如何下载带有进度条更新的文件

Question

我想下载带有更新进度条而不是 ProgressDialog 的文件。我使用 AsyncTask 下载文件。在 onProgressUpdate() 方法中，我想更新进度条进度但没有成功。在日志中，进度是打印但进度条不更新。我的代码在适配器中。

class DownloadFileFromURL extends AsyncTask<String, String, String>
{
    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... f_url)
    {
        int count;
        try
        {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();          
            int lenghtOfFile = conection.getContentLength();

            InputStream input = new BufferedInputStream(url.openStream(), 8192);

            OutputStream output = new FileOutputStream("/sdcard/downloadedfile.mp3");

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1)
            {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress(""+(int)((total*100)/lenghtOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();

        }
        catch (Exception e)
        {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }

    protected void onProgressUpdate(String... progress)
    {            
        ViewHolder.progressbar.setProgress(Integer.parseInt(progress[0]));
    }

} 

请帮帮我。

Answer 1

试试这个

    class DownloadFileFromURL extends AsyncTask<String, String, String>
{
    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
            pDialog = new ProgressDialog(getContext());
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();

    }

    @Override
    protected String doInBackground(String... f_url)
    {
        int count;
        try
        {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();          
            int lenghtOfFile = conection.getContentLength();
            InputStream input = new BufferedInputStream(url.openStream(), 8192);
            OutputStream output = new FileOutputStream("/sdcard/downloadedfile.mp3");
            byte data[] = new byte[1024];
            long total = 0;
            while ((count = input.read(data)) != -1)
            {
                total += count;
                publishProgress(""+(int)((total*100)/lenghtOfFile));
                output.write(data, 0, count);
            }
            output.flush();
            output.close();
            input.close();

        }
        catch (Exception e)
        {
            Log.e("Error: ", e.getMessage());
        }
        return null;
    }
    protected void onProgressUpdate(String... progress)
    {            
        ViewHolder.progressbar.setProgress(Integer.parseInt(progress[0]));
    }
    @Override
    protected void onPostExecute(String file_url) {

            Handler mHandler = new Handler();
            mHandler.postDelayed(new Runnable() {

                @Override
                public void run() {
                    Dismiss();
                }
            }, 1000L);
        }
    }
    public void Dismiss(){
        pDialog.dismiss();
    }

Answer 2

下面的代码正在运行，试试吧，也许它可以帮助你。

public class Demo extends AppCompatActivity {

private Button start;
private Button stop;
private static ProgressBar pb;
private static AsyncTask task;

private static int i = 1;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.demo);
    hookButtons();
}

private void hookButtons() {

    start = (Button) findViewById(R.id.btn_start);
    start.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            task = new Async().execute();
            start.setVisibility(View.GONE);
            stop.setVisibility(View.VISIBLE);
        }
    });

    stop = (Button) findViewById(R.id.btn_stop);
    stop.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(task != null){
                task.cancel(true);
                stop.setVisibility(View.GONE);
                start.setVisibility(View.VISIBLE);
            }
        }
    });


    pb = (ProgressBar) findViewById(R.id.pb);

}

private static class Async extends AsyncTask<Void, String, Void> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        Log.d("Async", "Started");
        i=0;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        Log.d("Async", "Finished");
    }

    @Override
    protected Void doInBackground(Void... voids) {
        while (i <= 10000 && !isCancelled()) {
            Thread timer = new Thread() {
                @Override
                public void run() {
                    super.run();
                    try {
                        sleep(1000);
                        publishProgress(String.valueOf((i / 1000) * 10));
                        i++;
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            };
            timer.start();
        }

        return null;
    }

    protected void onProgressUpdate(String... progress) {
        Log.e("Progress", progress[0]);
        pb.setProgress(Integer.parseInt(progress[0]));
        if(pb.getProgress() >=100){
            task.cancel(true);
            task = new Async().execute();
        }
    }

    @Override
    protected void onCancelled(Void aVoid) {
        super.onCancelled(aVoid);
        Log.d("Async", "Canceled");
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();

    if (task != null) {
        task.cancel(true);
    }

}}

下面是demo.xml中的代码（Demo Activity的布局）：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
>

<Button
    android:id="@+id/btn_start"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Start"
    />

<Button
    android:id="@+id/btn_stop"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Stop"
    android:visibility="gone"
    />

<ProgressBar
    android:id="@+id/pb"
    android:layout_width="80dp"
    android:layout_height="80dp"
    android:indeterminate="false"
    android:layout_marginBottom="10dp"
    android:max="100"
    android:progress="0"
    style="@style/Widget.AppCompat.ProgressBar.Horizontal"
    android:visibility="visible"/>

另外，不要忘记将此活动添加到清单中。