android 使用 surfaceView 获取 camera 预览界面图像数据

在android中，通过相机获取预览界面的需求似乎很变态，好像也没有什么使用场景。但是，有一个场景需要获取预览界面的图像，就是扫码，比如微信，支付宝的扫一扫，就是需要获取预览界面的图像数据的。

实现逻辑比较简单，不过肯定比打开系统相机要麻烦一点的。

下面简单说一下实现步骤：

实例化一个SurfaceView。
在surfaceCreated()回调中去实例化Camera对象，去自动对焦。
在onAutoFocus()回调中去调用camera.takePicture(null,null,callback);。
在第3步的callback里面去获取预览图像数据int data[]。
（可选）将获取的数据换成成文件。
（可选）将该文件对象加载成bitmap对象。
在不使用的使用释放相机资源。

代码细节：

清单文件：

    <uses-feature android:name="android.hardware.camera" />    <uses-feature android:name="android.hardware.camera.autofocus" />    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />    <uses-permission android:name="android.permission.CAMERA" />    <uses-permission android:name="android.permission.RECORD_AUDIO" />

java代码：

package com.python.cat.testgradle;import android.Manifest;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.hardware.Camera;import android.os.Bundle;import android.view.SurfaceHolder;import android.view.SurfaceView;import android.view.View;import android.widget.Button;import android.widget.FrameLayout;import android.widget.Toast;import com.apkfuns.logutils.LogUtils;import com.google.zxing.BinaryBitmap;import com.google.zxing.ChecksumException;import com.google.zxing.FormatException;import com.google.zxing.NotFoundException;import com.google.zxing.RGBLuminanceSource;import com.google.zxing.Result;import com.google.zxing.common.GlobalHistogramBinarizer;import com.google.zxing.qrcode.QRCodeReader;import com.yanzhenjie.permission.Action;import com.yanzhenjie.permission.AndPermission;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.util.Arrays;import java.util.List;public class UseCameraActivity extends Activity {    private Activity get() {        return this;    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_asome);        setTitle(getClass().getSimpleName());        final FrameLayout frameLayout = findViewById(R.id.prev_content_layout);        Button btn = findViewById(R.id.start_camera_preview);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                AndPermission.with(get())                        .permission(Manifest.permission.CAMERA,                                Manifest.permission.WRITE_EXTERNAL_STORAGE                        )                        .onDenied(new Action() {                            @Override                            public void onAction(List permissions) {                                LogUtils.e("error....." + permissions);                            }                        })                        .onGranted(new Action() {                            @Override                            public void onAction(List permissions) {                                LogUtils.w("you can do..");                                ScanView scanView = new ScanView(get());                                frameLayout.removeAllViews();                                frameLayout.addView(scanView);                            }                        }).start();            }        });    }    static class ScanView extends SurfaceView implements SurfaceHolder.Callback,            Camera.AutoFocusCallback {        private Camera mCamera;        private final File fileImg;        private ScanView self;        public ScanView(Context context) {            super(context);            fileImg = new File(context.getCacheDir(), "prev_view.jpg");            SurfaceHolder mHolder = getHolder();            self = this;            mHolder.addCallback(this);            // deprecated setting, but required on Android versions prior to 3.0            mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);        }        @Override        public void onAutoFocus(boolean success, Camera camera) {            LogUtils.w("auto focus..." + success);            if (mCamera != null) {                mCamera.takePicture(null, null, null, new Camera.PictureCallback() {                    @Override                    public void onPictureTaken(byte[] data, Camera camera) {                        mCamera.cancelAutoFocus();                        mCamera.stopPreview(); // 拿到数据就停止！！！                        LogUtils.w("========data========");                        LogUtils.w("----------data-----------------");//                        camera.startPreview();                        File pictureFile = fileImg;                        if (pictureFile == null) {                            LogUtils.e("Error creating media file, check storage permissions: " +                                    null);                            return;                        }                        if (data == null) {                            return;                        }                        try {                            LogUtils.d(data);                            FileOutputStream fos = new FileOutputStream(pictureFile);                            fos.write(data);                            fos.close();                            LogUtils.e("save preview complete###!!!");                            LogUtils.e("save preview complete###!!!" + pictureFile);                            BitmapFactory.Options options = new BitmapFactory.Options();                            options.inJustDecodeBounds = true;                            BitmapFactory.decodeFile(pictureFile.getAbsolutePath(), options);                            options.inJustDecodeBounds = false;                            int outWidth = options.outWidth;                            int outHeight = options.outHeight;                            if (outWidth >= getWidth() * 2) {                                options.inSampleSize = outWidth / getWidth();                            }                            if (outHeight >= getHeight() * 2) {                                options.inSampleSize = outHeight / getHeight();                            }                            Bitmap bmp = BitmapFactory.decodeFile(pictureFile.getAbsolutePath(), options);                            Result result = parseInfoFromBitmap(bmp);                            if (result != null) {                                Toast.makeText(getContext(), "INFO:" + result.getText(), Toast.LENGTH_SHORT).show();                                LogUtils.w("解析成功：" + result);                            } else {                                LogUtils.e("再次尝试中....");                                mCamera.startPreview();                                mCamera.autoFocus(self);                                // todo:这里也可以做最大重试次数的限制...                            }                        } catch (Exception e) {                            LogUtils.e("Error accessing file: " + e.getMessage());                        }                    }                });            }        }        public Result parseInfoFromBitmap(Bitmap bitmap) {            int[] pixels = new int[bitmap.getWidth() * bitmap.getHeight()];            bitmap.getPixels(pixels, 0, bitmap.getWidth(), 0, 0, bitmap.getWidth(), bitmap.getHeight());            LogUtils.w("### pixels dest==" + Arrays.toString(pixels));            RGBLuminanceSource source = new RGBLuminanceSource(bitmap.getWidth(),                    bitmap.getHeight(), pixels);            GlobalHistogramBinarizer binarizer = new GlobalHistogramBinarizer(source);            BinaryBitmap image = new BinaryBitmap(binarizer);            Result result = null;            try {                result = new QRCodeReader().decode(image);                return result;            } catch (NotFoundException e) {                e.printStackTrace();                Toast.makeText(getContext(), "非二维码图片，不能解析", Toast.LENGTH_SHORT).show();            } catch (ChecksumException e) {                e.printStackTrace();            } catch (FormatException e) {                e.printStackTrace();            }            return null;        }        @Override        public void surfaceCreated(SurfaceHolder holder) {            LogUtils.e("x surfaceCreated.. #####");            try {                mCamera = Camera.open();                mCamera.setPreviewDisplay(holder);                mCamera.setDisplayOrientation(90);                Camera.Parameters parameters = mCamera.getParameters();//                parameters.setPictureSize(1600, 1200);//                parameters.setPreviewSize(640, 480);                mCamera.setParameters(parameters);                mCamera.startPreview();                mCamera.autoFocus(this);                LogUtils.e("surfaceCreated.. #####");            } catch (IOException e) {                LogUtils.e("Error setting camera preview: " + e.getMessage());            }        }        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {            LogUtils.w("--change-");        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            LogUtils.w("destroy--");            if (mCamera != null) {                mCamera.cancelAutoFocus();                mCamera.stopPreview();                mCamera.release();            }        }    }}

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".UseCameraActivity">    <Button        android:id="@+id/start_camera_preview"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentBottom="true"        android:text="@string/start_camera_preview" />    <FrameLayout        android:id="@+id/prev_content_layout"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_above="@id/start_camera_preview">FrameLayout>RelativeLayout>

gradle配置（可选）：

implementation 'com.yanzhenjie:permission:2.0.0-rc4' // 运行时权限语法糖implementation 'com.google.zxing:core:3.3.1' // zxing 解析二维码图片

嗯，以上就是获取相机预览图像数据的代码了。不过，这里用的Camera接口是过时的了，不建议使用。不过可以运行。我目前的compileSdkVersion=26。

就酱咯。完整app代码也许有的吧。

=======

update: 关于Camera2，我选择放弃….

官方的说法是：

The android.hardware.camera2 package provides an interface to individual camera devices connected to an Android device. It replaces the deprecated Camera class.

This package models a camera device as a pipeline, which takes in input requests for capturing a single frame, captures the single image per the request, and then outputs one capture result metadata packet, plus a set of output image buffers for the request. The requests are processed in-order, and multiple requests can be in flight at once. Since the camera device is a pipeline with multiple stages, having multiple requests in flight is required to maintain full framerate on most Android devices.

反正是看懂了一句话，就是用来替代Camera的。

但是，真的很麻烦。我没有找到中文的，可以直接运行的案例，找到了两个外国人写的博客，里面给了完整的代码。不过估计不能直接访问。我把拷贝到我的项目里面去了。可以直接运行。

完整app代码
因为每一篇代码都很长，我就不贴出来了，说一下路径。

com.python.cat.testgradle.MainActivity.java[由于这个原始代码没有加动态权限申请，我手动添加了一下…]

com.python.cat.testgradle.AndroidCameraApi.java
我给的是我代码的路径，以及原始链接。

不清楚是出于什么考虑，camera2里面比camera多了好几类，复杂度也提升了不少。有需要的可以研究一下。上手难度大于camera。（目前我还是一头雾水，对于camera2）。

中文的找到一个：这个我并没有去下载运行验证，不过看博客里面写的挺多的。

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