Android实现调用摄像头进行拍照功能

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现在Android智能手机的像素都会提供照相的功能，大部分的手机的摄像头的像素都在1000万以上的像素，有的甚至会更高。它们大多都会支持光学变焦、曝光以及快门等等。

下面的程序Demo实例示范了使用Camera v2来进行拍照，当用户按下拍照键时，该应用会自动对焦，当对焦成功时拍下照片。

layout/activity_main.xml界面布局代码如下：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.fukaimei.camerav2test">

 <!-- 授予该程序使用摄像头的权限 -->
 <uses-permission android:name="android.permission.CAMERA" />

 <application
  android:allowBackup="true"
  android:icon="@mipmap/ic_launcher"
  android:label="@string/app_name"
  android:roundIcon="@mipmap/ic_launcher_round"
  android:supportsRtl="true"
  android:theme="@style/AppTheme"> 
  <activity android:name=".MainActivity">
   <intent-filter>
    <action android:name="android.intent.action.MAIN" />

    <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
  </activity>
 </application>

</manifest>

上面的程序的界面提供了一个自定义TextureView来显示预览取景，十分简单。该自定义TextureView类的代码如下：

AutoFitTextureView.java逻辑代码如下：

package com.fukaimei.camerav2test;

import android.content.Context;
import android.util.AttributeSet;
import android.view.TextureView;

/**
 * Created by FuKaimei on 2017/9/29.
 */

public class AutoFitTextureView extends TextureView {

 private int mRatioWidth = 0;
 private int mRatioHeight = 0;

 public AutoFitTextureView(Context context, AttributeSet attrs) {
  super(context, attrs);
 }

 public void setAspectRatio(int width, int height) {
  mRatioWidth = width;
  mRatioHeight = height;
  requestLayout();
 }

 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  int width = MeasureSpec.getSize(widthMeasureSpec);
  int height = MeasureSpec.getSize(heightMeasureSpec);
  if (0 == mRatioWidth || 0 == mRatioHeight) {
   setMeasuredDimension(width, height);
  } else {
   if (width < height * mRatioWidth / mRatioHeight) {
    setMeasuredDimension(width, width * mRatioHeight / mRatioWidth);
   } else {
    setMeasuredDimension(height * mRatioWidth / mRatioHeight, height);
   }
  }
 }
}

接来了的MainActivity.java程序将会使用CameraManager来打开CameraDevice，并通过CameraDevice创建CameraCaptureSession，然后即可通过CameraCaptureSession进行预览或拍照了。

MainActivity.java逻辑代码如下：

package com.fukaimei.camerav2test;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.content.res.Configuration;
import android.graphics.ImageFormat;
import android.graphics.SurfaceTexture;
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.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.RequiresApi;
import android.support.v4.app.ActivityCompat;
import android.util.Log;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
public class MainActivity extends Activity implements View.OnClickListener {

 private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
 private static final String TAG = "MainActivity";

 static {
  ORIENTATIONS.append(Surface.ROTATION_0, 90);
  ORIENTATIONS.append(Surface.ROTATION_90, 0);
  ORIENTATIONS.append(Surface.ROTATION_180, 270);
  ORIENTATIONS.append(Surface.ROTATION_270, 180);
 }

 private AutoFitTextureView textureView;
 // 摄像头ID（通常0代表后置摄像头，1代表前置摄像头）
 private String mCameraId = "0";
 // 定义代表摄像头的成员变量
 private CameraDevice cameraDevice;
 // 预览尺寸
 private Size previewSize;
 private CaptureRequest.Builder previewRequestBuilder;
 // 定义用于预览照片的捕获请求
 private CaptureRequest previewRequest;
 // 定义CameraCaptureSession成员变量
 private CameraCaptureSession captureSession;
 private ImageReader imageReader;
 private final TextureView.SurfaceTextureListener mSurfaceTextureListener
   = new TextureView.SurfaceTextureListener() {
  @Override
  public void onSurfaceTextureAvailable(SurfaceTexture texture
    , int width, int height) {
   // 当TextureView可用时，打开摄像头
   openCamera(width, height);
  }

  @Override
  public void onSurfaceTextureSizeChanged(SurfaceTexture texture
    , int width, int height) {
  }

  @Override
  public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
   return true;
  }

  @Override
  public void onSurfaceTextureUpdated(SurfaceTexture texture) {
  }
 };
 private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
  // 摄像头被打开时激发该方法
  @Override
  public void onOpened(CameraDevice cameraDevice) {
   MainActivity.this.cameraDevice = cameraDevice;
   // 开始预览
   createCameraPreviewSession(); // ②
  }

  // 摄像头断开连接时激发该方法
  @Override
  public void onDisconnected(CameraDevice cameraDevice) {
   cameraDevice.close();
   MainActivity.this.cameraDevice = null;
  }

  // 打开摄像头出现错误时激发该方法
  @Override
  public void onError(CameraDevice cameraDevice, int error) {
   cameraDevice.close();
   MainActivity.this.cameraDevice = null;
   MainActivity.this.finish();
  }
 };

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textureView = (AutoFitTextureView) findViewById(R.id.texture);
  // 为该组件设置监听器
  textureView.setSurfaceTextureListener(mSurfaceTextureListener);
  findViewById(R.id.capture).setOnClickListener(this);
 }

 @Override
 public void onClick(View view) {
  captureStillPicture();
 }

 private void captureStillPicture() {
  try {
   if (cameraDevice == null) {
    return;
   }
   // 创建作为拍照的CaptureRequest.Builder
   final CaptureRequest.Builder captureRequestBuilder =
     cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
   // 将imageReader的surface作为CaptureRequest.Builder的目标
   captureRequestBuilder.addTarget(imageReader.getSurface());
   // 设置自动对焦模式
   captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
     CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
   // 设置自动曝光模式
   captureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
     CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
   // 获取设备方向
   int rotation = getWindowManager().getDefaultDisplay().getRotation();
   // 根据设备方向计算设置照片的方向
   captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION
     , ORIENTATIONS.get(rotation));
   // 停止连续取景
   captureSession.stopRepeating();
   // 捕获静态图像
   captureSession.capture(captureRequestBuilder.build()
     , new CameraCaptureSession.CaptureCallback() // ⑤
     {
      // 拍照完成时激发该方法
      @Override
      public void onCaptureCompleted(CameraCaptureSession session
        , CaptureRequest request, TotalCaptureResult result) {
       try {
        // 重设自动对焦模式
        previewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
          CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);
        // 设置自动曝光模式
        previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
          CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        // 打开连续取景模式
        captureSession.setRepeatingRequest(previewRequest, null,
          null);
       } catch (CameraAccessException e) {
        e.printStackTrace();
       }
      }
     }, null);
  } catch (CameraAccessException e) {
   e.printStackTrace();
  }
 }

 // 打开摄像头
 private void openCamera(int width, int height) {
  setUpCameraOutputs(width, height);
  CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
  try {
   // 打开摄像头
   if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
    // TODO: Consider calling
    // ActivityCompat#requestPermissions
    // here to request the missing permissions, and then overriding
    // public void onRequestPermissionsResult(int requestCode, String[] permissions,
    //           int[] grantResults)
    // to handle the case where the user grants the permission. See the documentation
    // for ActivityCompat#requestPermissions for more details.
    return;
   }
   manager.openCamera(mCameraId, stateCallback, null); // ①
  } catch (CameraAccessException e) {
   e.printStackTrace();
  }
 }

 private void createCameraPreviewSession() {
  try {
   SurfaceTexture texture = textureView.getSurfaceTexture();
   texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());
   Surface surface = new Surface(texture);
   // 创建作为预览的CaptureRequest.Builder
   previewRequestBuilder = cameraDevice
     .createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
   // 将textureView的surface作为CaptureRequest.Builder的目标
   previewRequestBuilder.addTarget(new Surface(texture));
   // 创建CameraCaptureSession，该对象负责管理处理预览请求和拍照请求
   cameraDevice.createCaptureSession(Arrays.asList(surface
     , imageReader.getSurface()), new CameraCaptureSession.StateCallback() // ③
     {
      @Override
      public void onConfigured(CameraCaptureSession cameraCaptureSession) {
       // 如果摄像头为null，直接结束方法
       if (null == cameraDevice) {
        return;
       }

       // 当摄像头已经准备好时，开始显示预览
       captureSession = cameraCaptureSession;
       try {
        // 设置自动对焦模式
        previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
          CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
        // 设置自动曝光模式
        previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
          CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        // 开始显示相机预览
        previewRequest = previewRequestBuilder.build();
        // 设置预览时连续捕获图像数据
        captureSession.setRepeatingRequest(previewRequest,
          null, null); // ④
       } catch (CameraAccessException e) {
        e.printStackTrace();
       }
      }

      @Override
      public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
       Toast.makeText(MainActivity.this, "配置失败！"
         , Toast.LENGTH_SHORT).show();
      }
     }, null
   );
  } catch (CameraAccessException e) {
   e.printStackTrace();
  }
 }

 private void setUpCameraOutputs(int width, int height) {
  CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
  try {
   // 获取指定摄像头的特性
   CameraCharacteristics characteristics
     = manager.getCameraCharacteristics(mCameraId);
   // 获取摄像头支持的配置属性
   StreamConfigurationMap map = characteristics.get(
     CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);

   // 获取摄像头支持的最大尺寸
   Size largest = Collections.max(
     Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
     new CompareSizesByArea());
   // 创建一个ImageReader对象，用于获取摄像头的图像数据
   imageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
     ImageFormat.JPEG, 2);
   imageReader.setOnImageAvailableListener(
     new ImageReader.OnImageAvailableListener() {
      // 当照片数据可用时激发该方法
      @Override
      public void onImageAvailable(ImageReader reader) {
       // 获取捕获的照片数据
       Image image = reader.acquireNextImage();
       ByteBuffer buffer = image.getPlanes()[0].getBuffer();
       byte[] bytes = new byte[buffer.remaining()];
       // 使用IO流将照片写入指定文件
       File file = new File(getExternalFilesDir(null), "pic.jpg");
       buffer.get(bytes);
       try (
         FileOutputStream output = new FileOutputStream(file)) {
        output.write(bytes);
        Toast.makeText(MainActivity.this, "保存: " + file, Toast.LENGTH_LONG).show();
       } catch (Exception e) {
        e.printStackTrace();
       } finally {
        image.close();
       }
      }
     }, null);

   // 获取最佳的预览尺寸
   previewSize = chooseOptimalSize(map.getOutputSizes(
     SurfaceTexture.class), width, height, largest);
   // 根据选中的预览尺寸来调整预览组件（TextureView的）的长宽比
   int orientation = getResources().getConfiguration().orientation;
   if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
    textureView.setAspectRatio(
      previewSize.getWidth(), previewSize.getHeight());
   } else {
    textureView.setAspectRatio(
      previewSize.getHeight(), previewSize.getWidth());
   }
  } catch (CameraAccessException e) {
   e.printStackTrace();
  } catch (NullPointerException e) {
   Log.d(TAG, "出现错误");
  }
 }

 private static Size chooseOptimalSize(Size[] choices
   , int width, int height, Size aspectRatio) {
  // 收集摄像头支持的打过预览Surface的分辨率
  List<Size> bigEnough = new ArrayList<>();
  int w = aspectRatio.getWidth();
  int h = aspectRatio.getHeight();
  for (Size option : choices) {
   if (option.getHeight() == option.getWidth() * h / w &&
     option.getWidth() >= width && option.getHeight() >= height) {
    bigEnough.add(option);
   }
  }
  // 如果找到多个预览尺寸，获取其中面积最小的。
  if (bigEnough.size() > 0) {
   return Collections.min(bigEnough, new CompareSizesByArea());
  } else {
   System.out.println("找不到合适的预览尺寸！！！");
   return choices[0];
  }
 }

 // 为Size定义一个比较器Comparator
 static class CompareSizesByArea implements Comparator<Size> {
  @Override
  public int compare(Size lhs, Size rhs) {
   // 强转为long保证不会发生溢出
   return Long.signum((long) lhs.getWidth() * lhs.getHeight() -
     (long) rhs.getWidth() * rhs.getHeight());
  }
 }
}

上面的程序中序号①的代码是用于打开系统摄像头，openCamera()方法的第一个参数代表请求打开的摄像头ID，此处传入的摄像头ID为“0”，这代表打开设备后置摄像头；如果需要打开设备指定摄像头（比如前置摄像头），可以在调用openCamera()方法时传入相应的摄像头ID。

注意：由于该程序需要使用手机的摄像头，因此还需要在清单文件AndroidManifest.xml文件中授权相应的权限：

<!-- 授予该程序使用摄像头的权限 -->
 <uses-permission android:name="android.permission.CAMERA" />

Demo程序运行效果界面截图如下：

Demo程序源码下载地址

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