上一篇可以生成QRcode那這篇來說說掃描QRcode

如果要掃描QRcode一定要先取得相機權限

private void getPermissionsCamera(){
    if(ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED){
        ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA},1);
    }
}

接著是code

public class CameraActivity extends AppCompatActivity {
    SurfaceView surfaceView;
    TextView textView;
    CameraSource cameraSource;
    BarcodeDetector barcodeDetector;
​
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera);
​
        surfaceView=findViewById(R.id.surfaceView);
        textView=findViewById(R.id.textView);
​
        barcodeDetector = new BarcodeDetector.Builder(this).setBarcodeFormats(Barcode.QR_CODE).build();
        cameraSource=new CameraSource.Builder(this,barcodeDetector).setRequestedPreviewSize(300,300).build();
        surfaceView.getHolder().addCallback(new SurfaceHolder.Callback(){
            @Override
            public void surfaceCreated(@NonNull SurfaceHolder surfaceHolder) {
                if(ActivityCompat.checkSelfPermission(getApplicationContext(),Manifest.permission.CAMERA)
                        !=PackageManager.PERMISSION_GRANTED)
                    return;
                try{
                    cameraSource.start(surfaceHolder);
                }catch (IOException e){
                    e.printStackTrace();
                }
            }
​
            @Override
            public void surfaceChanged(@NonNull SurfaceHolder surfaceHolder, int i, int i1, int i2) {
​
            }
​
            @Override
            public void surfaceDestroyed(@NonNull SurfaceHolder surfaceHolder) {
                cameraSource.stop();
            }
        });
        barcodeDetector.setProcessor(new Detector.Processor<Barcode>(){
​
            @Override
            public void release() {
​
            }
​
            @Override
            public void receiveDetections(Detector.Detections<Barcode> detections) {
                final SparseArray<Barcode> qrCodes=detections.getDetectedItems();
                if(qrCodes.size()!=0){
                    textView.post(new Runnable() {
                        @Override
                        public void run() {
                            textView.setText(qrCodes.valueAt(0).displayValue);
                        }
                    });
                }
            }
        });
​
    }
​
​
}

然後是xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".CameraActivity">
​
    <TextView
        android:id="@+id/textView"
        android:layout_width="350dp"
        android:layout_height="70dp"
        android:layout_marginBottom="172dp"
        android:text="網址在這"
        android:textSize="30sp"
        android:gravity="center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.491"
        app:layout_constraintStart_toStartOf="parent" />
​
    <SurfaceView
        android:id="@+id/surfaceView"
        android:layout_width="350dp"
        android:layout_height="350dp"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.491"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.573" />
</androidx.constraintlayout.widget.ConstraintLayout>

成果如下