How to find the focal length of an Android camera?

Question

I have earned many times using stackoverflow and google. I need to calculate the distance between my camera and the specified object.

To do this, I need to find the focal length of my camera. I also created a sample project, but I am throwing a Null Pointer Exception. Please, help..

The code is as follows.

public class MainActivity extends Activity { Camera mcamera; int focul_length; Parameters params; File mFile; public int PICTURE_ACTIVITY_CODE = 1; public String FILENAME = "sdcard/photo.jpg"; Camera.Parameters cameraParameters; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); launchTakePhoto(); } private void launchTakePhoto() { Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); cameraParameters = mcamera.getParameters(); CameraInfo myinfo = new CameraInfo(); float l=cameraParameters.getFocalLength(); // Here its creating Null Pointer Exception mFile = new File(FILENAME); System.out.println("My Focul Length:--"+l); Uri outputFileUri = Uri.fromFile(mFile); intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri); startActivityForResult(intent, PICTURE_ACTIVITY_CODE); } Also If possible please provide the code to get angle of Elevation.If possible.I need this very badly.I need your help guys!! @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == PICTURE_ACTIVITY_CODE) { if (resultCode == RESULT_OK) { ImageView myimageView = (ImageView) findViewById(R.id.imageView1); Uri inputFileUri = Uri.fromFile(mFile); myimageView.setImageURI(inputFileUri); } } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } } 

Answer 1

Are you initializing the Camera object? Try something like this in onCreate()

 mcamera = Camera.open();