我创建了一个数据库表，其中有、id和作为列。我的 xml 有 3 个元素，用户名、密码编辑文本和登录按钮。DatabaseActivity.java 中的方法进行验证。usernamepasswordemailvalidateLogin
错误
方法 getWritableDatabase() 未定义类型 DbHelper 行 ----- SQLiteDatabase db = mydb.getWritableDatabase();----
这是我的 DatabaseActivity.java 文件
package com.login.recscores;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
@SuppressLint("Registered")
public class DatabaseActivity extends Activity implements OnClickListener {
Button mLogin;
Button mNewUser;
Button mShowAll;
EditText mUsername;
EditText mPassword;
DbHelper mydb = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
mNewUser = (Button)findViewById(R.id.sign_in_button);
mNewUser.setOnClickListener(this);
}
public void onClick(View v) {
switch(v.getId()){
case R.id.sign_in_button:
mUsername = (EditText)findViewById(R.id.email);
mPassword = (EditText)findViewById(R.id.password);
String uname = mUsername.getText().toString();
String pass = mPassword.getText().toString();
if(uname.equals("") || uname == null){
Toast.makeText(getApplicationContext(), "email Empty", Toast.LENGTH_SHORT).show();
}else if(pass.equals("") || pass == null){
Toast.makeText(getApplicationContext(), "Password Empty", Toast.LENGTH_SHORT).show();
}else{
boolean validLogin = validateLogin(uname, pass, DatabaseActivity.this);
if(validLogin){
System.out.println("In Valid");
Intent i = new Intent(DatabaseActivity.this, UserHome.class);
startActivity(i);
finish();
}
}
break;
}
}
// @SuppressWarnings("deprecation")
public boolean validateLogin(String uname, String pass, Context context) {
mydb = new DbHelper(this);
SQLiteDatabase db = mydb.getWritableDatabase();
//SELECT
String[] columns = {"_id"};
//WHERE clause
String selection = "username=? AND password=?";
//WHERE clause arguments
String[] selectionArgs = {uname,pass};
Cursor cursor = null;
try{
//SELECT _id FROM login WHERE username=uname AND password=pass
cursor = db.query(DbHelper.RECSCORES_TABLE_NAME, columns, selection, selectionArgs, null, null, null);
// startManagingCursor(cursor);
}catch(Exception e){
e.printStackTrace();
}
int numberOfRows = cursor.getCount();
if(numberOfRows <= 0){
Toast.makeText(getApplicationContext(), "Wha Failed..\nTry Again", Toast.LENGTH_SHORT).show();
return false;
}
return true;
}
public void onDestroy(){
super.onDestroy();
mydb.close();
}
}
DbHelper.java 是
package com.login.recscores;
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 DbHelper {
private static final String DATABASE_NAME = "recscores.db";
public static final String KEY_ROWID = "_id";
public static final String KEY_USERNAME = "username";
public static final String KEY_PASSWORD = "password";
public static final String KEY_EMAIL = "email";
private static final String TAG = "DbHelper";
private static final int DATABASE_VERSION = 1;
public static final String RECSCORES_TABLE_NAME = "users";
private static final String RECSCORES_TABLE_CREATE =
"CREATE TABLE " + RECSCORES_TABLE_NAME + "(" +
"_id INTEGER PRIMARY KEY AUTOINCREMENT,"+
"username VARCHAR NOT NULL, password VARCHAR NOT NULL, email VARCHAR NOT NULL);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DbHelper(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(RECSCORES_TABLE_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 titles");
onCreate(db);
}
}
//---opens the database---
public DbHelper open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a title into the database---
public long insertTitle(String Id, String username, String password, String email)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_ROWID, Id);
initialValues.put(KEY_USERNAME, username);
initialValues.put(KEY_PASSWORD, password);
initialValues.put(KEY_EMAIL, email);
return db.insert(RECSCORES_TABLE_NAME, null, initialValues);
}
//---deletes a particular title---
public boolean deleteTitle(long rowId)
{
return db.delete(RECSCORES_TABLE_NAME, KEY_ROWID +
"=" + rowId, null) > 0;
}
//---retrieves all the titles---
public Cursor getAllTitles()
{
return db.query(RECSCORES_TABLE_NAME, new String[] {
KEY_ROWID,
KEY_USERNAME,
KEY_PASSWORD,
KEY_EMAIL},
null,null,null,null,null);
}
//---retrieves a particular title---
public Cursor getTitle(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, RECSCORES_TABLE_NAME, new String[] {
KEY_ROWID,
KEY_USERNAME,
KEY_PASSWORD,
KEY_EMAIL
},
KEY_ROWID + "=" + rowId,
null,null,null,null,null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---updates a title---
public boolean updateTitle(long rowId, String isbn,
String title, String publisher)
{
ContentValues args = new ContentValues();
args.put(KEY_USERNAME, isbn);
args.put(KEY_PASSWORD, title);
args.put(KEY_EMAIL, publisher);
return db.update(RECSCORES_TABLE_NAME, args,
KEY_ROWID + "=" + rowId, null) > 0;
}
}