看官方的API很简单，它是webkit下的一个接口，该接口就一个抽象方法：onDownloadStart：

public abstract void onDownloadStart (String url, String userAgent, String contentDisposition, String mimetype, long contentLength)

不用多解释。

下面是它的源码，也非常简单：

/**
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.webkit;

public interface DownloadListener {

    /***
     * Notify the host application that a file should be downloaded
     * @param url The full url to the content that should be downloaded
     * @param userAgent the user agent to be used for the download.
     * @param contentDisposition Content-disposition http header, if 
     *                           present.
     * @param mimetype The mimetype of the content reported by the server
     * @param contentLength The file size reported by the server
     */
    public void onDownloadStart(String url, String userAgent,
            String contentDisposition, String mimetype, long contentLength);

}

webkit下DownloadListener,布布扣,bubuko.com

webkit下DownloadListener