我试图写一个简单的应用程序得到更新。为此，我需要一个简单的函数，可以下载文件并在ProgressDialog中显示当前进度。我知道如何做的ProgressDialog，但我不确定如何显示当前的进度，以及如何下载文件放在第一位。
当前回答
我已经修改了AsyncTask类来处理progressDialog在同一上下文中的创建。我认为下面的代码将更可重用。 (它可以从任何活动调用，只要传递上下文，目标文件，对话框消息)
public static class DownloadTask extends AsyncTask<String, Integer, String> {
private ProgressDialog mPDialog;
private Context mContext;
private PowerManager.WakeLock mWakeLock;
private File mTargetFile;
//Constructor parameters :
// @context (current Activity)
// @targetFile (File object to write,it will be overwritten if exist)
// @dialogMessage (message of the ProgresDialog)
public DownloadTask(Context context,File targetFile,String dialogMessage) {
this.mContext = context;
this.mTargetFile = targetFile;
mPDialog = new ProgressDialog(context);
mPDialog.setMessage(dialogMessage);
mPDialog.setIndeterminate(true);
mPDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mPDialog.setCancelable(true);
// reference to instance to use inside listener
final DownloadTask me = this;
mPDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
@Override
public void onCancel(DialogInterface dialog) {
me.cancel(true);
}
});
Log.i("DownloadTask","Constructor done");
}
@Override
protected String doInBackground(String... sUrl) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
URL url = new URL(sUrl[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
// expect HTTP 200 OK, so we don't mistakenly save error report
// instead of the file
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return "Server returned HTTP " + connection.getResponseCode()
+ " " + connection.getResponseMessage();
}
Log.i("DownloadTask","Response " + connection.getResponseCode());
// this will be useful to display download percentage
// might be -1: server did not report the length
int fileLength = connection.getContentLength();
// download the file
input = connection.getInputStream();
output = new FileOutputStream(mTargetFile,false);
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
// allow canceling with back button
if (isCancelled()) {
Log.i("DownloadTask","Cancelled");
input.close();
return null;
}
total += count;
// publishing the progress....
if (fileLength > 0) // only if total length is known
publishProgress((int) (total * 100 / fileLength));
output.write(data, 0, count);
}
} catch (Exception e) {
return e.toString();
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
// take CPU lock to prevent CPU from going off if the user
// presses the power button during download
PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
getClass().getName());
mWakeLock.acquire();
mPDialog.show();
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
// if we get here, length is known, now set indeterminate to false
mPDialog.setIndeterminate(false);
mPDialog.setMax(100);
mPDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(String result) {
Log.i("DownloadTask", "Work Done! PostExecute");
mWakeLock.release();
mPDialog.dismiss();
if (result != null)
Toast.makeText(mContext,"Download error: "+result, Toast.LENGTH_LONG).show();
else
Toast.makeText(mContext,"File Downloaded", Toast.LENGTH_SHORT).show();
}
}
其他回答
我已经修改了AsyncTask类来处理progressDialog在同一上下文中的创建。我认为下面的代码将更可重用。 (它可以从任何活动调用，只要传递上下文，目标文件，对话框消息)
public static class DownloadTask extends AsyncTask<String, Integer, String> {
private ProgressDialog mPDialog;
private Context mContext;
private PowerManager.WakeLock mWakeLock;
private File mTargetFile;
//Constructor parameters :
// @context (current Activity)
// @targetFile (File object to write,it will be overwritten if exist)
// @dialogMessage (message of the ProgresDialog)
public DownloadTask(Context context,File targetFile,String dialogMessage) {
this.mContext = context;
this.mTargetFile = targetFile;
mPDialog = new ProgressDialog(context);
mPDialog.setMessage(dialogMessage);
mPDialog.setIndeterminate(true);
mPDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mPDialog.setCancelable(true);
// reference to instance to use inside listener
final DownloadTask me = this;
mPDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
@Override
public void onCancel(DialogInterface dialog) {
me.cancel(true);
}
});
Log.i("DownloadTask","Constructor done");
}
@Override
protected String doInBackground(String... sUrl) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
URL url = new URL(sUrl[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
// expect HTTP 200 OK, so we don't mistakenly save error report
// instead of the file
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
return "Server returned HTTP " + connection.getResponseCode()
+ " " + connection.getResponseMessage();
}
Log.i("DownloadTask","Response " + connection.getResponseCode());
// this will be useful to display download percentage
// might be -1: server did not report the length
int fileLength = connection.getContentLength();
// download the file
input = connection.getInputStream();
output = new FileOutputStream(mTargetFile,false);
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
// allow canceling with back button
if (isCancelled()) {
Log.i("DownloadTask","Cancelled");
input.close();
return null;
}
total += count;
// publishing the progress....
if (fileLength > 0) // only if total length is known
publishProgress((int) (total * 100 / fileLength));
output.write(data, 0, count);
}
} catch (Exception e) {
return e.toString();
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException ignored) {
}
if (connection != null)
connection.disconnect();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
// take CPU lock to prevent CPU from going off if the user
// presses the power button during download
PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
getClass().getName());
mWakeLock.acquire();
mPDialog.show();
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
// if we get here, length is known, now set indeterminate to false
mPDialog.setIndeterminate(false);
mPDialog.setMax(100);
mPDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(String result) {
Log.i("DownloadTask", "Work Done! PostExecute");
mWakeLock.release();
mPDialog.dismiss();
if (result != null)
Toast.makeText(mContext,"Download error: "+result, Toast.LENGTH_LONG).show();
else
Toast.makeText(mContext,"File Downloaded", Toast.LENGTH_SHORT).show();
}
}
重要的
AsyncTask在Android 11中已弃用。
欲了解更多信息，请查看以下帖子
Android AsyncTask API在Android 11中已弃用。有什么替代方案? https://developer.android.com/reference/android/os/AsyncTask
可能应该移动到谷歌建议的并发框架
我遇到了一个简单文件下载库 获取，重要的是，它有存储访问框架，内容提供程序和URI支持。如果有人还在寻找，可能会有帮助。
//AndroidX .tonyodev.fetch2:xfetch2:3.1.6
实现"com.tonyodev.fetch2:fetch2:3.0.12" //支持lib
需要的权限，如果你不是使用应用程序特定的目录。
< uses-permission android: name = " android.permission.WRITE_EXTERNAL_STORAGE " / >
< uses-permission android: name = " android.permission.READ_EXTERNAL_STORAGE " / >
网络权限
< uses-permission android: name = " android.permission.INTERNET " / >
private Fetch fetch;
FetchConfiguration fetchConfiguration = new FetchConfiguration.Builder(this)
.setDownloadConcurrentLimit(3)//Concurrent Download limit
.build();
fetch = Fetch.Impl.getInstance(fetchConfiguration);
String url = "http:www.example.com/test.txt";//URL of file
String file = "/downloads/test.txt";//Path of file
final Request request = new Request(url, file);
request.setPriority(Priority.HIGH);
request.setNetworkType(NetworkType.ALL);//Preferred network type
request.addHeader("clientKey", "SD78DF93_3947&MVNGHE1WONG");//Auth header if any
fetch.enqueue(request, updatedRequest -> {
//Request was successfully enqueued for download.
}, error -> {
//An error occurred enqueuing the request.
});
}
倾听更新和进展
FetchListener fetchListener = new FetchListener() {
@Override
public void onQueued(@NotNull Download download, boolean waitingOnNetwork) {
if (request.getId() == download.getId()) {
showDownloadInList(download);
}
}
@Override
public void onCompleted(@NotNull Download download) {
}
@Override
public void onError(@NotNull Download download) {
Error error = download.getError();
}
@Override
public void onProgress(@NotNull Download download, long etaInMilliSeconds, long downloadedBytesPerSecond) {
if (request.getId() == download.getId()) {
updateDownload(download, etaInMilliSeconds);
}
int progress = download.getProgress();
}
@Override
public void onPaused(@NotNull Download download) {
}
@Override
public void onResumed(@NotNull Download download) {
}
@Override
public void onCancelled(@NotNull Download download) {
}
@Override
public void onRemoved(@NotNull Download download) {
}
@Override
public void onDeleted(@NotNull Download download) {
}
};
fetch.addListener(fetchListener);
//Remove listener when done.
fetch.removeListener(fetchListener);
此示例代码取自所有者页面，所有功劳都归于Tonyo Francis
权限
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
使用HttpURLConnection
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.app.Dialog;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
public class DownloadFileUseHttpURLConnection extends Activity {
ProgressBar pb;
Dialog dialog;
int downloadedSize = 0;
int totalSize = 0;
TextView cur_val;
String dwnload_file_path =
"http://coderzheaven.com/sample_folder/sample_file.png";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button b = (Button) findViewById(R.id.b1);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
showProgress(dwnload_file_path);
new Thread(new Runnable() {
public void run() {
downloadFile();
}
}).start();
}
});
}
void downloadFile(){
try {
URL url = new URL(dwnload_file_path);
HttpURLConnection urlConnection = (HttpURLConnection)
url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
//connect
urlConnection.connect();
//set the path where we want to save the file
File SDCardRoot = Environment.getExternalStorageDirectory();
//create a new file, to save the downloaded file
File file = new File(SDCardRoot,"downloaded_file.png");
FileOutputStream fileOutput = new FileOutputStream(file);
//Stream used for reading the data from the internet
InputStream inputStream = urlConnection.getInputStream();
//this is the total size of the file which we are downloading
totalSize = urlConnection.getContentLength();
runOnUiThread(new Runnable() {
public void run() {
pb.setMax(totalSize);
}
});
//create a buffer...
byte[] buffer = new byte[1024];
int bufferLength = 0;
while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
fileOutput.write(buffer, 0, bufferLength);
downloadedSize += bufferLength;
// update the progressbar //
runOnUiThread(new Runnable() {
public void run() {
pb.setProgress(downloadedSize);
float per = ((float)downloadedSize/totalSize) *
100;
cur_val.setText("Downloaded " + downloadedSize +
"KB / " + totalSize + "KB (" + (int)per + "%)" );
}
});
}
//close the output stream when complete //
fileOutput.close();
runOnUiThread(new Runnable() {
public void run() {
// pb.dismiss(); // if you want close it..
}
});
} catch (final MalformedURLException e) {
showError("Error : MalformedURLException " + e);
e.printStackTrace();
} catch (final IOException e) {
showError("Error : IOException " + e);
e.printStackTrace();
}
catch (final Exception e) {
showError("Error : Please check your internet connection " +
e);
}
}
void showError(final String err){
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(DownloadFileDemo1.this, err,
Toast.LENGTH_LONG).show();
}
});
}
void showProgress(String file_path){
dialog = new Dialog(DownloadFileDemo1.this);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialog.setContentView(R.layout.myprogressdialog);
dialog.setTitle("Download Progress");
TextView text = (TextView) dialog.findViewById(R.id.tv1);
text.setText("Downloading file from ... " + file_path);
cur_val = (TextView) dialog.findViewById(R.id.cur_pg_tv);
cur_val.setText("Starting download...");
dialog.show();
pb = (ProgressBar)dialog.findViewById(R.id.progress_bar);
pb.setProgress(0);
pb.setProgressDrawable(
getResources().getDrawable(R.drawable.green_progress));
}
}
我正在为我现在使用的其他解决方案添加另一个答案，因为Android查询太大了，无法保持健康。所以我搬到了这个https://github.com/amitshekhariitbhu/Fast-Android-Networking。
AndroidNetworking.download(url,dirPath,fileName).build()
.setDownloadProgressListener(new DownloadProgressListener() {
public void onProgress(long bytesDownloaded, long totalBytes) {
bar.setMax((int) totalBytes);
bar.setProgress((int) bytesDownloaded);
}
}).startDownload(new DownloadListener() {
public void onDownloadComplete() {
...
}
public void onError(ANError error) {
...
}
});
推荐文章
- 警告:API ' variable . getjavacompile()'已过时，已被' variable . getjavacompileprovider()'取代
- 安装APK时出现错误
- 在流中使用Java 8 foreach循环移动到下一项
- 访问限制:'Application'类型不是API(必需库rt.jar的限制)
- 用Java计算两个日期之间的天数
- 碎片中的onCreateOptionsMenu
- 如何配置slf4j-simple
- 在Jar文件中运行类
- 带参数的可运行?
- TextView粗体通过XML文件?
- 如何使线性布局的孩子之间的空间?
- 我如何得到一个字符串的前n个字符而不检查大小或出界?
- 我可以在Java中设置enum起始值吗?
- Java中的回调函数
- c#和Java中的泛型有什么不同?和模板在c++ ?
