Core Technology Principles of Camera View Framework in Java Class Libraares
The core technical principle of the camera view framework in the Java class library
The camera view framework is an important component used in the Java class library to handle the camera preview or take.It provides a simple and efficient way to access the camera function of the device, and achieves core functions such as preview, camera, video recording.This article will introduce the core technical principles of the camera view framework and provide some Java code examples.
1. Basic principle of camera view framework
The basic principle of the camera view framework is to obtain preview or camera data through interaction with the camera of the device, and display or process these data in the user interface.It mainly involves the following core technical principles:
1.1 Camera access and configuration
The camera view framework first needs to access and configure the camera on the device.The Java class library provides the Camera or Camera2 class to realize the interaction with the device camera.Applications can open the camera through these classes, configure camera parameters (such as preview size, focus mode, etc.), and set up camera recovery and listeners.
The following is an example code using the Camera class to open the camera:
Camera camera = Camera.open();
1.2 Preview data acquisition and display
The camera view framework needs to obtain the camera preview data and display it in the interface.The acquisition of preview data is realized through the camera callback. When the camera captures a new preview frame, the corresponding callback method is called.
The following is an example code that uses the Camera class to obtain preview data:
Camera.PreviewCallback previewCallback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
// Process preview data
}
};
camera.setPreviewCallback(previewCallback);
The preview data obtained can be displayed through SurfaceView or TextureView.
1.3 Implementation of camera function implementation
Camera view frameworks usually provide camera function.Realizing the camera function involves the following steps:
1. Open the camera and configure the camera parameter.
2. Set up a photo recovery. When the photo is completed, the corresponding callback method will be called.
3. Call the camera's camera method.
The following is a sample code using the Camera class to implement the camera function:
Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
// Process camera data
}
};
camera.takePicture(null, null, pictureCallback);
2. Use scene of the camera view framework
Camera view frameworks are widely used in applications that need to use device cameras for previews or photography, such as camera applications, video call applications, and face recognition applications.
Below is a simple camera view framework for example code:
import android.app.Activity;
import android.hardware.Camera;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class CameraPreviewActivity extends Activity implements SurfaceHolder.Callback {
private Camera mCamera;
private SurfaceView mSurfaceView;
private SurfaceHolder mHolder;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera_preview);
mSurfaceView = findViewById(R.id.surfaceView);
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
mCamera = Camera.open();
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
if (mHolder.getSurface() == null) {
return;
}
try {
mCamera.stopPreview();
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mCamera.stopPreview();
mCamera.release();
mCamera = null;
}
}
The above example code demonstrates how to use the camera view framework in an Activity.
In summary, the camera view framework is an important component used in the Java class library to handle the camera preview or taking pictures.By accessing and configuration of cameras, obtaining preview data, displaying preview data, and implementation of camera function, the camera view framework can provide applications with simple and efficient camera use capabilities.
