Android移动开发-调用摄像头进行拍照的实现

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：
  

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Demo程序源码下载地址