几个概念：
SurfaceView：图像显示的地方
SurfaceHolder：连接图像显示地方与外部的通道，相当于接口
CameraManager：摄像机的管理类
CameraDevice：具体相机的操作类
调用流程：
1、获取摄像机管理类：mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
2、打开某个具体的摄像机：mCameraManager.openCamera(cameraId, stateCallback, null);
3、在打开成功的回调里面，创建预览请求：mCameraDevice.createCaptureSession
4、在创建预览请求的回调里面，设置预览模式：mCameraCaptureSession.setRepeatingRequest
大概分为以上4个步骤
实现代码如下：
package com.example.grammartest;
import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CaptureRequest;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import java.io.IOException;
import java.util.Arrays;
import android.widget.Toast;
public class Camera2Activity extends AppCompatActivity {
String tag = "Camera2Activity";
private static final String[] REQUIRED_PERMISSIONS = {Manifest.permission.CAMERA};
private static final int REQUEST_PERMISSIONS_CODE = 1;
private CameraManager mCameraManager;//摄像头管理器
CameraDevice mCameraDevice;
String FRONTId, BACKId;
private SurfaceHolder mSurfaceHolder;
private CameraCaptureSession mCameraCaptureSession;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera2);
InitView();
InitCameraInfo();
}
void InitView() {
Button ViewBt = findViewById(R.id.Camera2PlayBt);
Button ViewCloseBt = findViewById(R.id.Camera2CloseBt);
SurfaceView surfaceView = findViewById(R.id.Camera2surfaceViewId);
mSurfaceHolder = surfaceView.getHolder();
ViewBt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.i(tag,"setOnClickListener");
OpenCamera(BACKId);
}
});
ViewCloseBt.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
CloseCamera();
}
});
}
void InitCameraInfo() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
String[] cameraList = new String[0];
try {
cameraList = mCameraManager.getCameraIdList();
} catch (CameraAccessException e) {
e.printStackTrace();
}
for (String item : cameraList) {
Log.i(tag, "Camera2Activity:" + item);
String FrontItem = CameraCharacteristics.LENS_FACING_FRONT + "";
String BackItem = CameraCharacteristics.LENS_FACING_BACK + "";
if (item.equals(FrontItem)) {
FRONTId = item;
} else if (item.equals(BackItem)) {
BACKId = item;
}
}
}
}
void OpenCamera(String cameraId) {
if (false == isRequiredPermissionsGranted()) {
Log.i(tag, "isRequiredPermissionsGranted false");
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(REQUIRED_PERMISSIONS, REQUEST_PERMISSIONS_CODE);
}
return;
}
try {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
return;
}
mCameraManager.openCamera(cameraId, stateCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
void CloseCamera(){
if (null != mCameraDevice){
mCameraDevice.close();
mCameraDevice = null;
}
}
private void takePreview() {
try {
// 创建CameraCaptureSession，该对象负责管理处理预览请求和拍照请求
mCameraDevice.createCaptureSession(Arrays.asList(mSurfaceHolder.getSurface()), new CameraCaptureSession.StateCallback() // ③
{
@Override
public void onConfigured(CameraCaptureSession cameraCaptureSession) {
if (null == mCameraDevice) return;
// 当摄像头已经准备好时，开始显示预览
mCameraCaptureSession = cameraCaptureSession;
try {
// 创建预览需要的CaptureRequest.Builder
final CaptureRequest.Builder previewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
// 将SurfaceView的surface作为CaptureRequest.Builder的目标
previewRequestBuilder.addTarget(mSurfaceHolder.getSurface());
// 自动对焦
previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
// 打开闪光灯
previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
// 显示预览
CaptureRequest previewRequest = previewRequestBuilder.build();
mCameraCaptureSession.setRepeatingRequest(previewRequest, null, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
Toast.makeText(Camera2Activity.this, "配置失败", Toast.LENGTH_SHORT).show();
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
mCameraDevice = camera;
Log.i(tag, "CameraDevice onOpened");
takePreview();
}
@Override
public void onDisconnected(@NonNull CameraDevice camera) {
Log.i(tag, "CameraDevice Disconnected");
}
@Override
public void onError(@NonNull CameraDevice camera, int error) {
Log.e(tag, "CameraDevice Error");
}
};
private boolean isRequiredPermissionsGranted() {
for (String permission : REQUIRED_PERMISSIONS) {
if (ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_DENIED) {
return false;
}
}
return true;
}
}
