Android 扫描二维码

在Android中，可以使用ZXing库来实现二维码的扫描功能。下面是一个简单的示例代码：

1. 首先，在你的项目中添加ZXing库的依赖。可以在build.gradle文件中添加以下代码：

implementation 'com.google.zxing:core:3.4.0'
implementation 'com.journeyapps:zxing-android-embedded:3.6.0'

2. 在你的布局文件中添加一个用于显示相机预览的SurfaceView：

<SurfaceView
    android:id="@+id/camera_preview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

3. 创建一个扫描二维码的Activity，并在其中初始化相机和二维码扫描器：

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.Result;
import com.journeyapps.barcodescanner.BarcodeCallback;
import com.journeyapps.barcodescanner.BarcodeResult;
import com.journeyapps.barcodescanner.CompoundBarcodeView;

import java.util.Arrays;
import java.util.Collection;
import java.util.List;

public class QRCodeScannerActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    private static final int CAMERA_PERMISSION_REQUEST_CODE = 100;

    private CompoundBarcodeView barcodeView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_qr_code_scanner);

        barcodeView = findViewById(R.id.barcode_scanner);

        // 检查相机权限
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
        } else {
            // 初始化相机和二维码扫描器
            initScanner();
        }
    }

    private void initScanner() {
        barcodeView.getBarcodeView().setDecoderFactory(new DefaultDecoderFactory(Arrays.asList(BarcodeFormat.QR_CODE)));
        barcodeView.initializeFromIntent(getIntent());
        barcodeView.decodeContinuous(new BarcodeCallback() {
            @Override
            public void barcodeResult(BarcodeResult result) {
                // 扫描结果回调
                String qrCode = result.getText();
                Log.d("QRCodeScanner", "QR Code: " + qrCode);
                Toast.makeText(QRCodeScannerActivity.this, "QR Code: " + qrCode, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void possibleResultPoints(List<ResultPoint> resultPoints) {
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
        barcodeView.resume();
    }

    @Override
    protected void onPause() {
        super.onPause();
        barcodeView.pause();
    }

    @Override
    public void surfaceCreated(@NonNull SurfaceHolder holder) {
        barcodeView.resume();
    }

    @Override
    public void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {
    }

    @Override
    public void surfaceDestroyed(@NonNull SurfaceHolder holder) {
        barcodeView.pause();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 初始化相机和二维码扫描器
                initScanner();
            } else {
                Toast.makeText(this, "Camera permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

这样，你就可以在你的Android应用中实现二维码的扫描功能了。