Guten Tag,
Ich hab mir jetzt mal vorgenommen ein bisschen mit Android zu spielen.
Mein Ziel ist es erstmal die Anzahl der Gesichter aus einer Kamera Preview zu bekommen.
Meine Start-Activity sieht so aus:
Dann hab ich noch das CameraFragment und eine Camera Preview, die weitestgehend von google kommen:
Jetzt ist meine Frage, wann (und wo überall) muss ich den FaceDetectionListener regestrieren?
Desweiteren hab ich das Problem, das die App das OnResum() nicht überlebt, also beim zurückkehren aus dem Hintergrund stürzt sie ab. Was ist da noch falsch?
mfg. Dagobert
Ich hab mir jetzt mal vorgenommen ein bisschen mit Android zu spielen.
Mein Ziel ist es erstmal die Anzahl der Gesichter aus einer Kamera Preview zu bekommen.
Meine Start-Activity sieht so aus:
Java:
package de.muehlensoft;
import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.hardware.Camera;
import android.hardware.Camera.Face;
import android.hardware.Camera.FaceDetectionListener;
import android.os.Bundle;
public class FaceAppActivity extends Activity implements FaceDetectionListener{
private FaceFragment infoFragment;
private CameraFragment cameraFragment;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
FragmentManager fm = getFragmentManager();
cameraFragment = new CameraFragment();
infoFragment = new FaceFragment();
FragmentTransaction ta = fm.beginTransaction();
ta.add(R.id.camerafragment, cameraFragment);
ta.add(R.id.infofragment, infoFragment);
ta.commit();
// cameraFragment.setFaceDetectionListener(this); <- Fehler, da camera noch null ist
}
public void onFaceDetection(Face[] faces, Camera camera) {
infoFragment.setFaceCount(faces.length);
}
}Dann hab ich noch das CameraFragment und eine Camera Preview, die weitestgehend von google kommen:
Java:
package de.muehlensoft;
import android.app.Fragment;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.hardware.Camera.FaceDetectionListener;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class CameraFragment extends Fragment {
private CameraPreview mPreview;
Camera mCamera;
int mNumberOfCameras;
int mCurrentCamera; // Camera ID currently chosen
int mCameraCurrentlyLocked; // Camera ID that's actually acquired
// The first rear facing camera
int mDefaultCameraId;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Create a container that will hold a SurfaceView for camera previews
mPreview = new CameraPreview(this.getActivity());
// Find the total number of cameras available
mNumberOfCameras = Camera.getNumberOfCameras();
// Find the ID of the rear-facing ("default") camera
CameraInfo cameraInfo = new CameraInfo();
for (int i = 0; i < mNumberOfCameras; i++) {
Camera.getCameraInfo(i, cameraInfo);
if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {
mCurrentCamera = mDefaultCameraId = i;
}
}
setHasOptionsMenu(mNumberOfCameras > 1);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return mPreview;
}
@Override
public void onResume() {
super.onResume();
// Use mCurrentCamera to select the camera desired to safely restore
// the fragment after the camera has been changed
mCamera = Camera.open(mCurrentCamera);
mCameraCurrentlyLocked = mCurrentCamera;
mPreview.setCamera(mCamera);
}
@Override
public void onPause() {
super.onPause();
// Because the Camera object is a shared resource, it's very
// important to release it when the activity is paused.
if (mCamera != null) {
mPreview.setCamera(null);
mCamera.release();
mCamera = null;
}
}
public void setFaceDetectionListener(FaceDetectionListener l){
mPreview.setFaceDetectionListener(l);
}
}
Java:
package de.muehlensoft;
import java.io.IOException;
import java.util.List;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.FaceDetectionListener;
import android.hardware.Camera.Size;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
/**
* A simple wrapper around a Camera and a SurfaceView that renders a centered
* preview of the Camera to the surface. We need to center the SurfaceView
* because not all devices have cameras that support preview sizes at the same
* aspect ratio as the device's display.
*/
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private final String TAG = "Preview";
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
boolean mSurfaceCreated = false;
private FaceDetectionListener mFaceListener;
CameraPreview(Context context) {
super(context);
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters()
.getSupportedPreviewSizes();
if (mSurfaceCreated)
requestLayout();
}
}
public void switchCamera(Camera camera) {
setCamera(camera);
try {
camera.setPreviewDisplay(mHolder);
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(),
widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(),
heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize = getOptimalPreviewSize(mSupportedPreviewSizes, width,
height);
}
if (mCamera != null) {
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
mCamera.setParameters(parameters);
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
if(mFaceListener != null)
mCamera.setFaceDetectionListener(mFaceListener);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
if (mPreviewSize == null)
requestLayout();
mSurfaceCreated = true;
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
if (mCamera != null) {
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null)
return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE)
continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
if(mFaceListener != null)
mCamera.setFaceDetectionListener(mFaceListener);
}
public void setFaceDetectionListener(FaceDetectionListener l){
mFaceListener = l;
if(mCamera != null){
mCamera.setFaceDetectionListener(mFaceListener);
}
}
}Jetzt ist meine Frage, wann (und wo überall) muss ich den FaceDetectionListener regestrieren?
Desweiteren hab ich das Problem, das die App das OnResum() nicht überlebt, also beim zurückkehren aus dem Hintergrund stürzt sie ab. Was ist da noch falsch?
mfg. Dagobert
Zuletzt bearbeitet von einem Moderator:
