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
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;
}
}
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) {
...
}
});
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中添加一个依赖
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)
}
}
开始下载通过工作管理器在活动类
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
}
}
}
}
})
}
您可以使用LiveData和协程观察下载管理器的进度，参见下面的要点
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()
}
}
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