In this article we will look about how to read a file in Kotlin Programming language, whether it is a text file, or a raw json file, from assets folder of our Android Studio Project.
What we are going to achieve:
Our intention in this article is simple, to fetch a local json file into a string using Kotlin Programming Language and use it according to our need.
Good old days using Java:
Let us recap how we used to read a file using Java.
Here is the code snippet used to read the contents of a file using Java Programming Language:
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| BufferedReader reader = null; | |
| try { | |
| reader = new BufferedReader( | |
| new InputStreamReader(getAssets().open("news_data_file.json"), "UTF-8")); | |
| // do reading, usually loop until end of file reading | |
| String mLine; | |
| while ((mLine = reader.readLine()) != null) { | |
| //process line | |
| … | |
| } | |
| } catch (IOException e) { | |
| //log the exception | |
| } finally { | |
| if (reader != null) { | |
| try { | |
| reader.close(); | |
| } catch (IOException e) { | |
| //log the exception | |
| } | |
| } | |
| } |
How to achieve this in Kotlin?
Let us see how to achieve the same using Kotlin Programming Language. Here is the code snippet to perform the same in Kotlin:
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| try { | |
| val inputStream:InputStream = assets.open("news_data_file.json") | |
| val inputStreamReader = InputStreamReader(inputStream) | |
| val sb = StringBuilder() | |
| var line: String? | |
| val br = BufferedReader(inputStreamReader) | |
| line = br.readLine() | |
| while (br.readLine() != null) { | |
| sb.append(line) | |
| line = br.readLine() | |
| } | |
| br.close() | |
| Log.d(TAG,sb.toString()) | |
| } catch (e:Exception){ | |
| Log.d(TAG, e.toString()) | |
| } |
So, Whats so Special in Kotlin ? Is there a simple way to achive the same differently and in a simple way?
The Answer is Yes, we can do so by means of available extension functions, a Powerful feature in Kotlin.
Read File in a simplified way using Extension Function
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| try { | |
| val inputStream:InputStream = assets.open("news_data_file.json") | |
| val inputString = inputStream.bufferedReader().use{it.readText()} | |
| Log.d(TAG,inputString) | |
| } catch (e:Exception){ | |
| Log.d(TAG, e.toString()) | |
| } |
In the above code snippet, bufferedReader() is an extension function in Kotlin IO package which can be readily used to achieve the same as the above Java code snippet.
