android简单登陆和注册功能实现+SQLite数据库学习

╰半夏微凉° 2022-05-21 09:39 235阅读 0赞

这里我只是建立了一个用简单的存储用户名和密码的表单

**MyDBHelper.java**

public class MyDBHelper extends SQLiteOpenHelper {
        
        public static final String CREATE_USERDATA="create table userData(" +
                "id integer primary key autoincrement,"
                +"nametext,"
                +"password text)";
    
        private Context mContext;
    
        public MyDBHelper(Context context, String name, SQLiteDatabase.CursorFactory cursorFactory,int version){
            super(context,name,cursorFactory,version);
            mContext=context;
        }
    
        public  void onCreate(SQLiteDatabase db){
            db.execSQL(CREATE_USERDATA);
        }
    
        public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){
            //onCreate(db);
        }
    
    }

Main2Activity.java

public class Main2Activity extends AppCompatActivity {
    
        private MyDBHelper dbHelper;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main2);
    
            dbHelper = new MyDBHelper(this,"UserStore.db",null,1);
        }
    
        public void logon(View view){
            //SQLiteDatabase db=dbHelper.getWritableDatabase();
    
            EditText editText3=(EditText)findViewById(R.id.editText3);
            EditText editText4=(EditText)findViewById(R.id.editText4);
            String newname =editText3.getText().toString();
            String password=editText4.getText().toString();
            if (CheckIsDataAlreadyInDBorNot(newname)) {
                Toast.makeText(this,"该用户名已被注册，注册失败",Toast.LENGTH_SHORT).show();
            }
            else {
    
                if (register(newname, password)) {
                    Toast.makeText(this, "插入数据表成功", Toast.LENGTH_SHORT).show();
                }
            }
        }
    //向数据库插入数据
        public boolean register(String username,String password){
            SQLiteDatabase db= dbHelper.getWritableDatabase();
            /*String sql = "insert into userData(name,password) value(?,?)";
            Object obj[]={username,password};
            db.execSQL(sql,obj);*/
            ContentValues values=new ContentValues();
            values.put("name",username);
            values.put("password",password);
            db.insert("userData",null,values);
            db.close();
            //db.execSQL("insert into userData (name,password) values (?,?)",new String[]{username,password});
            return true;
        }
    //检验用户名是否已存在
        public boolean CheckIsDataAlreadyInDBorNot(String value){
            SQLiteDatabase db=dbHelper.getWritableDatabase();
            String Query = "Select * from userData where name =?";
            Cursor cursor = db.rawQuery(Query,new String[] { value });
            if (cursor.getCount()>0){
                cursor.close();
                return  true;
            }
            cursor.close();
            return false;
        }
    
    }

`登陆：`

MainActivity.java

public class MainActivity extends AppCompatActivity {
        private MyDBHelper dbHelper;
        private EditText username;
        private EditText userpassword;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            //requestWindowFeature(Window.FEATURE_NO_TITLE);
            setContentView(R.layout.activity_main);
            
            dbHelper = new MyDBHelper(this,"UserStore.db",null,1);
        }
        
         //点击注册按钮进入注册页面
        public void logonClicked(View view){
            Intent intent = new Intent(MainActivity.this,Main2Activity.class);
            startActivity(intent);
        }
    
    
        //点击登录按钮
        public void loginClicked(View view) {
            username=(EditText)findViewById(R.id.editText2);
            userpassword=(EditText)findViewById(R.id.editText);
            String userName=username.getText().toString();
            String passWord=userpassword.getText().toString();
            if (login(userName,passWord)) {
                Toast.makeText(MainActivity.this, "登陆成功（ZY，111）", Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(MainActivity.this, "登陆失败", Toast.LENGTH_SHORT).show();
            }
        }
    
        //验证登录
        public boolean login(String username,String password) {
            SQLiteDatabase db = dbHelper.getWritableDatabase();
            String sql = "select * from userData where name=? and password=?";
            Cursor cursor = db.rawQuery(sql, new String[] {username, password});
            if (cursor.moveToFirst()) {
                cursor.close();
                return true;
            }
            return false;
        }