The technical principles of exploring the camera view framework in the Java library
In the Java library, the camera view framework is a technology that is used to process the camera view -related function.It provides a simple way to handle the camera preview, camera and video operations.The technical principles of the camera view framework will be explored below.
The camera view framework is built based on the Camera API or Camera2 API of the Android system. These two APIs provide the function of accessing device cameras.The camera view framework interacts with the device camera through these APIs and realizes various camera operations.
First, before using the camera view framework, we need to obtain the camera list available on the device.You can use Camera API's Camera.getNumberofcameras () method or CameraManager class of Camera2 API to obtain the number and ID available on the device.These methods can help us find camera resources that interact with device cameras.
Next, we need to create a Cameraview instance for camera preview.Camera view is a custom view that displays the camera preview image in real time.We can add a Cameraview to the layout file and get the corresponding instance in the Java code.
After Cameraview instantiated, we need to initialize and open the camera.In Camera API, you can use the Camera.open () method to open the camera.In Camera2 API, the OpenCamera () method of the Cameramanager class can be used to open the camera.By opening the camera, we can start previewing the camera image.
During the preview, we can set various parameters to the camera.For example, you can set the resolution, focus mode, flash, exposure compensation, etc. of the camera.These parameters can be configured through the Camera.parameters class (Camera API) or CameraCharacteristics (Camera2 API).According to the need, we can use the corresponding method to set and get these parameters.
When you need to take a picture, you can use Camera.takepicTure () or CameraCaptureSession.capture () (Camera2 API) to capture images.These methods will trigger the camera to take pictures and pass the image data to the callback function for processing.We can get the photos taken in the callback function and follow the follow -up processing, such as saving local or performing image processing operations.
In addition to the camera function, the camera view framework also supports the video function.You can complete the video configuration by setting the camera's MediaReCorder parameter.Then, call the Start () and Stop () methods of the MediaReCorder to start and stop recording.The recorded video can be saved in the local file.
When using the camera view framework, you need to pay attention to the correct release of camera resources.When we do not use the camera, we should turn off the camera in time to release the occupied resources to avoid memory leakage and other problems.In Camera API, you can use the Camera.release () method to release camera resources.In the Camera2 API, you can use CameraDevice.close () to close the camera.
The above is the basic technical principle of the camera view framework.Through this framework, we can quickly and easily achieve camera -related functions.Here are a simple Java code example to demonstrate how to use the camera view framework for camera preview:
// Import related classes
import android.content.Context;
import android.hardware.Camera;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
// Create a custom Cameraview class
public class CameraView extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder holder;
private Camera camera;
public CameraView(Context context) {
super(context);
holder = getHolder();
holder.addCallback(this);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
camera = Camera.open();
try {
camera.setPreviewDisplay(holder);
camera.startPreview();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// Preview Size and other parameters adjustment
if (holder.getSurface() == null) {
return;
}
try {
camera.stopPreview();
} catch (Exception e) {
e.printStackTrace();
}
try {
camera.setPreviewDisplay(holder);
camera.startPreview();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
camera.stopPreview();
camera.release();
}
}
The above code is a simple custom Cameraview class that inherits the SurfaceView and implements the SurfaceHolder.Callback interface.In the SurfaceCreated () method, turn on the camera and display the preview on the SurfaceHolder.In the SurfaceChanged () method, parameters and other parameters can be adjusted as needed.Release camera resources in the SurfaceDestRoyed () method.
Through this example code, we can better understand the usage of the camera view framework.Of course, this is just a simple example. In fact, the camera view framework can also achieve more functions, such as taking pictures, videos, and setting camera parameters.I hope this article will help you understand the technical principles of the camera view framework.
