[英]Sqlite database problem android
我在sqlite數據庫中有問題。首先我在外部創建數據庫,然后將其放在assets文件夾中。以下代碼復制數據庫。
public class DbH extends SQLiteOpenHelper{
private Context mycontext;
private String DB_PATH = "/data/data/com.android.quotes/databases/";
private static String ROW_ID="_id";
private static String DB_NAME = "mdb1.db";
public SQLiteDatabase myDataBase;
/*private String DB_PATH = "/data/data/"
+ mycontext.getApplicationContext().getPackageName()
+ "/databases/";
*/
public DbH(Context context) throws IOException {
super(context,DB_NAME,null,1);
this.mycontext=context;
boolean dbexist = checkdatabase();
if(dbexist){
//System.out.println("Database exists");
opendatabase();
} else {
System.out.println("Database doesn't exist");
createdatabase();
}
}
public void createdatabase() throws IOException{
boolean dbexist = checkdatabase();
if(dbexist){
System.out.println(" Database exists.");
} else {
this.getReadableDatabase();
try{
copydatabase();
} catch(IOException e){
throw new Error("Error copying database");
}
}
}
private boolean checkdatabase() {
//SQLiteDatabase checkdb = null;
boolean checkdb = false;
try{
String myPath = DB_PATH + DB_NAME;
File dbfile = new File(myPath);
SQLiteDatabase.openDatabase
(myPath,null,SQLiteDatabase.OPEN_READWRITE);
checkdb = dbfile.exists();
} catch(SQLiteException e){
System.out.println("Database doesn't exist");
}
return checkdb;
}
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 byte to inputfile to 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{
//Open the database
String mypath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(
mypath, null, SQLiteDatabase.OPEN_READWRITE
);
}
public synchronized void close(){
if(myDataBase != null){
myDataBase.close();
}
super.close();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Empty
}
@Override
public void onCreate(SQLiteDatabase arg0) {
// TODO Auto-generated method stub
}
}
在主要活動中,我首先調用createdatabase,然后調用opendatabase。 現在我只在sqlite數據庫中創建了兩個表,一個是android_metadata,第二個是mTable。當我運行程序時,發生以下錯誤。
任何我出錯的建議。 我從一周開始拉我的頭發。 請幫忙。 提前致謝。
首先檢查數據庫數據庫是否存在於內部存儲中,如果不是復制
private void checkDatabase() {
StringBuffer dbPath = new StringBuffer();
File databaseFile;
// Location of the database file, where it will be stored to access
// throughout the program.
dbPath.append("/data/data/");
dbPath.append(getBaseContext().getPackageName());
dbPath.append("/databases/");
// Location of the database file stored in assets folder.
String storedDatabase = Constants.DATABASE_FILE_NAME;
// copy the database
try {
databaseFile = new File(dbPath.toString(), Constants.DATABASE_FILE_NAME);
if (databaseFile.exists()) {
Log.i("database", "database already Exists");
} else {
SQLiteDatabase database = openOrCreateDatabase(Constants.DATABASE_FILE_NAME,
SQLiteDatabase.OPEN_READONLY, null);
database.close();
copyDatasbase(getBaseContext().getAssets(), storedDatabase,
dbPath + Constants.DATABASE_FILE_NAME);
}
} catch (IOException ioException) {
ioException.printStackTrace();
} catch (Exception exception) {
exception.printStackTrace();
}
}
如果數據庫不存在則從資產復制到內部存儲
private void copyDatasbase(AssetManager manager, String sourceFileName,
String destinationFileName) throws IOException {
// Read file from AccessManager
InputStream inputStream = manager.open(sourceFileName);
OutputStream outputStream = new FileOutputStream(destinationFileName);
Log.d("-->", "src: " + sourceFileName);
Log.d("-->", "Des: " + destinationFileName);
byte[] buffer = new byte[3072];
int length;
while ((length = inputStream.read(buffer)) > 0) {
// Write the database file to the folder "databases"
outputStream.write(buffer, 0, length);
}
outputStream.flush();
outputStream.close();
inputStream.close();
outputStream = null;
inputStream = null;
}
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