Android

我们的App中常常会涉及到与下载相关的内容，这时候就不得不提及DownloadManager这个类

闲话少说，直接上代码，这里封装成了一个工具类:

1.DownloadUtil.class

package com.mythmayor.download;import android.app.DownloadManager;import android.content.Context;import android.database.Cursor;import android.net.Uri;import android.os.Environment;import android.os.Handler;/** * Created by mythmayor on 2017/4/26. */public class DownloadUtil {    private String mUrl;    private String mName;    private Handler mHandler;    private Context mContext;    private DownloadManager mManager;    private long requestId;    public DownloadUtil(Context context, String url, Handler handler, String name) {        this.mContext = context;        this.mUrl = url;        this.mHandler = handler;        this.mName = name;        //获得DownloadManager对象        mManager = (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);    }    public long startDownload() {        //获得下载id，这是下载任务生成时的唯一id，可通过此id获得下载信息        requestId = mManager.enqueue(CreateRequest(mUrl, mName));        //查询下载信息方法        queryDownloadProgress(requestId, mManager);        return requestId;    }    public int cancelDownload() {        return mManager.remove(requestId);    }    private void queryDownloadProgress(long requestId, DownloadManager downloadManager) {        DownloadManager.Query query = new DownloadManager.Query();        //根据任务编号id查询下载任务信息        query.setFilterById(requestId);        try {            boolean isGoging = true;            while (isGoging) {                Cursor cursor = downloadManager.query(query);                if (cursor != null && cursor.moveToFirst()) {                    //获得下载状态                    int state = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));                    switch (state) {                        case DownloadManager.STATUS_SUCCESSFUL://下载成功                            isGoging = false;                            mHandler.obtainMessage(downloadManager.STATUS_SUCCESSFUL).sendToTarget();//发送到主线程，更新ui                            break;                        case DownloadManager.STATUS_FAILED://下载失败                            isGoging = false;                            mHandler.obtainMessage(downloadManager.STATUS_FAILED).sendToTarget();//发送到主线程，更新ui                            break;                        case DownloadManager.STATUS_RUNNING://下载中                            /**                             * 计算下载下载率；                             */                            int totalSize = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));                            int currentSize = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));                            int progress = (int) (((float) currentSize) / ((float) totalSize) * 100);                            mHandler.obtainMessage(downloadManager.STATUS_RUNNING, progress).sendToTarget();//发送到主线程，更新ui                            break;                        case DownloadManager.STATUS_PAUSED://下载停止                            mHandler.obtainMessage(DownloadManager.STATUS_PAUSED).sendToTarget();                            break;                        case DownloadManager.STATUS_PENDING://准备下载                            mHandler.obtainMessage(DownloadManager.STATUS_PENDING).sendToTarget();                            break;                    }                }                if (cursor != null) {                    cursor.close();                }            }        } catch (Exception e) {            e.printStackTrace();        }    }    private DownloadManager.Request CreateRequest(String url, String name) {        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));        //request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_HIDDEN);// 隐藏notification        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);//显示notification        request.setAllowedNetworkTypes(request.NETWORK_WIFI);//设置下载网络环境为wifi        request.setDestinationInExternalFilesDir(mContext, Environment.DIRECTORY_DOWNLOADS, name);//指定apk缓存路径，默认是在SD卡中的Download文件夹        return request;    }}

2.DownloadUtil的使用

//定义Handler处理下载状态private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            switch (msg.what) {                case DownloadManager.STATUS_SUCCESSFUL:                                    Toast.makeText(MainActivity.this, "下载任务已经完成！", Toast.LENGTH_SHORT).show();                                      break;                case DownloadManager.STATUS_RUNNING:                    break;                case DownloadManager.STATUS_FAILED:                    break;                case DownloadManager.STATUS_PENDING:                    break;            }        }    };private DownloadUtil mUtil;mUtil = new DownloadUtil(MainActivity.this, url, handler, fileName);//开始下载new Thread() {    @Override     public void run() {         long l = mUtil.startDownload();         ToastUtil.showToast(MainActivity.this, "requestId = " + l);     }}.start();//取消下载int i = mUtil.cancelDownload();if (i == 1) {    ToastUtil.showToast(this, "下载已取消 ");}

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