Android/kotlin/http通信

準備

AndroidManifext.xmlに以下を追加しておく。

<uses-permission android:name="android.permission.INTERNET" />

サンプル

HttpRequest.kt

class HttpRequest {
    private var body = "";
    fun request(requestUrl: String): Boolean {
        if (requestUrl.isEmpty()) {
            Log.w(TAG, "URLが空です。")
            return false
        }
        val url = URL(requestUrl)
        val urlConnection = url.openConnection() as HttpURLConnection
        urlConnection.requestMethod = "GET"
        urlConnection.connect()
        val br = BufferedReader(InputStreamReader(urlConnection.inputStream))
        val sb = StringBuilder()
        for (line: String? in br.readLines()) {
            line?.let { sb.append(line) }
        }
        br.close()
        body = sb.toString()
        return true
    }
    fun getBody(): String {
        return body
    }
    companion object {
        private const val TAG = "HttpRequest"
    }
}

参考：https://qiita.com/naoi/items/8df1409ad48ad8f3c632

AsyncTsnkでアクセス

直アクセスだとアクセスできないのでAsyncTaskをかます。

起動方法

var task = HttpAsyncTask();
task.execute();

HttpAsyncTask.kt

import android.os.AsyncTask
class HttpAsyncTask : AsyncTask<Void, Void, Boolean>() {
    override fun onPreExecute() {
        Log.i(TAG, "onPreExecute")
    }
    override fun doInBackground(vararg p: Void?): Boolean {
        var httpRequest = HttpRequest()
        var success: Boolean = httpRequest.request("https://example.com/?hogehoge")
        Log.i(TAG, "body=" + httpRequest.getBody())
        return true
    }
    override fun onPostExecute(flag: Boolean) {
        Log.i(TAG, "onPostExecute flag=" + flag)
        super.onPostExecute(flag)
    }
}

コールチンでアクセス

AsyncTaskの代わりにkotlin1.3より公式となったコールチンでもアクセスできます。

Coroutines 正式 httprequest

import androidx.appcompat.app.AppCompatActivity import android.os.Bundle import android.util.Log import kotlinx.android.synthetic.main.activity_main.* import kotlinx.coroutines.CoroutineScope import kotlinx.coroutines.Dispatchers import kotlinx.coroutines.launch import kotlinx.coroutines.withContext

class MainActivity : AppCompatActivity() {

   val scope = CoroutineScope(Dispatchers.Default)
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       setContentView(R.layout.activity_main)
       scope.launch {
           httpTask()
       }
   }
   private suspend fun httpTask() {
       try {
           withContext(Dispatchers.Main) {
               Log.i(localClassName, "onPreExecute")
           }
           var httpRequest = HttpRequest()
           //var http = HttpUtil()
           var success: Boolean = httpRequest.request("https://h2ch.com/?hogehoge")
           Log.i(localClassName, "body=" + httpRequest.getBody())

           withContext(Dispatchers.Main) {
               Log.i(localClassName, "onPostExecute")
           }
       } catch (e: Exception) {
           Log.e(localClassName, "onCancelled", e)
       }
   }

}