预览camera2时，SurfaceView永远不会填充？

Question

我使用SurfaceView预览camera2 api的相机。但它总是偏黑，如下图所示。

我的xml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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.Toolbar
        android:id="@+id/tool_bar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:elevation="4dp"
        android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
        <TextView
            android:text="Egos"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    </android.support.v7.widget.Toolbar>

    <Button
        android:id="@+id/button"
        android:text="Record"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:onClick="record"/>

    <SurfaceView
        android:id="@+id/surface_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/tool_bar"
        android:layout_above="@id/button"/>

</RelativeLayout>

部分回叫。

mSurfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mSurfaceHolder = holder;
        try {
            tryPre();
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
}

预先方法。

private void tryPre() throws CameraAccessException {
    if (mSurfaceHolder == null) {
        return;
    }
    // mSurfaceHolder.setFixedSize(1080, 1530); // no use
    List<Surface> outputSurfaces = new ArrayList<>(1);
    Surface surface = mSurfaceHolder.getSurface();
    outputSurfaces.add(surface);
    final CaptureRequest.Builder captureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
    captureBuilder.addTarget(surface);
    final int rotation = getWindowManager().getDefaultDisplay().getRotation();
    captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));
    mCameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
        @Override
        public void onConfigured(CameraCaptureSession session) {
            if (null == mCameraDevice) {
                return;
            }
            try {
                captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                session.setRepeatingRequest(captureBuilder.build(),
                        captureCallback, mHandler);
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
        @Override
        public void onConfigureFailed(CameraCaptureSession session) {
        }
    }, mHandler);
}