I got a full camera app up and running, but I'd like to have the captured picture show on the screen before saving them (they're not going to the gallery). I've googled extensively and I can't find anything on the topic. I also have no idea how to start, so any advice or links to relevant information I didn't find would be wonderful. Thanks!
First of all, I'm assuming you are using the original Camera APIs, not Camera2. That functionality is really built into the preview capturing, so I'm assuming your code is just clearing the preview too quickly.
After calling Camera.startPreview() to render the live preview on the active surface, at some point Camera.takePicture() is called to trigger the image capture and the result is returned to the PictureCallback. As soon as the image is captured, the camera preview surface is frozen on that frame until it is restarted. So as long as you don't call Camera.startPreview() again inside of onPictureTaken() to restart that process, the SurfaceView will remain frozen on the frame you want the user to see already.
Then if they want to save, you can write the JPEG data to disk, and if not toss away the data.
Related
The Media Projection package is new Lollipop, and allows an app to capture the device's screen in realtime for streaming to video. I was hoping this could also be used to capture a single still screenshot, but so far I have not been successful. Of course, the first frame of a captured video could work, but I'm aiming for a perfect, lossless screenshot matching the pixel resolution of the device. A still from a captured video cannot provide that.
I've tried a lot of things, but the closest I came to a solution was to first launch an invisible activity. This activity then follows the API example for starting screen capture, which can include asking the user's permission. Once screen capture is enabled, the screen image is live in a SurfaceView. However, I cannot find a way to capture a bitmap from the SurfaceView. There are lots of questions and discussions about this, but no solutions seem to work, and there is some evidence that it is impossible.
Any ideas?
You can't capture the contents of a SurfaceView.
What you can do is replace the SurfaceView with a Surface object that has an in-process consumer, such as SurfaceTexture. In the android-ScreenCapture example linked from the question, mMediaProjection.createVirtualDisplay() wants a Surface to send images to. If you create a SurfaceTexture, and use that to construct a Surface, the images generated by the MediaProjection will be available from an OpenGL ES texture.
If GLES isn't your thing, the ImageReader class can be used. It also provides a Surface that can be passed to createVirtualDisplay(), but it's easier to access the pixels from software.
I have open camera preview for many times in surface view..but this time it is really challenging.I have to show front and back camera in same time in one surface view..I have no idea how to deal with this .
Please guide me..any tutorial will be very helpful for me..I am showing the preview which I have to do with front and back cameras
Like described in the API:
Your application should only have one Camera object active at a time
for a particular hardware camera.
here:
http://developer.android.com/reference/android/hardware/Camera.html#open%28%29
So, it is not possible and not recommended to use two camera objects at the same time.
when I make a call to mCamera.takePicture(null, null, null, null); (for simplicity I have omitted the callbacks) the preview freezes and shows a preview of the scene that was just captured. Why is that the case. Can I somehow control this behaviour? And, what does actually happen? Is there a new view that gets attached or does my camera preview simple stop?
What does actually happen? Is there a new view that gets attached or does my camera preview simply stop?
No new view gets attached by default. The preview just stops. The documentation for Camera states this clearly:
Preview will be stopped after the image is taken; callers must call startPreview() again if they want to re-start preview or take more pictures.
It also goes on to say:
After calling this method, you must not call startPreview() or take another picture until the JPEG callback has returned.
So, the best place to call startPreview() again would be the JPEG callback. Any time before that, the camera hardware is still processing the previous image, and wouldn't be able to give you a preview. That's the main reason that it "freezes"; the camera hardware is just busy.
It's also a visual cue to the user that:
a picture was taken
the picture looks like "this"
That's icing on the cake, but even if you didn't care about that, it would still do it.
Can I somehow control this behaviour?
Through the publicly expose API? Definitely not. You can restart the preview once the camera is done processing(as above), but you can't prevent it from freeze-framing when you call takePicture().
Whether it's possible by going further into the camera firmware, I can't really say. However, since there are roughly a bazillion different cameras used in Android devices, this would likely be an exercise in futility if you weren't working on one specific device.
Even with one specific device, I can't see how you'd overcome it altogether. At a bare minimum, the camera will be busy processing the image for some amount of time. Even high-end DSLR cameras that I've seen freeze the preview at least for the duration of the exposure.
After calling takePicture() you can hide the preview surface under another view (e.g. ImageView). If you use OpenGL to render the preview texture instead of SurfaceView, you have even more tricks in your sleeve.
As you may notice, camera in android phones stops working when we minimize it (for example when we start a new application). My question is: Is there any way to create an app with android camera, which records even if we minimize it so it could be recording videos while we are doing something different on our phone? Or may be it is only possible if we create such camera without using MediaStore? If you share some links or code which might help me, I'll be grateful. Thanks in advance.
I believe the answer to this is that one must use
public final void setPreviewTexture (SurfaceTexture surfaceTexture)
Added in API level 11
Sets the SurfaceTexture to be used for live preview.
Either a surface or surface texture is necessary for preview,
and preview is necessary to take pictures.
from https://developer.android.com/reference/android/hardware/Camera.html . And
from https://developer.android.com/reference/android/graphics/SurfaceTexture.html :
The image stream may come from either camera preview or video decode.
A SurfaceTexture may be used in place of a SurfaceHolder when specifying the
output destination of a Camera or MediaPlayer object. Doing so will cause all the
frames from the image stream to be sent to the SurfaceTexture object rather than
to the device's display.
and I would really like to try this and send you some code, but I have no phone more recent than gingerbread, and this was introduced with honeycomb.
Using a surface associated with an Activity, surfaceDestroyed is called sometime between onPause and onStop when the Activity is being minimised, although, oddly, not when the phone is being put to sleep: How SurfaceHolder callbacks are related to Activity lifecycle? But I hope that a surfaceTexture is not destroyed in this way.
I am developing an application where I have to take picture without using Media intent i-e without previewing this camera.How can I do this can anyone help me in this regard.
waiting for your reply
Altaf
You cannot take a picture without a preview. Whether it is the preview offered by the Intent or it is a preview that you create yourself with a SurfaceView when you use the Camera object, there has to be a preview.
Just use takePicture() directly on the camera object:
http://developer.android.com/reference/android/hardware/Camera.html#takePicture
I believe some of the older devices wouldn't capture correctly unless preview was setup, but I don't think that's an issue any more. And if you are looking to target devices that require preview you can just resize the preview surface to a single pixel somewhere and put another control on top of it. Still eats resources, but shouldn't be visible.