
e.printStackTrace();
}
}
private int InsertSettingsData() {
// TODO Auto-generated method stub
Log.d(TAG, "InsertConfigInitialData");
try {
ContentValues resourceTable = new ContentValues();
resourceTable.put(SETTINGS_COLUMN_ID, SETTINGS_ID);
resourceTable.put(SETTINGS_COLUMN_PROFILE_ID,
"123456");
int resourceId = (int) mDataBase.insert(SETTINGS_TABLE, null,
resourceTable);
if (resourceId >= 0) {
return resourceId;
}
} catch (Exception e) {
Log.d(TAG, "InsertConfigInitialData failed : " + e.toString());
e.printStackTrace();
}
return -1;
}
public boolean UpdateConfigData() {
Log.d(TAG, "UpdateConfigData");
try {
String condition = SETTINGS_COLUMN_ID + "=" + SETTINGS_ID;
ContentValues resourceTable = new ContentValues();
resourceTable.put(SETTINGS_COLUMN_PROFILE_ID,
"34567");
int totalUpdated = mDataBase.update(SETTINGS_TABLE,
resourceTable, condition, null);
if (totalUpdated > 0) {
return true;
} else {
Log.d(TAG, "UpdateConfigData failed, no records updated");
}
} catch (Exception e) {
Log.d(TAG, "UpdateConfigData failed : " + e.toString());
}
return false;
}
public SettingsObject getSettings() {
Log.d(TAG, "LoadConfigs");
SettingsObject settings = new SettingsObject();
String condition = SETTINGS_COLUMN_ID + "=" + SETTINGS_ID;
try {
Cursor cursor = mDataBase.query(SETTINGS_TABLE, null,
condition, null, null, null, null);
if (cursor != null && cursor.moveToFirst()) {
SettingsObject.setProfile_id(cursor.getString(cursor
.getColumnIndex(SETTINGS_COLUMN_PROFILE_ID)));
cursor.close();
}
} catch (Exception e) {
e.printStackTrace();
Log.d(TAG, "LoadConfigs failed : " + e.getMessage());
}
return settings;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
在我的活动课上我这样打电话
DataBaseHelper myDbHelper = new DataBaseHelper(this);
myDbHelper = new DataBaseHelper(this);
try {
myDbHelper.createDataBase();
}
catch (IOException ioe)
{
throw new Error("Unable to create database");
}
try
{
myDbHelper.openDataBase();
}
catch(SQLException sqle){
throw sqle;
}
SettingsObject object = myDbHelper.getSettings();
System.out.println("settings profile Id" + object.getProfile_id());
Edit1:
我可以用以下方法调用创建数据库表吗
//Open the database, so we can query it
public boolean openDataBase() throws SQLException
{
String mPath = DB_PATH + DB_NAME;
//Log.v("mPath", mPath);
mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
//mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
mDataBase = getWritableDatabase();
mDataBase.execSQL(SETTINGS_TABLE_CREATE);
InsertSettingsData();
return mDataBase != null;
}
在创建表语法中有一个额外的字符
,
。您需要从语法中删除最后一个字符(逗号)
你的语法
private final String SETTINGS_TABLE_CREATE = "create table " + SETTINGS_TABLE
+ "(" + SETTINGS_COLUMN_ID + " integer primary key autoincrement, "
+ SETTINGS_COLUMN_PROFILE_ID + " varchar(100), );";
更新到
private final String SETTINGS_TABLE_CREATE = "create table if not exists " + SETTINGS_TABLE
+ "(" + SETTINGS_COLUMN_ID + " integer primary key autoincrement, "
+ SETTINGS_COLUMN_PROFILE_ID + " varchar(100) );";
现在,您的语法已准备就绪。在创建表语法中有一个额外的字符
,
。您需要从语法中删除最后一个字符(逗号)
你的语法
private final String SETTINGS_TABLE_CREATE = "create table " + SETTINGS_TABLE
+ "(" + SETTINGS_COLUMN_ID + " integer primary key autoincrement, "
+ SETTINGS_COLUMN_PROFILE_ID + " varchar(100), );";
更新到
private final String SETTINGS_TABLE_CREATE = "create table if not exists " + SETTINGS_TABLE
+ "(" + SETTINGS_COLUMN_ID + " integer primary key autoincrement, "
+ SETTINGS_COLUMN_PROFILE_ID + " varchar(100) );";
现在您的语法已准备就绪。onCreate()
将不会被调用,因为数据库已经存在——如果数据库不存在,您的代码表明您正在从资产复制数据库,因此在调用SQLiteOpenHelper时,它确实存在,并且将跳过onCreate()
。在您的特殊情况下,您不能依赖SQLiteOpenHelper来分派正确的事件,而是需要从资产中复制,然后立即打开并修改模式
你会想要这样的东西:
boolean mDataBaseExist = checkDataBase();
if(!mDataBaseExist)
{
try
{
//Copy the database from assests
copyDataBase();
Log.e(TAG, "createDatabase database created");
SQLiteDatabase db = getWriteableDatabase();
db.execSQL( ...create ddl... );
}
catch (IOException mIOException)
{
throw new Error("ErrorCopyingDataBase");
}
}
onCreate()
将不会被调用,因为数据库已经存在——如果数据库不存在,您的代码将显示您正在从资产复制数据库,因此在调用SQLiteOpenHelper时,它确实存在,并且将跳过onCreate()
。在您的特殊情况下,您不能依赖SQLiteOpenHelper来分派正确的事件,而是需要从资产中复制,然后立即打开并修改模式
你会想要这样的东西:
boolean mDataBaseExist = checkDataBase();
if(!mDataBaseExist)
{
try
{
//Copy the database from assests
copyDataBase();
Log.e(TAG, "createDatabase database created");
SQLiteDatabase db = getWriteableDatabase();
db.execSQL( ...create ddl... );
}
catch (IOException mIOException)
{
throw new Error("ErrorCopyingDataBase");
}
}
主要问题是onCreate没有得到执行 实际上,除非在SQLiteOpenHelper类上调用getWritableDatabase或getReadableDatabase方法,否则根本不会调用onCreate:
myDbHelper.getWritableDatabase();
或
onCreate不是从其构造函数调用的,它是在您尝试访问(读/写)数据库时由Android框架调用的。主要问题是onCreate没有得到执行 实际上,除非在SQLiteOpenHelper类上调用getWritableDatabase或getReadableDatabase方法,否则根本不会调用onCreate:
myDbHelper.getWritableDatabase();
或
onCreate不是从其构造函数调用的,它是在您尝试访问(读/写)数据库时由Android框架调用的。您是如何发现onCreate方法没有运行的?您是否已停止进程并重新启动应用程序?@JermaineXu,我已卸载应用程序并重新安装。遇到同样的问题您更新的代码很有用,现在就写答案。您是如何发现onCreate方法没有运行的?您是否已停止进程并重新启动应用程序?@JermaineXu,我已卸载应用程序并重新安装。遇到同样的问题您更新的代码很有用,现在就写答案。我认为“如果不存在创建表”更好。@Husker,感谢您的建议,尽管我无法创建表,因为Oncreate方法没有触发。请检查一下,将System.out.println(“Oncreate table”)更改为Log.d(…),然后检查日志是否会被打印出来@ChandraSekhar@JermaineXu,我也试过了,但没用。它没有调用我认为“如果不存在创建表”更好。@Husker,谢谢你的建议,尽管我无法创建表,因为Oncreate方法没有被触发。请检查一下,将System.out.println(“Oncreate table”)更改为Log.d(…),然后检查日志是否会被打印出来@ChandraSekhar@JermaineXu,我也试过了,但没用。它不叫edit1,请检查我的edit1,请让我知道代码可以使用吗?请检查我的edit1,请让我知道代码可以使用吗?