我有我的应用程序中的自定义列表视图。我使用http请求以JSON格式获取数据。有一个asynctask加载列表视图的全部数据(图像除外)。Android:无法实现懒惰列表视图上的搜索
在这个asyntask的onpostexecute()中,我调用另一个asynctask来获取listview的图像。
现在我想实现在使用textchangedlistener
的问题是与背景图像得到加载列表视图搜索功能,我经常碰到空指针异常。
任何人都可以建议我一种方法来摆脱这一点。我现在正在做的是,我没有显示搜索框edittext,直到加载图像。但是这会让用户等待很长时间,特别是对于长列表。
整个代码太长,无法发布。所以,我只是在这里粘贴它的简要提纲。如果你需要其他东西,请告诉我。我也会这样做。
public class abcd extends Activity {
ListView todlistview;
List<HashMap<String, Object>> cnt = null;
ArrayList<HashMap<String, Object>> searchResults;/
.
.
/** AsyncTask to parse json data and load ListView */
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
@Override
protected SimpleAdapter doInBackground(String... strJson) {
.
.
.
adapter = new SimpleAdapter(getBaseContext(), cnt, com.example.promoapp.R.layout.textviewfield, from, to);
return adapter;
}
@Override
protected void onPostExecute(SimpleAdapter adapter) {
searchResults=new ArrayList<HashMap<String, Object>> (cnt);
// Setting adapter for the listview
todlistview.setAdapter(adapter);
for(int i=0;i<adapter.getCount();i++){
HashMap<String, Object> hm = (HashMap<String, Object>) adapter.getItem(i);
.
.
ImageLoaderTask imageLoaderTask = new ImageLoaderTask();
// Starting ImageLoaderTask to download and populate image in the listview
imageLoaderTask.execute(hm);
}
}
}
/** AsyncTask to download and load an image in ListView */
private class ImageLoaderTask extends AsyncTask<HashMap<String, Object>, Void, HashMap<String, Object>>{
Dialog dil;
@Override
protected HashMap<String, Object> doInBackground(HashMap<String, Object>... hm) {
InputStream iStream=null;
.
// Create a hashmap object to store image path and its position in the listview
// Storing the path to the temporary image file
// Storing the position of the image in the listview
// Returning the HashMap object containing the image path and position
}
@Override
protected void onPostExecute(HashMap<String, Object> result) {
}
}
private TextWatcher filterTextWatcher = new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start, int before,
int count) {
String searchString=Search.getText().toString();
int textLength=searchString.length();
searchResults.clear();
for(int i=0;i<cnt.size();i++)
{
String placeName=cnt.get(i).get("country").toString();
if(textLength<=placeName.length()){
//compare the String in EditText with Names in the ArrayList
if(searchString.equalsIgnoreCase(placeName.substring(0,textLength))){
//Toast.makeText(getApplicationContext(),placeName,1).show();
searchResults.add(cnt.get(i));
}
}
}
String[] from = { "country","flag","details"};
int[] to = { com.example.promoapp.R.id.tv_country,com.example.promoapp.R.id.iv_flag,com.example.promoapp.R.id.tv_country_details};
adapter = new SimpleAdapter(getBaseContext(), searchResults, com.example.promoapp.R.layout.textviewfield, from, to);
todlistview.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
};
}
添加您的logcat错误! – Janmejoy 2013-03-26 15:00:56
除非您特别初始化cnt List和HashMaps以清空对象,否则value对象'Object'将为空。 – 2013-03-26 15:31:38
不幸的是,我打算几天后发布这个问题。我在代码中做了许多其他更改,现在正在发生其他错误并且没有logcat。 但我得到的错误是空指针异常..索引x与y的大小请求..我会尝试复制错误并发布logcat – ambit 2013-03-26 15:40:01