JianYA JianYA - 6 months ago 66
Android Question

Android load images from URL into custom listview adapter without Picasso

I am trying to load images from a url and I have used Picasso, however I'd like to know how to do it without an external library if possible. I know I have to get an Asynctask going but I'm not sure how to implement it.

This is my getview code

@Override
public View getView(int position, View convertView, ViewGroup parent) {

View row = convertView;
if(position==0){

NewsObj currNews = news.get(position);
DataHandler dh;
if(convertView==null){
LayoutInflater inflater = (LayoutInflater)this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = inflater.inflate(R.layout.firstnews,parent,false);
dh = new DataHandler();
dh.newsTitle = (TextView)row.findViewById(R.id.newsTitle);
dh.newsDate = (TextView)row.findViewById(R.id.newsDate);
dh.newsIcon = (ImageView)row.findViewById(R.id.newsIcon);
row.setTag(dh);
}else{
dh = (DataHandler)row.getTag();
}
NewsObj no = (NewsObj)this.getItem(position);
new AsyncDownloadTask().execute(row,no.getImgurl());
dh.newsTitle.setText(no.getTitle());
dh.newsDate.setText(no.getDate());

}else{

NewsObj currNews = news.get(position);
DataHandler dh;
if(convertView==null){
LayoutInflater inflater = (LayoutInflater)this.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = inflater.inflate(R.layout.newslist,parent,false);
dh = new DataHandler();
dh.newsTitle = (TextView)row.findViewById(R.id.newsTitle);
dh.newsDate = (TextView)row.findViewById(R.id.newsDate);
dh.newsIcon = (ImageView)row.findViewById(R.id.newsIcon);
row.setTag(dh);
}else{
dh = (DataHandler)row.getTag();
}
NewsObj no = (NewsObj)this.getItem(position);
new AsyncDownloadTask().execute(row,no.getImgurl());

dh.newsTitle.setText(no.getTitle());
dh.newsDate.setText(no.getDate());

}
return row;
}


private class AsyncDownloadTask extends AsyncTask<Object, String, Bitmap>{

private View view;
private Bitmap bitmap = null;
@Override
protected void onPreExecute() {
super.onPreExecute();
}

@Override
protected void onPostExecute(Bitmap bitmap) {
if(bitmap!=null&&view!=null){
ImageView newsIcon = (ImageView)view.getTag(R.id.newsIcon);
newsIcon.setImageBitmap(bitmap);
}
}

@Override
protected Bitmap doInBackground(Object... params) {
view = (View)params[0];
String uri = (String)params[1];
try{
InputStream inputStream = new URL(uri).openStream();
bitmap = BitmapFactory.decodeStream(inputStream);
}catch (Exception e){
e.printStackTrace();
}
return bitmap;
}
}


This is my async task

UPDATE : Encountering null pointer exceptions

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference

Answer

Simply you can use java.net.URL for loading an image into ImageView like

    ImageView loadedImage;

    @override
    protected Bitmap doInBackground(String... url) {
        String URL_OF_IMAGE = url[0];
        Bitmap bitmap = null;
        try {
            InputStream in = new java.net.URL(URL_OF_IMAGE).openStream();
            bitmap= BitmapFactory.decodeStream(in);
        } catch (Exception e) {
        }
        return bitmap;
    }

    protected void onPostExecute(Bitmap result) {
        loadedImage.setImageBitmap(result);
    }

But notice that you should have extend AsyncTask that should have first parameter as String and last as Bitmap like

private class DowmloadImage extends AsyncTask<String, Void, Bitmap>
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