From 4e1bf80e123a3684657465e6ed566875c2b29c6d Mon Sep 17 00:00:00 2001
From: Grishka <git@grishka.me>
Date: Thu, 13 Jun 2024 17:08:24 +0300
Subject: [PATCH] Make WebViewFragment work with predictive back

---
 .../android/fragments/WebViewFragment.java    | 46 ++++++++++++++-----
 1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/mastodon/src/main/java/org/joinmastodon/android/fragments/WebViewFragment.java b/mastodon/src/main/java/org/joinmastodon/android/fragments/WebViewFragment.java
index 6146abc7..7cd3022a 100644
--- a/mastodon/src/main/java/org/joinmastodon/android/fragments/WebViewFragment.java
+++ b/mastodon/src/main/java/org/joinmastodon/android/fragments/WebViewFragment.java
@@ -1,6 +1,7 @@
 package org.joinmastodon.android.fragments;
 
 import android.os.Bundle;
+import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -10,14 +11,18 @@ import android.webkit.WebResourceRequest;
 import android.webkit.WebView;
 import android.webkit.WebViewClient;
 
+import org.joinmastodon.android.BuildConfig;
 import org.joinmastodon.android.api.MastodonErrorResponse;
 
 import me.grishka.appkit.Nav;
 import me.grishka.appkit.fragments.LoaderFragment;
-import me.grishka.appkit.fragments.OnBackPressedListener;
 
-public abstract class WebViewFragment extends LoaderFragment implements OnBackPressedListener{
+public abstract class WebViewFragment extends LoaderFragment{
+	private static final String TAG="WebViewFragment";
+
 	protected WebView webView;
+	private Runnable backCallback=this::onGoBack;
+	private boolean backCallbackSet;
 
 	@Override
 	public View onCreateContentView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
@@ -31,18 +36,28 @@ public abstract class WebViewFragment extends LoaderFragment implements OnBackPr
 		webView.setWebViewClient(new WebViewClient(){
 			@Override
 			public void onPageFinished(WebView view, String url){
+				if(BuildConfig.DEBUG){
+					Log.d(TAG, "onPageFinished: "+url);
+				}
 				dataLoaded();
+				updateBackCallback();
 			}
 
 			@Override
 			public void onReceivedError(WebView view, WebResourceRequest request, WebResourceError error){
 				onError(new MastodonErrorResponse(error.getDescription().toString(), -1, null));
+				updateBackCallback();
 			}
 
 			@Override
 			public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request){
 				return WebViewFragment.this.shouldOverrideUrlLoading(request);
 			}
+
+			@Override
+			public void doUpdateVisitedHistory(WebView view, String url, boolean isReload){
+				updateBackCallback();
+			}
 		});
 		webView.getSettings().setJavaScriptEnabled(true);
 		return webView;
@@ -58,19 +73,28 @@ public abstract class WebViewFragment extends LoaderFragment implements OnBackPr
 		webView.reload();
 	}
 
-	@Override
-	public boolean onBackPressed(){
-		if(webView.canGoBack()){
-			webView.goBack();
-			return true;
-		}
-		return false;
-	}
-
 	@Override
 	public void onToolbarNavigationClick(){
 		Nav.finish(this);
 	}
 
+	private void updateBackCallback(){
+		boolean canGoBack=webView.canGoBack();
+		if(canGoBack!=backCallbackSet){
+			if(canGoBack){
+				addBackCallback(backCallback);
+				backCallbackSet=true;
+			}else{
+				removeBackCallback(backCallback);
+				backCallbackSet=false;
+			}
+		}
+	}
+
+	private void onGoBack(){
+		if(webView.canGoBack())
+			webView.goBack();
+	}
+
 	protected abstract boolean shouldOverrideUrlLoading(WebResourceRequest req);
 }