在Fragment中集成ZXingScannerView实现二维码扫描求助

Got it, let's get your QR scanner working in that Drawer Layout Fragment—this is a common pitfall when adapting Activity-based examples to Fragments, so let's break it down step by step.

1. Add ZXing Dependency First #

First, make sure you have the right ZXing library in your app-level build.gradle (Module level):

implementation 'com.journeyapps:zxing-android-embedded:4.3.0'
// If using AndroidX, include this compatibility dependency (newer versions may handle it automatically)
implementation 'androidx.appcompat:appcompat:1.6.1'

Sync your project after adding these lines.

2. Create the Scanner Fragment Layout #

Make a simple layout fragment_scanner.xml to hold the scanner view—this keeps your view hierarchy clean:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/scanner_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</FrameLayout>

3. Implement the Scanner Fragment #

Here's the full Fragment code, with lifecycle handling, camera permissions, and scan result processing—this fixes the main issues people run into when porting from Activity to Fragment:

import android.Manifest
import android.content.pm.PackageManager
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.app.ActivityCompat
import androidx.core.content.ContextCompat
import androidx.fragment.app.Fragment
import com.journeyapps.barcodescanner.BarcodeCallback
import com.journeyapps.barcodescanner.BarcodeResult
import com.journeyapps.barcodescanner.CompoundBarcodeView

class ScannerFragment : Fragment() {
    private lateinit var barcodeScanner: CompoundBarcodeView
    private val CAMERA_PERMISSION_REQUEST_CODE = 1001

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_scanner, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        // Initialize the scanner view and add it to the fragment's container
        barcodeScanner = CompoundBarcodeView(requireContext())
        view.findViewById<ViewGroup>(R.id.scanner_container).addView(barcodeScanner)

        // Check camera permission before starting the scanner
        if (ContextCompat.checkSelfPermission(requireContext(), Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED
        ) {
            ActivityCompat.requestPermissions(
                requireActivity(),
                arrayOf(Manifest.permission.CAMERA),
                CAMERA_PERMISSION_REQUEST_CODE
            )
        } else {
            startScanning()
        }
    }

    private fun startScanning() {
        // Set up callback for when a QR code is scanned
        barcodeScanner.decodeContinuous(object : BarcodeCallback {
            override fun barcodeResult(result: BarcodeResult) {
                // Handle the scanned content here (e.g., send to main activity)
                val scannedQrText = result.text
                (activity as MainActivity).handleScannedQrCode(scannedQrText)
                // Pause scanning after a successful read
                barcodeScanner.pause()
            }
        })
        barcodeScanner.resume()

        // Optional: Lock the drawer so it doesn't interfere with scanning
        (activity as MainActivity).drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED)
    }

    // Handle camera permission request result
    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE) {
            if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startScanning()
            } else {
                // Show an error message or prompt the user to enable permission
                // Toast.makeText(requireContext(), "Camera permission is required to scan QR codes", Toast.LENGTH_SHORT).show()
            }
        }
    }

    // Bind scanner lifecycle to fragment lifecycle to avoid crashes/leaks
    override fun onResume() {
        super.onResume()
        if (::barcodeScanner.isInitialized) {
            barcodeScanner.resume()
        }
    }

    override fun onPause() {
        super.onPause()
        if (::barcodeScanner.isInitialized) {
            barcodeScanner.pause()
            // Unlock the drawer when leaving the scanner fragment
            (activity as MainActivity).drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_UNLOCKED)
        }
    }

    override fun onDestroyView() {
        super.onDestroyView()
        if (::barcodeScanner.isInitialized) {
            barcodeScanner.pauseAndWait()
        }
    }
}

4. Add the Fragment to Your Drawer Navigation #

In your main Activity's drawer item click handler, add code to replace the current Fragment with ScannerFragment:

// Example in MainActivity's onNavigationItemSelected method
when (menuItem.itemId) {
    R.id.nav_scanner -> {
        supportFragmentManager.beginTransaction()
            .replace(R.id.nav_host_fragment, ScannerFragment())
            .commit()
        drawerLayout.closeDrawers()
    }
    // Handle other drawer items here...
}

Common Mistakes to Avoid #

• Missing Permission Handling: The scanner will crash immediately if camera permission isn't granted—always check and request permissions first.
• Unbound Lifecycle: Forgetting to call resume()/pause() on the scanner with the Fragment's lifecycle leads to memory leaks or camera access errors.
• Drawer Interference: Locking the drawer during scanning ensures the user doesn't accidentally open it mid-scan, breaking the camera view.

内容的提问来源于stack exchange，提问作者Miguel