Summary: Nested Classes | Methods | Inherited Methods

Preview

Kotlin |Java

public final class Preview
extends UseCase

java.lang.Object
↳	androidx.camera.core.UseCase
	↳	androidx.camera.core.Preview

A use case that provides a camera preview stream for displaying on-screen.

The preview stream is connected to the Surface provided via Preview.SurfaceProvider. The application decides how the Surface is shown, and is responsible for managing the Surface lifecycle after providing it.

To display the preview with the correct orientation, app needs to take different actions based on the source of the Surface. If the Surface is backed by a SurfaceView, it will always be in the device's display orientation. If the Surface is backed by ImageReader, MediaCodec or other objects, it's the application's responsibility to calculate the rotation. If the Surface is backed by a SurfaceTexture, SurfaceTexture.getTransformMatrix(float[]) can be used to transform the preview to natural orientation. The value is available after a frame is pushed to the SurfaceTexture and its SurfaceTexture.OnFrameAvailableListener.onFrameAvailable(SurfaceTexture) has been called. TextureView handles this automatically and always puts the preview in the natural orientation. To further transform the TextureView to display orientation, the app needs to apply the current display rotation. Example:

     
         switch (getWindowManager().getDefaultDisplay().getRotation()) {
             case Surface.ROTATION_0:
                 displayRotation = 0;
                 break;
             case Surface.ROTATION_90:
                 displayRotation = 90;
                 break;
             case Surface.ROTATION_180:
                 displayRotation = 180;
                 break;
             case Surface.ROTATION_270:
                 displayRotation = 270;
                 break;
             default:
                 throw new UnsupportedOperationException(
                         "Unsupported display rotation: " + displayRotation);
         }
         matrix.postRotate(-displayRotation, centerX, centerY);
         textureView.setTransform(matrix);

Summary

Nested classes
`class`	`Preview.Builder` Builder for a `Preview`.
`interface`	`Preview.SurfaceProvider` A interface implemented by the application to provide a `Surface` for `Preview`.

Public methods
`int`	`getTargetRotation()` Returns the rotation that the intended target resolution is expressed in.
`void`	`setSurfaceProvider(Executor executor, Preview.SurfaceProvider surfaceProvider)` Sets a `Preview.SurfaceProvider` to provide a `Surface` for Preview.
`void`	`setSurfaceProvider(Preview.SurfaceProvider surfaceProvider)` Sets a `Preview.SurfaceProvider` to provide a `Surface` for Preview.
`String`	`toString()`

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()`
`boolean`	`equals(Object arg0)`
`void`	`finalize()`
`final Class<?>`	`getClass()`
`int`	`hashCode()`
`final void`	`notify()`
`final void`	`notifyAll()`
`String`	`toString()`
`final void`	`wait(long arg0, int arg1)`
`final void`	`wait(long arg0)`
`final void`	`wait()`

Public methods

getTargetRotation

public int getTargetRotation ()

Returns the rotation that the intended target resolution is expressed in.

The rotation is set when constructing an Preview instance using Preview.Builder.setTargetRotation(int). If not set, the target rotation defaults to the value of Display.getRotation() of the default display at the time the use case is created.

Returns
`int`	The rotation of the intended target.

setSurfaceProvider

public void setSurfaceProvider (Executor executor, 
                Preview.SurfaceProvider surfaceProvider)

Sets a Preview.SurfaceProvider to provide a Surface for Preview.

Setting the provider will signal to the camera that the use case is ready to receive data. If the provider is removed by calling this again with a null SurfaceProvider then the camera will stop producing data for this Preview instance.

Parameters
`executor`	`Executor`: on which the surfaceProvider will be invoked.
`surfaceProvider`	`Preview.SurfaceProvider`: SurfaceProvider that provides a `Surface` for Preview. This will replace the previous SurfaceProvider set either this method or `setSurfaceProvider(SurfaceProvider)`.

setSurfaceProvider

public void setSurfaceProvider (Preview.SurfaceProvider surfaceProvider)

Sets a Preview.SurfaceProvider to provide a Surface for Preview.

Setting the provider will signal to the camera that the use case is ready to receive data. The provider will be triggered on main thread. If the provider is removed by calling this again with a null SurfaceProvider then the camera will stop producing data for this Preview instance.

Parameters
`surfaceProvider`	`Preview.SurfaceProvider`: SurfaceProvider that provides a `Surface` for Preview. This will replace the previous SurfaceProvider set either this method or `setSurfaceProvider(Executor, SurfaceProvider)`.

toString

public String toString ()

Returns
`String`

Preview

Summary

Nested classes

Public methods

Inherited methods

Public methods

getTargetRotation

setSurfaceProvider

setSurfaceProvider

toString