Thursday, July 23, 2020

android kotlin - Coroutines get html from url

MainActivity.kt

package com.example.coroutine

import android.os.Bundle
import android.text.method.ScrollingMovementMethod
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.lifecycleScope
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.coroutines.*
import java.io.IOException
import java.net.MalformedURLException
import java.net.URL


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // make text view text scrollable
        textView.movementMethod =ScrollingMovementMethod()

        // url to get html
        val url: URL? = try {
                URL("https://developer.android.com/kotlin/")
            } catch (e: MalformedURLException) {
                // catch invalid url exception
                button.isEnabled = false
                textView.text = e.message
                null
            }


        button.setOnClickListener {
            progressBar.visibility = View.VISIBLE

            // asynchronously read html from url
            // io dispatcher for background thread network operation
            val result = lifecycleScope.async(Dispatchers.IO) {
                try {
                    url?.readText()
                } catch (e: IOException) {
                    // catch exception while reading it
                    "Error....\n\n$e"
                }
            }

            // main dispatcher for interacting with ui views
            lifecycleScope.launch(Dispatchers.Main) {
                // finally, display the html to text view when available
                textView.text = result.await()

                progressBar.visibility = View.INVISIBLE
            }
        }
    }
}
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#DBD7D2"
    tools:context=".MainActivity">

    <com.google.android.material.button.MaterialButton
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:backgroundTint="#66023C"
        android:text="Get HTML From URL"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="@+id/button"
        app:layout_constraintStart_toEndOf="@+id/button"
        app:layout_constraintTop_toTopOf="@+id/button" />

    <com.google.android.material.textview.MaterialTextView
        android:id="@+id/textView"
        style="@style/TextAppearance.MaterialComponents.Headline6"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="12dp"
        android:padding="8dp"
        android:fontFamily="sans-serif-thin"
        android:textColor="#59260B"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button"
        tools:text="TextView" />

</androidx.constraintlayout.widget.ConstraintLayout>
build.gradle (app) [code to add]

dependencies {
    // kotlin coroutines
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.7'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.7'

    // life cycle
    def lifecycle_version = "2.2.0"
    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"
}