Question

I just started programming in Java, and I need to get a simple application up that shows the camera, takes a picture, and sends that picture data somewhere.

I have been searching all over the web trying to find a good camera tutorial that worked as expected, but apparently they all require some inner knowledge that I do not have yet.

On this page, commonsWare pointed to code that had some sample code in it for using the camera. I have taken the PictureDemo code and got it running with no errors. However, it only brings up a black screen. I assume this is because the program is not actually activating the preview, or camera in the main function, but every time I try adding the code I think I need, I am getting exceptions.

So my question is, what do I need to add in the main function to get the camera going? Or is there a better tutorial somewhere that I can see simple basic code for getting the camera up?

package assist.core;

import android.app.Activity;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.KeyEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
import java.io.File;
import java.io.FileOutputStream;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class MainActivity extends Activity
{
    private SurfaceView preview = null;
    private SurfaceHolder previewHolder = null;
    private Camera camera = null;
    private boolean inPreview = false;

    /**
     * 
     */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        //Call the parent class
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        preview = (SurfaceView) findViewById(R.id.preview);
        previewHolder = preview.getHolder();
        previewHolder.addCallback(surfaceCallback);
        previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @Override
    public void onResume() {
        super.onResume();
        //Get the camera instance
        camera = CameraFinder.INSTANCE.open();
    }

    @Override
    public void onPause() {
        if (inPreview) {
            camera.stopPreview();
        }

        camera.release();
        camera = null;
        inPreview = false;

        super.onPause();
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_CAMERA || keyCode == KeyEvent.KEYCODE_SEARCH) {
            if (inPreview) {
                camera.takePicture(null, null, photoCallback);
                inPreview = false;
            }

            return(true);
        }

        return(super.onKeyDown(keyCode, event));
    }

    private Camera.Size getBestPreviewSize(int width, int height, Camera.Parameters parameters) {
        Camera.Size result = null;

        for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
            if (size.width <= width && size.height <= height) {
                if (result == null) {
                  result=size;
                }
                else {
                    int resultArea = result.width * result.height;
                    int newArea = size.width * size.height;

                    if (newArea > resultArea) {
                        result = size;
                    }
                }
            }
        }

        return(result);
    }

    SurfaceHolder.Callback surfaceCallback = new SurfaceHolder.Callback() {
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                camera.setPreviewDisplay(previewHolder);
            }
            catch (Throwable t) {
                Log.e("MainActivity-surfaceCallback", "Exception in setPreviewDisplay()", t);
                Toast.makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG).show();
            }
        }

        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            Camera.Parameters parameters = camera.getParameters();
            Camera.Size size = getBestPreviewSize(width, height, parameters);

            if (size != null) {
                parameters.setPreviewSize(size.width, size.height);
                parameters.setPictureFormat(PixelFormat.JPEG);

                camera.setParameters(parameters);
                camera.startPreview();
                inPreview = true;
            }
        }

        public void surfaceDestroyed(SurfaceHolder holder) {
            // no-op
        }
    };

    Camera.PictureCallback photoCallback = new Camera.PictureCallback() {
        public void onPictureTaken(byte[] data, Camera camera) {
            new SavePhotoTask().execute(data);
            camera.startPreview();
            inPreview = true;
        }
    };

    class SavePhotoTask extends AsyncTask<byte[], String, String> {
        @Override
        protected String doInBackground(byte[]... jpeg) {
            File photo = new File(Environment.getExternalStorageDirectory(), "photo.jpg");
            if(photo.exists()) {
                photo.delete();
            }

            try {
                FileOutputStream fos = new FileOutputStream(photo.getPath());
                fos.write(jpeg[0]);
                fos.close();
            }
            catch (java.io.IOException e) {
                Log.e("MainActivity", "Exception in photoCallback", e);
            }

            return(null);
        }
    }
}

Update

As for the exceptions I was getting, if I tried making the main function like the code below,

public void onCreate(Bundle savedInstanceState)
{
    //Call the parent class
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    preview = (SurfaceView) findViewById(R.id.preview);
    previewHolder = preview.getHolder();
    previewHolder.addCallback(surfaceCallback);
    previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    Camera.Parameters parameters = camera.getParameters();
    parameters.setPictureFormat(PixelFormat.JPEG);
    camera.setParameters(parameters);

    try {
        //Start the camera preview display
        camera.setPreviewDisplay(previewHolder);
        camera.startPreview();
    } 
    catch (IOException ex) {
        Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex);
    }
}

I get “The application has stopped unexpectedly. Please Try again.” I was basically trying to follow the steps that the android documention specifies. I also tried putting this code into the onResume function after the camera object is retrieved, and then calling this.onResume.

Answer 1

If what you need is just open up a camera, take a picture, and get the image.
then you can do:
launch Camera using Intents

Your above code is the integrated version. That integrates the camera into your app.
I am not sure if you have the real android device to test.
The simulator will show either black or “android icon” screen in replacing the real camera.

so test it on real device if you weren’t.

And could you be more specified on the exceptions you got?