PreviewView

<init>

PreviewView(@NonNull context: Context)

<init>

PreviewView(
    @NonNull context: Context, 
    @Nullable attrs: AttributeSet?)

<init>

PreviewView(
    @NonNull context: Context, 
    @Nullable attrs: AttributeSet?, 
    defStyleAttr: Int)

<init>

PreviewView(
    @NonNull context: Context, 
    @Nullable attrs: AttributeSet?, 
    defStyleAttr: Int, 
    defStyleRes: Int)

createMeteringPointFactory

@NonNull open fun createMeteringPointFactory(@NonNull cameraSelector: CameraSelector): MeteringPointFactory

Creates a MeteringPointFactory by a given CameraSelector

The returned MeteringPointFactory is capable of creating MeteringPoints from (x, y) coordinates in the PreviewView. This conversion takes into account its ScaleType. It is recommended to call this method to create a new factory every time you start a focus and metering action, instead of caching the factory instance.

When the PreviewView has a width and/or height equal to zero, or when a preview Surface is not yet requested, the returned factory will always create invalid MeteringPoints which could lead to the failure of androidx.camera.core.CameraControl#startFocusAndMetering(FocusMeteringAction) but it won't cause any crash.

createSurfaceProvider

@NonNull @UiThread open fun createSurfaceProvider(): Preview.SurfaceProvider

Gets the Preview.SurfaceProvider to be used with Preview#setSurfaceProvider(Executor, Preview.SurfaceProvider).

The returned Preview.SurfaceProvider will provide a preview android.view.Surface to the camera that's either managed by a android.view.TextureView or android.view.SurfaceView. This option is determined by the preferred implementation mode and the device's capabilities.

getBitmap

@Nullable open fun getBitmap(): Bitmap?

Returns a Bitmap representation of the content displayed on the preview Surface, or null if the camera preview hasn't started yet.

The returned Bitmap uses the Bitmap.Config#ARGB_8888 pixel format, and its dimensions depend on the PreviewView's ScaleType. When the ScaleType is ScaleType#FILL_START, ScaleType#FILL_CENTER or ScaleType#FILL_END, the returned Bitmap has the same size as the PreviewView. However, when the ScaleType is ScaleType#FIT_START, ScaleType#FIT_CENTER or ScaleType#FIT_END, the returned Bitmap might be smaller than the PreviewView, since it doesn't also include its background.

Do not invoke this method from a drawing method (View#onDraw(Canvas) for instance).

If an error occurs during the copy, an empty Bitmap will be returned.

getDeviceRotationForRemoteDisplayMode

open fun getDeviceRotationForRemoteDisplayMode(): Int

Returns the device rotation value currently applied to the preview.

getPreferredImplementationMode

@NonNull open fun getPreferredImplementationMode(): PreviewView.ImplementationMode

Returns the preferred ImplementationMode for preview.

If the preferred ImplementationMode hasn't been set using setPreferredImplementationMode(ImplementationMode), it defaults to ImplementationMode#SURFACE_VIEW.

getPreviewStreamState

@NonNull open fun getPreviewStreamState(): LiveData<PreviewView.StreamState!>

Gets the LiveData of current preview StreamState.

There are two states, StreamState#IDLE and StreamState#STREAMING. StreamState#IDLE represents the preview is currently not visible and streaming is stopped. StreamState#STREAMING means the preview is streaming.

When it's in STREAMING state, it guarantees preview is visible only when implementationMode is TEXTURE_VIEW. When in SURFACE_VIEW implementationMode, it is possible that preview becomes visible slightly after state changes to STREAMING. For apps relying on the preview visible signal to be working correctly, please set TEXTURE_VIEW mode by setPreferredImplementationMode.

getScaleType

@NonNull open fun getScaleType(): PreviewView.ScaleType

Returns the ScaleType currently applied to the preview.

By default, ScaleType#FILL_CENTER is applied to the preview.

setDeviceRotationForRemoteDisplayMode

open fun setDeviceRotationForRemoteDisplayMode(deviceRotation: Int): Unit

Provides the device rotation value to the preview in remote display mode.

The device rotation value will only take effect when detecting current view is on a remote display. If current view is on the device builtin display, PreviewView will directly use view's rotation value to do the transformation related calculations.

The preview transform calculations have strong dependence on the device rotation value. When a application is running in remote display, the rotation value obtained from current view will cause incorrect transform calculation results. To make the preview output result correct in remote display mode, the developers need to provide the device rotation value obtained from android.view.OrientationEventListener.

The mapping between the device rotation value and the orientation value obtained from android.view.OrientationEventListener are listed as the following.

android.view.OrientationEventListener#ORIENTATION_UNKNOWN: orientation == -1

Surface#ROTATION_0: orientation >= 315 || orientation < 45

Surface#ROTATION_90: orientation >= 225 && orientation < 315

Surface#ROTATION_180: orientation >= 135 && orientation < 225

Surface#ROTATION_270: orientation >= 45 && orientation < 135

setPreferredImplementationMode

open fun setPreferredImplementationMode(@NonNull preferredMode: PreviewView.ImplementationMode): Unit

Specifies the preferred ImplementationMode to use for preview.

When the preferred ImplementationMode is ImplementationMode#SURFACE_VIEW but the device doesn't support this mode (e.g. devices with API level not newer than Android 7.0 or a supported camera hardware level android.hardware.camera2.CameraCharacteristics#INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY), the actual implementation mode will be ImplementationMode#TEXTURE_VIEW.

setScaleType

open fun setScaleType(@NonNull scaleType: PreviewView.ScaleType): Unit

Applies a ScaleType to the preview.

Note that the ScaleType#FILL_CENTER is applied to the preview by default.

onAttachedToWindow

protected open fun onAttachedToWindow(): Unit

onDetachedFromWindow

protected open fun onDetachedFromWindow(): Unit