一、迁移

// 简述步骤
// 对sdcard目录下的文件以及文件夹 批量移动到 当前应用的私有目录下，如：files以及cache目录

二、适配操作

1. AndroidQ及以上使用 MediaStore操作媒体等文件，并且应用自己文件归类保存在 沙盒目录内
   其中注意 Data字段的变化以及操作修改其他应用的权限申请以及捕获SecurityException异常进行用户授权处理
2. AndroidQ一下就正常文件操作

val appFilePath = getExternalFilesDir(null)?.path?:""
val appImagePath = getExternalFilesDir(Environment.DIRECTORY_DCIM)?.path?:""
val appCustomPath = getExternalFilesDir("Demo")?.path?:""
val appCachePath = getExternalCacheDir()?.path?:""

// 如果应用卸载后又重新安装，删除卸载之前保存的文件就无法直接删除，或者删除其他应用创建的媒体文件也不能直接删除，
// 此时需要申请READ_EXTERNAL_STORAGE权限，删除需要捕获SecurityException异常

// App卸载后，对应的沙盒目录也会被删除，如果APP想要在卸载时保留沙盒目录下的数据，要在AndroidManifest.xml中声明
// android:hasFragileUserData="true"，这样在 APP卸载时就会有弹出框提示用户是否保留应用数据

三、MediaStore操作

1. 通过contentResolve等获取uri,在根据uri获取文件描述符，最后使用FileOutputStream(pfd.fileDescriptor)等流将数据流进行存取等操作
2. os = resolver.openOutputStream(insertUri)

3.1 ContentValues

/**
 * ```
 * values.put(MediaStore.Images.Media.IS_PENDING, isPending)
 * Android Q , MediaStore中添加 MediaStore.Images.Media.IS_PENDING flag，用来表示文件的 isPending 状态，0是可见，其他不可见
 * ```
 * @param displayName 文件名
 * @param description 描述
 * @param mimeType 媒体类型
 * @param title 标题
 * @param relativePath 相对路径 eg: ${Environment.DIRECTORY_PICTURES}/xxx
 * @param isPending 默认0 , 0是可见，其他不可见
 */
// val RELATIVE_PATH = "${Environment.DIRECTORY_PICTURES}${File.separator}img"
/* val values = createContentValues(
            "BitmapImage.png",
            "This is an image",
            "image/png",
            "Image.png",
            RELATIVE_PATH,
            1
        )
*/
fun createContentValues(
    displayName: String? = null, description: String? = null, mimeType: String? = null, title: String? = null,
    relativePath: String? = null, isPending: Int? = 1,
): ContentValues {
    return ContentValues().apply {
        put(MediaStore.Images.Media.DISPLAY_NAME, displayName)
        put(MediaStore.Images.Media.DESCRIPTION, description)
        put(MediaStore.Images.Media.MIME_TYPE, mimeType)
        put(MediaStore.Images.Media.TITLE, title)
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            put(MediaStore.Images.Media.RELATIVE_PATH, relativePath)
            put(MediaStore.Images.Media.IS_PENDING, isPending)
        }
    }
}

3.2 访问其他应用创建文件权限检查

when (FileOperator.getContext()
    .checkUriPermission(uri, android.os.Process.myPid(), android.os.Process.myUid(), Intent.FLAG_GRANT_READ_URI_PERMISSION)) {
    PackageManager.PERMISSION_GRANTED -> {
    }
    PackageManager.PERMISSION_DENIED -> {
        FileOperator.getContext().grantUriPermission(FileOperator.getApplication().packageName, uri, Intent.FLAG_GRANT_READ_URI_PERMISSION)
    }
}   

3.3 完整例子

val imageList = mutableListOf<MediaStoreImage>()
val external = MediaStore.Images.Media.EXTERNAL_CONTENT_URI

val cursor: Cursor?
try {
    cursor = createMediaCursor(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, projectionArgs, sortOrder, querySelectionStatement)
    FileLogger.i("Found ${cursor?.count} images")

    cursor?.use {
        // Cache column indices.
        val idColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media._ID)
        val nameColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.DISPLAY_NAME)
        val sizeColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.SIZE)
        val descColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.DESCRIPTION)
        val titleColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.TITLE)
        val mimeColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.MIME_TYPE)
        val dateModifiedColumn = it.getColumnIndexOrThrow(MediaStore.Images.Media.DATE_ADDED)

        while (it.moveToNext()) { //moveToFirst  moveToNext
            val id = it.getLong(idColumn)
            val name = it.getString(nameColumn)
            val size = it.getInt(sizeColumn)
            val desc = it.getString(descColumn)
            val titleRs = it.getString(titleColumn)
            val mimeTypeRs = it.getString(mimeColumn)
            val dateModified = Date(TimeUnit.SECONDS.toMillis(it.getLong(dateModifiedColumn)))

            val contentUri: Uri = ContentUris.withAppendedId(external, id)
            imageList += MediaStoreImage(
                id, contentUri, name, size.toLong(),
                desc, titleRs, mimeTypeRs, dateModified
            )
        }
        if (imageList.isNullOrEmpty()) {
            FileLogger.e("查询失败!")
        }
        imageList.let { l ->
            l.forEach { img ->
                FileLogger.d("查询成功，Uri路径  ${img.uri}")
            }
        }
    }
    return imageList
} catch (e: Exception) {
    FileLogger.e("查询失败! ${e.message}")
}


fun createMediaCursor(
    uri: Uri, projectionArgs: Array<String>? = arrayOf(MediaStore.Video.Media._ID),
    sortOrder: String? = null, querySelectionStatement: FileGlobal.QuerySelectionStatement? = null,
): Cursor? {
    // Need the READ_EXTERNAL_STORAGE permission if accessing video files that your app didn't create.
    when (FileOperator.getContext()
        .checkUriPermission(uri, android.os.Process.myPid(), android.os.Process.myUid(), Intent.FLAG_GRANT_READ_URI_PERMISSION)) {
        PackageManager.PERMISSION_GRANTED -> {
        }
        PackageManager.PERMISSION_DENIED -> {
            FileOperator.getContext().grantUriPermission(FileOperator.getApplication().packageName, uri, Intent.FLAG_GRANT_READ_URI_PERMISSION)
        }
    }

    return FileOperator.getContext().contentResolver.query(
        uri, projectionArgs,
        querySelectionStatement?.selection.toString(),
        querySelectionStatement?.selectionArgs?.toTypedArray(),
        sortOrder
    )
}

四、SAF操作

更多查看源码

4.1 选择文件

fun selectFile(activity: Activity, mimeType: String, requestCode: Int) {
    val intent = Intent(Intent.ACTION_OPEN_DOCUMENT).apply {
        addCategory(Intent.CATEGORY_OPENABLE)
        type = mimeType
    }
    activity.startActivityForResult(intent, requestCode)
}


selectFile(activity, "image/*", requestCode)

五、Uri

5.1 文件描述符

通过文件描述符方位uri
 var pfd: ParcelFileDescriptor? = null
    try {
        pfd = contentResolver.openFileDescriptor(queryUri!!, "r")
        if (pfd != null) {
            val bitmap = BitmapFactory.decodeFileDescriptor(pfd.fileDescriptor)
            imageIv.setImageBitmap(bitmap)
        }
    } catch (e: IOException) {
        e.printStackTrace()
    } finally {
        pfd?.close()
    }

在Android Q以下只使用DATA字段，Android Q及以上不使用DATA字段，改为使用RELATEIVE_PATH字段

5.2 检查uri有效性

fun checkUri(uri: Uri?): Boolean {
    if (uri == null) return false
    val resolver = FileOperator.getContext().contentResolver

    //1. Check Uri
    var cursor: Cursor? = null
    val isUriExist: Boolean = try {
        cursor = resolver.query(uri, null, null, null, null)
        //cursor null: content Uri was invalid or some other error occurred
        //cursor.moveToFirst() false: Uri was ok but no entry found.
        (cursor != null && cursor.moveToFirst())
    } catch (t: Throwable) {
        FileLogger.e("1.Check Uri Error: ${t.message}")
        false
    } finally {
        try {
            cursor?.close()
        } catch (t: Throwable) {
        }
    }

    //2. Check File Exist
    //如果系统 db 存有 Uri 相关记录, 但是文件失效或者损坏 (If the system db has Uri related records, but the file is invalid or damaged)
    var ins: InputStream? = null
    val isFileExist: Boolean = try {
        ins = resolver.openInputStream(uri)
        // file exists
        true
    } catch (t: Throwable) {
        // File was not found eg: open failed: ENOENT (No such file or directory)
        FileLogger.e("2. Check File Exist Error: ${t.message}")
        false
    } finally {
        try {
            ins?.close()
        } catch (t: Throwable) {
        }
    }
    return isUriExist && isFileExist
}

源码地址：FileOperator