android.hardware.Camera

1. android.hardware.Camera

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The Camera class is used to set image capture settings, start/stop preview, snap pictures, and retrieve frames for encoding for video. This class is a client for the Camera service, which manages the actual camera hardware.

To access the device camera, you must declare theCAMERA permission in your Android Manifest. Also be sure to include the<uses-feature> manifest element to declare camera features used by your application. For example, if you use the camera and auto-focus feature, your Manifest should include the following:

 <uses-permission android:name="android.permission.CAMERA" /> <uses-feature android:name="android.hardware.camera" /> <uses-feature android:name="android.hardware.camera.autofocus" />

To take pictures with this class, use the following steps:

1. Obtain an instance of Camera from open(int).
2. Get existing (default) settings with getParameters().
3. If necessary, modify the returned Camera.Parameters object and callsetParameters(Camera.Parameters).
4. If desired, call setDisplayOrientation(int).
5. Important: Pass a fully initializedSurfaceHolder tosetPreviewDisplay(SurfaceHolder). Without a surface, the camera will be unable to start the preview.
6. Important: Call startPreview() to start updating the preview surface. Preview must be started before you can take a picture.
7. When you want, call takePicture(Camera.ShutterCallback, Camera.PictureCallback, Camera.PictureCallback, Camera.PictureCallback) to capture a photo. Wait for the callbacks to provide the actual image data.
8. After taking a picture, preview display will have stopped. To take more photos, callstartPreview() again first.
9. Call stopPreview() to stop updating the preview surface.
10. Important: Call release() to release the camera for use by other applications. Applications should release the camera immediately inonPause() (and re-open() it inonResume()).

To quickly switch to video recording mode, use these steps:

1. Obtain and initialize a Camera and start preview as described above.
2. Call unlock() to allow the media process to access the camera.
3. Pass the camera to setCamera(Camera). SeeMediaRecorder information about video recording.
4. When finished recording, call reconnect() to re-acquire and re-lock the camera.
5. If desired, restart preview and take more photos or videos.
6. Call stopPreview() andrelease() as described above.

This class is not thread-safe, and is meant for use from one event thread. Most long-running operations (preview, focus, photo capture, etc) happen asynchronously and invoke callbacks as necessary. Callbacks will be invoked on the event threadopen(int) was called from. This class's methods must never be called from multiple threads at once.

Caution: Different Android-powered devices may have different hardware specifications, such as megapixel ratings and auto-focus capabilities. In order for your application to be compatible with more devices, you should not make assumptions about the device camera specifications.

Developer Guides

For more information about using cameras, read theCamera developer guide.

转自：http://developer.android.com/reference/android/hardware/Camera.html

2. Building a Camera App

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Some developers may require a camera user interface that is customized to the look of their application or provides special features. Creating a customized camera activity requires more code thanusing an intent, but it can provide a more compelling experience for your users.

The general steps for creating a custom camera interface for your application are as follows:

• Detect and Access Camera - Create code to check for the existence of cameras and request access.
• Create a Preview Class - Create a camera preview class that extendsSurfaceView and implements theSurfaceHolder interface. This class previews the live images from the camera.
• Build a Preview Layout - Once you have the camera preview class, create a view layout that incorporates the preview and the user interface controls you want.
• Setup Listeners for Capture - Connect listeners for your interface controls to start image or video capture in response to user actions, such as pressing a button.
• Capture and Save Files - Setup the code for capturing pictures or videos and saving the output.
• Release the Camera - After using the camera, your application must properly release it for use by other applications.

Camera hardware is a shared resource that must be carefully managed so your application does not collide with other applications that may also want to use it. The following sections discusses how to detect camera hardware, how to request access to a camera, how to capture pictures or video and how to release the camera when your application is done using it.

Caution: Remember to release theCamera object by calling theCamera.release() when your application is done using it! If your application does not properly release the camera, all subsequent attempts to access the camera, including those by your own application, will fail and may cause your or other applications to be shut down.

 

 

 

 

转自：http://developer.android.com/guide/topics/media/camera.html#custom-camera