Android - 错误提示：无法使用提供的参数调用以下函数：DataBaseHelper 类中的 Toast.maketest() 函数

Question

我在 android 中的 DatabaseHandler.kt 类中实现了一个 Toast 方法，但出现了错误，即无法使用提供的参数（即 Toast.makeTest() 函数）调用任何函数。 代码如下：

package com.example.pama.pamaDB


import android.annotation.SuppressLint
import android.content.ContentValues
import android.content.Context
import android.database.sqlite.SQLiteDatabase
import android.database.sqlite.SQLiteOpenHelper
import android.os.Build
import android.widget.Toast
import androidx.annotation.RequiresApi
import androidx.core.content.ContentProviderCompat.requireContext
import org.mindrot.jbcrypt.BCrypt
import java.util.regex.Pattern

const val dbname = "UserDb"
const val tbname = "Users"
const val col_username = "username"
const val col_email = "email"
const val col_passwordHash = "passwordHash" // Store hashed password instead of plain text
const val col_id = "id"

class DatabaseHandler(context: Context) : SQLiteOpenHelper(context, dbname, null, 1) {

    override fun onCreate(db: SQLiteDatabase?) {
        val createTable = "CREATE TABLE " + tbname + "(" +
                col_id + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                col_username + " VARCHAR(256) UNIQUE," + // Enforce unique usernames
                col_email + " VARCHAR(256) UNIQUE," + // Enforce unique emails
                col_passwordHash + " VARCHAR(256) NOT NULL" + // Store hashed password securely
                ")"
        db?.execSQL(createTable)
    }

    override fun onUpgrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        // TODO: Implement migration logic if needed
    }

    // Securely inserts a new user with password hashing
    @RequiresApi(Build.VERSION_CODES.O)
    fun insertData(user: Users) {
        val db = writableDatabase
        val cv = ContentValues()
        val context = this

        // Validate email format:
        if (!isValidEmail(user.email)) {

            val context = this
            val text: CharSequence = "Invalid Email Format"
            val duration: Int = Toast.LENGTH_SHORT
            val toast = Toast.makeText(context, text, duration)
            toast.show()
        }

        // Enforce unique username and email:
        if (isUsernameUnique(user.username) && isEmailUnique(user.email)) {
            // Hash password securely using BCrypt algorithm
            val workFactor = 12
            user.passwordHash = BCrypt.hashpw(user.password, BCrypt.gensalt(workFactor)) // Implement secure hashing
            cv.put(col_username, user.username)
            cv.put(col_email, user.email)
            cv.put(col_passwordHash, user.passwordHash as String)

            val result = db.insert(tbname, null, cv)

            if (result == -1L) {
                Toast.makeText(context, "Failed", Toast.LENGTH_LONG).show()

            } else {
                Toast.makeText(context, "Success", Toast.LENGTH_LONG).show()
            }
        } else {
            Toast.makeText(context, "Username or email already exists", Toast.LENGTH_SHORT).show()
        }
    }



    private fun requireContext() {
        val context: Context
        return
    }


    private fun isEmailUnique(email: String): Boolean {
        val db = writableDatabase
        val query = "SELECT COUNT(*) FROM $tbname WHERE $col_email = ?"
        val cursor = db.rawQuery(query, arrayOf(email))

        return if (cursor.moveToFirst()) {
            val count = cursor.getInt(0)
            cursor.close()
            count == 0 // Username is unique if count is 0
        } else {
            cursor.close()
            false // Error checking: assume non-unique if query fails
        }
    }


    private fun isUsernameUnique(username: String): Boolean {
        val db = writableDatabase
        val query = "SELECT COUNT(*) FROM $tbname WHERE $col_username = ?"
        val cursor = db.rawQuery(query, arrayOf(username))

        return if (cursor.moveToFirst()) {
            val count = cursor.getInt(0)
            cursor.close()
            count == 0 // Username is unique if count is 0
        } else {
            cursor.close()
            false // Error checking: assume non-unique if query fails
        }

    }

    // Securely finds a user by username with password comparison
    @RequiresApi(Build.VERSION_CODES.O)
    @SuppressLint("Range")
    fun findUserByUsername(username: String): Users? {
        val db = writableDatabase
        val query = "SELECT * FROM $tbname WHERE $col_username = ?"
        val cursor = db.rawQuery(query, arrayOf(username))

        if (cursor.moveToFirst()) {
            val user = Users(
                cursor.getInt(cursor.getColumnIndex(col_id)),
                cursor.getString(cursor.getColumnIndex(col_username)),
                cursor.getString(cursor.getColumnIndex(col_email)),
                null
            )


            // Securely compare entered password with stored hash using BCrypt:
            return if (BCrypt.checkpw(col_passwordHash, user.passwordHash.toString())) {
                cursor.close()
                return user
            } else {
                // Invalid password
                cursor.close()
                null
            }
        } else {
            cursor.close()
            return null
        }
    }

    // Optimized email validation with Pattern:
    @SuppressLint("Range")
    private fun isValidEmail(email: String): Boolean {
        val emailRegex = "^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$"

        // Optimize using Pattern for repeated validation:
        val pattern = Pattern.compile(emailRegex)
        return pattern.matcher(email).matches()
    }
}

我尝试直接使用此关键字代替上下文作为变量，但没有任何改变。请提供任何帮助。

Answer 1

val context=this

导致上下文不是

Context

，但它将是

DatabaseHandler

对象的实例；这就是问题所在。

• 即this用于引用类的当前实例，该类是

  DatabaseHandler

  类的实例。

您需要一种将 Context 传递给使用 Context 的函数的方法，或者一种检索适当 Context 的方法，这可能更难以正确检索。

也许是这样的：-

fun insertData(user: Users, context: Context) {
    ....
}

• 没有线

  val context=this

简单演示

使用 DatabaseHandler 的精简版本，如下所示：-

class DatabaseHandler(context: Context) : SQLiteOpenHelper(context, dbname, null, 1) {

    override fun onCreate(db: SQLiteDatabase?) {
        val createTable = "CREATE TABLE " + tbname + "(" +
                col_id + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                col_username + " VARCHAR(256) UNIQUE," + // Enforce unique usernames
                col_email + " VARCHAR(256) UNIQUE," + // Enforce unique emails
                col_passwordHash + " VARCHAR(256) NOT NULL" + // Store hashed password securely
                ")"
        db?.execSQL(createTable)
    }

    override fun onUpgrade(db: SQLiteDatabase?, oldVersion: Int, newVersion: Int) {
        // TODO: Implement migration logic if needed
    }

    // Securely inserts a new user with password hashing
    @RequiresApi(Build.VERSION_CODES.O)
    fun insertData(user: Users, context: Context) {
        val db = writableDatabase
        val cv = ContentValues()

        // Validate email format:
        //if (!isValidEmail(user.email)) {

            //val context = this
            val text: CharSequence = "Invalid Email Format"
            val duration: Int = Toast.LENGTH_SHORT
            val toast = Toast.makeText(context, text, duration)
            toast.show()
        //}
    }
}

还有活动代码（可以转换为上下文）：-

class MainActivity : AppCompatActivity() {
    lateinit var databaseHandler: DatabaseHandler
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        databaseHandler = DatabaseHandler(this)
        databaseHandler.insertData(Users(100,"Fred","[email protected]","blah"),this)
        databaseHandler.insertData(Users(200,"Mary","[email protected]","blah"),this)
        databaseHandler.insertData(Users(300,"Jane","[email protected]","blah"),this)
    }
}

• 注意 DatabaseHandler 实例的

  insertData

  函数的使用

运行时：-

• Toast 出现