Android 如何在异步任务下载程序中重试? 公共类PreviewDownload扩展异步任务{ 公共静态最终字符串TAG=“PreviewDownload”; 公共字符串inputPath=null; 公共字符串outputFolder=null; 公共IRIssue问题=空; @凌驾 受保护的字符串背景(字符串…参数){ InputStream输入=null; OutputStream输出=null; HttpURLConnection=null; issue=Broker.model.issueDataStore.getIRIssue(参数[0]); outputFolder=IRConstant.issueFolder(issue.year、issue.month、issue.day、issue.pubKey); 试一试{ inputPath=IRConstant.downloadFile(issue.year、issue.month、issue.day、issue.pubKey,“预览”,“0”); URL=新URL(输入路径); Log.d(标签,“输入:”+inputPath); connection=(HttpURLConnection)url.openConnection(); connection.connect(); if(connection.getResponseCode()!=HttpURLConnection.HTTP\u确定) 返回null; //return“Server returned HTTP”+connection.getResponseCode() //+“”+连接。getResponseMessage(); //下载该文件 输入=连接。getInputStream(); output=newfileoutputstream(outputFolder+“/preview.zip”); Log.d(标签,“输出:”+输出); 字节数据[]=新字节[1024]; 整数计数; 而((计数=输入。读取(数据))!=-1){ 输出.写入(数据,0,计数); } }捕获(例外e){ //返回e.toString(); 返回null; }最后{ 试一试{ if(输出!=null) output.close(); 如果(输入!=null) input.close(); }捕获(忽略IOException){ } if(连接!=null) 连接断开(); } 返回outputFolder; } @凌驾 受保护的void onPostExecute(字符串输出文件夹){ //TODO自动生成的方法存根 super.onPostExecute(outputFolder); if(outputFolder!=null){ File zipFile=新文件(outputFolder+“/preview.zip”); if(Utils.unzip(outputFolder,outputFolder+“/preview.zip”)){ zipFile.delete(); issue.isthumb=1; }否则{ issue.isthumb=0; } }否则{ Toast.makeText(Broker.launchectivity.getBaseContext(),R.string.wordCantDownload,Toast.LENGTH_LONG.show(); issue.isthumb=0; } issue.updateProgress(issue.progress); } }
这是我实现的下载程序,问题是,当网络丢失时,输出变为null并显示错误消息,但是,如果我想在显示错误消息之前重试两次,有什么方法可以做到这一点?如果我希望不传入对象而不是字符串,是否不建议这样做?谢谢Android 如何在异步任务下载程序中重试? 公共类PreviewDownload扩展异步任务{ 公共静态最终字符串TAG=“PreviewDownload”; 公共字符串inputPath=null; 公共字符串outputFolder=null; 公共IRIssue问题=空; @凌驾 受保护的字符串背景(字符串…参数){ InputStream输入=null; OutputStream输出=null; HttpURLConnection=null; issue=Broker.model.issueDataStore.getIRIssue(参数[0]); outputFolder=IRConstant.issueFolder(issue.year、issue.month、issue.day、issue.pubKey); 试一试{ inputPath=IRConstant.downloadFile(issue.year、issue.month、issue.day、issue.pubKey,“预览”,“0”); URL=新URL(输入路径); Log.d(标签,“输入:”+inputPath); connection=(HttpURLConnection)url.openConnection(); connection.connect(); if(connection.getResponseCode()!=HttpURLConnection.HTTP\u确定) 返回null; //return“Server returned HTTP”+connection.getResponseCode() //+“”+连接。getResponseMessage(); //下载该文件 输入=连接。getInputStream(); output=newfileoutputstream(outputFolder+“/preview.zip”); Log.d(标签,“输出:”+输出); 字节数据[]=新字节[1024]; 整数计数; 而((计数=输入。读取(数据))!=-1){ 输出.写入(数据,0,计数); } }捕获(例外e){ //返回e.toString(); 返回null; }最后{ 试一试{ if(输出!=null) output.close(); 如果(输入!=null) input.close(); }捕获(忽略IOException){ } if(连接!=null) 连接断开(); } 返回outputFolder; } @凌驾 受保护的void onPostExecute(字符串输出文件夹){ //TODO自动生成的方法存根 super.onPostExecute(outputFolder); if(outputFolder!=null){ File zipFile=新文件(outputFolder+“/preview.zip”); if(Utils.unzip(outputFolder,outputFolder+“/preview.zip”)){ zipFile.delete(); issue.isthumb=1; }否则{ issue.isthumb=0; } }否则{ Toast.makeText(Broker.launchectivity.getBaseContext(),R.string.wordCantDownload,Toast.LENGTH_LONG.show(); issue.isthumb=0; } issue.updateProgress(issue.progress); } },android,asynchronous,android-asynctask,download,Android,Asynchronous,Android Asynctask,Download,这是我实现的下载程序,问题是,当网络丢失时,输出变为null并显示错误消息,但是,如果我想在显示错误消息之前重试两次,有什么方法可以做到这一点?如果我希望不传入对象而不是字符串,是否不建议这样做?谢谢int expectedLength=connection.getContentLength(); 您能否与预期长度和下载长度进行比较并重试?在出现错误时,是什么阻止您从catch块重新实例化和重新执行“Downloader” 您可以在dowloader实例之间使用一个公共共享对象来计算尝试次数,
int expectedLength=connection.getContentLength();
您能否与预期长度和下载长度进行比较并重试?在出现错误时,是什么阻止您从catch块重新实例化和重新执行“Downloader”
您可以在dowloader实例之间使用一个公共共享对象来计算尝试次数,或者更好地向每个尝试传递一个参数。在catch块中,如果未达到限制,您将重试,并增加传递给新下载程序的值。。。递归的东西。在深入研究这个方向之前,我可以请您阅读以下内容吗:?这意味着对于每个下载对象,我需要添加一个整数重试时间字段?是的。这就是重点。但实际上,请阅读我作为评论添加的另一个链接。
public class PreviewDownload extends AsyncTask<String, Void, String> {
public static final String TAG = "PreviewDownload";
public String inputPath = null;
public String outputFolder = null;
public IRIssue issue = null;
@Override
protected String doInBackground(String... parms) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
issue = Broker.model.issueDataStore.getIRIssue(parms[0]);
outputFolder = IRConstant.issueFolder(issue.year, issue.month, issue.day, issue.pubKey);
try {
inputPath = IRConstant.downloadFile(issue.year, issue.month, issue.day, issue.pubKey, "preview", "0");
URL url = new URL(inputPath);
Log.d (TAG,"input: " + inputPath);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
return null;
// return "Server returned HTTP " + connection.getResponseCode()
// + " " + connection.getResponseMessage();
// download the file
input = connection.getInputStream();
output = new FileOutputStream(outputFolder + "/preview.zip");
Log.d (TAG,"output: " + output);
byte data[] = new byte[1024];
int count;
while ((count = input.read(data)) != -1) {
output.write(data, 0, count);
}
} catch (Exception e) {
// return e.toString();
return null;
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return outputFolder;
}
@Override
protected void onPostExecute(String outputFolder) {
// TODO Auto-generated method stub
super.onPostExecute(outputFolder);
if (outputFolder != null) {
File zipFile = new File (outputFolder + "/preview.zip");
if (Utils.unzip(outputFolder,outputFolder + "/preview.zip" )) {
zipFile.delete();
issue.isThumbDownloaded = 1;
} else {
issue.isThumbDownloaded = 0;
}
} else {
Toast.makeText(Broker.launcherActivity.getBaseContext(), R.string.wordCantDownload, Toast.LENGTH_LONG).show();
issue.isThumbDownloaded = 0;
}
issue.updateProgress(issue.progress);
}
}