android使用zxing实现扫码功能并附上demo

好的，下面是使用ZXing实现Android扫码功能的示例代码。

首先，添加ZXing依赖库到你的项目中。可以使用Gradle，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'

然后，在你的layout文件中添加一个用于预览扫描结果的SurfaceView：

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

接下来，在你的Activity中实现扫描逻辑。首先，初始化扫描器并启动扫描：

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
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.BarcodeEncoder;
import com.journeyapps.barcodescanner.BarcodeResult;
import com.journeyapps.barcodescanner.CaptureManager;
import com.journeyapps.barcodescanner.DecoratedBarcodeView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {
    private static final String TAG = MainActivity.class.getSimpleName();
    private static final int REQUEST_CAMERA_PERMISSION = 101;

    private CaptureManager capture;
    private DecoratedBarcodeView barcodeScannerView;
    private SurfaceView surfaceView;

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

        surfaceView = findViewById(R.id.surfaceView);
        barcodeScannerView = findViewById(R.id.barcodeScannerView);

        // Check camera permission
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
        } else {
            startCamera();
        }
    }

    private void startCamera() {
        barcodeScannerView.getBarcodeView().setDecoderFactory(new DefaultDecoderFactory(getBarcodeFormats()));

        capture = new CaptureManager(this, barcodeScannerView);
        capture.initializeFromIntent(getIntent(), savedInstanceState);
        capture.decode();
    }

    private List<BarcodeFormat> getBarcodeFormats() {
        List<BarcodeFormat> formats = new ArrayList<>();
        formats.add(BarcodeFormat.QR_CODE);
        return formats;
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (capture != null) {
            capture.onResume();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        if (capture != null) {
            capture.onPause();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (capture != null) {
            capture.onDestroy();
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        if (capture != null) {
            capture.onSaveInstanceState(outState);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startCamera();
            } else {
                Toast.makeText(this, "Camera permission required", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        if (capture != null) {
            capture.onSurfaceCreated(holder);
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        if (capture != null) {
            capture.onSurfaceChanged(holder, format, width, height);
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if (capture != null) {
            capture.onSurfaceDestroyed(holder);
        }
    }
}

这里使用了ZXing官方提供的CaptureManager和DecoratedBarcodeView来处理扫描逻辑和预览界面。在onCreate方法中，首先检查相机权限，然后初始化扫描器并启动扫描。在onResume、onPause、onDestroy、onSaveInstanceState等方法中，分别处理扫描器的生命周期。

最后，在AndroidManifest.xml文件中添加相机权限：

<uses-permission android:name="android.permission.CAMERA" />

这样，就可以实现基本的扫码功能了。当用户扫描了一张二维码后，可以在onActivityResult方法中获取扫描结果：

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == RESULT_OK && requestCode == REQUEST_CODE_SCAN) {
        String result = data.getStringExtra(Intents.Scan.RESULT);
        Log.d(TAG, "Scan result: " + result);
    }
}

完整的示例代码可以参考这个GitHub项目：https://github.com/journeyapps/zxing-android-embedded