"Type mismatch: inferred type is Fragment but Context was expected" 和 "None of the following functions can be called with the arguments supplied:"

Question

package com.example.mobilewarehousesystem.ui.import

import android.Manifest
import android.content.DialogInterface
import android.content.Intent
import android.content.pm.PackageManager
import android.graphics.Bitmap
import android.os.Bundle
import android.provider.MediaStore
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.activity.result.ActivityResult
import androidx.activity.result.ActivityResultCallback
import androidx.activity.result.ActivityResultLauncher
import androidx.activity.result.contract.ActivityResultContracts
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.fragment.app.Fragment
import com.example.mobilewarehousesystem.databinding.FragmentImportBinding
import com.google.mlkit.vision.barcode.Barcode
import com.google.mlkit.vision.barcode.BarcodeScanner
import com.google.mlkit.vision.common.InputImage
import androidx.appcompat.app.AlertDialog

class ImportFragment : Fragment() {
    //show UI
    private var _binding: FragmentImportBinding?=null
    private val binding get() = _binding!!
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
        _binding = FragmentImportBinding.inflate(inflater, container, false)
        setHasOptionsMenu(true)
        return binding.root
    }

    private val CAMERA_PERMISSION_CODE=123
    private val READ_STORAGE_PERMISSION_CODE=113
    private val WRITE_STORAGE_PERMISSION_CODE=113
    private lateinit var cameraLauncher: ActivityResultLauncher<Intent>
    private lateinit var galleryLauncher: ActivityResultLauncher<Intent>
    private val TAG = "My Tag"
    lateinit var inputImage: InputImage
    lateinit var barcodeScanner: BarcodeScanner
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        cameraLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult(), object :ActivityResultCallback<ActivityResult>{
            override fun onActivityResult(result: ActivityResult?) {
                    val data=result?.data
                    try{
                        val photo = data?.extras?.get("data") as Bitmap
                        inputImage= InputImage.fromBitmap(photo, 0)
                        processQr()
                    }catch(e:Exception){
                        Log.d(TAG, "onActivityResult:"+e.message)
                    }
                }
            })
        galleryLauncher = registerForActivityResult(ActivityResultContracts.StartActivityForResult(), object :ActivityResultCallback<ActivityResult>{
                override fun onActivityResult(result: ActivityResult?) {
                    val data=result?.data
                    inputImage = InputImage.fromFilePath(this@ImportFragment, data?.data)
                    processQr()
                }
            })
        binding.btnScanBarcode.setOnClickListener{
            val options=arrayOf("camera","gallery")

            val builder=AlertDialog.Builder(this@ImportFragment)
            builder.setTitle("Pick a option")

            builder.setItems(options, DialogInterface.OnClickListener { dialog, which ->
                if(which==0){
                    val cameraIntent=Intent(MediaStore.ACTION_IMAGE_CAPTURE)
                    cameraLauncher.launch(cameraIntent)
                }else{
                    val storageIntent=Intent()
                    storageIntent.setType("image/*")
                    storageIntent.setAction(Intent.ACTION_GET_CONTENT)
                    galleryLauncher.launch(storageIntent)
                }
            })
            builder.show()
        }
    }
    private fun processQr(){
        binding.ivQrCode.visibility=View.GONE
        binding.tvResult.visibility=View.GONE
        barcodeScanner.process(inputImage).addOnSuccessListener{
            for (barcode:Barcode in it){
                val valueType=barcode.valueType
                when (valueType) {
                    Barcode.TYPE_WIFI -> {
                        val ssid = barcode.wifi!!.ssid
                        val password = barcode.wifi!!.password
                        val type = barcode.wifi!!.encryptionType
                        binding.tvResult.text = "ssid ${ssid} \n password ${password} \n type ${type}"
                    }
                    Barcode.TYPE_URL -> {
                        val title = barcode.url!!.title
                        val url = barcode.url!!.url
                        binding.tvResult.text = "title ${title} \n url ${url}"
                    }
                    Barcode.TYPE_TEXT->{
                        val data = barcode.displayValue
                        binding.tvResult.text="Result ${data}"
                    }
                }
            }
        }.addOnFailureListener{
            Log.d(TAG, "processQr: ${it.message}")
        }
    }
    override fun onResume() {
        super.onResume()
        checkPermission(Manifest.permission.CAMERA,CAMERA_PERMISSION_CODE)
    }
    private fun checkPermission(permission:String, requestCode:Int){
        if(ContextCompat.checkSelfPermission(this@ImportFragment, permission)== PackageManager.PERMISSION_DENIED){
            ActivityCompat.requestPermissions(this@ImportFragment, arrayOf(permission),requestCode)
        }
    }
    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)

        if(requestCode==CAMERA_PERMISSION_CODE){
            if(grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                checkPermission(
                    android.Manifest.permission.READ_EXTERNAL_STORAGE,
                    READ_STORAGE_PERMISSION_CODE)
            }else{
                Toast.makeText(this@ImportFragment, "Camera Permission Denied", Toast.LENGTH_SHORT).show()
            }
        }else if(requestCode==READ_STORAGE_PERMISSION_CODE){
            if((grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED)){
                checkPermission(
                    android.Manifest.permission.WRITE_EXTERNAL_STORAGE,
                    WRITE_STORAGE_PERMISSION_CODE)
            }else{
                Toast.makeText(this@ImportFragment, "Storage Permission Denied", Toast.LENGTH_SHORT).show()
            }
        }else if(requestCode==WRITE_STORAGE_PERMISSION_CODE) {
            if (!(grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED)) {
                Toast.makeText(this@ImportFragment, "Storage Permission Denied", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

我有7个错误，难道都是实现错误？？这些代码是在有限的知识下从 MainActivity 1 1 转换为 Fragment 的，我找到了一些解决方案，但仍然不知道如何应用到我的。

code	error	line
`inputImage = InputImage.fromFilePath(this@ImportFragment, data?.data)`	Type mismatch: inferred type is ImportFragment but Context! was expected	63
`val builder=AlertDialog.Builder(this@ImportFragment)`	Type mismatch: inferred type is ImportFragment but Context! was expected	70
`if(ContextCompat.checkSelfPermission(this@ImportFragment, permission)== PackageManager.PERMISSION_DENIED){`	Type mismatch: inferred type is ImportFragment but Context! was expected	120
`ActivityCompat.requestPermissions(this@ImportFragment, arrayOf(permission),requestCode)`	Type mismatch: inferred type is ImportFragment but Activity was expected	121
`Toast.makeText(this@ImportFragment, "Camera Permission Denied", Toast.LENGTH_SHORT).show()`	None of the following functions can be called with the arguments supplied: public open fun makeText(context: Context!, text: CharSequence!, duration: Int): Toast! defined in android.widget.Toast public open fun makeText(context: Context!, resId: Int, duration: Int): Toast! defined in android.widget.Toast	133
`Toast.makeText(this@ImportFragment, "Storage Permission Denied", Toast.LENGTH_SHORT).show()`	None of the following functions can be called with the arguments supplied: public open fun makeText(context: Context!, text: CharSequence!, duration: Int): Toast! defined in android.widget.Toast public open fun makeText(context: Context!, resId: Int, duration: Int): Toast! defined in android.widget.Toast	141, 145

Answer 1

您必须使用上下文而不是 this@ImportFragment。

替换：

this@ImportFragment

和

requireContext()

或者尝试把

 context!!

一般来说，如果你写 context!! Android studio 建议你用 requireContext() 替换它，这里有更多详细信息：

/**
 * Return the {@link Context} this fragment is currently associated with.
 *
 * @throws IllegalStateException if not currently associated with a context.
 * @see #getContext()
 */
@NonNull
public final Context requireContext() {
    Context context = getContext();
    if (context == null) {
        throw new IllegalStateException("Fragment " + this + " not attached to a context.");
    }
    return context;
}

"Type mismatch: inferred type is Fragment but Context was expected" 和 "None of the following functions can be called with the arguments supplied:"

"Type mismatch: inferred type is Fragment but Context was expected" and "None of the following functions can be called with the arguments supplied:"

android

android-fragments

kotlin