我正在尝试使用AsyncTask以编程方式从服务器下载和读取pdf，但是没有任何反应。我还有一个seekBar，它会显示下载进度。
我在哪里弄错了？
private void initSeekBar() {
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
int val = (progress * (seekBar.getWidth() - 3
* seekBar.getThumbOffset())) / seekBar.getMax();
mProgressText.setText("" + progress);
mProgressText.setX(seekBar.getX() + val + seekBar.getThumbOffset() / 2);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
}
下载文件
private void downloadFile(final String fileName){
new AsyncTask<Void, Integer, Boolean>() {
@Override
protected Boolean doInBackground(Void... params) {
return downloadFile();
}
@Nullable
private Boolean downloadFile(){
try {
File file = getFileStreamPath(fileName);
if (file.exists()) {
downloadButton.setText("Start Reading");
return true;
}
try {
seekBar.setVisibility(View.VISIBLE);
mProgressText.setVisibility(View.VISIBLE);
FileOutputStream fileOutputStream = openFileOutput(fileName, Context.MODE_PRIVATE);
URL url = new URL(document);
URLConnection urlConnection = url.openConnection();
int contentLength = urlConnection.getContentLength();
InputStream inputStream = new BufferedInputStream(url.openStream());
byte data[] = new byte[contentLength];
long total = 0;
int count;
while ((count = inputStream.read(data)) != -1) {
total += count;
publishProgress((int) ((total * 100) / contentLength));
fileOutputStream.write(data, 0, count);
}
fileOutputStream.flush();
fileOutputStream.close();
inputStream.close();
return true;
} catch (final Exception e) {
e.printStackTrace();
return false; //swallow a 404
}
}catch (Exception e){
e.printStackTrace();
}
return false;
}
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
seekBar.setProgress(values[0]);
}
@Override
protected void onPostExecute(Boolean aBoolean) {
super.onPostExecute(aBoolean);
if(aBoolean){
downloadButton.setText("Start Reading");
} else {
Toast.makeText(BookDetailsActivity.this, "Download error", Toast.LENGTH_SHORT).show();
downloadButton.setText("Download");
}
seekBar.setVisibility(View.GONE);
mProgressText.setVisibility(View.GONE);
}
};
}
答案 0 :(得分：0)
使用此代码可能会对您有所帮助。 我正在创建一个从服务器下载pdf文件的一键单击事件。
import java.io.File;
import java.io.IOException;
import android.app.Activity;
import android.content.ActivityNotFoundException;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;
public class DownloadActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_download);
}
public void download(View v)
{
new DownloadFile().execute("your url", "save file name .pdf extenstion");
}
public void view(View v)
{
File pdfFile = new File(Environment.getExternalStorageDirectory() + "/test/" + "demo.pdf"); // -> filename = demo.pdf
Uri path = Uri.fromFile(pdfFile);
Intent pdfIntent = new Intent(Intent.ACTION_VIEW);
pdfIntent.setDataAndType(path, "application/pdf");
pdfIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
try{
startActivity(pdfIntent);
}catch(ActivityNotFoundException e){
Toast.makeText(MainActivity.this, "No Application available to view PDF", Toast.LENGTH_SHORT).show();
}
}
private class DownloadFile extends AsyncTask<String, Void, Void>{
@Override
protected Void doInBackground(String... strings) {
String fileUrl = strings[0];
String fileName = strings[1];
String extStorageDirectory = Environment.getExternalStorageDirectory().toString();
File folder = new File(extStorageDirectory, "test");
folder.mkdir();
File pdfFile = new File(folder, fileName);
try{
pdfFile.createNewFile();
}catch (IOException e){
e.printStackTrace();
}
FileDownloader.downloadFile(fileUrl, pdfFile);
return null;
}
}
}
用于下载pdf文件的FileDownloader类
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class FileDownloader {
private static final int MEGABYTE = 1024 * 1024;
public static void downloadFile(String fileUrl, File directory){
try {
URL url = new URL(fileUrl);
HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
//urlConnection.setRequestMethod("GET");
//urlConnection.setDoOutput(true);
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream(directory);
int totalSize = urlConnection.getContentLength();
byte[] buffer = new byte[MEGABYTE];
int bufferLength = 0;
while((bufferLength = inputStream.read(buffer))>0 ){
fileOutputStream.write(buffer, 0, bufferLength);
}
fileOutputStream.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
最后，将此权限添加到清单文件中。
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>
感谢...编码愉快...
答案 1 :(得分：0)
最后，我找到了解决我问题的方法。我不得不打这条线，
async Task<TResult[]> WhenSome<TResult>(int atLeast, List<Task<TResult>> tasks)
{
List<Task<TResult>> completedTasks = new List<System.Threading.Tasks.Task<TResult>>();
int completed = 0;
List<Exception> exceptions = new List<Exception>();
while (completed < atLeast && tasks.Any()) {
var completedTask = await Task.WhenAny(tasks);
tasks.Remove(completedTask);
if (completedTask.IsCanceled)
{
continue;
}
if (completedTask.IsFaulted)
{
exceptions.Add(completedTask.Exception);
continue;
}
completed++;
completedTasks.Add(completedTask);
}
if (completed >= atLeast)
{
return completedTasks.Select(t => t.Result).ToArray();
}
throw new AggregateException(exceptions).Flatten();
}
这是完整的代码：
asyncTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
下载文件
private void initSeekBar() {
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
int val = (progress * (seekBar.getWidth() - 3
* seekBar.getThumbOffset())) / seekBar.getMax();
mProgressText.setText("" + progress);
mProgressText.setX(seekBar.getX() + val + seekBar.getThumbOffset() / 2);
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
}