feat(android): define WebView class in kotlin (#672)

.changes/webview-class.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+Added the `RustWebView` class on Android.

build.rs

@@ -50,8 +50,18 @@ fn main() {
           .to_string_lossy()
           .to_uppercase()
       );
+      let class_init_env = format!(
+        "WRY_{}_CLASS_INIT",
+        file
+          .path()
+          .file_stem()
+          .unwrap()
+          .to_string_lossy()
+          .to_uppercase()
+      );
 
       println!("cargo:rerun-if-env-changed={}", class_extension_env);
+      println!("cargo:rerun-if-env-changed={}", class_init_env);
 
       let content = fs::read_to_string(file.path())
         .expect("failed to read kotlin file as string")
@@ -60,6 +70,10 @@ fn main() {
         .replace(
           "{{class-extension}}",
           &std::env::var(&class_extension_env).unwrap_or_default(),
+        )
+        .replace(
+          "{{class-init}}",
+          &std::env::var(&class_init_env).unwrap_or_default(),
         );
 
       let mut out = String::from("THIS FILE IS AUTO-GENERATED. DO NOT MODIFY!!\n\n");

src/webview/android/kotlin/RustWebView.kt

@@ -0,0 +1,13 @@
+package {{app-domain-reversed}}.{{app-name-snake-case}}
+
+import android.webkit.*
+import android.content.Context
+
+class RustWebView(context: Context): WebView(context) {
+    init {
+        this.settings.javaScriptEnabled = true
+        {{class-init}}
+    }
+
+    {{class-extension}}
+}

src/webview/android/main_pipe.rs

@@ -38,29 +38,26 @@ impl MainPipe<'_> {
       match message {
         WebViewMessage::CreateWebView(url, initialization_scripts, devtools) => {
           // Create webview
-          let class = env.find_class("android/webkit/WebView")?;
-          let webview =
-            env.new_object(class, "(Landroid/content/Context;)V", &[activity.into()])?;
-
-          // Enable Javascript
-          let settings = env
-            .call_method(
-              webview,
-              "getSettings",
-              "()Landroid/webkit/WebSettings;",
-              &[],
-            )?
-            .l()?;
-          env.call_method(settings, "setJavaScriptEnabled", "(Z)V", &[true.into()])?;
+          let rust_webview_class = find_my_class(
+            env,
+            activity,
+            format!("{}/RustWebView", PACKAGE.get().unwrap()),
+          )?;
+          let webview = env.new_object(
+            rust_webview_class,
+            "(Landroid/content/Context;)V",
+            &[activity.into()],
+          )?;
 
           // Load URL
           if let Ok(url) = env.new_string(url) {
             env.call_method(webview, "loadUrl", "(Ljava/lang/String;)V", &[url.into()])?;
           }
 
           // Enable devtools
+          #[cfg(debug_assertions)]
           env.call_static_method(
-            class,
+            rust_webview_class,
             "setWebContentsDebuggingEnabled",
             "(Z)V",
             &[devtools.into()],