datenbank guide

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class SettingsDbAdapter {
public static final String KEY_HOST = "vdrHost";
public static final String KEY_PORT = "vdrPort";
public static final String KEY_ROWID = "_id";

private static final String TAG = "SettingsDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;

/**
* Database creation sql statement
*/
private static final String DATABASE_CREATE =
"create table settings (_id integer primary key autoincrement, "
+ "vdrHost text not null, vdrPort text not null);";

private static final String DATABASE_NAME = "vdrData";
private static final String DATABASE_TABLE = "settings";
private static final int DATABASE_VERSION = 2;

private final Context mCtx;

private static class DatabaseHelper extends SQLiteOpenHelper {

DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {

db.execSQL(DATABASE_CREATE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS settings");
onCreate(db);
}
}

/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param ctx the Context within which to work
*/
public SettingsDbAdapter(Context ctx) {
this.mCtx = ctx;
}

/**
* Open the database. If it cannot be opened, try to create a new
* instance of the database. If it cannot be created, throw an exception to
* signal the failure
*
* @return this (self reference, allowing this to be chained in an
* initialization call)
* @throws SQLException if the database could be neither opened or created
*/
public SettingsDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}

public void close() {
mDbHelper.close();
}


/**
* Create a new data entry using the title and body provided. If the entry is
* successfully created return the new rowId for that entry, otherwise return
* a -1 to indicate failure.
*
* @param title the title of the data entry
* @param body the body of the entry
* @return rowId or -1 if failed
*/
public long createEntry(String host, String port) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_HOST, host);
initialValues.put(KEY_PORT, port);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}

/**
* Delete the entry with the given rowId
*
* @param rowId id of entry to delete
* @return true if deleted, false otherwise
*/
public boolean deleteEntry(long rowId) {

return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}

/**
* Return a Cursor over the list of all entries in the database
*
* @return Cursor over all entries
*/
public Cursor fetchAllEntries() {

return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_HOST,
KEY_PORT}, null, null, null, null, null);
}

/**
* Return a Cursor positioned at the entry that matches the given rowId
*
* @param rowId id of entry to retrieve
* @return Cursor positioned to matching entry, if found
* @throws SQLException if entry could not be found/retrieved
*/
public Cursor fetchEntry(long rowId) throws SQLException {

Cursor mCursor =

mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
KEY_HOST, KEY_PORT}, KEY_ROWID + "=" + rowId, null,
null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;

}

/**
* Update the entry using the details provided. The entry to be updated is
* specified using the rowId, and it is altered to use the title and body
* values passed in
*
* @param rowId id of entry to update
* @param title value to set entry title to
* @param body value to set entry body to
* @return true if the entry was successfully updated, false otherwise
*/
public boolean updateEntry(long rowId, String title, String body) {
ContentValues args = new ContentValues();
args.put(KEY_HOST, title);
args.put(KEY_PORT, body);

return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}

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mDbHelper = new SettingsDbAdapter(this);
mDbHelper.open();
handleDbData();

private void handleDbData() {

Cursor c = mDbHelper.fetchAllEntries();
startManagingCursor(c);

int colHostIdx = c.getColumnIndex(SettingsDbAdapter.KEY_HOST);
int colPortIdx = c.getColumnIndex(SettingsDbAdapter.KEY_PORT);
int colIdIdx = c.getColumnIndex(SettingsDbAdapter.KEY_ROWID);

boolean ok = c.moveToFirst();
if(ok == true){
vdrHost = c.getString(colHostIdx);
vdrPort = Integer.valueOf(c.getString(colPortIdx));
dbRow = c.getLong(colIdIdx);
}
else{
dbRow = mDbHelper.createEntry(vdrHost, String.valueOf(vdrPort));
}
}

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