如何在 Xamarin.Android 中更改 Surface View 高度？

Question

我的布局代码。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:showIn="@layout/Main">
<LinearLayout
    android:id="@+id/camera_ll"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:weightSum="100"
    android:orientation="vertical">
    <FrameLayout
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:id="@+id/frameLayout"
        android:layout_weight="90" />
    <Button
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:id="@+id/btn_capture"
        android:text="Scan Answer Sheet"
        fontPath="Fonts/Verb-Semibold.otf"
        android:textColor="@android:color/white"
        android:background="@drawable/bttn_green"
        android:layout_weight="10" />
     </LinearLayout>
  </RelativeLayout>

我的 Java 代码是这样的。

    public class CameraPreview : Activity, Android.Hardware.Camera.IPictureCallback, Android.Hardware.Camera.IPreviewCallback, Android.Hardware.Camera.IShutterCallback
{
    String PICTURE_FILENAME = "picture.jpg";
    Preview mPreview;
    Camera mCamera;
    int numberOfCameras;
    int cameraCurrentlyLocked;

    // The first rear facing camera
    int defaultCameraId;
    FrameLayout frameLayout;
    Button btn_capture;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        // Hide the window title and go fullscreen.
        RequestWindowFeature(WindowFeatures.NoTitle);
        Window.AddFlags(WindowManagerFlags.Fullscreen);

        // Create our Preview view and set it as the content of our activity.

        SetContentView(Resource.Layout.CameraPriview);
        frameLayout = FindViewById<FrameLayout>(Resource.Id.frameLayout);
        btn_capture = FindViewById<Button>(Resource.Id.btn_capture);
        mPreview = new Preview(this, frameLayout);
        frameLayout.AddView(mPreview);
        btn_capture.Click += TakeAPicture;
        // Find the total number of cameras available
        numberOfCameras = Camera.NumberOfCameras;

        // Find the ID of the default camera
        Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
        for (int i = 0; i < numberOfCameras; i++)
        {
            Camera.GetCameraInfo(i, cameraInfo);
            if (cameraInfo.Facing == CameraFacing.Back)
            {
                defaultCameraId = i;
            }
        }
    }
    private void TakeAPicture(object sender, EventArgs eventArgs)
    {

        Android.Hardware.Camera.Parameters p = mCamera.GetParameters();
        p.PictureFormat = Android.Graphics.ImageFormatType.Jpeg;
        mCamera.SetParameters(p);
        mCamera.TakePicture(this, this, this);

    }
    void Camera.IPictureCallback.OnPictureTaken(byte[] data, Android.Hardware.Camera camera)
    {
        FileOutputStream outStream = null;
        File dataDir = Android.OS.Environment.ExternalStorageDirectory;
        if (data != null)
        {
            try
            {
                outStream = new FileOutputStream(dataDir + "/" + PICTURE_FILENAME);
                outStream.Write(data);
                outStream.Close();
            }
            catch (FileNotFoundException e)
            {
                System.Console.Out.WriteLine(e.Message);
            }
            catch (IOException ie)
            {
                System.Console.Out.WriteLine(ie.Message);
            }
        }
    }

    void Camera.IPreviewCallback.OnPreviewFrame(byte[] b, Android.Hardware.Camera c)
    {

    }

    void Camera.IShutterCallback.OnShutter()
    {

    }
    protected override void OnResume()
    {
        base.OnResume();

        // Open the default i.e. the first rear facing camera.
        mCamera = Camera.Open();
        cameraCurrentlyLocked = defaultCameraId;
        mPreview.PreviewCamera = mCamera;
        mCamera.SetDisplayOrientation(90);



    }


    protected override void OnPause()
    {
        base.OnPause();

        // Because the Camera object is a shared resource, it's very
        // important to release it when the activity is paused.
        if (mCamera != null)
        {
            mPreview.PreviewCamera = null;
            mCamera.Release();
            mCamera = null;
        }
    }

    public override bool OnCreateOptionsMenu(IMenu menu)
    {
        // Inflate our menu which can gather user input for switching camera
        //MenuInflater.Inflate(Resource.Menu.camera_menu, menu);
        return true;
    }


}

表面视图代码。

  class Preview : ViewGroup, ISurfaceHolderCallback
{
    string TAG = "Preview";
    FrameLayout f;
    SurfaceView mSurfaceView;
    ISurfaceHolder mHolder;
    Camera.Size mPreviewSize;
    IList<Camera.Size> mSupportedPreviewSizes;
    Camera _camera;

    public Camera PreviewCamera
    {
        get { return _camera; }
        set
        {
            _camera = value;
            if (_camera != null)
            {
                mSupportedPreviewSizes = PreviewCamera.GetParameters().SupportedPreviewSizes;
                RequestLayout();
            }
        }
    }

    public Preview(Context context, FrameLayout f) : base(context)
    {
        this.f = f;
        mSurfaceView = new SurfaceView(context);
        AddView(mSurfaceView);

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = mSurfaceView.Holder;
        mHolder.AddCallback(this);
        mHolder.SetType(SurfaceType.PushBuffers);

    }

    public void SwitchCamera(Camera camera)
    {
        PreviewCamera = camera;

        try
        {
            camera.SetPreviewDisplay(mHolder);
        }
        catch (Java.IO.IOException exception)
        {
            Log.Error(TAG, "IOException caused by setPreviewDisplay()", exception);
        }

        Camera.Parameters parameters = camera.GetParameters();
        parameters.SetPreviewSize(mPreviewSize.Width, mPreviewSize.Height);

        RequestLayout();

        camera.SetParameters(parameters);
    }

    protected override 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.
        int width = ResolveSize(SuggestedMinimumWidth, widthMeasureSpec);
        int height = ResolveSize(SuggestedMinimumHeight, heightMeasureSpec);
        SetMeasuredDimension(width, height);

        if (mSupportedPreviewSizes != null)
        {
           mPreviewSize = GetOptimalPreviewSize(mSupportedPreviewSizes, width, height);
        }
    }

    protected override void OnLayout(bool changed, int l, int t, int r, int b)
    {
        if (changed && ChildCount > 0)
        {
            View child = GetChildAt(0);

            int width = r - l;
            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)
            {
                int scaledChildWidth = previewWidth * height / previewHeight;
                child.Layout((width - scaledChildWidth) / 2, 0,
                             (width + scaledChildWidth) / 2, height);
            }
            else
            {
                int scaledChildHeight = previewHeight * width / previewWidth;
                child.Layout(0, (height - scaledChildHeight) / 2,
                             width, (height + scaledChildHeight) / 2);
            }
        }
    }

    public void SurfaceCreated(ISurfaceHolder holder)
    {
        // The Surface has been created, acquire the camera and tell it where
        // to draw.
        try
        {
            if (PreviewCamera != null)
            {

                PreviewCamera.SetPreviewDisplay(holder);

            }
        }
        catch (Java.IO.IOException exception)
        {
            Log.Error(TAG, "IOException caused by setPreviewDisplay()", exception);
        }
    }

    public void SurfaceDestroyed(ISurfaceHolder holder)
    {
        // Surface will be destroyed when we return, so stop the preview.
        if (PreviewCamera != null)
        {
            PreviewCamera.StopPreview();
        }
    }

    private Camera.Size GetOptimalPreviewSize(IList<Camera.Size> sizes, int w, int h)
    {
        const double ASPECT_TOLERANCE = 0.1;
        double targetRatio = (double)w / h;

        if (sizes == null)
            return null;

        Camera.Size optimalSize = null;
        double minDiff = Double.MaxValue;

        int targetHeight = h;

        // Try to find an size match aspect ratio and size
        foreach (Camera.Size size in sizes)
        {
            double ratio = (double)size.Width / size.Height;

            if (Math.Abs(ratio - targetRatio) > ASPECT_TOLERANCE)
                continue;

            if (Math.Abs(size.Height - targetHeight) < minDiff)
            {
                optimalSize = size;
                minDiff = Math.Abs(size.Height - targetHeight);
            }
        }

        // Cannot find the one match the aspect ratio, ignore the requirement
        if (optimalSize == null)
        {
            minDiff = Double.MaxValue;
            foreach (Camera.Size size in sizes)
            {
                if (Math.Abs(size.Height - targetHeight) < minDiff)
                {
                    optimalSize = size;
                    minDiff = Math.Abs(size.Height - targetHeight);
                }
            }
        }


        return optimalSize;
    }

    public void SurfaceChanged(ISurfaceHolder holder, Android.Graphics.Format format, int w, int h)
    {
        // Now that the size is known, set up the camera parameters and begin
        // the preview.
        Camera.Parameters parameters = PreviewCamera.GetParameters();
        parameters.SetPreviewSize(mPreviewSize.Width, mPreviewSize.Height);
        RequestLayout();

        PreviewCamera.SetParameters(parameters);
        PreviewCamera.StartPreview();
    }


}

输出：

现在我想增加相机高度以填充所有可用的space，但对我没有任何作用。如果有人知道解决方案请帮助谢谢。

Answer 1

Now i want to increase the camera height to fill all available space but nothing working for me. If anyone know the solution please help thanks.

预览尺寸的设置代码在Preview的OnLayout方法中：

protected override void OnLayout(bool changed, int l, int t, int r, int b)
{
    if (changed && ChildCount > 0)
    {
        View child = GetChildAt(0);

        int width = r - l;
        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)
        {
            int scaledChildWidth = previewWidth * height / previewHeight;
            child.Layout((width - scaledChildWidth) / 2, 0,
                         (width + scaledChildWidth) / 2, height);
        }
        else
        {
            int scaledChildHeight = previewHeight * width / previewWidth;
            child.Layout(0, (height - scaledChildHeight) / 2,
                         width, (height + scaledChildHeight) / 2);
        }
    }
}

这里我不明白代码的意思。但是通过 child.Layout(0, (height - scaledChildHeight) / 2,width, (height + scaledChildHeight) / 2);，您正在将预览 window 的顶部边界和底部边界减小到 (height - scaledChildHeight) / 2 和 (height + scaledChildHeight) / 2)。

因此，要增加相机高度以填充所有可用的 space，您需要修改此代码段。例如：

int LeftBoundary=0,TopBoundary=0;
int RightBoundary=r,BottomBoundary=b;
child.Layout(LeftBoundary,TopBoundary,RightBoundary,BottomBoundary));

如何在 Xamarin.Android 中更改 Surface View 高度？

How to change Surface View Height in Xamarin.Android?

camera

android

surfaceview

xamarin.android