我创建了用于从网址下载多张图片的应用程序，问题是当下载所有图片（有3000张图片）时，它是一个多进程，而不是一个进程。单进程我的意思是先下载然后保存，再下载然后保存等等。 可以一次下载多个图像吗？
这是我的代码：
private CoordinatorLayout mCLayout;
private ProgressDialog mProgressDialog;
private LinearLayout mLLayout;
private AsyncTask mMyTask;
private final URL[] URLS = {
stringToURL("https://d1rkccsb0jf1bk.cloudfront.net/products/3d/100009884/images/I_20.jpg"),
stringToURL("https://d3inagkmqs1m6q.cloudfront.net/2280/media-photos/azk0w23602-black-new-calvin-klein-watches-k0w23602.jpg"),
stringToURL("https://www.designerswatch.com.au/media/catalog/product/cache/1/image/800x800/9df78eab33525d08d6e5fb8d27136e95/k/2/k2y211c3-1.jpg"),
stringToURL("http://demandware.edgesuite.net/sits_pod35/dw/image/v2/ABAD_PRD/on/demandware.static/-/Sites-calvinklein-hk-master/default/dw521470a6/images/hi-res/K7Y214CZ-000/K7Y214CZ-000-ITEM-1.jpg?sw=500"),
stringToURL("https://ethos-cdn1.ethoswatches.com/pub/media/catalog/product/cache/749a04adc68de020ef4323397bb5eac7/c/a/calvin-klein-party-k8u2m116.jpg")
// and so on
};
int count;
// List of url image
List<URL> imageName = new ArrayList<>();
File file;
ContextWrapper wrapper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get the application context
getApplicationContext();
Activity mActivity = MainActivity.this;
// Get the widget reference from XML layout
mCLayout = findViewById(R.id.coordinator_layout);
Button mButtonDo = findViewById(R.id.btn_do);
mLLayout = findViewById(R.id.ll);
//-------------------set image--------------------------
ImageView setImage = findViewById(R.id.setImage);
// Initialize ContextWrapper
wrapper = new ContextWrapper(getApplicationContext());
file = wrapper.getDir("Images",MODE_PRIVATE);
file = new File(file, "I_20.jpg");
if(file.exists()) {
Bitmap myBitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
setImage.setImageBitmap(myBitmap);
}
//-------------------set image--------------------------
// Initialize the progress dialog
mProgressDialog = new ProgressDialog(mActivity);
mProgressDialog.setIndeterminate(false);
// Progress dialog horizontal style
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
// Progress dialog title
mProgressDialog.setTitle("AsyncTask");
// Progress dialog message
mProgressDialog.setMessage("Please wait, we are downloading your image files...");
mProgressDialog.setCancelable(true);
// Set a progress dialog dismiss listener
mProgressDialog.setOnDismissListener(new DialogInterface.OnDismissListener() {
@Override
public void onDismiss(DialogInterface dialogInterface) {
// Cancel the AsyncTask
mMyTask.cancel(false);
}
});
// Initialize a new click listener for positive button widget
mButtonDo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Execute the async task
mMyTask = new DownloadTask().execute(URLS);
}
});
}
/*
* First parameter URL for doInBackground
* Second parameter Integer for onProgressUpdate
* Third parameter List<Bitmap> for onPostExecute
*/
@SuppressLint("StaticFieldLeak")
private class DownloadTask extends AsyncTask<URL,Integer,List<Bitmap>>{
// Before the tasks execution
protected void onPreExecute(){
// Display the progress dialog on async task start
mProgressDialog.show();
mProgressDialog.setProgress(0);
}
// Do the task in background/non UI thread
protected List<Bitmap> doInBackground(URL...urls){
Log.d("doInBackground", "doInBackground: ");
count = urls.length;
//URL url = urls[0];
HttpURLConnection connection = null;
List<Bitmap> bitmaps = new ArrayList<>();
// Loop through the urls
for(int i=0;i<count;i++){
URL currentURL = urls[i];
// So download the image from this url
try{
// Initialize a new http url connection
connection = (HttpURLConnection) currentURL.openConnection();
// Connect the http url connection
connection.connect();
// Get the input stream from http url connection
InputStream inputStream = connection.getInputStream();
// Initialize a new BufferedInputStream from InputStream
BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
// Convert BufferedInputStream to Bitmap object
Bitmap bmp = BitmapFactory.decodeStream(bufferedInputStream);
// Add the bitmap to list
bitmaps.add(bmp);
// add the url to list URL
imageName.add(currentURL);
// Publish the async task progress
// Added 1, because index start from 0
publishProgress((int) (((i+1) / (float) count) * 100));
if(isCancelled()){
break;
}
}catch(IOException e){
e.printStackTrace();
}finally{
// Disconnect the http url connection
assert connection != null;
connection.disconnect();
}
}
// Return bitmap list
return bitmaps;
}
// On progress update
protected void onProgressUpdate(Integer... progress){
// Update the progress bar
mProgressDialog.setProgress(progress[0]);
}
// On AsyncTask cancelled
protected void onCancelled(){
Snackbar.make(mCLayout,"Task Cancelled.",Snackbar.LENGTH_LONG).show();
}
// When all async task done
protected void onPostExecute(List<Bitmap> result){
// Hide the progress dialog
mProgressDialog.dismiss();
// Remove all views from linear layout
mLLayout.removeAllViews();
Log.d("result", String.valueOf(result));
// Loop through the bitmap list
for(int i=0;i<result.size();i++){
Bitmap bitmap = result.get(i);
// Save the bitmap to internal storage
Uri imageInternalUri = saveImageToInternalStorage(bitmap, i);
// Display the bitmap from memory
addNewImageViewToLayout(bitmap);
// Display bitmap from internal storage
// addNewImageViewToLayout(imageInternalUri);
}
}
}
// Custom method to convert string to url
protected URL stringToURL(String urlString){
try{
return new URL(urlString);
}catch(MalformedURLException e){
e.printStackTrace();
}
return null;
}
// Custom method to save a bitmap into internal storage
protected Uri saveImageToInternalStorage(Bitmap bitmap, int index){
Log.d("count", String.valueOf(count));
// Initializing a new file
// The bellow line return a directory in internal storage
file = wrapper.getDir("Images",MODE_PRIVATE);
// Create a file to save the image
// First get name of image from url, and then saved with that name
file = new File(file, getFileNameFromUrl(imageName.get(index)));
Log.d("TAG", String.valueOf(file));
try{
// Initialize a new OutputStream
OutputStream stream;
// If the output file exists, it can be replaced or appended to it
stream = new FileOutputStream(file);
// Compress the bitmap
bitmap.compress(Bitmap.CompressFormat.JPEG,100,stream);
// Flushes the stream
stream.flush();
// Closes the stream
stream.close();
}catch (IOException e) // Catch the exception
{
e.printStackTrace();
}
// Parse the gallery image url to uri
// Return the saved image Uri
return Uri.parse(file.getAbsolutePath());
}
/**
* This function will take an URL as input and return the file name.
* Examples :
* http://example.com/a/b/c/test.txt -> test.txt
* http://example.com/ -> an empty string
* http://example.com/test.txt?param=value -> test.txt
* http://example.com/test.txt#anchor -> test.txt
*
* @param url The input URL
* @return The URL file name
*/
public static String getFileNameFromUrl(URL url) {
// String file
String urlString = url.getFile();
// Return image name
return urlString.substring(urlString.lastIndexOf('/') + 1).split("\\?")[0].split("#")[0];
}
// Custom method to add a new image view using bitmap
protected void addNewImageViewToLayout(Bitmap bitmap){
// Initialize a new ImageView widget
ImageView iv = new ImageView(getApplicationContext());
// Set an image for ImageView
iv.setImageBitmap(bitmap);
// Create layout parameters for ImageView
LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, 500);
// Add layout parameters to ImageView
iv.setLayoutParams(lp);
// Finally, add the ImageView to layout
mLLayout.addView(iv);
}
// Custom method to add a new image view using uri
protected void addNewImageViewToLayout(Uri uri){
// Initialize a new ImageView widget
ImageView iv = new ImageView(getApplicationContext());
// Set an image for ImageView
iv.setImageURI(uri);
// Create layout parameters for ImageView
LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, 300);
// Add layout parameters to ImageView
iv.setLayoutParams(lp);
// Finally, add the ImageView to layout
mLLayout.addView(iv);
}
我的目标是像这样，因为我遇到了错误，Clamp target GC heap我认为问题是BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);，因为有很多图像。
非常感谢
答案 0 :(得分：0)
使用DownloadManager下载多张图片
public static void downloadFile(String uRl, Context context) {
File myDir = new File(Environment.getExternalStorageDirectory(), "MyApp/");
if (!myDir.exists()) {
myDir.mkdirs();
}
DownloadManager mgr = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
Uri downloadUri = Uri.parse(uRl);
DownloadManager.Request request = new DownloadManager.Request(
downloadUri);
request.setAllowedNetworkTypes(
DownloadManager.Request.NETWORK_WIFI
| DownloadManager.Request.NETWORK_MOBILE).setAllowedOverMetered(true)
.setAllowedOverRoaming(true).setTitle("Myapp - " + "Downloading " + uRl).
setVisibleInDownloadsUi(true)
.setDestinationInExternalPublicDir("MyApp" + "/", uRl);
mgr.enqueue(request);
}
用法：-
// Initialize a new click listener for positive button widget
mButtonDo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Execute the async task
// mMyTask = new DownloadTask().execute(URLS);
for (int i = 0; i < URLS .size(); i++) {
downloadFile(urls[i],Activityname.this);
}
}
});
要更改路径，请编辑此
File myDir = new File(Environment.getExternalStorageDirectory(), "MyApp/");