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