我正在开发一个类似于camscanner的应用程序。在我的应用程序中，我有一个相机api我打电话。首次打开应用程序并按下相机按钮时，它可以工作，但是当我单击主页按钮并再次打开我的应用程序时，它会冻结并显示黑屏而不会导致应用程序崩溃。我发现了类似的问题，但没有一个能给我一个正确的答案，我知道我可能不得不改变onResume或onPause中的某些内容，并需要帮助来弄清楚是什么。
下面我有我的CameraScreen活动：
公共类CameraScreen扩展了Activity {
ImageView image;
Activity context;
Preview preview;
Camera camera;
Button exitButton;
ImageView fotoButton;
LinearLayout progressLayout;
String path = "/sdcard/KutCamera/cache/images/";
FrameLayout frame;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.camera_layout);
context=this;
fotoButton = (ImageView) findViewById(R.id.imageView_foto);
exitButton = (Button) findViewById(R.id.button_exit);
image = (ImageView) findViewById(R.id.imageView_photo);
progressLayout = (LinearLayout) findViewById(R.id.progress_layout);
preview = new Preview(this,
(SurfaceView) findViewById(R.id.KutCameraFragment));
frame = (FrameLayout) findViewById(R.id.preview);
frame.addView(preview);
preview.setKeepScreenOn(true);
fotoButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
takeFocusedPicture();
} catch (Exception e) {
}
exitButton.setClickable(true);
fotoButton.setClickable(false);
progressLayout.setVisibility(View.VISIBLE);
}
});
}
@Override
protected void onPause() {
super.onPause();
//releaseMediaRecorder(); // if you are using MediaRecorder, release it first
//releaseCamera();
if(null != camera){
camera.release();
camera = null;
}
frame.removeView(preview);
preview = null;// release the camera immediately on pause event
}
private void releaseCamera(){
if (camera != null){
camera.release(); // release the camera for other applications
camera = null;
}
}
@Override
protected void onResume() {
super.onResume();
// TODO Auto-generated method stub
if(camera==null){
Log.d("Camera tes", "Camera==null");
//camera.setPreviewCallback(null);
camera = Camera.open();
camera.startPreview();
camera.setErrorCallback(new ErrorCallback() {
public void onError(int error, Camera mcamera) {
camera.release();
camera = Camera.open();
Log.d("Camera died", "error camera");
}
});
}
if (camera != null) {
//camera.setPreviewCallback(null);
Log.d("Camera tes", "Camera!=null");
if (Build.VERSION.SDK_INT >= 14)
setCameraDisplayOrientation(context,
CameraInfo.CAMERA_FACING_BACK, camera);
preview.setCamera(camera);
}
}
private void setCameraDisplayOrientation(Activity activity, int cameraId,
android.hardware.Camera camera) {
android.hardware.Camera.CameraInfo info = new android.hardware.Camera.CameraInfo();
android.hardware.Camera.getCameraInfo(cameraId, info);
int rotation = activity.getWindowManager().getDefaultDisplay()
.getRotation();
int degrees = 0;
switch (rotation) {
case Surface.ROTATION_0:
degrees = 0;
break;
case Surface.ROTATION_90:
degrees = 90;
break;
case Surface.ROTATION_180:
degrees = 180;
break;
case Surface.ROTATION_270:
degrees = 270;
break;
}
int result;
if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
result = (info.orientation + degrees) % 360;
result = (360 - result) % 360; // compensate the mirror
} else { // back-facing
result = (info.orientation - degrees + 360) % 360;
}
camera.setDisplayOrientation(result);
}
Camera.AutoFocusCallback mAutoFocusCallback = new Camera.AutoFocusCallback() {
@Override
public void onAutoFocus(boolean success, Camera camera) {
try{
camera.takePicture(mShutterCallback, null, jpegCallback);
}catch(Exception e){
}
}
};
Camera.ShutterCallback mShutterCallback = new ShutterCallback() {
@Override
public void onShutter() {
// TODO Auto-generated method stub
}
};
public void takeFocusedPicture() {
camera.autoFocus(mAutoFocusCallback);
}
PictureCallback rawCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
// Log.d(TAG, "onPictureTaken - raw");
}
};
PictureCallback jpegCallback = new PictureCallback() {
@SuppressWarnings("deprecation")
public void onPictureTaken(byte[] data, Camera camera) {
FileOutputStream outStream = null;
Calendar c = Calendar.getInstance();
File videoDirectory = new File(path);
if (!videoDirectory.exists()) {
videoDirectory.mkdirs();
}
try {
// Write to SD Card
outStream = new FileOutputStream(path + c.getTime().getSeconds() + ".jpg");
outStream.write(data);
outStream.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
Bitmap realImage;
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 5;
options.inPurgeable=true; //Tell to gc that whether it needs free memory, the Bitmap can be cleared
options.inInputShareable=true; //Which kind of reference will be used to recover the Bitmap data after being clear, when it will be used in the future
realImage = BitmapFactory.decodeByteArray(data,0,data.length,options);
ExifInterface exif = null;
try {
exif = new ExifInterface(path + c.getTime().getSeconds()
+ ".jpg");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
Log.d("EXIF value",
exif.getAttribute(ExifInterface.TAG_ORIENTATION));
if (exif.getAttribute(ExifInterface.TAG_ORIENTATION)
.equalsIgnoreCase("1")) {
realImage = rotate(realImage, 90);
} else if (exif.getAttribute(ExifInterface.TAG_ORIENTATION)
.equalsIgnoreCase("8")) {
realImage = rotate(realImage, 90);
} else if (exif.getAttribute(ExifInterface.TAG_ORIENTATION)
.equalsIgnoreCase("3")) {
realImage = rotate(realImage, 90);
} else if (exif.getAttribute(ExifInterface.TAG_ORIENTATION)
.equalsIgnoreCase("0")) {
realImage = rotate(realImage, 90);
}
} catch (Exception e) {
}
image.setImageBitmap(realImage);
fotoButton.setClickable(true);
camera.startPreview();
progressLayout.setVisibility(View.GONE);
exitButton.setClickable(true);
}
};
public static Bitmap rotate(Bitmap source, float angle) {
Matrix matrix = new Matrix();
matrix.postRotate(angle);
return Bitmap.createBitmap(source, 0, 0, source.getWidth(),
source.getHeight(), matrix, false);
}
}
这里我有我的预览课程：
类预览扩展ViewGroup实现SurfaceHolder.Callback { private final String TAG =“预览”;
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
int heightmax ;
int widthmax ;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
@SuppressWarnings("deprecation")
Preview(Context context, SurfaceView sv) {
super(context);
mSurfaceView = sv;
// addView(mSurfaceView);
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes = mCamera.getParameters().getSupportedPictureSizes();
requestLayout();
// get Camera parameters
Camera.Parameters params = mCamera.getParameters();
List<String> focusModes = params.getSupportedFocusModes();
if (focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) {
// set the focus mode
params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
// set Camera parameters
mCamera.setParameters(params);
}
}
}
@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=maxSize();
}
}
public Size maxSize(){
Size sizeMax=mSupportedPreviewSizes.get(0);
maxsize=mSupportedPreviewSizes.get(0)
.height*mSupportedPreviewSizes.get(0).width;
for(Size size:mSupportedPreviewSizes){
if(size.height*size.width>sizeMax.width*sizeMax.height){
sizeMax = size;
}
}
return sizeMax;
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height / previewHeight;
child.layout((width - scaledChildWidth) / 2, 0,
(width + scaledChildWidth) / 2, height);
} else {
final int scaledChildHeight = previewHeight * width / previewWidth;
child.layout(0, (height - scaledChildHeight) / 2,
width, (height + scaledChildHeight) / 2);
}
}
}
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);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()", exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the preview.
/*
mCamera.stopPreview();
mCamera.setPreviewCallback(null);
mCamera.release();
mCamera = null;
if (mCamera != null) {
mCamera.stopPreview();
}
*/
}
Camera.AutoFocusCallback mnAutoFocusCallback = new Camera.AutoFocusCallback() {
@Override
public void onAutoFocus(boolean success, Camera camera) {
}
};
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
/*
if(mCamera != null) {
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPictureSize(mPreviewSize.width, mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
}
*/
}
}
我会劝告你能给我的任何帮助或指南。