我正在尝试编写一个可以更新的简单应用程序。为此，我需要一个简单的函数，它可以下载文件并在ProgressDialog 中显示当前进度。我知道如何做ProgressDialog，但我不确定如何显示当前进度以及如何首先下载文件。
【问题讨论】：
标签： java android download android-asynctask
下载文件的方法有很多种。下面我将发布最常用的方法；由您决定哪种方法更适合您的应用。
AsyncTask 并在对话框中显示下载进度此方法将允许您执行一些后台进程并同时更新 UI（在这种情况下，我们将更新进度条）。
进口：
import android.os.PowerManager;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.net.HttpURLConnection;
这是一个示例代码：
// declare the dialog as a member field of your activity
ProgressDialog mProgressDialog;
// instantiate it within the onCreate method
mProgressDialog = new ProgressDialog(YourActivity.this);
mProgressDialog.setMessage("A message");
mProgressDialog.setIndeterminate(true);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(true);
// execute this when the downloader must be fired
final DownloadTask downloadTask = new DownloadTask(YourActivity.this);
downloadTask.execute("the url to the file you want to download");
mProgressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
@Override
public void onCancel(DialogInterface dialog) {
downloadTask.cancel(true); //cancel the task
}
});
AsyncTask 将如下所示：
// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
private class DownloadTask extends AsyncTask<String, Integer, String> {
private Context context;
private PowerManager.WakeLock mWakeLock;
public DownloadTask(Context context) {
this.context = context;
}
@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();
}
// 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("/sdcard/file_name.extension");
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
// allow canceling with back button
if (isCancelled()) {
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;
}
上面的方法 (doInBackground) 总是在后台线程上运行。你不应该在那里做任何 UI 任务。另一方面，onProgressUpdate 和 onPreExecute 在 UI 线程上运行，因此您可以更改进度条：
@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) context.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
getClass().getName());
mWakeLock.acquire();
mProgressDialog.show();
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
// if we get here, length is known, now set indeterminate to false
mProgressDialog.setIndeterminate(false);
mProgressDialog.setMax(100);
mProgressDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(String result) {
mWakeLock.release();
mProgressDialog.dismiss();
if (result != null)
Toast.makeText(context,"Download error: "+result, Toast.LENGTH_LONG).show();
else
Toast.makeText(context,"File downloaded", Toast.LENGTH_SHORT).show();
}
要运行此程序，您需要 WAKE_LOCK 权限。
<uses-permission android:name="android.permission.WAKE_LOCK" />
这里最大的问题是：如何从服务更新我的活动？。在下一个示例中，我们将使用您可能不知道的两个类：ResultReceiver 和 IntentService。 ResultReceiver 是允许我们从服务更新线程的那个； IntentService 是 Service 的子类，它产生一个线程来从那里做后台工作（你应该知道 Service 实际上在你的应用程序的同一个线程中运行；当你扩展 Service 时，你必须手动产生新线程来运行 CPU 阻塞操作）。
下载服务可能如下所示：
public class DownloadService extends IntentService {
public static final int UPDATE_PROGRESS = 8344;
public DownloadService() {
super("DownloadService");
}
@Override
protected void onHandleIntent(Intent intent) {
String urlToDownload = intent.getStringExtra("url");
ResultReceiver receiver = (ResultReceiver) intent.getParcelableExtra("receiver");
try {
//create url and connect
URL url = new URL(urlToDownload);
URLConnection connection = url.openConnection();
connection.connect();
// this will be useful so that you can show a typical 0-100% progress bar
int fileLength = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(connection.getInputStream());
String path = "/sdcard/BarcodeScanner-debug.apk" ;
OutputStream output = new FileOutputStream(path);
byte data[] = new byte[1024];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
Bundle resultData = new Bundle();
resultData.putInt("progress" ,(int) (total * 100 / fileLength));
receiver.send(UPDATE_PROGRESS, resultData);
output.write(data, 0, count);
}
// close streams
output.flush();
output.close();
input.close();
} catch (IOException e) {
e.printStackTrace();
}
Bundle resultData = new Bundle();
resultData.putInt("progress" ,100);
receiver.send(UPDATE_PROGRESS, resultData);
}
}
将服务添加到您的清单中：
<service android:name=".DownloadService"/>
活动将如下所示：
// initialize the progress dialog like in the first example
// this is how you fire the downloader
mProgressDialog.show();
Intent intent = new Intent(this, DownloadService.class);
intent.putExtra("url", "url of the file to download");
intent.putExtra("receiver", new DownloadReceiver(new Handler()));
startService(intent);
这里有ResultReceiver来玩：
private class DownloadReceiver extends ResultReceiver{
public DownloadReceiver(Handler handler) {
super(handler);
}
@Override
protected void onReceiveResult(int resultCode, Bundle resultData) {
super.onReceiveResult(resultCode, resultData);
if (resultCode == DownloadService.UPDATE_PROGRESS) {
int progress = resultData.getInt("progress"); //get the progress
dialog.setProgress(progress);
if (progress == 100) {
dialog.dismiss();
}
}
}
}
Groundy 是一个库，基本上可以帮助您在后台服务中运行代码片段，它基于上面显示的ResultReceiver 概念。该库目前已弃用。这就是整个代码的样子：
您正在显示对话框的活动...
public class MainActivity extends Activity {
private ProgressDialog mProgressDialog;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.btn_download).setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String url = ((EditText) findViewById(R.id.edit_url)).getText().toString().trim();
Bundle extras = new Bundler().add(DownloadTask.PARAM_URL, url).build();
Groundy.create(DownloadExample.this, DownloadTask.class)
.receiver(mReceiver)
.params(extras)
.queue();
mProgressDialog = new ProgressDialog(MainActivity.this);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(false);
mProgressDialog.show();
}
});
}
private ResultReceiver mReceiver = new ResultReceiver(new Handler()) {
@Override
protected void onReceiveResult(int resultCode, Bundle resultData) {
super.onReceiveResult(resultCode, resultData);
switch (resultCode) {
case Groundy.STATUS_PROGRESS:
mProgressDialog.setProgress(resultData.getInt(Groundy.KEY_PROGRESS));
break;
case Groundy.STATUS_FINISHED:
Toast.makeText(DownloadExample.this, R.string.file_downloaded, Toast.LENGTH_LONG);
mProgressDialog.dismiss();
break;
case Groundy.STATUS_ERROR:
Toast.makeText(DownloadExample.this, resultData.getString(Groundy.KEY_ERROR), Toast.LENGTH_LONG).show();
mProgressDialog.dismiss();
break;
}
}
};
}
Groundy 使用GroundyTask 实现来下载文件并显示进度：
public class DownloadTask extends GroundyTask {
public static final String PARAM_URL = "com.groundy.sample.param.url";
@Override
protected boolean doInBackground() {
try {
String url = getParameters().getString(PARAM_URL);
File dest = new File(getContext().getFilesDir(), new File(url).getName());
DownloadUtils.downloadFile(getContext(), url, dest, DownloadUtils.getDownloadListenerForTask(this));
return true;
} catch (Exception pokemon) {
return false;
}
}
}
只需将其添加到清单中：
<service android:name="com.codeslap.groundy.GroundyService"/>
我想这再简单不过了。只需获取最新的 jar from Github 即可开始使用。请记住，Groundy 的主要目的是在后台服务中调用外部 REST API 并将结果轻松发布到 UI。如果你在你的应用中做类似的事情，它可能真的很有用。
DownloadManager 类（仅限GingerBread 和更高版本）GingerBread 带来了一个新功能DownloadManager，它允许您轻松下载文件并将处理线程、流等的繁重工作委托给系统。
首先，我们来看一个实用方法：
/**
* @param context used to check the device version and DownloadManager information
* @return true if the download manager is available
*/
public static boolean isDownloadManagerAvailable(Context context) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
return true;
}
return false;
}
方法的名称说明了一切。一旦您确定DownloadManager 可用，您可以执行以下操作：
String url = "url you want to download";
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
request.setDescription("Some descrition");
request.setTitle("Some title");
// in order for this if to run, you must use the android 3.2 to compile your app
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "name-of-the-file.ext");
// get download service and enqueue file
DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
下载进度将显示在通知栏中。
第一种和第二种方法只是冰山一角。如果您希望您的应用程序健壮，您必须记住很多事情。这是一个简短的列表：
INTERNET 和WRITE_EXTERNAL_STORAGE）；如果您想检查互联网可用性，也可以ACCESS_NETWORK_STATE。除非您需要详细控制下载过程，否则请考虑使用DownloadManager (3)，因为它已经处理了上面列出的大部分项目。
但也要考虑到您的需求可能会发生变化。例如，DownloadManagerdoes no response caching。它会多次盲目下载同一个大文件。事后没有简单的方法可以修复它。如果您从基本的HttpURLConnection (1, 2) 开始，那么您只需添加一个HttpResponseCache。因此，初步学习基本的标准工具可能是一项不错的投资。
此类在 API 级别 26 中已弃用。ProgressDialog 是一种模式 对话框，它会阻止用户与应用程序交互。反而 使用此类，您应该使用进度指示器，例如 ProgressBar，可以嵌入到应用程序的 UI 中。或者， 您可以使用通知来通知用户任务的进度。更多详情Link
【讨论】：
close()finally中的流（output）而不是try，否则如果在close()之前抛出任何异常，你有未关闭的流挂起周围。
sdcard/ 改用Environment.getExternalStorageDirectory()。
如果您要从 Internet 下载内容，请不要忘记为您的清单文件添加权限！
<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>
【讨论】：
是的，上面的代码将起作用。但是如果您在 onProgressUpdate 或 Asynctask 中更新您的 progressbar，并且您按下后退按钮或完成您的活动，AsyncTask 会在您的 UI 中失去它的轨道。当您离开时回到您的活动，即使下载在后台运行，您也不会在进度条上看到任何更新。所以在OnResume() 上尝试运行一个类似runOnUIThread 的线程，并使用一个定时器任务更新你的progressbar，并使用从AsyncTask 运行背景更新的值。
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;
}
}
【讨论】：
【讨论】：
我已经修改了AsyncTask 类以处理在同一上下文中创建progressDialog。我认为以下代码将更可重用。
（它可以从任何活动中调用，只需传递上下文、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();
}
}
【讨论】：
我发现this的博文很有帮助，它使用loopJ来下载文件，它只有一个简单的功能，对一些新的android人会有帮助。
【讨论】：
不要忘记用 new File("/mnt/sdcard/...") 替换 "/sdcard..." 否则你会得到一个 FileNotFoundException
【讨论】：
Environment.getExternalStorageDirectory().getAbsolutePath() 用于获取 sdcard 的路径。另外不要忘记检查外部存储是否已安装 - Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED) (Mannaz)
当我开始学习 android 开发时，我了解到ProgressDialog 是要走的路。 ProgressDialog 的 setProgress 方法可以在文件下载时被调用以更新进度级别。
我在许多应用程序中看到的最好的一点是，它们自定义了此进度对话框的属性，以便为进度对话框提供比普通版本更好的外观和感觉。很好地让用户参与一些像青蛙、大象或可爱的猫/小狗这样的动画。进度对话框中的任何动画都会吸引用户，他们不会觉得等待太久。
【讨论】：
我的个人建议是使用进度对话框并在执行前建立，或者在OnPreExecute()发起，如果你使用进度对话框的进度条的水平样式，请经常发布进度。剩下的就是优化doInBackground的算法了。
【讨论】：
使用 Android Query 库，确实很酷。您可以将其更改为使用 ProgressDialog，就像您在其他示例中看到的那样，这将显示您布局中的进度视图并在完成后将其隐藏。
File target = new File(new File(Environment.getExternalStorageDirectory(), "ApplicationName"), "tmp.pdf");
new AQuery(this).progress(R.id.progress_view).download(_competition.qualificationScoreCardsPdf(), target, new AjaxCallback<File>() {
public void callback(String url, File file, AjaxStatus status) {
if (file != null) {
// do something with file
}
}
});
【讨论】：
我们可以使用协程和工作管理器在kotlin中下载文件。
在 build.gradle 中添加依赖
implementation "androidx.work:work-runtime-ktx:2.3.0-beta01"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.1"
WorkManager 类
import android.content.Context
import android.os.Environment
import androidx.work.CoroutineWorker
import androidx.work.WorkerParameters
import androidx.work.workDataOf
import com.sa.chat.utils.Const.BASE_URL_IMAGE
import com.sa.chat.utils.Constants
import kotlinx.coroutines.delay
import java.io.BufferedInputStream
import java.io.File
import java.io.FileOutputStream
import java.net.URL
class DownloadMediaWorkManager(appContext: Context, workerParams: WorkerParameters)
: CoroutineWorker(appContext, workerParams) {
companion object {
const val WORK_TYPE = "WORK_TYPE"
const val WORK_IN_PROGRESS = "WORK_IN_PROGRESS"
const val WORK_PROGRESS_VALUE = "WORK_PROGRESS_VALUE"
}
override suspend fun doWork(): Result {
val imageUrl = inputData.getString(Constants.WORK_DATA_MEDIA_URL)
val imagePath = downloadMediaFromURL(imageUrl)
return if (!imagePath.isNullOrEmpty()) {
Result.success(workDataOf(Constants.WORK_DATA_MEDIA_URL to imagePath))
} else {
Result.failure()
}
}
private suspend fun downloadMediaFromURL(imageUrl: String?): String? {
val file = File(
getRootFile().path,
"IMG_${System.currentTimeMillis()}.jpeg"
)
val url = URL(BASE_URL_IMAGE + imageUrl)
val connection = url.openConnection()
connection.connect()
val lengthOfFile = connection.contentLength
// download the file
val input = BufferedInputStream(url.openStream(), 8192)
// Output stream
val output = FileOutputStream(file)
val data = ByteArray(1024)
var total: Long = 0
var last = 0
while (true) {
val count = input.read(data)
if (count == -1) break
total += count.toLong()
val progress = (total * 100 / lengthOfFile).toInt()
if (progress % 10 == 0) {
if (last != progress) {
setProgress(workDataOf(WORK_TYPE to WORK_IN_PROGRESS,
WORK_PROGRESS_VALUE to progress))
}
last = progress
delay(50)
}
output.write(data, 0, count)
}
output.flush()
output.close()
input.close()
return file.path
}
private fun getRootFile(): File {
val rootDir = File(Environment.getExternalStorageDirectory().absolutePath + "/AppName")
if (!rootDir.exists()) {
rootDir.mkdir()
}
val dir = File("$rootDir/${Constants.IMAGE_FOLDER}/")
if (!dir.exists()) {
dir.mkdir()
}
return File(dir.absolutePath)
}
}
通过activity类中的工作管理器开始下载
private fun downloadImage(imagePath: String?, id: String) {
val data = workDataOf(WORK_DATA_MEDIA_URL to imagePath)
val downloadImageWorkManager = OneTimeWorkRequestBuilder<DownloadMediaWorkManager>()
.setInputData(data)
.addTag(id)
.build()
WorkManager.getInstance(this).enqueue(downloadImageWorkManager)
WorkManager.getInstance(this).getWorkInfoByIdLiveData(downloadImageWorkManager.id)
.observe(this, Observer { workInfo ->
if (workInfo != null) {
when {
workInfo.state == WorkInfo.State.SUCCEEDED -> {
progressBar?.visibility = View.GONE
ivDownload?.visibility = View.GONE
}
workInfo.state == WorkInfo.State.FAILED || workInfo.state == WorkInfo.State.CANCELLED || workInfo.state == WorkInfo.State.BLOCKED -> {
progressBar?.visibility = View.GONE
ivDownload?.visibility = View.VISIBLE
}
else -> {
if(workInfo.progress.getString(WORK_TYPE) == WORK_IN_PROGRESS){
val progress = workInfo.progress.getInt(WORK_PROGRESS_VALUE, 0)
progressBar?.visibility = View.VISIBLE
progressBar?.progress = progress
ivDownload?.visibility = View.GONE
}
}
}
}
})
}
【讨论】：
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));
}
}
【讨论】：
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 Query 太大且未维护以保持健康。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) {
...
}
});
【讨论】：
您可以使用 LiveData 和协程观察下载管理器的进度，请参阅下面的要点
https://gist.github.com/FhdAlotaibi/678eb1f4fa94475daf74ac491874fc0e
data class DownloadItem(val bytesDownloadedSoFar: Long = -1, val totalSizeBytes: Long = -1, val status: Int)
class DownloadProgressLiveData(private val application: Application, private val requestId: Long) : LiveData<DownloadItem>(), CoroutineScope {
private val downloadManager by lazy {
application.getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
}
private val job = Job()
override val coroutineContext: CoroutineContext
get() = Dispatchers.IO + job
override fun onActive() {
super.onActive()
launch {
while (isActive) {
val query = DownloadManager.Query().setFilterById(requestId)
val cursor = downloadManager.query(query)
if (cursor.moveToFirst()) {
val status = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS))
Timber.d("Status $status")
when (status) {
DownloadManager.STATUS_SUCCESSFUL,
DownloadManager.STATUS_PENDING,
DownloadManager.STATUS_FAILED,
DownloadManager.STATUS_PAUSED -> postValue(DownloadItem(status = status))
else -> {
val bytesDownloadedSoFar = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR))
val totalSizeBytes = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES))
postValue(DownloadItem(bytesDownloadedSoFar.toLong(), totalSizeBytes.toLong(), status))
}
}
if (status == DownloadManager.STATUS_SUCCESSFUL || status == DownloadManager.STATUS_FAILED)
cancel()
} else {
postValue(DownloadItem(status = DownloadManager.STATUS_FAILED))
cancel()
}
cursor.close()
delay(300)
}
}
}
override fun onInactive() {
super.onInactive()
job.cancel()
}
}
【讨论】：
重要
AsyncTask 在 Android 11 中已弃用。
更多信息请查看以下帖子
可能应该按照 google 的建议迁移到 concorency Framework
【讨论】：
private class DownloadTask extends AsyncTask<String, Integer, String> {
private PowerManager.WakeLock mWakeLock;
String onlinePathBundle, onlinePathMusic, offlinePathBundle, offlinePathMusic;
CircleProgressBar progressBar;
RelativeLayout rl_progress;
ImageView btn_download;
TextView tv_progress;
public DownloadTask(String onlinePathBundle, String onlinePathMusic, String offlinePathBundle, String offlinePathMusic, CircleProgressBar progressBar, RelativeLayout rl_progress, ImageView btn_download,
TextView tv_progress) {
this.offlinePathBundle = offlinePathBundle;
this.offlinePathMusic = offlinePathMusic;
this.progressBar = progressBar;
this.rl_progress = rl_progress;
this.btn_download = btn_download;
this.tv_progress = tv_progress;
this.onlinePathBundle = onlinePathBundle;
this.onlinePathMusic = onlinePathMusic;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
progressBar.setMax(100);
rl_progress.setVisibility(View.VISIBLE);
btn_download.setVisibility(View.GONE);
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
mWakeLock.acquire();
}
@Override
protected String doInBackground(String... sUrl) {
String firstResult = downTask(onlinePathBundle, 1, offlinePathBundle);
String seondResult = downTask(onlinePathMusic, 2, offlinePathMusic);
if (firstResult != null) {
Toast.makeText(SplashActivity.this, "Download error: " + firstResult, Toast.LENGTH_LONG).show();
return firstResult;
} else {
return seondResult;
}
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
progressBar.setProgress(progress[0]);
tv_progress.setText(progress[0] + "%");
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
rl_progress.setVisibility(View.GONE);
btn_download.setVisibility(View.VISIBLE);
if (result != null) {
Toast.makeText(SplashActivity.this, "Download error: " + result, Toast.LENGTH_LONG).show();
} else {
rl_progress.setVisibility(View.GONE);
btn_download.setVisibility(View.GONE);
}
}
public String downTask(String onlineNewPath, int numberOfTask, String offlineNewPath) {
InputStream input = null;
OutputStream output = null;
HttpURLConnection connection = null;
try {
URL url = new URL(onlineNewPath);
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();
}
// 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(offlineNewPath);
byte data[] = new byte[4096];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
// allow canceling with back button
if (isCancelled()) {
input.close();
return null;
}
total += count;
// publishing the progress....
if (fileLength > 0) {// only if total length is known
if (numberOfTask == 1) {
publishProgress((int) (total * 50 / fileLength));
} else if (numberOfTask == 2) {
publishProgress(((int) (total * 50 / fileLength)) + 50);
}
}
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;
}
}
【讨论】：