Android 利用系统相机进行简易拍照

参考：

https://developer.android.google.cn/training/camera/photobasics

https://juejin.im/entry/59c9ae4ff265da0658153544

一、基本步骤：

1. 检查权限

2. 检查是否有相机资源

3. 通过FileProvide创建共享文件

4. 启动相机

5. 处理返回的数据

二、代码

1、获取完整照片

private static final int REQUEST_TAKE_PHOTO = 1;
private String currentPhotoPath;

if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED){
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    /**
     *Notice that the startActivityForResult() method is protected by a condition that       *calls resolveActivity(), which returns the first activity component that can handle      *the intent. Performing this check is important because if you call                   *startActivityForResult() using an intent that no app can handle, your app will         *crash. So as long as the result is not null, it's safe to use the intent.
     *粗略理解为检测是否有相机应用
     **/
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        File photoFile = null;
        try {
            //使用自定义函数创建文件
            photoFile = createImageFile();
        } catch (IOException ex) {
            Log.d(TAG, "文件创建失败");
        }
        if (photoFile != null) {
            //创建共享文件，由于Android7.0行为变更所以使用FileProvide共享文件，
           //FileProvide是ContentProvide的子类，所以需要在Manifest中注册
           /**
             * <provider
             *    android:name="android.support.v4.content.FileProvider"
             *    android:authorities="这里填写自己的包名要和getUriForFile()函数中传的一致"
             *    android:exported="false"
             *    android:grantUriPermissions="true">
             *    <meta-data
             *       android:name="android.support.FILE_PROVIDER_PATHS"
             *      <!--需要在res文件夹下创建xml文件夹中的file_paths文件-->
             *       android:resource="@xml/file_paths">
             *    </meta-data>
             * </provider>
             *
             *file_paths文件内容
             *<?xml version="1.0" encoding="utf-8"?>
             *<paths xmlns:android="http://schemas.android.com/apk/res/android">
             *<external-path name="my_images" path="Android/data/这里填写应用包名/files/Pictures" />
             *</paths>
             **/
            Uri photoURI;
            if (Build.VERSION.SDK_INT >= 24){
                photoURI = FileProvider.getUriForFile(this,
                                                     getPackageName(),
                                                     photoFile);
            }else {
                photoURI = Uri.fromFile(photoFile);
            }
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI);
            startActivityForResult(takePictureIntent, REQUEST_TAKE_PHOTO);
        }
    }
}

/**
 *创建文件函数
 **/
private File createImageFile() throws IOException {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.CHINA).format(new Date());
        String imageFileName = "IMG_" + timeStamp + "_";
        //获取外部储存路径
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(
                imageFileName,
                ".jpg",
                storageDir
        );
        //保存当前文件的路径
        currentPhotoPath = image.getAbsolutePath();
        return image;
    }

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_TAKE_PHOTO && resultCode == RESULT_OK){
        //处理图片信息处理
    }
}

附Android7.0行为变更好文：https://blog.csdn.net/lmj623565791/article/details/72859156

2、获取缩略图

调用系统相机拍照时，如果不传路径，图片默认返回缩略图。

static final int REQUEST_IMAGE_CAPTURE = 1;

private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        Bundle extras = data.getExtras();
        Bitmap imageBitmap = (Bitmap) extras.get("data");
        //继续处理
    }
}