我在onPause()和onResume()相机生命周期的处理上遇到了一些问题：
使用预览的相机以及拍照功能都可以正常工作。但有一个例外：
当我启动应用程序，点击主屏幕键，切换回应用程序并再次拍摄时，会发生某些问题。
结果：快门回调仍然被执行（请参见代码），但JPEG回调不再执行！ 然后我的Galaxy S手机会振动，而屏幕会一直保持黑色，因为在jpegCallback之后并未重新启动startPreview（）。对我来说，堆栈跟踪远非有用。奇怪的是，这只发生在我的Galaxy S手机上，而不是模拟器上。我真的不知道该怎么办了:/有人有什么好的想法吗？10-28 18:59:40.649: ERROR/SecCamera(4291): SetRotate(angle(0)) 10-28 18:59:40.649: ERROR/CameraHardwareSec(4291): ====setParameters processingmethod = (null) 10-28 18:59:40.649: ERROR/SecCamera(4291): setRecordingSize(width(800), height(480)) 10-28 18:59:40.673: ERROR/SecCamera(4291): SetRotate(angle(0)) 10-28 18:59:40.673: ERROR/CameraHardwareSec(4291): ====setParameters processingmethod = (null) 10-28 18:59:40.673: ERROR/SecCamera(4291): setRecordingSize(width(800), height(480)) 10-28 18:59:40.692: ERROR/SecCamera(4291): SetRotate(angle(0)) 10-28 18:59:40.692: ERROR/CameraHardwareSec(4291): ====setParameters processingmethod = (null) 10-28 18:59:40.692: ERROR/SecCamera(4291): setRecordingSize(width(800), height(480)) 10-28 18:59:40.712: ERROR/SecCamera(4291): SetRotate(angle(0)) 10-28 18:59:40.712: ERROR/CameraHardwareSec(4291): ====setParameters processingmethod = (null) 10-28 18:59:40.712: ERROR/SecCamera(4291): setRecordingSize(width(800), height(480)) 10-28 18:59:40.751: ERROR/CameraHardwareSec(4291): stopPreview() 10-28 18:59:40.751: ERROR/SecCamera(4291): cancelAutofocus() 10-28 18:59:40.751: ERROR/SecCamera(4291): cancelAutofocus() end, 0, 4 10-28 18:59:40.768: ERROR/SecCamera(4291): stopPreview() 10-28 18:59:40.768: ERROR/SecCamera(4291): fimc_v4l2_streamoff() 10-28 18:59:40.797: ERROR/CameraHardwareSec(4291): stopPreview() end 10-28 18:59:41.622: ERROR/SecCamera(4291): fimc_v4l2_streamoff() 10-28 18:59:46.536: ERROR/dalvikvm(2993): Failed to write stack traces to /data/anr/traces.txt (2775 of 2970): Unknown error: 0 10-28 18:59:46.540: ERROR/dalvikvm(2919): Failed to write stack traces to /data/anr/traces.txt (-1 of 3414): Math result not representable 10-28 18:59:46.610: ERROR/dalvikvm(3044): Failed to write stack traces to /data/anr/traces.txt (3354 of 7154): Math result not representable ...
以下是我（精简后的）代码：
public class CameraActivity extends Activity implements MenuViewCallback, CutoutPathManagerCallback {
public static final String TAG = "CutoutCamera";
Preview preview;
OverlayView overlay;
static MenuView menuView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// 隐藏窗口标题。
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
...
preview = (Preview) this.findViewById(R.id.preview);
...
}
...
@Override
protected void onResume() {
super.onResume();
this.log("onResume()");
preview.openCamera();
}
@Override
protected void onPause() {
super.onPause();
this.log("onPause()");
if (preview.camera != null) {
preview.camera.release();
preview.camera = null;
}
}
// 当快门打开时调用
ShutterCallback shutterCallback = new ShutterCallback() { //
public void onShutter() {
Log.d(TAG, "onShutter'd");
}
};
// 处理原始图片数据
PictureCallback rawCallback = new PictureCallback() { //
public void onPictureTaken(byte[] data, Camera camera) {
Log.d(TAG, "onPictureTaken - raw");
}
};
// 处理JPEG格式图片数据
PictureCallback jpegCallback = new PictureCallback() { //
public void onPictureTaken(byte[] data, Camera camera) {
Log.d(TAG, "onPictureTaken - jpeg");
...
}
};
@Override
public void shootButtonClicked() {
preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback);
}
@Override
public void focusButtonClicked() {
preview.camera.autoFocus(new Camera.AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
}
});
}
}
/**
* 执行顺序:
* openCamera()
* onMeasure()
* onLayout()
* onMeasure()
* onLayout()
* surfaceCreated()
* surfaceChanged()
* onMeasure()
* onLayout()
* onMeasure()
*
*/
class Preview extends ViewGroup implements SurfaceHolder.Callback { //
private static final String TAG = "Preview";
SurfaceHolder mHolder; //
public Camera camera; //
private List supportedPreviewSizes;
private Size previewSize;
SurfaceView mSurfaceView;
CameraActivity cameraActivity;
int l2 = 0, t2 = 0, r2 = 0, b2 = 0;
int padding = 20;
Size optimalPreviewSize, optimalPictureSize;
// 此视图的大小。在 onMeasure() 中设置。
int fullWidth, fullHeight;
public Preview(Context context) {
super(context);
init(context);
}
public Preview(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public Preview(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}
private void init(Context context) {
setKeepScreenOn(true);
cameraActivity = (CameraActivity) context;
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
mHolder = mSurfaceView.getHolder(); //
mHolder.addCallback(this); //
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); //
}
...
public void openCamera() {
cameraActivity.log("openCamera()");
if (this.camera == null) {
cameraActivity.log("Camera.open()");
this.camera = Camera.open();
//supportedPreviewSizes = camera.getParameters().getSupportedPreviewSizes();
requestLayout(); // -> onMeassure() -> onLayout()
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
cameraActivity.log("onMeasure()");
// 我们故意忽略子视图的测量，因为它作为一个包装器，
// 将相机预览居中而不是拉伸它。
fullWidth = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
fullHeight = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
setMeasuredDimension(fullWidth, fullHeight);
if(this.camera != null){
cameraActivity.log("fullSize:"+fullWidth+"x"+fullHeight);
this.setCameraPreviewSize();
this.setCameraPictureSize();
}
}
private void calcScaledPreviewSize(){
...
}
...
private void setCameraPreview