如何显示相机看到的片段？

Question

The application purpose is to basically compare what's camera seeing vs an image from the gallery. I don't know which control gives you access to the camera without opening the default system app.

I know this app will be useless on split-screen phones (camera on one side and gallery in the other) but is intended to be used in phones without this Nougat functionality (marshmallow or lollipop).

I've seen some apps that display camera like Barcode readers and some quick photo editors.

Answer 1

You can use Camera api. You will need to create your own SurfaceView to display preview of what camera is seeing. There are a lot of tutorial on internet for this.

public class ImageSurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    private Camera camera;
    private SurfaceHolder surfaceHolder;

    public ImageSurfaceView(Context context, Camera camera) {
        super(context);
        this.camera = camera;
        this.surfaceHolder = getHolder();
        this.surfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            this.camera.setPreviewDisplay(holder);
            this.camera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        this.camera.stopPreview();
        this.camera.release();
    }
}



public class MainActivity extends Activity  implements SensorEventListener {
    private Camera mCamera;
    private ImageSurfaceView cameraView;

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

    protected void onResume(){
        super.onResume();
        mCamera = getCameraInstance();
        mCamera.setDisplayOrientation(90);
        cameraView = new ImageSurfaceView(this, mCamera);
        mainView.addView(cameraView);
        mainView.bringChildToFront(buttonView);
        senSensorManager.registerListener(this, senRotation, SensorManager.SENSOR_DELAY_GAME);
    }

    /** A safe way to get an instance of the Camera object. */
    public Camera getCameraInstance(){
        Camera c = null;
        try{
            c = Camera.open(); // attempt to get a Camera instance
            Camera.Parameters parameters = c.getParameters();
            parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
            c.setParameters(parameters);
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
        }

        return c; // returns null if camera is unavailable
    }
}