我使用DataBaseHelper类从SQLite文件夹中复制assets数据库文件，但是当我运行此代码时：
DataBaseHelper dbhelper=new DataBaseHelper(this);
SQLiteDatabase db=dbhelper.getReadableDatabase();
Cursor cur=db.rawQuery("SELECT * FROM data", null);
我收到此错误：android.database.sqlite.SQLiteException: no such table: data
但我确信那张桌子存在......
班级代码：
class DataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/com.example.amin.rendertest/databases/";
private static String DB_NAME = "db.db";
private SQLiteDatabase myDataBase;
private final Context myContext;
public DataBaseHelper (Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void crateDatabase() throws IOException {
boolean vtVarMi = isDatabaseExist();
if (!vtVarMi) {
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
private void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
private boolean isDatabaseExist() {
SQLiteDatabase kontrol = null;
try {
String myPath = DB_PATH + DB_NAME;
kontrol = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
kontrol = null;
}
if (kontrol != null) {
kontrol.close();
}
return kontrol != null ? true : false;
}
public void openDataBase() throws SQLException {
// Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
public Cursor Sample_use_of_helper() {
return myDataBase.query("TABLE_NAME", null, null, null, null, null, null);
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
答案 0 :(得分：1)
试试这堂课。
public class DataBaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static String DB_NAME = "database_db.sqlite";
private static String DB_PATH = "";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
if (android.os.Build.VERSION.SDK_INT >= 17)
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
else
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
Log.d("path", DB_PATH);
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase(DB_NAME,DB_NAME);
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created empty database in the
* system folder, from where it can be accessed and handled.
* This is done by transfering bytestream.
* */
private void copyDataBase(String assest , String db) throws IOException{
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(assest);
// Path to the just created empty db
String outFileName = DB_PATH + db;
//Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
//transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
//Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
try {
createDataBase();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
快乐编码..
答案 1 :(得分：0)