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我有一个带有自定义适配器的android Listview。列表视图中的每个项目都会在图像视图中携带新闻图片，并且需要使用其URL来加载图像。我的代码如下。当我运行它时，我只能看到前几个项目的图片。当我向下滚动到其余项目时，我会一直看到每个图像视图中的进度条永久旋转。我可以在Log中看到某些图片无法加载，但我不明白为什么这会影响所有图片，因为我正在处理该例外情况。如果我能知道我正在犯什么错误，我会很感激。将URL中的图片加载到ListView中的图像查看
下面是我的自定义适配器
public class CustomAdapter extends BaseAdapter {
private LayoutInflater inflater;
private ArrayList<CustomObject> objects;
private Activity activity;
private ArrayList<Bitmap> newsImageList;
private class ViewHolder {
TextView titleTextView;
TextView dateTextView;
TextView bodyTextView;
ImageView logoView;
ImageView newsImageView;
ProgressBar progressBar;
}
public CustomAdapter(Context context, ArrayList<CustomObject> objects, Activity activity) {
// super(context, R.layout.news_item, objects);
inflater = LayoutInflater.from(context);
this.objects = objects;
this.activity= activity;
this.newsImageList= new ArrayList<Bitmap>();
for(int i=0; i<objects.size(); i++)
newsImageList.add(null);
}
@Override
public int getCount() {
return objects.size();
}
@Override
public CustomObject getItem(int position) {
return objects.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
System.out.println("IN GET VIEW");
ViewHolder holder = null;
if(convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.news_item, null);
holder.titleTextView = (TextView) convertView.findViewById(R.id.txtTitle);
holder.dateTextView = (TextView) convertView.findViewById(R.id.txtDate);
holder.bodyTextView = (TextView) convertView.findViewById(R.id.txtBody);
holder.logoView= (ImageView) convertView.findViewById(R.id.source_imageView);
holder.newsImageView= (ImageView) convertView.findViewById(R.id.news_imageView);
holder.progressBar= (ProgressBar) convertView.findViewById(R.id.img_progress_bar);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.titleTextView.setText(objects.get(position).getTitle());
holder.dateTextView.setText(objects.get(position).getDate());
holder.bodyTextView.setText(objects.get(position).getBody());
//for the source logo
String uri = "@drawable/"+objects.get(position).getSource_logo()+"_logo";
int imageResource = activity.getResources().getIdentifier(uri, null, activity.getPackageName());
Drawable res =activity.getResources().getDrawable(imageResource);
holder.logoView.setImageDrawable(res);
//the news image
String newsImageURL = objects.get(position).getNewsImageURL();
if(newsImageURL!=null) {
// show The Image in a ImageView
//already loaded
if(newsImageList.get(position)!=null) {
holder.progressBar.setVisibility(View.INVISIBLE);
holder.newsImageView.setImageBitmap(newsImageList.get(position));
}
else
new DownloadImageTask(holder.newsImageView, holder, position)
.execute(newsImageURL);
}
else
{
System.out.println("NO IMAGE");
//adjusting the view
holder.progressBar.setVisibility(View.INVISIBLE);
holder.newsImageView.setVisibility(View.GONE);
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) holder.bodyTextView.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.txtDate);
}
return convertView;
}
//subclass
class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView bmImage;
boolean imageLoadingFailure=false;//default is false
ViewHolder holder;
int index;
public DownloadImageTask(ImageView bmImage,ViewHolder holder, int index) {
this.bmImage = bmImage;
this.holder= holder;
this.index=index;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
holder.newsImageView.setImageResource(android.R.color.transparent);//clear the news image view
holder.progressBar.setVisibility(View.VISIBLE);//show the progress bar
holder.newsImageView.setVisibility(View.VISIBLE);//show the image view
}
protected Bitmap doInBackground(String... urls) {
return downloadBitmap(urls[0]);
}
protected void onPostExecute(Bitmap result) {
if(imageLoadingFailure)
{
//adjusting the view
System.out.println("IMAGE LOADING FAILED!");
/*
holder.progressBar.setVisibility(View.INVISIBLE);
holder.newsImageView.setVisibility(View.GONE);
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) holder.bodyTextView.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.txtDate);
*/
}
else {
holder.progressBar.setVisibility(View.INVISIBLE);
bmImage.setImageBitmap(result);
newsImageList.set(index, result);
}
}
//code source: http://stacktips.com/tutorials/android/loading-image-asynchronously-in-android-listview
private Bitmap downloadBitmap(String url) {
HttpURLConnection urlConnection = null;
try {
URL uri = new URL(url);
urlConnection = (HttpURLConnection) uri.openConnection();
int statusCode = urlConnection.getResponseCode();
/*if (statusCode != HttpStatus.SC_OK) {
return null;
}*/
InputStream inputStream = urlConnection.getInputStream();
if (inputStream != null) {
Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
return bitmap;
}
} catch (Exception e) {
urlConnection.disconnect();
imageLoadingFailure=true;
Log.w("ImageDownloader", "Error downloading image from " + url);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return null;
}
}
}
下面是在ListView
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<TextView
android:id="@+id/txtTitle"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dip"
android:textSize="16dip"
android:textStyle="bold"
android:gravity="right"
android:textDirection="rtl"
>
</TextView>
<ImageView
android:id="@+id/source_imageView"
android:layout_height="60dp"
android:layout_width="60dp"
android:layout_marginRight="10dp"
android:layout_below="@+id/txtTitle"
android:layout_marginTop="-15dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
/>
<TextView
android:id="@+id/txtDate"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dip"
android:textSize="16dip"
android:gravity="right"
android:textDirection="rtl"
android:textStyle="italic"
android:layout_below="@id/source_imageView"
android:layout_marginTop="-20dp"
>
</TextView>
<RelativeLayout
android:id="@+id/relative_container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/txtDate"
android:layout_centerInParent="true">
<ImageView
android:id="@+id/news_imageView"
android:layout_height="200dp"
android:layout_width="340dp"
android:layout_centerInParent="true"
/>
<ProgressBar
android:id="@+id/img_progress_bar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:indeterminate="true"
android:layout_centerInParent="true"/>
</RelativeLayout>
<TextView
android:id="@+id/txtBody"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dip"
android:textSize="16dip"
android:gravity="right"
android:textDirection="rtl"
android:layout_below="@id/relative_container"
>
</TextView>
</RelativeLayout>
尝试使用Glide从URL加载图像 – Anmol
使用_Glide_ ... – Piyush
有许多[可用于Android的图像加载库]（https://android-arsenal.com/tag/46）。大多数人知道如何处理视图回收（'ListView'，'RecyclerView'等）。我强烈建议您使用这些库中的一个。 – CommonsWare