How to convert this code of Java to Kotlin for Android Studio for retrieving data of a file?

Question

I have searched over how to retrieve a file in Kotlin, and I found this code in Java.

public void load(View v) {
    FileInputStream fis = null;

    try {
        fis = openFileInput(FILE_NAME);
        InputStreamReader isr = new InputStreamReader(fis);
        BufferedReader br = new BufferedReader(isr);
        StringBuilder sb = new StringBuilder();
        String text;

        while ((text = br.readLine()) != null) {
            sb.append(text).append("\n");
        }

        mEditText.setText(sb.toString());

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (fis != null) {
            try {
                fis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

How to write this in Kotlin Language...? So far by myself, I have tried to convert it in Kotlin but there are still some errors on some lines (denoted by ). Please help me in solving these errors.

var fis = File(FILE_NAME).inputStream     //<ror>Unresolved reference File 
try {
    fis = openFileInput(FILE_NAME)
    var isr = InputStreamReader(fis)
    val br = BufferedReader(isr)
    val sb = StringBuilder()
    var text:List<String> = br.readLines()

    while ((text) != null) {                //<ror>
        sb.append(text).append("\n")
    }

    mEditText?.text(sb.toString())          //<ror>

} catch (e : FileNotFoundException) {
    e.printStackTrace()
} catch (e : IOException) {
    e.printStackTrace()
} finally {
    if (fis != null) {
        try {
            fis.close()
        } catch (e : IOException) {
            e.printStackTrace()
        }
    }
}

Answer 1

File(FILE_NAME).readLines().fold(StringBuilder()){ builder, next ->
   builder.appendln(next)
}.also {
   mEditText.setText(it.toString())
}

Answer 2

Try below code

fun load(v: View, fileName: String ) {
        var fis = File(fileName).inputStream()                             

        try {
            fis = openFileInput(fileName)
            var isr = InputStreamReader(fis)
            val br = BufferedReader(isr)
            val sb = StringBuilder()
            var text:List<String> = br.readLines() //Do not use this function for huge files.

            while (true) {                                      
                sb.append(text).append("\n")
            }

            mEditText?.text(sb.toString())       //mEditText is your EditText                          

        } catch (e : FileNotFoundException) {
            e.printStackTrace()
        } catch (e : IOException) {
            e.printStackTrace()
        } finally {
            try {
                fis.close()
            } catch (e : IOException) {
                e.printStackTrace()
            }
        }
    }

Answer 3

Just paste your java code in Android Studio.kt file, It will suggest you to convert it into Kotlin. There you get 99% of the kotlin code. Then change some missing elements.

Answer 4

My solution is:

var fis = File(FILE_NAME).inputStream()                             

    try {
        fis = openFileInput(FILE_NAME)
        val isr = InputStreamReader(fis)
        val br = BufferedReader(isr)
        val sb = StringBuilder()
        var lines = br.readLines()

        for (line in lines) {                                       
            sb.append(line).append("\n")
        }

        mEditText?.setText(sb.toString())                           

    } catch (e : FileNotFoundException) {
        e.printStackTrace()
    } catch (e : IOException) {
        e.printStackTrace()
    } finally {
        try {
            fis.close()
        } catch (e : IOException) {
            e.printStackTrace()
        }

    }

It looks like you have infinite loop there so I change it to for each loop to read all the lines from the InputStream

Answer 5

Here is my solution:

fun load(v: View?) {
    var fis: FileInputStream? = null

    try {
        fis = openFileInput(FILE_NAME)
        val isr = InputStreamReader(fis)
        val br = BufferedReader(isr)
        val lines = br.readLines()
        val output = lines.joinToString("\n")

        mEditText.setText(output)
    } catch (e: FileNotFoundException) {
        e.printStackTrace()
    } catch (e: IOException) {
        e.printStackTrace()
    } finally {
        try {
            fis?.close()
        } catch (e: IOException) {
            e.printStackTrace()
        }
    }
}

Answer 6

fun void load(v: View) {
    try {
        openFileInput(FILE_NAME).use { fis ->
            val br = BufferedReader(InputStreamReader(fis))

            var text: String? = null

            while(true) {
                text = br.readLine() ?: break
                sb.append(text).append("\n")
            }

            editText.setText(sb.toString())
        }
    } catch(e: Exception) {
        e.printStackTrace()
    }
}

This should be reasonably equivalent. Please note that the if((text = br.readLine() != null) { cannot be written like that directly in Kotlin, however you can replace it with a while(true) { break; .

Manual close() is not needed if you are using .use { .