我有一个 LoginActivity.java
package com.example.teachify;
/**
* Created by Sayan on 8/24/13.
*/
import android.app.Activity;
import android.content.Intent;
import android.database.SQLException;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.Button;
import android.database.Cursor;
import android.widget.EditText;
public class LoginActivity extends Activity {
EditText txtUserName;
EditText txtPassword;
Button btnLogin;
Button btnCancel;
UserDetails udt;
private DataBaseManager dataBase;
String strDetails;
DatabaseHandler db = new DatabaseHandler(this);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setting default screen to login.xml
setContentView(R.layout.login);
//creates and open the database so we can use it
dataBase = DataBaseManager.instance();
TextView registerScreen = (TextView) findViewById(R.id.link_to_register);
txtUserName=(EditText)this.findViewById(R.id.txtUserName);
txtPassword=(EditText)this.findViewById(R.id.txtPassword);
// Listening to register new account link
registerScreen.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Switching to Register screen
Intent i = new Intent(getApplicationContext(), RegisterActivity.class);
i.putExtra("extra", txtUserName.getText().toString());
startActivityForResult(i,0);
}
});
btnLogin=(Button)this.findViewById(R.id.btnLogin);
btnLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Cursor cursor=null;
try {
cursor = dataBase.select("SELECT UserName,Password FROM User WHERE UserName='" + txtUserName.getText().toString() + "'");
}
catch( SQLException e) {
strDetails="";
if (cursor == null){
cursor.close();
}
else {
cursor.moveToFirst();
strDetails=cursor.getString(0);
cursor.close();
}
if((txtUserName.getText().toString()).equals(strDetails)){
Toast.makeText(LoginActivity.this, "Login Successful",Toast.LENGTH_LONG).show();
} else{
Toast.makeText(LoginActivity.this, e.getMessage(),Toast.LENGTH_LONG).show();
}
}
}
});
}
}
数据库管理器.java
package com.example.teachify;
/**
* Created by Sayan on 9/5/13.
*/
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class DataBaseManager extends SQLiteOpenHelper {
// The Android's default system path of your application database.
//data/data/ and /databases remain the same always. The one that must be changed is com.example which represents
//the MAIN package of your project
private static String DB_PATH = "/data/data/com.example.teachify/databases/";
//the name of your database
private static String DB_NAME = "user";
private static SQLiteDatabase mDataBase;
private static DataBaseManager sInstance = null;
// database version
private static final int DATABASE_VERSION = 1;
/**
* Constructor Takes and keeps a reference of the passed context in order to
* access to the application assets and resources.
*/
private DataBaseManager() {
super(ApplicationContextProvider.getContext(), DB_NAME, null, DATABASE_VERSION);
try {
createDataBase();
openDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Singleton for DataBase
*
* @return singleton instance
*/
public static DataBaseManager instance() {
if (sInstance == null) {
sInstance = new DataBaseManager();
}
return sInstance;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
*
* @throws java.io.IOException io exception
*/
private void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling this method an 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();
} catch (IOException e) {
throw new Error(e.toString());
}
}
}
/**
* 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 doesn't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null;
}
/**
* 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.
*
* @throws java.io.IOException io exception
*/
public void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = ApplicationContextProvider.getContext().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 void openDataBase() throws SQLException {
// Open the database
String myPath = DB_PATH + DB_NAME;
mDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READWRITE);
}
/**
* Select method
*
* @param query select query
* @return - Cursor with the results
* @throws android.database.SQLException sql exception
*/
public Cursor select(String query) throws SQLException {
return mDataBase.rawQuery(query, null);
}
/**
* Insert method
*
* @param table - name of the table
* @param values values to insert
* @throws android.database.SQLException sql exception
*/
public void insert(String table, ContentValues values) throws SQLException {
mDataBase.insert(table, null, values);
}
/**
* Delete method
*
* @param table - table name
* @param where WHERE clause, if pass null, all the rows will be deleted
* @throws android.database.SQLException sql exception
*/
public void delete(String table, String where) throws SQLException {
mDataBase.delete(table, where, null);
}
/**
* Update method
*
* @param table - table name
* @param values - values to update
* @param where - WHERE clause, if pass null, all rows will be updated
*/
public void update(String table, ContentValues values, String where) {
mDataBase.update(table, values, where, null);
}
/**
* Let you make a raw query
*
* @param command - the sql comand you want to run
*/
public void sqlCommand(String command) {
mDataBase.execSQL(command);
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
但是当我在模拟器中执行此操作时： AVD_for_Nexus_by_Google 我收到错误没有这样的表
我做了一张桌子。谁能帮帮我吗...