Java 我怎样才能写一份登记表&;在Android Studio中使用SQLite登录系统?
我已经编写了一个简单的SQLite R&L系统。但我在运行之后遇到了一个问题-当我按loginBtn时,系统总是弹出一个祝酒词“Ac不存在” 代码如下: LoginActivity.javaJava 我怎样才能写一份登记表&;在Android Studio中使用SQLite登录系统?,java,android,sqlite,android-studio,Java,Android,Sqlite,Android Studio,我已经编写了一个简单的SQLite R&L系统。但我在运行之后遇到了一个问题-当我按loginBtn时,系统总是弹出一个祝酒词“Ac不存在” 代码如下: LoginActivity.java package com.example; import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.text.Editab
package com.example;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class LoginActivity extends AppCompatActivity {
EditText usernameTxt, passwordTxt;
Button loginBtn, newAcBtn;
DatabaseHandler dbHelper;
List<UsersDatabase> Users = new ArrayList<UsersDatabase>();
public void define(){
usernameTxt = (EditText)findViewById(R.id.txtUsername);
passwordTxt = (EditText)findViewById(R.id.txtPassword);
loginBtn = (Button)findViewById(R.id.btnLogin);
newAcBtn = (Button)findViewById(R.id.btnNewAccount);
dbHelper = new DatabaseHandler(getApplicationContext());
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
define();
NewAccountBtnOnClick();
LoginBtnEnable();
LoginBtnOnClick();
}
public void NewAccountBtnOnClick(){
newAcBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent LoginToMain = new Intent(LoginActivity.this, MainActivity.class);
startActivity(LoginToMain);
}
});
}
public void LoginBtnEnable(){
usernameTxt.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
if (String.valueOf(usernameTxt.getText()).trim().length() > 0) {
passwordTxt.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
loginBtn.setEnabled(String.valueOf(passwordTxt.getText()).trim().length() > 0);
}
@Override
public void afterTextChanged(Editable s) {
}
});
}
}
@Override
public void afterTextChanged(Editable s) {
}
});
}
public void LoginBtnOnClick(){
loginBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
UsersDatabase user = new UsersDatabase(dbHelper.getUserCount(), String.valueOf(usernameTxt.getText()), String.valueOf(passwordTxt.getText()));
if (!userExists(user)) {
Toast.makeText(getApplicationContext(), " Ac does not exist.", Toast.LENGTH_SHORT).show();
return;
}
Intent LoginToMain = new Intent(LoginActivity.this, MainActivity.class);
startActivity(LoginToMain);
}
});
}
private boolean userExists(UsersDatabase user)
{
String name = user.getUsername();
int userCount = Users.size();
for (int i = 0; i < userCount; i++)
{
if (name.compareToIgnoreCase(Users.get(i).getUsername()) ==0)
return true;
}
return false;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_login, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
和DatabaseHandler.java
package com.example;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import java.util.List;
public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "usersManager",
TABLE_USERS = "Users",
KEY_UID = "uid",
KEY_USERNAME = "username",
KEY_PASSWORD = "password";
public DatabaseHandler(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL("CREATE TABLE " + TABLE_USERS + " (" + KEY_UID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_USERNAME + " TEXT," + KEY_PASSWORD + " TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS);
onCreate(db);
}
public void createUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_USERNAME, user.getUsername());
values.put(KEY_PASSWORD, user.getPassword());
db.insert(TABLE_USERS, null, values);
db.close();
}
public UsersDatabase getUser(int id)
{
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.query(TABLE_USERS, new String[] { KEY_UID, KEY_USERNAME, KEY_PASSWORD}, KEY_UID + "=?", new String[] { String.valueOf(id)},null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
UsersDatabase user = new UsersDatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1), cursor.getString(2));
db.close();
cursor.close();
return user;
}
public void deleteUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
db.delete(TABLE_USERS, KEY_UID + "=?", new String[] { String.valueOf(user.getUserId())});
db.close();
}
public int getUserCount()
{
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_USERS, null);
int count = cursor.getCount();
db.close();
cursor.close();
return count;
}
public int updateUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_USERNAME, user.getUsername());
values.put(KEY_PASSWORD, user.getPassword());
int rowsAffected = db.update(TABLE_USERS, values, KEY_UID + "=?", new String[]{String.valueOf(user.getUserId())});
db.close();
return rowsAffected;
}
public List<UsersDatabase> getAllUsers()
{
List<UsersDatabase> users = new ArrayList<UsersDatabase>();
SQLiteDatabase db = getWritableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_USERS, null);
if (cursor.moveToFirst()) {
do {
users.add(new UsersDatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1), cursor.getString(2)));
}
while (cursor.moveToNext());
}
cursor.close();
db.close();
return users;
}
}
package.com.example;
导入android.content.ContentValues;
导入android.content.Context;
导入android.database.Cursor;
导入android.database.sqlite.SQLiteDatabase;
导入android.database.sqlite.SQLiteOpenHelper;
导入java.util.ArrayList;
导入java.util.List;
公共类DatabaseHandler扩展了SQLiteOpenHelper{
私有静态最终int数据库_VERSION=1;
私有静态最终字符串数据库\u NAME=“usersManager”,
表_USERS=“USERS”,
KEY\u UID=“UID”,
KEY_USERNAME=“USERNAME”,
KEY_PASSWORD=“PASSWORD”;
公共数据库处理程序(上下文)
{
super(上下文、数据库名称、null、数据库版本);
}
@凌驾
public void onCreate(SQLiteDatabase db)
{
db.execSQL(“创建表”+表用户+”(“+KEY\u UID+”整数主键自动递增“+KEY\u用户名+”文本“+KEY\u密码+”文本)”);
}
@凌驾
public void onUpgrade(SQLiteDatabase db,int-oldVersion,int-newVersion){
db.execSQL(“如果存在删除表”+表用户);
onCreate(db);
}
公共void createUser(UsersDatabase用户)
{
SQLiteDatabase db=getWritableDatabase();
ContentValues=新的ContentValues();
value.put(KEY_USERNAME,user.getUsername());
value.put(KEY_PASSWORD,user.getPassword());
db.insert(表_用户,空,值);
db.close();
}
公共用户数据库getUser(int-id)
{
SQLiteDatabase db=getReadableDatabase();
Cursor Cursor=db.query(表用户,新字符串[]{KEY\u UID,KEY\u USERNAME,KEY\u PASSWORD},KEY\u UID+“=?”,新字符串[]{String.valueOf(id)},null,null,null);
如果(光标!=null)
cursor.moveToFirst();
UsersDatabase user=newusersdatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1),cursor.getString(2));
db.close();
cursor.close();
返回用户;
}
公共void deleteUser(UsersDatabase用户)
{
SQLiteDatabase db=getWritableDatabase();
delete(TABLE_USERS,KEY_UID+“=?”,新字符串[]{String.valueOf(user.getUserId())});
db.close();
}
public int getUserCount()
{
SQLiteDatabase db=getReadableDatabase();
Cursor Cursor=db.rawQuery(“SELECT*FROM”+表格用户,null);
int count=cursor.getCount();
db.close();
cursor.close();
返回计数;
}
public int updateUser(UsersDatabase用户)
{
SQLiteDatabase db=getWritableDatabase();
ContentValues=新的ContentValues();
value.put(KEY_USERNAME,user.getUsername());
value.put(KEY_PASSWORD,user.getPassword());
int rowsAffected=db.update(表_USERS,values,KEY_UID+“=?”,新字符串[]{String.valueOf(user.getUserId())});
db.close();
返回受影响的行;
}
公共列表getAllUsers()
{
列表用户=新建ArrayList();
SQLiteDatabase db=getWritableDatabase();
Cursor Cursor=db.rawQuery(“SELECT*FROM”+表格用户,null);
if(cursor.moveToFirst()){
做{
add(新的UsersDatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1),cursor.getString(2));
}
while(cursor.moveToNext());
}
cursor.close();
db.close();
返回用户;
}
}
我现在解决了这个问题。
我将用户更改为dbHandler.getAllUsers()
private boolean userExists(UsersDatabase user)
{
字符串名称=user.getUsername();
int userCount=dbHandler.getAllUsers().size();
for(int i=0;i
package com.example;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import java.util.List;
public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "usersManager",
TABLE_USERS = "Users",
KEY_UID = "uid",
KEY_USERNAME = "username",
KEY_PASSWORD = "password";
public DatabaseHandler(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL("CREATE TABLE " + TABLE_USERS + " (" + KEY_UID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_USERNAME + " TEXT," + KEY_PASSWORD + " TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERS);
onCreate(db);
}
public void createUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_USERNAME, user.getUsername());
values.put(KEY_PASSWORD, user.getPassword());
db.insert(TABLE_USERS, null, values);
db.close();
}
public UsersDatabase getUser(int id)
{
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.query(TABLE_USERS, new String[] { KEY_UID, KEY_USERNAME, KEY_PASSWORD}, KEY_UID + "=?", new String[] { String.valueOf(id)},null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
UsersDatabase user = new UsersDatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1), cursor.getString(2));
db.close();
cursor.close();
return user;
}
public void deleteUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
db.delete(TABLE_USERS, KEY_UID + "=?", new String[] { String.valueOf(user.getUserId())});
db.close();
}
public int getUserCount()
{
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_USERS, null);
int count = cursor.getCount();
db.close();
cursor.close();
return count;
}
public int updateUser(UsersDatabase user)
{
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_USERNAME, user.getUsername());
values.put(KEY_PASSWORD, user.getPassword());
int rowsAffected = db.update(TABLE_USERS, values, KEY_UID + "=?", new String[]{String.valueOf(user.getUserId())});
db.close();
return rowsAffected;
}
public List<UsersDatabase> getAllUsers()
{
List<UsersDatabase> users = new ArrayList<UsersDatabase>();
SQLiteDatabase db = getWritableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_USERS, null);
if (cursor.moveToFirst()) {
do {
users.add(new UsersDatabase(Integer.parseInt(cursor.getString(0)),cursor.getString(1), cursor.getString(2)));
}
while (cursor.moveToNext());
}
cursor.close();
db.close();
return users;
}
}
private boolean userExists(UsersDatabase user)
{
String name = user.getUsername();
int userCount = dbHandler.getAllUsers().size();
for (int i = 0; i < userCount; i++)
{
if (name.compareToIgnoreCase(dbHandler.getAllUsers().get(i).getUsername()) ==0)
return true;
}
return false;
}