[url_launcher] Re-land v2 embedding support (#2204)

This is identical to the original PR, except it correctly increments the Flutter SDK version to the latest stable and fixes some minor Java style nits.

packages/url_launcher/url_launcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 5.2.2
+
+* Re-land embedder v2 support with correct Flutter SDK constraints.
+
 ## 5.2.1
 
 * Revert the migration since the Flutter dependency was too low.

packages/url_launcher/url_launcher/android/build.gradle

@@ -44,4 +44,40 @@ android {
     lintOptions {
         disable 'InvalidPackage'
     }
+    testOptions {
+        unitTests.includeAndroidResources = true
+    }
+}
+
+dependencies {
+    compileOnly 'androidx.annotation:annotation:1.0.0'
+    testImplementation 'junit:junit:4.12'
+    testImplementation 'org.mockito:mockito-core:1.10.19'
+    testImplementation 'androidx.test:core:1.0.0'
+    testImplementation 'org.robolectric:robolectric:4.3'
+}
+
+// TODO(mklim): Remove this hack once androidx.lifecycle is included on stable. https://github.com/flutter/flutter/issues/42348
+afterEvaluate {
+    def containsEmbeddingDependencies = false
+    for (def configuration : configurations.all) {
+        for (def dependency : configuration.dependencies) {
+            if (dependency.group == 'io.flutter' &&
+                dependency.name.startsWith('flutter_embedding') &&
+                dependency.isTransitive())
+            {
+                containsEmbeddingDependencies = true
+                break
+            }
+        }
+    }
+    if (!containsEmbeddingDependencies) {
+        android {
+            dependencies {
+                def lifecycle_version = "2.1.0"
+                api "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
+                api "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"
+            }
+        }
+    }
 }

packages/url_launcher/url_launcher/android/src/main/AndroidManifest.xml

@@ -1,7 +1,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="io.flutter.plugins.urllauncher">
   <application>
-    <activity android:name=".WebViewActivity"
+    <activity android:name="io.flutter.plugins.urllauncher.WebViewActivity"
       android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
       android:exported="false"/>
   </application>

packages/url_launcher/url_launcher/android/src/main/java/io/flutter/plugins/urllauncher/MethodCallHandlerImpl.java

@@ -0,0 +1,113 @@
+package io.flutter.plugins.urllauncher;
+
+import android.os.Bundle;
+import android.util.Log;
+import androidx.annotation.Nullable;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
+import io.flutter.plugin.common.MethodChannel.Result;
+import io.flutter.plugins.urllauncher.UrlLauncher.LaunchStatus;
+import java.util.Map;
+
+/**
+ * Translates incoming UrlLauncher MethodCalls into well formed Java function calls for {@link
+ * UrlLauncher}.
+ */
+final class MethodCallHandlerImpl implements MethodCallHandler {
+  private static final String TAG = "MethodCallHandlerImpl";
+  private final UrlLauncher urlLauncher;
+  @Nullable private MethodChannel channel;
+
+  /** Forwards all incoming MethodChannel calls to the given {@code urlLauncher}. */
+  MethodCallHandlerImpl(UrlLauncher urlLauncher) {
+    this.urlLauncher = urlLauncher;
+  }
+
+  @Override
+  public void onMethodCall(MethodCall call, Result result) {
+    final String url = call.argument("url");
+    switch (call.method) {
+      case "canLaunch":
+        onCanLaunch(result, url);
+        break;
+      case "launch":
+        onLaunch(call, result, url);
+        break;
+      case "closeWebView":
+        onCloseWebView(result);
+        break;
+      default:
+        result.notImplemented();
+        break;
+    }
+  }
+
+  /**
+   * Registers this instance as a method call handler on the given {@code messenger}.
+   *
+   * <p>Stops any previously started and unstopped calls.
+   *
+   * <p>This should be cleaned with {@link #stopListening} once the messenger is disposed of.
+   */
+  void startListening(BinaryMessenger messenger) {
+    if (channel != null) {
+      Log.wtf(TAG, "Setting a method call handler before the last was disposed.");
+      stopListening();
+    }
+
+    channel = new MethodChannel(messenger, "plugins.flutter.io/url_launcher");
+    channel.setMethodCallHandler(this);
+  }
+
+  /**
+   * Clears this instance from listening to method calls.
+   *
+   * <p>Does nothing if {@link #startListening} hasn't been called, or if we're already stopped.
+   */
+  void stopListening() {
+    if (channel == null) {
+      Log.d(TAG, "Tried to stop listening when no MethodChannel had been initialized.");
+      return;
+    }
+
+    channel.setMethodCallHandler(null);
+    channel = null;
+  }
+
+  private void onCanLaunch(Result result, String url) {
+    result.success(urlLauncher.canLaunch(url));
+  }
+
+  private void onLaunch(MethodCall call, Result result, String url) {
+    final boolean useWebView = call.argument("useWebView");
+    final boolean enableJavaScript = call.argument("enableJavaScript");
+    final boolean enableDomStorage = call.argument("enableDomStorage");
+    final Map<String, String> headersMap = call.argument("headers");
+    final Bundle headersBundle = extractBundle(headersMap);
+
+    LaunchStatus launchStatus =
+        urlLauncher.launch(url, headersBundle, useWebView, enableJavaScript, enableDomStorage);
+
+    if (launchStatus == LaunchStatus.NO_ACTIVITY) {
+      result.error("NO_ACTIVITY", "Launching a URL requires a foreground activity.", null);
+    } else {
+      result.success(true);
+    }
+  }
+
+  private void onCloseWebView(Result result) {
+    urlLauncher.closeWebView();
+    result.success(null);
+  }
+
+  private static Bundle extractBundle(Map<String, String> headersMap) {
+    final Bundle headersBundle = new Bundle();
+    for (String key : headersMap.keySet()) {
+      final String value = headersMap.get(key);
+      headersBundle.putString(key, value);
+    }
+    return headersBundle;
+  }
+}

packages/url_launcher/url_launcher/android/src/main/java/io/flutter/plugins/urllauncher/UrlLauncher.java

@@ -0,0 +1,91 @@
+package io.flutter.plugins.urllauncher;
+
+import android.app.Activity;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.net.Uri;
+import android.os.Bundle;
+import android.provider.Browser;
+import androidx.annotation.Nullable;
+
+/** Launches components for URLs. */
+class UrlLauncher {
+  private final Context applicationContext;
+  @Nullable private Activity activity;
+
+  /**
+   * Uses the given {@code applicationContext} for launching intents.
+   *
+   * <p>It may be null initially, but should be set before calling {@link #launch}.
+   */
+  UrlLauncher(Context applicationContext, @Nullable Activity activity) {
+    this.applicationContext = applicationContext;
+    this.activity = activity;
+  }
+
+  void setActivity(@Nullable Activity activity) {
+    this.activity = activity;
+  }
+
+  /** Returns whether the given {@code url} resolves into an existing component. */
+  boolean canLaunch(String url) {
+    Intent launchIntent = new Intent(Intent.ACTION_VIEW);
+    launchIntent.setData(Uri.parse(url));
+    ComponentName componentName =
+        launchIntent.resolveActivity(applicationContext.getPackageManager());
+
+    return componentName != null
+        && !"{com.android.fallback/com.android.fallback.Fallback}"
+            .equals(componentName.toShortString());
+  }
+
+  /**
+   * Attempts to launch the given {@code url}.
+   *
+   * @param headersBundle forwarded to the intent as {@code Browser.EXTRA_HEADERS}.
+   * @param useWebView when true, the URL is launched inside of {@link WebViewActivity}.
+   * @param enableJavaScript Only used if {@param useWebView} is true. Enables JS in the WebView.
+   * @param enableDomStorage Only used if {@param useWebView} is true. Enables DOM storage in the
+   * @return {@link LaunchStatus#NO_ACTIVITY} if there's no available {@code applicationContext}.
+   *     {@link LaunchStatus#OK} otherwise.
+   */
+  LaunchStatus launch(
+      String url,
+      Bundle headersBundle,
+      boolean useWebView,
+      boolean enableJavaScript,
+      boolean enableDomStorage) {
+    if (activity == null) {
+      return LaunchStatus.NO_ACTIVITY;
+    }
+
+    Intent launchIntent;
+    if (useWebView) {
+      launchIntent =
+          WebViewActivity.createIntent(
+              activity, url, enableJavaScript, enableDomStorage, headersBundle);
+    } else {
+      launchIntent =
+          new Intent(Intent.ACTION_VIEW)
+              .setData(Uri.parse(url))
+              .putExtra(Browser.EXTRA_HEADERS, headersBundle);
+    }
+
+    activity.startActivity(launchIntent);
+    return LaunchStatus.OK;
+  }
+
+  /** Closes any activities started with {@link #launch} {@code useWebView=true}. */
+  void closeWebView() {
+    applicationContext.sendBroadcast(new Intent(WebViewActivity.ACTION_CLOSE));
+  }
+
+  /** Result of a {@link #launch} call. */
+  enum LaunchStatus {
+    /** The intent was well formed. */
+    OK,
+    /** No activity was found to launch. */
+    NO_ACTIVITY,
+  }
+}