我是通过创建一个
Bitmap[]
数组变量来存储图片的方式来解决这个问题的,然后在适配器的
getView()
方法中,使用位置信息来检查
Bitmap[]
数组中的图像是否为
null
或者已有值。如果它有值,那么我就使用该值而不是再次调用
new DownloadImageTask()
构造函数。
例如:
YourCustomArrayAdapter.java
public class MyCustomArrayAdapter extends ArrayAdapter {
private static Bitmap[] myListViewImageViewsArray = new Bitmap[listViewItemsArray.length];
private String[] myListViewImageURLsArray = new String[listViewItemsArray.length]{
"image_url_1",
"image_url_2",
...
...
};
@Override
public View getView(int position, View view, ViewGroup parent){
CustomViewHolder vHolder;
if(view == null){
view = inflater.inflate(R.layout.movies_coming_soon_content_template, null, true);
vHolder = new CustomViewHolder();
vHolder.imageView = (AppCompatImageView) view.findViewById(R.id.my_cutom_image);
vHolder.imageUrl = "";
view.setTag(vHolder);
}
else{
vHolder = (CustomViewHolder)view.getTag();
vHolder.imageView.setImageResource(null);
}
if(myListViewImageViewsArray[position] != null){
vHolder.imageView.setImageBitmap(myListViewImageViewsArray[position]);
}else{
new DownloadImageTask(position, vHolder.imageView).execute(vHolder.imageUrl);
}
}
}
然后,在您的图像下载器构造函数中,在下载图像后,将其插入到该位置的Bitmap[]
图像数组中。例如:
YourImageDownloaderClass.java
public class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
AppCompatImageView imageView;
int position;
public DownloadImageTask(int position, AppCompatImageView imageView){
this.imageView = imageView;
this.position = position;
}
@Override
protected Bitmap doInBackground(String...urls) {
String urlOfImage = urls[0];
Bitmap logo = null;
try{
logo = BitmapFactory.decodeStream((InputStream) new URL(urlOfImage).getContent());
}catch(Exception e){
e.printStackTrace();
}
return logo;
}
@Override
protected void onPostExecute(Bitmap result){
if(result != null) {
YourCustomArrayAdapter.myListViewImageViewsArray [position] = result;
imageView.setImageBitmap(result);
}else{
YourCustomArrayAdapter.myListViewImageViewsArray [position] = null;
imageView.setImageResource(null);
}
}
}