如何从活动结果 API 获取 requestCode

Question

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，我尝试使用 Intent 启动器来实现它，但在任何地方都没有对 requestCode 的引用，所以我被困在这里。如下图：

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？

Answer 1

ActivityResultContracts.StartActivityForResult 有两种方式。

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 中添加额外内容。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)
        }
    }
}