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79 lines
2.5 KiB
79 lines
2.5 KiB
6 years ago
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---
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layout: page
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title: "Camera Events"
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subtitle: "Events and lifecycle"
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category: docs
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date: 2018-12-20 20:02:08
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order: 1
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---
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The camera engine will notify anyone about camera events that took place, either on their own or
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after developer action. To access these events, set up one or more `CameraListener` instances.
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All actions taken on a `CameraView` instance are asynchronous, which means that the callback can be
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executed at any time in the future. For convenience, all of them are executed on the UI thread.
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```java
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camera.addCameraListener(new CameraListener() {
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public void onCameraOpened(CameraOptions options) {}
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public void onCameraClosed() {}
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public void onCameraError(CameraException error) {}
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public void onPictureTaken(PictureResult result) {}
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public void onVideoTaken(VideoResult result) {}
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public void onOrientationChanged(int orientation) {}
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public void onFocusStart(PointF point) {}
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public void onFocusEnd(boolean successful, PointF point) {}
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public void onZoomChanged(float newValue, float[] bounds, PointF[] fingers) {}
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public void onExposureCorrectionChanged(float newValue, float[] bounds, PointF[] fingers) {}
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});
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```
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### Lifecycle
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CameraView has its own lifecycle, which is basically made of an open and a closed state.
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You will listen to these events using `onCameraOpened` and `onCameraClosed` callbacks:
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```java
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camera.addCameraListener(new CameraListener() {
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/**
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* Notifies that the camera was opened.
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* The options object collects all supported options by the current camera.
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*/
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@Override
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public void onCameraOpened(CameraOptions options) {}
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/**
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* Notifies that the camera session was closed.
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*/
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@Override
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public void onCameraClosed() {}
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});
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```
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The open callback is especially important because the `CameraOptions` includes all the available
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options of the current sensor. This can be used to adjust the UI, for example, show a flash icon
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if flash is supported.
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### Related APIs
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|Method|Description|
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|------|-----------|
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|`open()`|Starts the engine. This will cause a future call to `onCameraOpened()` (or an error)|
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|`close()`|Stops the engine. This will cause a future call to `onCameraClosed()`|
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|`isOpened()`|Returns true if `open()` was called successfully. This does not mean that camera is showing preview already.|
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|`getCameraOptions()`|If camera was opened, returns non-null object with information about what is supported.|
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Take a look at public methods in `CameraOptions` to know more.
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