Camera2API的基本功能笔记 Android实现Camera2预览和拍照效果

简介

网上对于 Camera2 的介绍有很多，在 Github 上也有很多关于 Camera2 的封装库，但是对于那些库，封装性太强，有时候我们仅仅是需要个简简单单的拍照功能而已，因此，自定义一个 Camera 使之变得轻量级那是非常重要的了。(本文并非重复造轮子, 而是在于学习 Camera2API 的基本功能, 笔记之。)

学习要点:

(资料图片)

使用 Android Camera2 API 的基本功能。

迭代连接到设备的所有相机的特征。

显示相机预览和拍摄照片。

Camera2 API 为连接到 Android 设备的各个相机设备提供了一个界面。 它替代了已弃用的 Camera 类。

使用 getCameraIdList 获取所有可用摄像机的列表。 然后，您可以使用 getCameraCharacteristics，并找到适合您需要的最佳相机(前 / 后面，分辨率等)。

创建一个 CameraDevice.StateCallback 的实例并打开相机。 当相机打开时，准备开始相机预览。

使用 TextureView 显示相机预览。 创建一个 CameraCaptureSession 并设置一个重复的 CaptureRequest。

静像拍摄需要几个步骤。 首先，需要通过更新相机预览的 CaptureRequest 来锁定相机的焦点。

然后，以类似的方式，需要运行一个预捕获序列。之后，它准备拍摄一张照片。 创建一个新的 CaptureRequest 并调用 [capture] 。

完成后，别忘了解锁焦点。

实现效果环境

SDK>21

Camera2 类图

代码实现

CameraPreview.java

/**

* Created by shenhua on 2017-10-20-0020.

* Email shenhuanet@126.com

*/

public class CameraPreview extends TextureView {

private static final String TAG = "CameraPreview";

private static final SparseIntArray ORIENTATIONS = new SparseIntArray();//从屏幕旋转转换为JPEG方向

private static final int MAX_PREVIEW_WIDTH = 1920;//Camera2 API 保证的最大预览宽高

private static final int MAX_PREVIEW_HEIGHT = 1080;

private static final int STATE_PREVIEW = 0;//显示相机预览

private static final int STATE_WAITING_LOCK = 1;//焦点锁定中

private static final int STATE_WAITING_PRE_CAPTURE = 2;//拍照中

private static final int STATE_WAITING_NON_PRE_CAPTURE = 3;//其它状态

private static final int STATE_PICTURE_TAKEN = 4;//拍照完毕

private int mState = STATE_PREVIEW;

private int mRatioWidth = 0, mRatioHeight = 0;

private int mSensorOrientation;

private boolean mFlashSupported;

private Semaphore mCameraOpenCloseLock = new Semaphore(1);//使用信号量 Semaphore 进行多线程任务调度

private Activity activity;

private File mFile;

private HandlerThread mBackgroundThread;

private Handler mBackgroundHandler;

private Size mPreviewSize;

private String mCameraId;

private CameraDevice mCameraDevice;

private CaptureRequest.Builder mPreviewRequestBuilder;

private CaptureRequest mPreviewRequest;

private CameraCaptureSession mCaptureSession;

private ImageReader mImageReader;

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);

}

public CameraPreview(Context context) {

this(context, null);

}

public CameraPreview(Context context, AttributeSet attrs) {

this(context, attrs, 0);

}

public CameraPreview(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

mFile = new File(getContext().getExternalFilesDir(null), "pic.jpg");

}

@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);

}

}

}

public void onResume(Activity activity) {

this.activity = activity;

startBackgroundThread();

//当Activity或Fragment OnResume()时,可以冲洗打开一个相机并开始预览,否则,这个Surface已经准备就绪

if (this.isAvailable()) {

openCamera(this.getWidth(), this.getHeight());

} else {

this.setSurfaceTextureListener(mSurfaceTextureListener);

}

}

public void onPause() {

closeCamera();

stopBackgroundThread();

}

public void setOutPutDir(File file) {

this.mFile = file;

}

public void setAspectRatio(int width, int height) {

if (width < 0 || height < 0) {

throw new IllegalArgumentException("Size can"t be negative");

}

mRatioWidth = width;

mRatioHeight = height;

requestLayout();

}

public void setAutoFlash(CaptureRequest.Builder requestBuilder) {

if (mFlashSupported) {

requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,

CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

}

}

public void takePicture() {

lockFocus();

}

private void startBackgroundThread() {

mBackgroundThread = new HandlerThread("CameraBackground");

mBackgroundThread.start();

mBackgroundHandler = new Handler(mBackgroundThread.getLooper());

}

private void stopBackgroundThread() {

mBackgroundThread.quitSafely();

try {

mBackgroundThread.join();

mBackgroundThread = null;

mBackgroundHandler = null;

} catch (InterruptedException e) {

e.printStackTrace();

}

}

/**

* 处理生命周期内的回调事件

*/

private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() {

@Override

public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {

openCamera(width, height);

}

@Override

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

configureTransform(width, height);

}

@Override

public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {

return true;

}

@Override

public void onSurfaceTextureUpdated(SurfaceTexture texture) {

}

};

/**

* 相机状态改变回调

*/

private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {

@Override

public void onOpened(@NonNull CameraDevice cameraDevice) {

mCameraOpenCloseLock.release();

Log.d(TAG, "相机已打开");

mCameraDevice = cameraDevice;

createCameraPreviewSession();

}

@Override

public void onDisconnected(@NonNull CameraDevice cameraDevice) {

mCameraOpenCloseLock.release();

cameraDevice.close();

mCameraDevice = null;

}

@Override

public void onError(@NonNull CameraDevice cameraDevice, int error) {

mCameraOpenCloseLock.release();

cameraDevice.close();

mCameraDevice = null;

if (null != activity) {

activity.finish();

}

}

};

/**

* 处理与照片捕获相关的事件

*/

private CameraCaptureSession.CaptureCallback mCaptureCallback = new CameraCaptureSession.CaptureCallback() {

private void process(CaptureResult result) {

switch (mState) {

case STATE_PREVIEW: {

break;

}

case STATE_WAITING_LOCK: {

Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);

if (afState == null) {

captureStillPicture();

} else if (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||

CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState) {

Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);

if (aeState == null || aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {

mState = STATE_PICTURE_TAKEN;

captureStillPicture();

} else {

runPreCaptureSequence();

}

}

break;

}

case STATE_WAITING_PRE_CAPTURE: {

Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);

if (aeState == null ||

aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||

aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {

mState = STATE_WAITING_NON_PRE_CAPTURE;

}

break;

}

case STATE_WAITING_NON_PRE_CAPTURE: {

Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);

if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {

mState = STATE_PICTURE_TAKEN;

captureStillPicture();

}

break;

}

}

}

@Override

public void onCaptureProgressed(@NonNull CameraCaptureSession session,

@NonNull CaptureRequest request,

@NonNull CaptureResult partialResult) {

process(partialResult);

}

@Override

public void onCaptureCompleted(@NonNull CameraCaptureSession session,

@NonNull CaptureRequest request,

@NonNull TotalCaptureResult result) {

process(result);

}

};

/**

* 在确定相机预览大小后应调用此方法

*

* @param viewWidth 宽

* @param viewHeight 高

*/

private void configureTransform(int viewWidth, int viewHeight) {

if (null == mPreviewSize || null == activity) {

return;

}

int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();

Matrix matrix = new Matrix();

RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);

RectF bufferRect = new RectF(0, 0, mPreviewSize.getHeight(), mPreviewSize.getWidth());

float centerX = viewRect.centerX();

float centerY = viewRect.centerY();

if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {

bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());

matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);

float scale = Math.max(

(float) viewHeight / mPreviewSize.getHeight(),

(float) viewWidth / mPreviewSize.getWidth());

matrix.postScale(scale, scale, centerX, centerY);

matrix.postRotate(90 * (rotation - 2), centerX, centerY);

} else if (Surface.ROTATION_180 == rotation) {

matrix.postRotate(180, centerX, centerY);

}

this.setTransform(matrix);

}

/**

* 根据mCameraId打开相机

*/

private void openCamera(int width, int height) {

setUpCameraOutputs(width, height);

configureTransform(width, height);

CameraManager manager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);

try {

if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {

throw new RuntimeException("Time out waiting to lock camera opening.");

}

if (ActivityCompat.checkSelfPermission(activity, 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, mStateCallback, mBackgroundHandler);

} catch (CameraAccessException e) {

e.printStackTrace();

} catch (InterruptedException e) {

throw new RuntimeException("Interrupted while trying to lock camera opening.", e);

}

}

/**

* 关闭相机

*/

private void closeCamera() {

try {

mCameraOpenCloseLock.acquire();

if (null != mCaptureSession) {

mCaptureSession.close();

mCaptureSession = null;

}

if (null != mCameraDevice) {

mCameraDevice.close();

mCameraDevice = null;

}

if (null != mImageReader) {

mImageReader.close();

mImageReader = null;

}

} catch (InterruptedException e) {

throw new RuntimeException("Interrupted while trying to lock camera closing.", e);

} finally {

mCameraOpenCloseLock.release();

}

}

/**

* 设置相机相关的属性或变量

*

* @param width 相机预览的可用尺寸的宽度

* @param height 相机预览的可用尺寸的高度

*/

@SuppressWarnings("SuspiciousNameCombination")

private void setUpCameraOutputs(int width, int height) {

CameraManager manager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);

try {

for (String cameraId : manager.getCameraIdList()) {

CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

// 在这个例子中不使用前置摄像头

Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);

if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {

continue;

}

StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);

if (map == null) {

continue;

}

Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),

new CompareSizesByArea());

mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),

ImageFormat.JPEG, /*maxImages*/2);

mImageReader.setOnImageAvailableListener(

mOnImageAvailableListener, mBackgroundHandler);

int displayRotation = activity.getWindowManager().getDefaultDisplay().getRotation();

// noinspection ConstantConditions

mSensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);

boolean swappedDimensions = false;

switch (displayRotation) {

case Surface.ROTATION_0:

case Surface.ROTATION_180:

if (mSensorOrientation == 90 || mSensorOrientation == 270) {

swappedDimensions = true;

}

break;

case Surface.ROTATION_90:

case Surface.ROTATION_270:

if (mSensorOrientation == 0 || mSensorOrientation == 180) {

swappedDimensions = true;

}

break;

default:

Log.e(TAG, "Display rotation is invalid: " + displayRotation);

}

Point displaySize = new Point();

activity.getWindowManager().getDefaultDisplay().getSize(displaySize);

int rotatedPreviewWidth = width;

int rotatedPreviewHeight = height;

int maxPreviewWidth = displaySize.x;

int maxPreviewHeight = displaySize.y;

if (swappedDimensions) {

rotatedPreviewWidth = height;

rotatedPreviewHeight = width;

maxPreviewWidth = displaySize.y;

maxPreviewHeight = displaySize.x;

}

if (maxPreviewWidth > MAX_PREVIEW_WIDTH) {

maxPreviewWidth = MAX_PREVIEW_WIDTH;

}

if (maxPreviewHeight > MAX_PREVIEW_HEIGHT) {

maxPreviewHeight = MAX_PREVIEW_HEIGHT;

}

mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),

rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,

maxPreviewHeight, largest);

int orientation = getResources().getConfiguration().orientation;

if (orientation == Configuration.ORIENTATION_LANDSCAPE) {

setAspectRatio(mPreviewSize.getWidth(), mPreviewSize.getHeight());

} else {

setAspectRatio(mPreviewSize.getHeight(), mPreviewSize.getWidth());

}

Boolean available = characteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);

mFlashSupported = available == null ? false : available;

mCameraId = cameraId;

return;

}

} catch (CameraAccessException e) {

e.printStackTrace();

} catch (NullPointerException e) {

Log.e(TAG, "设备不支持Camera2");

}

}

/**

* 获取一个合适的相机预览尺寸

*

* @param choices 支持的预览尺寸列表

* @param textureViewWidth 相对宽度

* @param textureViewHeight 相对高度

* @param maxWidth 可以选择的最大宽度

* @param maxHeight 可以选择的最大高度

* @param aspectRatio 宽高比

* @return 最佳预览尺寸

*/

private static Size chooseOptimalSize(Size[] choices, int textureViewWidth, int textureViewHeight,

int maxWidth, int maxHeight, Size aspectRatio) {

List bigEnough = new ArrayList<>();

List notBigEnough = new ArrayList<>();

int w = aspectRatio.getWidth();

int h = aspectRatio.getHeight();

for (Size option : choices) {

if (option.getWidth() <= maxWidth && option.getHeight() <= maxHeight &&

option.getHeight() == option.getWidth() * h / w) {

if (option.getWidth() >= textureViewWidth &&

option.getHeight() >= textureViewHeight) {

bigEnough.add(option);

} else {

notBigEnough.add(option);

}

}

}

if (bigEnough.size() > 0) {

return Collections.min(bigEnough, new CompareSizesByArea());

} else if (notBigEnough.size() > 0) {

return Collections.max(notBigEnough, new CompareSizesByArea());

} else {

Log.e(TAG, "Couldn"t find any suitable preview size");

return choices[0];

}

}

/**

* 为相机预览创建新的CameraCaptureSession

*/

private void createCameraPreviewSession() {

try {

SurfaceTexture texture = this.getSurfaceTexture();

assert texture != null;

// 将默认缓冲区的大小配置为想要的相机预览的大小

texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());

Surface surface = new Surface(texture);

mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);

mPreviewRequestBuilder.addTarget(surface);

// 我们创建一个 CameraCaptureSession 来进行相机预览

mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),

new CameraCaptureSession.StateCallback() {

@Override

public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {

if (null == mCameraDevice) {

return;

}

// 会话准备好后，我们开始显示预览

mCaptureSession = cameraCaptureSession;

try {

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,

CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

setAutoFlash(mPreviewRequestBuilder);

mPreviewRequest = mPreviewRequestBuilder.build();

mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback, mBackgroundHandler);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

@Override

public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {

}

}, null);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

/**

* 从指定的屏幕旋转中检索照片方向

*

* @param rotation 屏幕方向

* @return 照片方向(0,90,270,360)

*/

private int getOrientation(int rotation) {

return (ORIENTATIONS.get(rotation) + mSensorOrientation + 270) % 360;

}

/**

* 锁定焦点

*/

private void lockFocus() {

try {

// 如何通知相机锁定焦点

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);

// 通知mCaptureCallback等待锁定

mState = STATE_WAITING_LOCK;

mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

/**

* 解锁焦点

*/

private void unlockFocus() {

try {

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,

CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);

setAutoFlash(mPreviewRequestBuilder);

mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback,

mBackgroundHandler);

mState = STATE_PREVIEW;

mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback,

mBackgroundHandler);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

/**

* 拍摄静态图片

*/

private void captureStillPicture() {

try {

if (null == activity || null == mCameraDevice) {

return;

}

final CaptureRequest.Builder captureBuilder =

mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);

captureBuilder.addTarget(mImageReader.getSurface());

captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,

CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

setAutoFlash(captureBuilder);

// 方向

int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();

captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));

CameraCaptureSession.CaptureCallback captureCallback

= new CameraCaptureSession.CaptureCallback() {

@Override

public void onCaptureCompleted(@NonNull CameraCaptureSession session,

@NonNull CaptureRequest request,

@NonNull TotalCaptureResult result) {

Toast.makeText(getContext(), "Saved: " + mFile, Toast.LENGTH_SHORT).show();

Log.d(TAG, mFile.toString());

unlockFocus();

}

};

mCaptureSession.stopRepeating();

mCaptureSession.abortCaptures();

mCaptureSession.capture(captureBuilder.build(), captureCallback, null);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

/**

* 运行preCapture序列来捕获静止图像

*/

private void runPreCaptureSequence() {

try {

// 设置拍照参数请求

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,

CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);

mState = STATE_WAITING_PRE_CAPTURE;

mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

/**

* 比较两者大小

*/

private static class CompareSizesByArea implements Comparator {

@Override

public int compare(Size lhs, Size rhs) {

return Long.signum((long) lhs.getWidth() * lhs.getHeight() -

(long) rhs.getWidth() * rhs.getHeight());

}

}

/**

* ImageReader的回调对象

*/

private final ImageReader.OnImageAvailableListener mOnImageAvailableListener

= new ImageReader.OnImageAvailableListener() {

@Override

public void onImageAvailable(ImageReader reader) {

mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));

}

};

/**

* 将捕获到的图像保存到指定的文件中

*/

private static class ImageSaver implements Runnable {

private final Image mImage;

private final File mFile;

ImageSaver(Image image, File file) {

mImage = image;

mFile = file;

}

@Override

public void run() {

ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();

byte[] bytes = new byte[buffer.remaining()];

buffer.get(bytes);

FileOutputStream output = null;

try {

output = new FileOutputStream(mFile);

output.write(bytes);

} catch (IOException e) {

e.printStackTrace();

} finally {

mImage.close();

if (null != output) {

try {

output.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

}

}

MainActivity.java

public class MainActivity extends AppCompatActivity {

CameraPreview cameraView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

cameraView = (CameraPreview) findViewById(R.id.cameraView);

}

@Override

protected void onResume() {

super.onResume();

cameraView.onResume(this);

}

@Override

protected void onPause() {

cameraView.onPause();

super.onPause();

}

public void takePic(View view) {

cameraView.takePicture();

}

}

activity_main.xml

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/constraintLayout"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="@android:color/black"

tools:context="com.shenhua.ocr.activity.Main2Activity">

android:id="@+id/cameraView"

android:layout_width="wrap_content"

android:layout_height="wrap_content" />

android:layout_width="70dp"

android:layout_height="70dp"

android:layout_gravity="center"

android:background="@drawable/ic_capture_200px"

android:onClick="takePic"

android:text="TAKE"

app:layout_constraintBottom_toBottomOf="@id/constraintLayout"

app:layout_constraintEnd_toEndOf="@id/constraintLayout"

app:layout_constraintStart_toStartOf="@id/constraintLayout"

app:layout_constraintTop_toTopOf="@id/cameraView"

app:layout_constraintVertical_bias="0.97" />

资源文件 ic_capture_200px.xml

android:viewportWidth="1024.0" android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">

其它

Manifest 权限:

Android6.0 运行时权限未贴出。(注意：为了方便读者手机端阅读，本文代码部分的成员变量使用了行尾注释，在正常编程习惯中，请使用 /* / 注释。)

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。