Add android version for incognito web view

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/FlutterWebView.java

@@ -1,7 +1,11 @@
 package io.flutter.plugins.webviewflutter;
 
 import android.content.Context;
+import android.os.Build;
+import android.os.Build.VERSION_CODES;
 import android.view.View;
+import android.webkit.CookieManager;
+import android.webkit.WebSettings;
 import android.webkit.WebView;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.common.MethodCall;
@@ -12,6 +16,7 @@
 import java.util.Map;
 
 public class FlutterWebView implements PlatformView, MethodCallHandler {
+
   private final WebView webView;
   private final MethodChannel methodChannel;
 
@@ -131,6 +136,11 @@ private void applySettings(Map<String, Object> settings) {
         case "jsMode":
           updateJsMode((Integer) settings.get(key));
           break;
+        case "incognito":
+          boolean isIncognito = (Boolean) settings.get(key);
+          if (isIncognito) {
+            Incognito.makeWebViewIncognito(webView);
+          }
         default:
           throw new IllegalArgumentException("Unknown WebView setting: " + key);
       }
@@ -151,5 +161,6 @@ private void updateJsMode(int mode) {
   }
 
   @Override
-  public void dispose() {}
+  public void dispose() {
+  }
 }

packages/webview_flutter/android/src/main/java/io/flutter/plugins/webviewflutter/Incognito.java

@@ -0,0 +1,46 @@
+package io.flutter.plugins.webviewflutter;
+
+import android.os.Build;
+import android.os.Build.VERSION_CODES;
+import android.webkit.CookieManager;
+import android.webkit.WebSettings;
+import android.webkit.WebView;
+import io.flutter.util.Preconditions;
+
+public final class Incognito {
+
+  private Incognito() {
+    // Utility cache. Do not instantiate.
+  }
+
+  public static void makeWebViewIncognito(WebView webView) {
+    Preconditions.checkNotNull(webView);
+    clearAndDisableAppCache(webView);
+    clearAndDisableCookies();
+    clearHistory(webView);
+  }
+
+  private static void clearAndDisableCookies() {
+    CookieManager cookieManager = CookieManager.getInstance();
+    if (Build.VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) {
+      cookieManager.removeAllCookies(null);
+    } else {
+      cookieManager.removeAllCookie();
+    }
+    cookieManager.setAcceptCookie(false);
+  }
+
+  private static void clearAndDisableAppCache(WebView webView) {
+    webView.clearCache(true);
+    webView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE);
+    webView.getSettings().setAppCacheEnabled(false);
+  }
+
+  /**
+   * Tells this WebView to clear its internal back/forward list. Not the global history.
+   */
+  private static void clearHistory(WebView webView) {
+    webView.clearHistory();
+  }
+
+}