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我对 Android Kotlin 编程非常陌生。我正在制作一个使用存储访问框架创建、读取和删除文件的应用程序。我通过实现已弃用的 startActivityForResult 意图来执行文件读取、创建、删除任务来做到这一点。我尝试使用 Activity Result API 来实现它，但我陷入了找不到它的请求代码中。在新的实现中，有 resultCode 但没有 requestCode。

我的实现如下。如何使用 Activity Result API 实现以下功能？

如何从 Activity Result API 获取请求代码？

fun createFile()
{
    val filename: String = etFileName.text.toString()
    val intent = Intent(Intent.ACTION_CREATE_DOCUMENT).apply {
        type = "text/*"
        addCategory(Intent.CATEGORY_OPENABLE)
        putExtra(Intent.EXTRA_TITLE, filename)
    }
    startActivityForResult(intent, WRITE_REQUEST_CODE)
}


fun readFile(){
    etFileName.setText("")
    val intent = Intent(Intent.ACTION_OPEN_DOCUMENT).apply {
        addCategory(Intent.CATEGORY_OPENABLE)
        type = "text/*"
    }
    startActivityForResult(intent, READ_REQUEST_CODE)
}

fun deleteFile(uri: Uri){
    val filename = queryName(contentResolver, uri)
    DocumentsContract.deleteDocument(contentResolver, uri)
    Toast.makeText(applicationContext, "Done deleting $filename", Toast.LENGTH_SHORT).show()
}

fun writeText(uri: Uri) : String{
    //var writetext: String = "typing high speed"
    var writeStream = contentResolver.openFileDescriptor(uri, "w")
    val filename: String = queryName(contentResolver, uri)
    etFileName.setText(filename)
    var fileOutputStream = FileOutputStream(writeStream?.fileDescriptor)
    fileOutputStream.write(filename.toByteArray())
    fileOutputStream.close()
    return filename.toString()
}

fun openFileContent(uri: Uri): String{
    val inputStream = contentResolver.openInputStream(uri)
    val reader = BufferedReader(InputStreamReader(inputStream))
    val stringBuilder = StringBuilder()

    val filename = queryName(contentResolver, uri)
    etFileName.setText(filename)
    var currentline = reader.readLine()

    while (currentline != null) {
        stringBuilder.append(currentline + "\n")
        currentline = reader.readLine()
    }
    inputStream?.close()
    val str =  stringBuilder.toString()
    Log.d("Uri Read", ": $str")
    return str
}

private fun queryName(resolver: ContentResolver, uri: Uri): String {
    val returnCursor: Cursor = resolver.query(uri, null, null, null, null)!!
    val nameIndex: Int = returnCursor.getColumnIndex(OpenableColumns.DISPLAY_NAME)
    returnCursor.moveToFirst()
    val name: String = returnCursor.getString(nameIndex)
    returnCursor.close()
    return name
}

override fun onActivityResult(requestCode: Int, resultCode: Int, resultData: Intent?) {
    super.onActivityResult(requestCode, resultCode, resultData)

    if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Read", "$uri")
        if (uri != null) {
            val readfile: String = openFileContent(uri)
            etContent.setText(readfile)
        }
    } else if (requestCode == WRITE_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        resultData?.data?.also { uri ->
            Log.i("Uri Write", "Uri: $uri")   // 1
            val write = writeText(uri)   // 2
            etContent.setText(write)
        }
    } else if (requestCode == DELETE_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Delete", "$uri")
        if (uri != null) {
            deleteFile(uri)
        }
    }
}

由于不推荐使用上述方法，因此我尝试使用 Intent 启动器来实现它，但是任何地方都没有对 requestCode 的引用，所以我被困在这里。如下图所示：

val startforFile: ActivityResultLauncher<Intent> = registerForActivityResult(ActivityResultContracts.StartActivityForResult()){
    result: ActivityResult ->

    // could not find reference to requestCode here

    if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Read", "$uri")
        if (uri != null) {
            val readfile: String = openFileContent(uri)
            etContent.setText(readfile)
        }
    } else if (requestCode == WRITE_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        resultData?.data?.also { uri ->
            Log.i("Uri Write", "Uri: $uri")   // 1
            val write = writeText(uri)   // 2
            etContent.setText(write)
        }
    } else if (requestCode == DELETE_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Delete", "$uri")
        if (uri != null) {
            deleteFile(uri)
        }
    }
}

谁能告诉我它是如何正确完成的？

4

1 回答 1

21

有两种方法ActivityResultContracts.StartActivityForResult。

  1. 通过注册多个监听器发出多个请求：
val startForFileRead: ActivityResultLauncher<Intent> = registerForActivityResult(ActivityResultContracts.StartActivityForResult()){
    result: ActivityResult ->
    if (resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Read", "$uri")
        if (uri != null) {
            val readfile: String = openFileContent(uri)
            etContent.setText(readfile)
        }
    } 
}

val startForFileWrite: ActivityResultLauncher<Intent> = registerForActivityResult(ActivityResultContracts.StartActivityForResult()){
    result: ActivityResult ->
    if (resultCode == Activity.RESULT_OK) {
        resultData?.data?.also { uri ->
            Log.i("Uri Write", "Uri: $uri")   // 1
            val write = writeText(uri)   // 2
            etContent.setText(write)
        }
    } 
}

val startForFileDelete: ActivityResultLauncher<Intent> = registerForActivityResult(ActivityResultContracts.StartActivityForResult()){
    result: ActivityResult ->
    if (resultCode == Activity.RESULT_OK) {
        val uri =resultData?.data
        Log.d("Uri Delete", "$uri")
        if (uri != null) {
            deleteFile(uri)
        }
    } 
}
  1. 在从其他活动返回的 Intent 中添加一个额外的内容。将其解压缩为您的请求代码。
const val REQUEST_CODE = "REQUEST_CODE"
//...

val startForFile: ActivityResultLauncher<Intent> =
    registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
    val requestCode = result.data?.extras?.getInt(REQUEST_CODE)
    if (requestCode == null) {
        Log.e("FileResultLauncher", "No REQUEST_CODE was returned in data intent.")
        return@registerForActivityResult
    }
    val uri = result.data?.data
    if (uri == null || result.resultCode != RESULT_OK) {
        Log.i("FileResultLauncher", "No Uri returned or result wasn't OK.")
        return@registerForActivityResult
    }
    when (requestCode) {
        READ_REQUEST_CODE -> {
            Log.d("Uri Read", "$uri")
            val readfile: String = openFileContent(uri)
            etContent.setText(readfile)
        }
        WRITE_REQUEST_CODE -> {
            Log.i("Uri Write", "Uri: $uri")   // 1
            val write = writeText(uri)   // 2
            etContent.setText(write)
        }
        DELETE_REQUEST_CODE -> {
            Log.d("Uri Delete", "$uri")
            deleteFile(uri)
        }
    }
}
于 2021-06-08T13:28:17.403 回答