我有一个带有 ArrayAdapter 的 ListView,其中包含带有图像和字符串的行。这工作正常,直到我决定图像的加载速度很慢,所以我无法在显示列表之前加载图像。所以我开始使用 AsyncTask
在单独的线程中加载图像。
在开始滚动列表之前,我对结果非常满意。加载了错误的图像,看起来不像是图像稍后加载的问题。如果我尝试对列表进行排序,问题就会变得非常糟糕,并且没有图像位于右行。
对我做错了什么有什么想法吗?
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
ImageView imageView;
TextView textView;
if (v == null) {
LayoutInflater vi = (LayoutInflater) getContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.drink_list_row, null);
}
Drink drink = allItems.get(position);
if (drink != null && v != null) {
imageView = (ImageView) v.findViewById(R.id.picture);
textView = (TextView) v.findViewById(R.id.drinkName);
imageView.setVisibility(View.GONE);
loadImageBitmap(drink, imageView);
textView.setText(drink.getName());
if (subItems != null && subItems.contains(drink)) {
textView.setVisibility(View.VISIBLE);
imageView.setVisibility(View.VISIBLE);
} else {
textView.setVisibility(View.GONE);
imageView.setVisibility(View.GONE);
}
}
return v;
}
最佳答案
问题来自您的 convertView:它是整个列表中使用的同一个实例,因此当您的异步加载完成时,当 listview 尝试使用相同的 convertView(或在这种情况下,它的子 imageView)。
painting position 1, uses placeholder, starts loading image 1 asynchronously
painting position 2, uses placeholder, starts loading image 2 asynchronously
image 1 loading is complete, calling setImageBitmap on imageView
painting position 3, uses image 1, starts loading image 3 asynchronously
etc.
不过,您可以做的是在列表适配器中保留一个位图缓存。像这样:
private Bitmap[] bitmapList;
private Bitmap bitmapPlaceholder;
private void initBitmapListWithPlaceholders(){
// call this whenever the list size changes
// you can also use a list or a map or whatever so you
// don't need to drop all the previously loaded bitmap whenever
// the list contents are modified
int count = getListCount();
bitmapList = new Bitmap[count];
for(int i=0;i<count;i++){
bitmapList[i]=bitmapPlaceholder
}
}
private void onBitmapLoaded(int position, Bitmap bmp){
// this is your callback when the load async is done
bitmapList[position] = bmp;
}
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
ImageView imageView;
TextView textView;
if (v == null) {
LayoutInflater vi = (LayoutInflater) getContext().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.drink_list_row, null);
}
Drink drink = allItems.get(position);
if (drink != null && v != null) {
imageView = (ImageView) v.findViewById(R.id.picture);
textView = (TextView) v.findViewById(R.id.drinkName);
imageView.setVisibility(View.GONE);
imageView.setImageBitmap(bitmapList[position]);
loadImageBitmap(drink, position); // this should call onBitmapLoaded(int position, Bitmap bmp) when finished to update the bitmapList and replace the placeholder
textView.setText(drink.getName());
if (subItems != null && subItems.contains(drink)) {
textView.setVisibility(View.VISIBLE);
imageView.setVisibility(View.VISIBLE);
} else {
textView.setVisibility(View.GONE);
imageView.setVisibility(View.GONE);
}
}
return v;
}
关于android - ListView 显示错误的图像,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6081497/