service+okhttp实现断点续传下载

最新推荐文章于 2025-06-10 22:17:58 发布

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最新推荐文章于 2025-06-10 22:17:58 发布

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CC 4.0 BY-SA版权

分类专栏： service

本文链接：https://blog.youkuaiyun.com/free_co/article/details/73506247

本文介绍如何结合DownloadListener、DownloadTask、DownloadService和MainActivity，利用OkHttp在Android中实现文件的断点续传下载功能。详细讲解了各个组件的作用，并提供了AndroidManifest.xml配置和源码下载链接。

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DownloadListener

public interface DownloadListener {
   
   

    void onProgress(int progress);

    void onSuccess();

    void onFailed();

    void onPause();

    void onCanceled();

}

DownloadTask

/**
 * 第一个参数表示后台任务
 * 第二个为进度
 * 第三个为执行结果
 */

public class DownloadTask extends AsyncTask<String, Integer, Integer>{
   
   

    public static final int TYPE_SUCCESS = 0;
    public static final int TYPE_FAILED = 1;
    public static final int TYPE_PAUSED = 2;
    public static final int TYPE_CANCELED = 3;

    private DownloadListener listener;

    private boolean isCanceled = false;
    private boolean isPauesd = false;
    private int lastProgress;


    public DownloadTask(DownloadListener listener){
        this.listener = listener;
    }

    @Override
    protected Integer doInBackground(String... params) {
        InputStream is = null;
        RandomAccessFile savedFile = null;
        File file = null;
        try{
            long downloadedLength = 0; //记录已下载的文件长度
            String downloadUrl = params[0];
            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
            //sd卡的download目录
            String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
            file = new File(directory + fileName);
            if(file.exists()){
                downloadedLength = file.length();
            }
            long contentLength = getContnetLength(downloadUrl);
            if(contentLength == 0){
                //文件有问题
                return TYPE_FAILED;
            }else if(contentLength == downloadedLength){
                //已下载字节和文件总字节相等，说明下载已经完成了
                return TYPE_SUCCESS;
            }
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    //告诉服务器从哪个字节开始下载
                    .addHeader("RANGE", "bytes=" + downloadedLength + "-")
                    .url(downloadUrl)
                    .build();
            Response response = client.newCall(request).execute();
            if(response !=