Develop Reference

task.execute url to bitmap mismatch

public class MainActivity extends Activity {
ImageView downloadedimg;
public class ImageDownloader extends AsyncTask<String,void,Bitmap> {
#Override
protected Bitmap doInBackground(String... urls) {
try{
URL url=new URL(urls[0]);
HttpURLConnection connection=(HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputStream=connection.getInputStream();
Bitmap mybitmap= BitmapFactory.decodeStream(inputStream);
return mybitmap;
}
catch(Exception e)
{
e.printStackTrace();
}
return null;
}
}
public void downloadImage(View view) {
ImageDownloader task = new ImageDownloader;
Bitmap myImage;
try {
myImage = task.execute("https://www.google.co.in/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwiOw5HvydXOAhVKqo8KHYHfAtIQjRwIBw&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FBart_Simpson&psig=AFQjCNFZSwEG2tjp15Km14uuzEsmZUZ_MQ&ust=1471974330385306");
downloadedimg.setImageBitmap(myImage);
}
catch (Exception e) {
e.printStackTrace();
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
downloadedimg=(ImageView)findViewById(R.id.imageView);
}
in the line
myImage = task.execute("some url to image address online");
the complier shows error that
incompatible type
required: android.graphics.Bitmap
found: android.os.AsyncTask "<"java.lang.String,void,android.graphics.Bitmap>
double code infront of java's bracket are not part of statement
#edit Thank you for previous advice i searched and found .get() method
i used task("").get() to return the bitmap image and code compiled without errors but now nothings happens when i click the download image button

AsyncTask.execute does not return the object downloaded. It can't, the entire idea of an AsyncTask is that its asynchronous. Any code that needs to use the result should either be put in onPostExecute (for UI changes) or at the end of doInBackground (for processing data).

android.os.NetworkOnMainThreadException in AsyncTask's doInBackground

Why do I get in an AsyncTask which should a android.os.NetworkOnMainThreadException? I thought that an AsyncTask is the solution to that problem. The exxeption is on line 7.
private class ImageDownloadTask extends AsyncTask<String, Integer, byte[]> {
#Override
protected byte[] doInBackground(String... params) {
try {
URL url = new URL(params[0]);
URLConnection connection = url.openConnection();
InputStream inputStream = connection.getInputStream();
ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
int len;
while ((len = inputStream.read(buffer)) != -1) {
byteBuffer.write(buffer, 0, len);
}
return byteBuffer.toByteArray();
} catch (IOException ex) {
return new byte[0];
}
}
}
I want to use it for downloading a picture.
public byte[] getProfilePicture(Context context, String id) {
String url = context.getString(R.string.facebook_picture_url_large, id);
ImageDownloadTask task = new ImageDownloadTask();
return task.doInBackground(url);
}

By calling doInBackground() directly, you are not actually using the AsyncTask functionality. Instead, you should call execute() and then use the results by overriding the AsyncTask's onPostExecute() method as explained in the Usage section of that same page.

Best way to download an image and attach it to a ImageView is passing the ImageView as the parameter in your async task and set the URL as a tag of the image view then after downloading the task in the OnPostExecute() set the image to the ImageView look at this example :
public class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
#Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
#Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
...
}
And the Usage will be like this
ImageView mChart = (ImageView) findViewById(R.id.imageview);
String URL = "http://www...someImageUrl ...";
mChart.setTag(URL);
new DownloadImageTask.execute(mChart);
The image will be attached automatically when done, for more memory optimization you could use WeakReference.
Good Luck.

App force closing when Async tries to get Bitmap from url

I have an Async running to get data from a page I've created. It get's the text just fine, but when I try and get the image from the image src via another class the app force closes. Here is the code that it force closes on:
public class FullReportActivity extends NavigationActivity {
private TextView textView;
private String url = "http://www.backcountryskiers.com/sac/sac-full.html";
private ImageView ivDangerRose;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// tell which region this covers
getSupportActionBar().setSubtitle("...from Sierra Avalanche Center");
setContentView(R.layout.activity_fullreport);
textView = (TextView) findViewById(R.id.todaysReport);
ivDangerRose = (ImageView) findViewById(R.id.dangerRose);
fetcher task = new fetcher();
task.execute();
}
// GET THE IMAGE and RETURN IT
public static Bitmap getBitmapFromURL(String src) {
try {
URL url = new URL(src);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
class fetcher extends AsyncTask<String, Void, String> {
private ProgressDialog dialog = new ProgressDialog(
FullReportActivity.this);
private Document doc = null;
private Document parse = null;
private String results = null;
private String reportDate = null;
private Bitmap bimage = null;
#Override
protected String doInBackground(String... params) {
try {
doc = Jsoup.connect(url).get();
Log.e("Jsoup", "...is working...");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.e("Exception", e.getMessage());
}
parse = Jsoup.parse(doc.html());
results = doc.select("#fullReport").outerHtml();
Element dangerRoseImg = doc.getElementById("reportRose")
.select("img").first();
String dangerRoseSrc = dangerRoseImg.absUrl("src");
Log.i("Report Rose IMG", dangerRoseSrc);
bimage = getBitmapFromURL(dangerRoseSrc);
ivDangerRose.setImageBitmap(bimage);
return results;
}
#Override
protected void onPostExecute(String result) {
dialog.dismiss();
// smooth out the long scrolling...
textView.setMovementMethod(ScrollingMovementMethod.getInstance());
reportDate = parse.select("#reportDate").outerHtml();
textView.setText(Html.fromHtml(reportDate + results));
textView.setPadding(30, 20, 20, 10);
}
#Override
protected void onPreExecute() {
dialog.setMessage("Loading Full Report from the Sierra Avalanche Center...");
dialog.show();
}
}
}
I have run this Async alone to get the image like so without a force close and I don't understand what i am doing different besides calling the method:
public class MainActivity extends Activity {
public String durl = "http://www.sierraavalanchecenter.org/dangerrose.png?a=2955";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new DownloadImageTask((ImageView) findViewById(R.id.dangerrose))
.execute(durl);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView bmImage;
public DownloadImageTask(ImageView bmImage) {
this.bmImage = bmImage;
}
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap drose = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
drose = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return drose;
}
protected void onPostExecute(Bitmap result) {
bmImage.setImageBitmap(result);
}
}
}
This class gets the image src and creates a bitmap and puts it into an ImageView, what is different here than on my first class???
Frustrated.

You can not modify UI from background thread.
move ivDangerRose.setImageBitmap(bimage); in onPostExecute

In the method doInBackground
remove --> ivDangerRose.setImageBitmap(bimage);
as you can't modify UI in background process.
If you still want you can try runOnUiThread Method

In doInBackground() we should not access the content of activity.

How to display the images from server asynchronously in Android?

I am displaying an image from a server in Android. For that I have gone through the tutorial Android Load Image From URL Example. It is very helpful. But it is taking 5 minutes to display the image from the server. So I want to display the image asynchronously. How can I do that?

The below snippets will help you.
DownloadHelper.java
public interface DownloadHelper
{
public void OnSucess(Bitmap bitmap);
public void OnFailure(String response);
}
MainActivity.java
public class GalleryExample extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
DownloadHelper downloadHelper = new DownloadHelper()
{
#Override
public void OnSucess(Bitmap bitmap)
{
ImageView imageView=(ImageView)findViewById(R.id.imageView);
imageView.setImageBitmap(bitmap);
}
#Override
public void OnFailure(String response)
{
Toast.makeText(context, response, Toast.LENGTH_LONG).show();
}
};
new MyTask(this,downloadHelper).execute("image url");
}
MyTask.java
public class DownloadTask extends AsyncTask<String, Integer, Object>
{
private Context context;
private DownloadHelper downloadHelper;
private ProgressDialog dialog;
public DownloadTask(Context context,DownloadHelper downloadHelper)
{
this.context = context;
}
#Override
protected void onPreExecute()
{
dialog = new ProgressDialog(context);
dialog.setTitle("Please Wait");
dialog.setMessage("Fetching Data!!");
dialog.setCancelable(false);
dialog.show();
super.onPreExecute();
}
#Override
protected Object doInBackground(String... params)
{
URL aURL = new URL(myRemoteImages[position]);
URLConnection conn = aURL.openConnection();
conn.connect();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
/* Decode url-data to a bitmap. */
Bitmap bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
return bm;
}
#Override
protected void onPostExecute(Object result)
{
dialog.dismiss();
if (result != null)
{
downloadHelper.OnSucess((Bitmap)result);
}
else
{
downloadHelper.OnFailure("Error in Downloading Data!!");
}
super.onPostExecute(result);
}
}

Android : Loading an image from the Web with Asynctask

How do I replace the following lines of code with an Asynctask ?
How do you "get back" the Bitmap from the Asynctask ? Thank you.
ImageView mChart = (ImageView) findViewById(R.id.Chart);
String URL = "http://www...anything ...";
mChart.setImageBitmap(download_Image(URL));
public static Bitmap download_Image(String url) {
//---------------------------------------------------
Bitmap bm = null;
try {
URL aURL = new URL(url);
URLConnection conn = aURL.openConnection();
conn.connect();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
} catch (IOException e) {
Log.e("Hub","Error getting the image from server : " + e.getMessage().toString());
}
return bm;
//---------------------------------------------------
}
I thought about something like this :
replace :
mChart.setImageBitmap(download_Image(graph_URL));
by something like :
mChart.setImageBitmap(new DownloadImagesTask().execute(graph_URL));
and
public class DownloadImagesTask extends AsyncTask<String, Void, Bitmap> {
#Override
protected Bitmap doInBackground(String... urls) {
return download_Image(urls[0]);
}
#Override
protected void onPostExecute(Bitmap result) {
mChart.setImageBitmap(result); // how do I pass a reference to mChart here ?
}
private Bitmap download_Image(String url) {
//---------------------------------------------------
Bitmap bm = null;
try {
URL aURL = new URL(url);
URLConnection conn = aURL.openConnection();
conn.connect();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
} catch (IOException e) {
Log.e("Hub","Error getting the image from server : " + e.getMessage().toString());
}
return bm;
//---------------------------------------------------
}
}
but How do I pass a reference to mChart in onPostExecute(Bitmap result) ???
Do I need to pass it with the URL in some way ?
I would like to replace all my lines of code :
mChart1.setImageBitmap(download_Image(URL_1));
mChart2.setImageBitmap(download_Image(URL_2));
with something similar ... but in Asynctask way !
mChart1.setImageBitmap(new DownloadImagesTask().execute(graph_URL_1));
mChart2.setImageBitmap(new DownloadImagesTask().execute(graph_URL_2));
Is there an easy solution for this ?
Do I get something wrong here ?

If there is no good reason to download the image yourself then I would recommend to use Picasso.
Picasso saves you all the problems with downloading, setting and caching images.
The whole code needed for a simple example is:
Picasso.with(context).load(url).into(imageView);
If you really want to do everything yourself use my older answer below.
If the image is not that big you can just use an anonymous class for the async task.
This would like this:
ImageView mChart = (ImageView) findViewById(R.id.imageview);
String URL = "http://www...anything ...";
mChart.setTag(URL);
new DownloadImageTask.execute(mChart);
The Task class:
public class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
#Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
#Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
...
}
Hiding the URL in the tag is a bit tricky but it looks nicer in the calling class if you have a lot of imageviews that you want to fill this way. It also helps if you are using the ImageView inside a ListView and you want to know if the ImageView was recycled during the download of the image.
I wrote if you Image is not that big because this will result in the task having a implicit pointer to the underlying activity causing the garbage collector to hold the whole activity in memory until the task is finished. If the user moves to another screen of your app while the bitmap is downloading the memory can't be freed and it may make your app and the whole system slower.

Try this code:
ImageView myFirstImage = (ImageView) findViewById(R.id.myFirstImage);
ImageView mySecondImage = (ImageView) findViewById(R.id.mySecondImage);
ImageView myThirdImage = (ImageView) findViewById(R.id.myThirdImage);
String URL1 = "http://www.google.com/logos/2013/estonia_independence_day_2013-1057005.3-hp.jpg";
String URL2 = "http://www.google.com/logos/2013/park_su-geuns_birthday-1055005-hp.jpg";
String URL3 = "http://www.google.com/logos/2013/anne_cath_vestlys_93rd_birthday-1035005-hp.jpg";
myFirstImage.setTag(URL1);
mySecondImage.setTag(URL2);
myThirdImage.setTag(URL3);
new DownloadImageTask.execute(myFirstImage);
new DownloadImageTask.execute(mySecondImage);
new DownloadImageTask.execute(myThirdImage);
public class DownloadImagesTask extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null;
#Override
protected Bitmap doInBackground(ImageView... imageViews) {
this.imageView = imageViews[0];
return download_Image((String)imageView.getTag());
}
#Override
protected void onPostExecute(Bitmap result) {
imageView.setImageBitmap(result);
}
private Bitmap download_Image(String url) {
Bitmap bmp =null;
try{
URL ulrn = new URL(url);
HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
InputStream is = con.getInputStream();
bmp = BitmapFactory.decodeStream(is);
if (null != bmp)
return bmp;
}catch(Exception e){}
return bmp;
}
}

you can create a class say..BkgProcess which contains an inner class that extends AsyncTask. while instantiating BkgProcess pass the context of your Activity class in BkgProcess constructor. for eg:
public class BkgProcess {
String path;
Context _context;
public Download(Downloader downloader, String path2){
this.path = path2;
_context = downloader;
}
public void callProgressDialog(){
new BkgProcess().execute((Void)null);
}
class Downloads extends AsyncTask<Void, Void, Boolean> {
private ProgressDialog dialog = new ProgressDialog(_context);
protected void onPreExecute(){
dialog.setMessage("Downloading image..");
dialog.show();
}
protected void onPostExecute(Boolean success) {
dialog.dismiss();
if(success)
Toast.makeText(_context, "Download complete", Toast.LENGTH_SHORT).show();
}
#Override
protected Boolean doInBackground(Void... params) {
return(startDownload(path));
}
public boolean startDownload(String img_url) {
// download img..
return true;
}
}
}
from your activity class..
BkgProcess dwn = new BkgProcess (Your_Activity_class.this, img_path);
dwn.callProgressDialog();

This will get you images of any size...
if you dont want the progress dialog just comment the codes in onPreExecute();
for(int i = 0 ; i < no_of_files ; i++ )
new FetchFilesTask().execute(image_url[i]);
private class FetchFilesTask extends AsyncTask<String, Void, Bitmap> {
private ProgressDialog dialog = new ProgressDialog(FileExplorer.this);
Bitmap bitmap[];
protected void onPreExecute(){
dialog.setMessage("fetching image from the server");
dialog.show();
}
protected Bitmap doInBackground(String... args) {
bitmap = getBitmapImageFromServer();
return bitmap;
}
protected void onPostExecute(Bitmap m_bitmap) {
dialog.dismiss();
if(m_bitmap != null)
//store the images in an array or do something else with all the images.
}
}
public Bitmap getBitmapImageFromServer(){
// fetch image form the url using the URL and URLConnection class
}