我想在android中录制视频时实现缩放功能。但是，我既不能在主要活动中也不能访问Camera 参数或Camera startSmoothZoom（）方法表面类。如果您在媒体记录器方法（ prepareMediaRecorder（））中访问相机参数a，则会抛出空指针异常。
此活动类-在 prepareMediaRecorder（）方法中无法访问相机参数，也无法设置startSmoothZoom（）。相机对象给出空指针异常。
public class CustomCameraPreview extends BaseActivity implements
OnClickListener, AlertPositiveListener, OrientationListener,
ActivityCompat.OnRequestPermissionsResultCallback {
RelativeLayout mLayout;
MediaRecorder mediaRecorder;
private PictureCallback mPictureCallback = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
try {
cameraData = data;
captureAngle = getRotation();
mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
}
catch (OutOfMemoryError e){
System.gc();
mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
}
// int rotation=getRotation();
Matrix matrix = new Matrix();
matrix.postRotate(getRotation());
/*mBitmap = Bitmap.createBitmap(mBitmap, 0, 0, mBitmap.getWidth(),
mBitmap.getHeight(), matrix, true);*/
mBitmap = Bitmap.createBitmap(mBitmap, 0, 0, mBitmap.getWidth(),
mBitmap.getHeight(), matrix, false);
if (mBitmap != null) {
mButtonRetake.setEnabled(true);
} else {
Message.displayToast(CustomCameraPreview.this,
getString(R.string.picture_not_taken));
}
mCamera.release();
mButtonCapture.setEnabled(false);
}
};
protected void onCreate(){
initiCameraForVideo();
}
private void initiCameraForVideo() {
params = mCamera.getParameters();
mButtonCapture.setBackgroundResource(R.drawable.videostart);
mShowCamera = new CameraSurfaceHolder(CustomCameraPreview.this,
mCamera);
mLayout = (RelativeLayout) findViewById(R.id.relativeLayout);
mLayout.removeAllViews();
mLayout.addView(mShowCamera);
List<Camera.Size> mSizeList_Video = null;// params.getSupportedPreviewSizes();
if (params.getSupportedVideoSizes() != null) {
mSizeList_Video = params.getSupportedVideoSizes();
} else {
// Video sizes may be null, which indicates that all the
// supported preview sizes are supported for video
// recording.
mSizeList_Video = mCamera.getParameters()
.getSupportedPreviewSizes();
}
}
@Override
public void onClick(View v) {
int viewId = v.getId();
switch (viewId) {
case R.id.button_Capture:
releaseCamera();
if (!prepareMediaRecorder()) {
Message.displayToast(
CustomCameraPreview.this,
getString(R.string.somethign_went_wrong));
} else {
mediaRecorder.start();
recording = true;
}
}
private boolean prepareMediaRecorder() \*method to setup media player to record video
{
mCamera = isCameraAvailable();
mediaRecorder = new MediaRecorder();
mCamera.unlock();
mediaRecorder.setCamera(mCamera);
mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
if(CamcorderProfile.hasProfile(findCameraID(), CamcorderProfile.QUALITY_480P)) {
mediaRecorder.setProfile(CamcorderProfile
.get(CamcorderProfile.QUALITY_480P));
}else{
mediaRecorder.setProfile(CamcorderProfile
.get(CamcorderProfile.QUALITY_LOW));
}
mediaRecorder.setOutputFile(getOutputVideoFile());
mediaRecorder.setMaxDuration(60000);
// mediaRecorder.setMaxFileSize(100 * 1000 * 1000);
mediaRecorder.setPreviewDisplay(mShowCamera.getHolder().getSurface());
try {
mediaRecorder.prepare();
}
}
@Override
protected void onPause() {
super.onPause();
releaseMediaRecorder();
releaseCamera();
}
private void releaseCamera() {
if (mCamera != null) {
mCamera.release();
mCamera = null;
}
}
和此表面预览类-
public class CameraSurfaceHolder extends SurfaceView implements
SurfaceHolder.Callback {
private static final String TAG = "CameraSurfaceHolder";
Context mContext;
private String errorMessage = "";
private SurfaceHolder mSurfaceHolder;
private Camera mCamera;
public CameraSurfaceHolder(Context context, Camera camera) {
super(context);
mContext = context;
mCamera = camera;
mSurfaceHolder = getHolder();
mSurfaceHolder.addCallback(this);
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
/*if (holder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
setCameraDisplayOrientation((Activity)mContext, Camera.CameraInfo.CAMERA_FACING_BACK, mCamera);
// start preview with new settings
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
}
*/
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
mCamera.setPreviewDisplay(mSurfaceHolder);
mCamera.startPreview();
} catch (Exception e) {
Logger.ex(e);
}
}
public void setCameraDisplayOrientation(Activity activity, int cameraId,
Camera camera) {
Camera.CameraInfo info = new Camera.CameraInfo();
Camera.getCameraInfo(cameraId, info);
/*Display mDisplay = ((WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
int rotation = mDisplay.getDisplayId();*/
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.Parameters mParameters = camera.getParameters();
mParameters.setRotation(rotation);
camera.setDisplayOrientation(result);
camera.setParameters(mParameters);
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
}
在上面的类中，我添加了以下代码，当用户触摸摄像机预览时，在访问摄像机参数时onTouchEvent（）中抛出了空指针异常。还尝试过在配置媒体记录器（ prepareMediaRecorder（））后再次将摄像机对象设置为活动的表面，但是缩放功能有效，但视频未记录。
@Override
public boolean onTouchEvent(MotionEvent event) {
// Get the pointer ID
Camera.Parameters params = mCamera.getParameters();
int action = event.getAction();
if (event.getPointerCount() > 1) {
// handle multi-touch events
if (action == MotionEvent.ACTION_POINTER_DOWN) {
mDist = getFingerSpacing(event);
} else if (action == MotionEvent.ACTION_MOVE && params.isZoomSupported()) {
mCamera.cancelAutoFocus();
handleZoom(event, params);
}
} else {
// handle single touch events
if (action == MotionEvent.ACTION_UP) {
handleFocus(event, params);
}
}
return true;
}
private void handleZoom(MotionEvent event, Camera.Parameters params) {
int maxZoom = params.getMaxZoom();
int zoom = params.getZoom();
float newDist = getFingerSpacing(event);
if (newDist > mDist) {
//zoom in
if (zoom < maxZoom)
zoom++;
} else if (newDist < mDist) {
//zoom out
if (zoom > 0)
zoom--;
}
mDist = newDist;
params.setZoom(zoom);
mCamera.setParameters(params);
}
public void handleFocus(MotionEvent event, Camera.Parameters params) {
int pointerId = event.getPointerId(0);
int pointerIndex = event.findPointerIndex(pointerId);
// Get the pointer's current position
float x = event.getX(pointerIndex);
float y = event.getY(pointerIndex);
List<String> supportedFocusModes = params.getSupportedFocusModes();
if (supportedFocusModes != null && supportedFocusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) {
mCamera.autoFocus(new Camera.AutoFocusCallback() {
@Override
public void onAutoFocus(boolean b, Camera camera) {
// currently set to auto-focus on single touch
}
});
}
}
/** Determine the space between the first two fingers */
private float getFingerSpacing(MotionEvent event) {
// ...
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return (float)Math.sqrt(x * x + y * y);
}