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
是的，上面的代码是可以工作的，但是如果你在Asynctask的onProgressUpdate中更新你的进度条，你按下后退按钮或完成你的活动，Asynctask将失去它与你的UI的跟踪，当你回到你的活动，即使下载正在后台运行，你也不会看到进度条上的更新。因此，OnResume()尝试运行一个线程，如runOnUIThread与一个定时器任务更新进度条的值从AsyncTask运行后台更新。
private void updateProgressBar(){
Runnable runnable = new updateProgress();
background = new Thread(runnable);
background.start();
}
public class updateProgress implements Runnable {
public void run() {
while(Thread.currentThread()==background)
//while (!Thread.currentThread().isInterrupted()) {
try {
Thread.sleep(1000);
Message msg = new Message();
progress = getProgressPercentage();
handler.sendMessage(msg);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} catch (Exception e) {
}
}
}
private Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
progress.setProgress(msg.what);
}
};
当你的活动不可见时，不要忘记销毁线程。
private void destroyRunningThreads() {
if (background != null) {
background.interrupt();
background=null;
}
}
我推荐你使用我的Project Netroid，它是基于Volley的。我添加了一些功能，如多事件回调，文件下载管理。这可能会有帮助。
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
如果你要从网上下载东西，别忘了给你的manifest文件添加权限!
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.helloandroid"
android:versionCode="1"
android:versionName="1.0">
<uses-sdk android:minSdkVersion="10" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>
<application
android:icon="@drawable/icon"
android:label="@string/app_name"
android:debuggable="true">
</application>
</manifest>
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();
}
}
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