我有一个可以保存图像的ListView。这取决于SDCARD中是否存在图像。
下面是我的示例代码:
public class MainActivity extends Activity {
ListView mListView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mListView = new ListView(this);
setContentView(mListView);
String[] arr = new String[] {
"/example/images/1.jpg", "/example/images/2.jpg",
"/example/images/3.jpg", "/example/images/4.jpg",
"/example/images/5.jpg", "/example/images/6.jpg",
"/example/images/7.jpg", "/example/images/8.jpg",
"/example/images/9.jpg", "/example/images/1.jpg",
"/example/images/2.jpg", "/example/images/3.jpg",
"/example/images/4.jpg", "/example/images/5.jpg",
"/example/images/6.jpg", "/example/images/7.jpg",
"/example/images/8.jpg", "/example/images/9.jpg",
"/example/images/1.jpg", "/example/images/2.jpg",
"/example/images/3.jpg", "/example/images/4.jpg",
"/example/images/5.jpg", "/example/images/6.jpg",
"/example/images/7.jpg", "/example/images/8.jpg",
"/example/images/9.jpg", "/example/images/1.jpg",
"/example/images/2.jpg", "/example/images/3.jpg",
"/example/images/4.jpg", "/example/images/5.jpg",
"/example/images/6.jpg", "/example/images/7.jpg",
"/example/images/8.jpg", "/example/images/9.jpg"};
List<String> list = Arrays.asList(arr);
MyAdapter adapter = new MyAdapter(this, R.layout.listitem_imv, list);
mListView.setAdapter(adapter);
}
class MyAdapter extends ArrayAdapter<String>{
List<String> mList;
LayoutInflater mInflater;
int mResource;
public MyAdapter(Context context, int resource,
List<String> objects) {
super(context, resource, objects);
mResource = resource;
mInflater = getLayoutInflater();
mList = objects;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view;
if(convertView == null){
view = mInflater.inflate(mResource, null);
}else{
view = convertView;
}
ImageView imageView = (ImageView) view.findViewById(R.id.imv);
TextView textView = (TextView) view.findViewById(R.id.txv);
imageView.setTag(mList.get(position));//tag of imageView == path to image
new LoadImage().execute(imageView);
textView.setText(mList.get(position).toString());
return view;
}
}
class LoadImage extends AsyncTask<Object, Void, Bitmap>{
private ImageView imv;
private String path;
@Override
protected Bitmap doInBackground(Object... params) {
imv = (ImageView) params[0];
path = imv.getTag().toString();
Bitmap bitmap = null;
File file = new File(
Environment.getExternalStorageDirectory().getAbsolutePath() + path);
if(file.exists()){
bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap result) {
if(result != null && imv != null){
imv.setVisibility(View.VISIBLE);
imv.setImageBitmap(result);
}else{
imv.setVisibility(View.GONE);
}
}
}
}
“sdcard/example/images”目录包含图像: 1.jpg、2.jpg、3.jpg、4.jpg、6.jpg、7.jpg和9.jpg。预期的结果是:
但是,如果我快速滚动列表,一些图像被插入到错误的项目中。这是由于在getView()方法中使用了convertView造成的。
如果我使用以下代码,代码可以正常工作:
//if(convertView == null){
// view = mInflater.inflate(mResource, null);
//}else{
// view = convertView;
//}
view = mInflater.inflate(mResource, null);
当列表快速滚动时,由于使用了convertView,两个asyncTasks可以引用同一个View。当视图不再可见时,如何取消AsyncTask?(并且正由ListView的另一项使用)
编辑
@Override
protected void onPostExecute(Bitmap result) {
if(result != null && imv != null){
if(imv.getTag().equals(path)){
imv.setVisibility(View.VISIBLE);
imv.setImageBitmap(result);
}else{
imv.setVisibility(View.GONE);
}
}else{
imv.setVisibility(View.GONE);
}
}
https://stackoverflow.com/questions/7729133
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