[Download Home] Add image thumbnail support

chrome/browser/android/download/ui/thumbnail_provider.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_ANDROID_DOWNLOAD_UI_THUMBNAIL_PROVIDER_H_
+#define CHROME_BROWSER_ANDROID_DOWNLOAD_UI_THUMBNAIL_PROVIDER_H_
+
+#include <string>
+
+#include "base/android/jni_android.h"
+#include "chrome/browser/image_decoder.h"
+
+// Kicks off asynchronous pipelines for creating thumbnails for local files.
+// The native-side ThumbnailProvider is owned by the Java-side and can be
+// safely destroyed while a request is being processed.
+class ThumbnailProvider {
+ public:
+  explicit ThumbnailProvider(const base::android::JavaParamRef<jobject>& jobj);
+
+  // Destroys the ThumbnailProvider.  Any currently running ImageRequest will
+  // delete itself when it has completed.
+  void Destroy(JNIEnv* env, const base::android::JavaParamRef<jobject>& jobj);
+
+  // Kicks off an asynchronous process to retrieve the thumbnail for the file
+  // located at |file_path| with a max size of |icon_size| in each dimension.
+  void RetrieveThumbnail(JNIEnv* env,
+                         const base::android::JavaParamRef<jobject>& jobj,
+                         jstring jfile_path,
+                         jint icon_size);
+
+  // Called when the thumbnail is ready.  |thumbnail| will be empty on failure.
+  void OnThumbnailRetrieved(const std::string& file_path,
+                            const SkBitmap& thumbnail);
+
+  // Registers the JNI bindings.
+  static bool RegisterThumbnailProvider(JNIEnv* env);
+
+ private:
+  ~ThumbnailProvider();
+
+  base::android::ScopedJavaGlobalRef<jobject> java_delegate_;
+  base::WeakPtrFactory<ThumbnailProvider> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThumbnailProvider);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_DOWNLOAD_UI_THUMBNAIL_PROVIDER_H_