Develop Reference

Xamarin - Setting Camera feed as background

So, I'm trying to make a login activity with the camera feed as the background. I've tested the example on https://developer.xamarin.com/guides/android/user_interface/textureview/ and got it to work, but I need to it to be part of an activity. So, I tried this:
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
// Create your application here
SetContentView(Resource.Layout.Login);
_textureView = this.FindViewById<TextureView>(Resource.Id.textureView);
_textureView.SurfaceTextureListener = this;
}
public void OnSurfaceTextureAvailable(
Android.Graphics.SurfaceTexture surface, int w, int h)
{
_cam = Camera.Open();
_textureView.LayoutParameters =
new FrameLayout.LayoutParams(w, h);
try
{
_cam.SetPreviewTexture(surface);
_cam.StartPreview();
}
catch (Java.IO.IOException ex)
{
Console.WriteLine(ex.Message);
}
}
The axml file looks somewhat like this:
<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextureView
android:id="#+id/textureView"
android:layout_width="match_parent"
android:layout_height="match_parent"
AbsoluteLayout.LayoutBounds="0,0,1,1"
AbsoluteLayout.LayoutFlags="SizeProportional" />
<LinearLayout
android:id="#+id/linearLayout"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/transparent"
AbsoluteLayout.LayoutBounds="0,0,1,1"
AbsoluteLayout.LayoutFlags="SizeProportional">
<!-- Some other controls -->
</LinearLayout>
</AbsoluteLayout>
However, the app now crashes after exiting the OnSurfaceTextureAvailable block, giving an unhandled exception. Breaking at the exception doesn't work, it's apparently in a thread that's not running anymore.
Would anyone know why it crashes and, more importantly, how to fix it?

Problem is with this code:
_textureView.LayoutParameters = new FrameLayout.LayoutParams(w, h);
I'm not sure why your need to reset the TextureView's layout parameters, in xml you've set it to match parent. And the parent here is AbsoluteLayout, not FrameLayout, that's why this error happens.
To solve this issue, since AbsoluteLayout is obsolete now, I suggest to use RelativeLayout as root container in your xml. Then you can code like this:
_textureView.LayoutParameters = new RelativeLayout.LayoutParams(width, height);
Of course you can also change AbsoluteLayout to FrameLayout in your xml, then the code _textureView.LayoutParameters = new FrameLayout.LayoutParams(w, h); doesn't need to be modified anymore.

How to add buttons on camera preview

I'm new on Android, and i trying to build a camera app.
I build an Camera Preview which extends SurfaceView and implements SurfaceHolder.Callback for previewing the camera on the Camera Activity.
here is the contractor :
public CameraPreview(Context context) {
super(context);
mContext = context;
mStartRequested = false;
mSurfaceAvailable = false;
mCamera = null;
mHolder = getHolder();
mHolder.addCallback(this);
}
and the onCreate(in CameraActivity.java) method which initialize the layout:
#Override
protected void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.activity_camera);
mPreview = new CameraPreview(this);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
and finally the Layout XML :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<FrameLayout
android:id="#+id/camera_preview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Button"
android:id="#+id/button"
android:layout_gravity="center_horizontal|bottom" />
</FrameLayout>
</LinearLayout>
AndroidMainifest.xml:
<application
...
android:theme="#android:style/Theme.Holo.Light.NoActionBar.Fullscreen" >
As you can see i tried to add a button on the camera preview but i cant see the button when the app is lunching.
can anyone see the mistake??
Thanks you !

The preview is probably on top of the button (in the Z-order). This line:
preview.addView(mPreview);
adds the CameraPreview to the end of the FrameLayout's internal list of child views. A FrameLayout renders its child views in order; as such, the preview is being drawn after the button, or "over" it. Try this instead:
preview.addView(mPreview, 0);
You can also order your CameraPreview by having it inflate from the XML instead, by using a tag with the fully qualified class name, like this:
<com.yourdomain.CameraPreview
.../>
...although you will need to override the View(Context context, AttributeSet attrs); constructor to make that work.

Android Landscape VideoView in portrait mode

I have an activity which should display a VideoView in landscape, but the activity itself must not be in landscape mode, so this is what i have.
<activity
android:name=".gui.VideoPlayer"
android:label="#string/app_name"
android:launchMode="singleTask"
android:screenOrientation="portrait" >
</activity>
<?xml version="1.0" encoding="utf-8"?>
Activity
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<VideoView
android:id="#+id/myvideoview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_gravity="center" />
</LinearLayout>
(The activity itself must remain in portrait mode because the device will be put in a case which covers the navigation and statusbars, but in landscape mode it wont cover them any more)

I know this is not the optimal answer but I had the same issue a while ago and found a pretty convenient workaround that might help you too.
Try to use a TextureView instead of VideoView because when you rotate it, the content inside rotates as well.
<TextureView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/my_texture_view"
android:rotation="90"
android:scaleX="1.8"
/>
Next you'll have to create a SurfaceTextureListener and set it to your view like below:
TextureView.SurfaceTextureListener mTextureListener = new TextureView.SurfaceTextureListener() {
#Override
public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int i, int i1) {
Surface s = new Surface(surfaceTexture);
try {
mMediaPlayer = new MediaPlayer();
mMediaPlayer.setDataSource(currentPageVideoUrl);
mMediaPlayer.setSurface(s);
mMediaPlayer.prepare();
}catch (Exception e){e.printStackTrace();}
}
#Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int i, int i1) {
}
#Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {
return false;
}
#Override
public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {
}
};
And now just set the listener to your TextureView:
mTextureView.setSurfaceTextureListener(mTextureListener);
All that's left to do is to call this to start the video:
mMediaPlayer.start();
BONUS:If you want to make more complex adjustments like adjusting the video aspect ratio You can check this library for more details.

Message while starting Camera preview on SurfaceView on Android

Let me begin with the coding first.
My xml file (relevant part of it) contains this:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1"
android:background="#ffffff">
<SurfaceView
android:id="#+id/cameraView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:visibility="gone" />
<LinearLayout
android:id="#+id/layStatus"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:visibility="gone">
<TextView
android:id="#+id/txtStatus"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#90000000"
android:paddingBottom="5dip"
android:paddingTop="5dip"
android:gravity="center_vertical|center_horizontal"
android:textSize="20dip" />
</LinearLayout>
</FrameLayout>
As you can see I've got a basic set up, a frame layout which contains a surfaceview (which has visibility set to gone) and another layout with a simple TextView.
Here is what I have in my activity:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mylayout);
cameraView = (SurfaceView)findViewById(R.id.cameraView);
surfaceHolder = cameraView.getHolder();
surfaceHolder.addCallback(CompassActivity.this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void btnCameraOnClick(View target) {
cameraView.setVisibility(View.VISIBLE);
}
Starting the camera preview is done in Surface changed, which fires when visibility of the surface changes.
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
txtStatus.setVisibility(View.Visible);
txtStatus.setText("Starting camera");
camera = Camera.open();
if (camera != null){
try {
camera.setDisplayOrientation(90);
Camera.Parameters parameters = camera.getParameters();
List<Size> sizes = parameters.getSupportedPreviewSizes();
Size size = sizes.get(0);
parameters.setPreviewSize(size.width, size.height);
camera.setParameters(parameters);
camera.setPreviewDisplay(holder);
camera.startPreview();
txtStatis.setVisibility(View.GONE);
} catch (IOException e) {
}
}
}
So what's the problem ? I want to simply display a text while the camera preview starts. To do this, I make the txtStatus visible and set a text to it. When the preview is started, I simply hide it. Well, it doesn't work like this, When I press a button to start camera preview, the UI thread freezes waiting for the preview and my status message is not displayed. How can I fix it ? There is a solution at HERE but I was thinking that maybe there is a simpler one.
Thank you for your time.

Camera start up takes some time - external process shall be started and everything set up. I would speculate, that surface changed callback is executed directly from setVisibility() and blocks UI thread. Solution is pretty simple - just spawn new thread and do camera init there.
In my OCR applicatios I start camera in onResume() - since I always need working preview
You may find my OCR android demos helpful:
http://sourceforge.net/projects/javaocr/
( camera preview, with overlays )

surfaceCreated is not called

I'm trying to put a camera preview (SurfaceView) together with a button on the display, but all I get is a blank screen only showing the button. If I'm setting the SurfaceView as the only content (with setContentView(surfaceView) then the preview is displaying fine on the screen. What am I doing wrong?
Thanks in advance
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="0px"
android:layout_weight="1">
<SurfaceView
android:id="#+id/camera_surface"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/trigger"
android:id="#+id/trigger_picture_button"
android:layout_gravity="bottom" />
</FrameLayout>
</LinearLayout>
My Activity:
public class CameraActivity extends Activity {
private SurfaceView cameraPreview;
private Button triggerPicture;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.camera);
cameraPreview = (SurfaceView) findViewById(R.id.camera_surface);
triggerPicture = (Button) findViewById(R.id.trigger_picture_button);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
cameraPreview = new CameraPreview(this);
// setContentView(cameraPreview);
}
My CameraPreview:
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder holder;
private Camera camera;
public CameraPreview(Context context) {
super(context);
holder = getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
camera = openFrontFacingCamera();
try {
camera.setPreviewDisplay(holder);
} catch (IOException e) {
camera.release();
camera = null;
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
camera.stopPreview();
camera.release();
camera = null;
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(width, height);
parameters.set("orientation", "portrait");
camera.setParameters(parameters);
camera.startPreview();
}
private Camera openFrontFacingCamera() {
// returns Camera.open(
}

When you declare SurfaceView in the layout you tell Android to use built-in class. What you need to do is make it use your class by replacing SurfaceView in XML with your.package.name.CameraPreview.
One other thing: you should add a constructor to the CameraPreview taking parameters Context and AttributeSet, otherwise layout inflater won't be able to inflate your class. Also you don't need the line cameraPreview = new CameraPreview(this);.

When your onCreate() is the right one, than you overriding the cameraPreview from the xml with a new created one which you never add to any layout (last line). That means its never inflated so there is never a surface created.

Maybe it's a bit late answer ,but it really works for me.
1、set the layout as below:
<FrameLayout
android:id="#+id/camera_preview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1"
/>
<Button
android:id="#+id/button_capture"
android:text="Capture"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
/>
2、In onCreate:
// Create our Preview view and set it as the content of our activity.
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
3、And in Manifest.xml:
android:screenOrientation="landscape"
, of course , don't forget permissions and features.
Hope it helps.