Soma: Created page with "==Notes==

 March 29 --------  So I'm trying to figure out how to implement the back button properly.  Currently, the back button gets triggered but doesn't work right, .goBack() isn't doing what we expected  - hypothesis: state changes are updating history too often, getting copies of current page and so can't keep track of last page properly  Two choices:  - integrate more tightly with webview history so we can better manipulate and interact with it  - ignore webv..."

2023-03-30T03:26:48Z

Created page with "==Notes== <pre> March 29 -------- So I'm trying to figure out how to implement the back button properly. Currently, the back button gets triggered but doesn't work right, .goBack() isn't doing what we expected - hypothesis: state changes are updating history too often, getting copies of current page and so can't keep track of last page properly Two choices: - integrate more tightly with webview history so we can better manipulate and interact with it - ignore webv..."

New page

==Notes==

<pre>
March 29
--------

So I'm trying to figure out how to implement the back button properly.

Currently, the back button gets triggered but doesn't work right, .goBack() isn't doing what we expected
- hypothesis: state changes are updating history too often, getting copies of current page and so can't keep track of last page properly

Two choices:
- integrate more tightly with webview history so we can better manipulate and interact with it
- ignore webview history, implement it all on our own and just push current page to the webview widget as needed
</pre>

==Code==

<syntaxhighlight lang="kotlin" line>
package carleton.comp2601.webviewcompose

import android.os.Bundle
import android.util.Log
import android.view.ViewGroup
import android.webkit.WebView
import android.webkit.WebViewClient
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.text.ClickableText
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.AnnotatedString
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.viewinterop.AndroidView

class MainActivity : ComponentActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
// Calling the composable function
// to display element and its contents
MainContent()
}
}
}

// Creating a composable
// function to display Top Bar
@Composable
fun MainContent() {
var curURL by remember { mutableStateOf("https://news.ycombinator.com") }
var navigate by remember { mutableStateOf("") }

Scaffold(
// topBar = { TopAppBar(title = {Text("COMP 2601")})},
topBar = {
Row {
ClickableText(
AnnotatedString(text = "Back"),
onClick = {
navigate = "back"
Log.d("webviewCompose", "navigate = back")
}
)
URLBar(curURL = curURL, updateURL = { curURL = it })
}
},
content = { MyContent(curURL = curURL, updateURL = {
curURL = it
Log.d("webviewCompose", "updating URL to $curURL")
},
navigate = navigate, resetNavigate = { navigate = ""}) }
)
}

@Composable
fun URLBar(curURL: String, updateURL: (String) -> Unit) {
var newURL = ""

TextField(
value = curURL,
//onFocusChange = { updateURL(newURL) },
//onValueChange = { updatedURL: String -> newURL = updatedURL},
onValueChange = updateURL,
label = { Text("Enter URL here") }
)
}

@Composable
fun MyContent(curURL: String, updateURL: (String) -> Unit,
navigate: String, resetNavigate: () -> Unit){

class ObservableWebViewClient : WebViewClient() {

override fun shouldOverrideUrlLoading(view: WebView?, url: String?): Boolean {
if (url != null) {
updateURL(url)
}
return false
}
}

fun logWebViewHistory(view: WebView) {
val history = view.copyBackForwardList()

val current = history.currentIndex

Log.d("webviewCompose", "Current history item: $current")

Log.d("webviewCompose", "Webview BackForwardList contents:")

for (i in 0..history.size -1) {
val item = history.getItemAtIndex(i)

if (item != null) {
val u = item.originalUrl
Log.d("webviewCompose", " $i: $u")
}
}
}

// Adding a WebView inside AndroidView
// with layout as full screen
AndroidView(factory = {
WebView(it).apply {
// layoutParams = ViewGroup.LayoutParams(
// ViewGroup.LayoutParams.MATCH_PARENT,
// ViewGroup.LayoutParams.MATCH_PARENT
// )
webViewClient = ObservableWebViewClient()
loadUrl(curURL)
}
}, update = {
if (navigate == "back") {
Log.d("webviewCompose", "Navigating back")
val currentURL = it.url
Log.d("webviewCompose", "currentURL = $currentURL")
it.goBack()
val prevURL = it.url
Log.d("webviewCompose", "prevURL = $prevURL")

if (currentURL == prevURL) {
Log.d("webviewCompose", "current and prev are the SAME!")
}
if (prevURL != null) {
Log.d("webviewCompose", "updating URL after back button")
updateURL(prevURL)
}
resetNavigate()

logWebViewHistory(it)
} else {
Log.d("webviewCompose", "loading URL $curURL")
it.loadUrl(curURL)
logWebViewHistory(it)
}
})
}

// For displaying preview in
// the Android Studio IDE emulator
@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
MainContent()
}
</syntaxhighlight>

Mobile Apps 2023W Lecture 21 - Revision history