android使用AsyncTask实现多线程下载实例

概述AsyncTask不仅方便我们在子线程中对UI进行更新 *** 作，还可以借助其本身的线程池来实现多线程任务。下面是一个使用AsyncTask来实现的多线程下载例子。

AsyncTask不仅方便我们在子线程中对UI进行更新 *** 作，还可以借助其本身的线程池来实现多线程任务。下面是一个使用AsyncTask来实现的多线程下载例子。

01 效果图

02 核心类 - DownloadTask.class

public class DownloadTask extends AsyncTask<String,Integer,Integer> {  public static final int TYPE_SUCCESS = 0;  public static final int TYPE_FAILURE = 1;  public static final int TYPE_PAUSE = 2;  public static final int TYPE_CANCEL = 3;  public int positionDownload;  private boolean isPaused = false;  private boolean isCancelled = false;  private DownloadListener downloadListener;  private int lastProgress;  public DownloadTask(DownloadListener downloadListener){    this.downloadListener = downloadListener;  }  public voID setDownloadListener(DownloadListener downloadListener){    this.downloadListener = downloadListener;  }  @OverrIDe  protected Integer doInBackground(String... params) {    inputStream is = null;    RandomAccessfile savedfile = null;    file file = null;    long downloadLength = 0;    String downloadUrl = params[0];    positionDownload = Integer.parseInt(params[1]);    String filename = downloadUrl.substring(downloadUrl.lastIndexOf("/"));    String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();    file = new file(directory + filename);    if(file.exists()){      downloadLength = file.length();    }    long contentLength = getContentLength(downloadUrl);    if(contentLength == 0){      return TYPE_FAILURE;    } else if(contentLength == downloadLength){      return TYPE_SUCCESS;    }    OkhttpClIEnt clIEnt = new OkhttpClIEnt();    Request request = new Request.Builder()                  .addheader("RANGE","bytes="+downloadLength+"-")                  .url(downloadUrl)                  .build();    try {      Response response = clIEnt.newCall(request).execute();      if(response != null){        is = response.body().byteStream();        savedfile = new RandomAccessfile(file,"rw");        savedfile.seek(downloadLength);        byte[] buffer = new byte[1024];        int total = 0;        int length;        while((length = is.read(buffer)) != -1){          if(isCancelled){            response.body().close();            return TYPE_CANCEL;          } else if(isPaused) {            response.body().close();            return TYPE_PAUSE;          }          total += length;          savedfile.write(buffer,length);          int progress = (int) ((total + downloadLength) * 100 / contentLength);          int currentDownload = (int) (total + downloadLength);          publishProgress(positionDownload,progress,currentDownload,(int) contentLength);        }        response.body().close();        return TYPE_SUCCESS;      }    } catch (IOException e) {      e.printstacktrace();    } finally {      try {        if(is != null) is.close();        if(savedfile != null) savedfile.close();        if(isCancelled && file != null) file.delete();      } catch (IOException e) {        e.printstacktrace();      }    }    return TYPE_FAILURE;  }  @OverrIDe  protected voID onProgressUpdate(Integer... values) {    int progress = values[1];    if(progress > lastProgress){      downloadListener.onProgress(values[0],values[2],values[3]);      lastProgress = progress;    }  }  @OverrIDe  protected voID onPostExecute(Integer status) {    switch (status){      case TYPE_SUCCESS:        downloadListener.onSuccess(positionDownload);        break;      case TYPE_FAILURE:        downloadListener.onFailure();        break;      case TYPE_PAUSE:        downloadListener.onPause();        break;      case TYPE_CANCEL:        downloadListener.onCancel();        break;    }  }  public voID pauseDownload(){    isPaused = true;  }  public voID cancelDownload(){    isCancelled = true;  }  private long getContentLength(String downloadUrl) {    OkhttpClIEnt clIEnt = new OkhttpClIEnt();    Request request = new Request.Builder()                  .url(downloadUrl)                  .build();    Response response = null;    try {      response = clIEnt.newCall(request).execute();      if(response != null && response.isSuccessful()){        long contentLength = response.body().contentLength();        response.body().close();        return contentLength;      }    } catch (IOException e) {      e.printstacktrace();    }    return 0;  }}

03 核心类 - DownloadService.class

public class DownloadService extends Service {  private Map<String,DownloadTask> downloadTaskMap = new HashMap<>();  private DownloadBinder mBinder = new DownloadBinder();  @OverrIDe  public IBinder onBind(Intent intent) {    return mBinder;  }  private Notification getNotification(String Title,int progress) {    Intent intent = new Intent(this,MainActivity.class);    PendingIntent pendingIntent = PendingIntent.getActivity(this,intent,0);    NotificationCompat.Builder builder = new NotificationCompat.Builder(this);    builder.setSmallicon(R.mipmap.ic_launcher);    builder.setLargeIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher));    builder.setContentIntent(pendingIntent);    builder.setContentTitle(Title);    if(progress > 0){      builder.setContentText(progress + "%");      builder.setProgress(100,false);    }    return builder.build();  }  private notificationmanager getnotificationmanager() {    return (notificationmanager) getSystemService(NOTIFICATION_SERVICE);  }  class DownloadBinder extends Binder {    public voID startDownload(String url,int position,DownloadListener Listener){      if(!downloadTaskMap.containsKey(url)){        DownloadTask downloadTask = new DownloadTask(Listener);        downloadTask.executeOnExecutor(AsyncTask.THREAD_POol_EXECUTOR,url,position+"");        downloadTaskMap.put(url,downloadTask);        if(downloadTaskMap.size() == 1){          startForeground(1,getNotification("正在下载" + downloadTaskMap.size(),-1));        } else{          getnotificationmanager().notify(1,-1));        }      }    }    public voID updateDownload(String url,DownloadListener Listener){      if(downloadTaskMap.containsKey(url)){        DownloadTask downloadTask = downloadTaskMap.get(url);        if(downloadTask != null){          downloadTask.setDownloadListener(Listener);        }      }    }    public voID pauseDownload(String url){      if(downloadTaskMap.containsKey(url)){        DownloadTask downloadTask = downloadTaskMap.get(url);        if(downloadTask != null){          downloadTask.pauseDownload();        }        downloadTaskMap.remove(url);        if(downloadTaskMap.size() > 0){          getnotificationmanager().notify(1,-1));        } else {          stopForeground(true);          getnotificationmanager().notify(1,getNotification("全部暂停下载",-1));        }      }    }    public voID downloadSuccess(String url){      if(downloadTaskMap.containsKey(url)){        DownloadTask downloadTask = downloadTaskMap.get(url);        downloadTaskMap.remove(url);        if(downloadTask != null){          downloadTask = null;        }        if(downloadTaskMap.size() > 0){          getnotificationmanager().notify(1,getNotification("下载成功",-1));        }      }    }    public boolean isDownloading(String url){      if(downloadTaskMap.containsKey(url)){        return true;      }      return false;    }    public voID cancelDownload(String url){      if(downloadTaskMap.containsKey(url)){        DownloadTask downloadTask = downloadTaskMap.get(url);        if(downloadTask != null){          downloadTask.cancelDownload();        }        downloadTaskMap.remove(url);        if(downloadTaskMap.size() > 0){          getnotificationmanager().notify(1,getNotification("全部取消下载",-1));        }      }      if(url != null){        String filename = url.substring(url.lastIndexOf("/"));        String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();        file file = new file(directory + filename);        if(file.exists()){          file.delete();          Toast.makeText(DownloadService.this,"Deleted",Toast.LENGTH_SHORT).show();        }      }    }  }}

04 源码

下载地址

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