我正在使用Universal Image Loader Libray，但我在这一行return imageUrls.length;得到NullPointerError这是我的代码，我正在尝试使用AsyncTask获取图像。有人可以帮帮我吗？
public class ImageGridFragment extends AbsListViewBaseFragment {
ProgressDialog mProgressDialog;
String results;
String jsonStr;
JSONObject jsonobjectdos;
JSONArray jsonarraydos;
ListView listview;
ArrayList<HashMap<String, String>> arraylist;
String[] elementos_proximos;
String mi_url;
ImageLoader imageLoader;
String[] imageUrls;
public static final int INDEX = 1;
DisplayImageOptions options;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
options = new DisplayImageOptions.Builder()
.showImageOnLoading(R.drawable.ic_stub)
.showImageForEmptyUri(R.drawable.ic_empty)
.showImageOnFail(R.drawable.ic_error)
.cacheInMemory(true)
.cacheOnDisk(true)
.considerExifParams(true)
.bitmapConfig(Bitmap.Config.RGB_565)
.build();
new DownloadJSONdos().execute();
}
//MIO PARA COGER IMÁGENES DINÁMICAMENTE
private class DownloadJSONdos extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(getActivity());
// Set progressdialog title
//mProgressDialog.setTitle("Android JSON Parse Tutorial");
// Set progressdialog message
mProgressDialog.setMessage("Actualizando...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create an array
elementos_proximos =new String[500];
// Retrieve JSON Objects from the given URL address
jsonobjectdos = JSONfunctions
.getJSONfromURL("myurl");
try {
// Locate the array name in JSON
if(jsonobjectdos == null)
return null;
jsonarraydos = jsonobjectdos.getJSONArray("results");
for (int i = 0; i < jsonarraydos.length(); i++) {
jsonobjectdos = jsonarraydos.getJSONObject(i);
// Retrive JSON Objects
mi_url= jsonobjectdos.getString("url");
elementos_proximos[i]=mi_url;
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void args) {
mProgressDialog.dismiss();
imageUrls= elementos_proximos;
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fr_image_grid, container, false);
listView = (GridView) rootView.findViewById(R.id.grid);
((GridView) listView).setAdapter(new ImageAdapter());
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
startImagePagerActivity(position);
}
});
return rootView;
}
public class ImageAdapter extends BaseAdapter {
private LayoutInflater inflater;
ImageAdapter() {
inflater = LayoutInflater.from(getActivity());
}
@Override
public int getCount() {
//return imageUrls.length;
return imageUrls.length;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final ViewHolder holder;
View view = convertView;
if (view == null) {
view = inflater.inflate(R.layout.item_grid_image, parent, false);
holder = new ViewHolder();
assert view != null;
holder.imageView = (ImageView) view.findViewById(R.id.image);
holder.progressBar = (ProgressBar) view.findViewById(R.id.progress);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
ImageLoader.getInstance()
.displayImage(imageUrls[position], holder.imageView, options, new SimpleImageLoadingListener() {
@Override
public void onLoadingStarted(String imageUri, View view) {
holder.progressBar.setProgress(0);
holder.progressBar.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
holder.progressBar.setVisibility(View.GONE);
}
@Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
holder.progressBar.setVisibility(View.GONE);
}
}, new ImageLoadingProgressListener() {
@Override
public void onProgressUpdate(String imageUri, View view, int current, int total) {
holder.progressBar.setProgress(Math.round(100.0f * current / total));
}
});
return view;
}
}
static class ViewHolder {
ImageView imageView;
ProgressBar progressBar;
}
}
这是我的日志猫
02-03 11:16:41.982: E/AndroidRuntime(24048): FATAL EXCEPTION: main
02-03 11:16:41.982: E/AndroidRuntime(24048): Process: com.nostra13.universalimageloader.sample, PID: 24048
02-03 11:16:41.982: E/AndroidRuntime(24048): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nostra13.universalimageloader.sample/com.nostra13.universalimageloader.sample.activity.SimpleImageActivity}: java.lang.NullPointerException
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread.access$800(ActivityThread.java:144)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.os.Handler.dispatchMessage(Handler.java:102)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.os.Looper.loop(Looper.java:136)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread.main(ActivityThread.java:5146)
02-03 11:16:41.982: E/AndroidRuntime(24048): at java.lang.reflect.Method.invokeNative(Native Method)
02-03 11:16:41.982: E/AndroidRuntime(24048): at java.lang.reflect.Method.invoke(Method.java:515)
02-03 11:16:41.982: E/AndroidRuntime(24048): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:796)
02-03 11:16:41.982: E/AndroidRuntime(24048): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:612)
02-03 11:16:41.982: E/AndroidRuntime(24048): at dalvik.system.NativeStart.main(Native Method)
02-03 11:16:41.982: E/AndroidRuntime(24048): Caused by: java.lang.NullPointerException
02-03 11:16:41.982: E/AndroidRuntime(24048): at com.nostra13.universalimageloader.sample.fragment.ImageGridFragment$ImageAdapter.getCount(ImageGridFragment.java:190)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.widget.GridView.setAdapter(GridView.java:186)
02-03 11:16:41.982: E/AndroidRuntime(24048): at com.nostra13.universalimageloader.sample.fragment.ImageGridFragment.onCreateView(ImageGridFragment.java:166)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1444)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:551)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.Activity.performStart(Activity.java:5241)
02-03 11:16:41.982: E/AndroidRuntime(24048): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)
02-03 11:16:41.982: E/AndroidRuntime(24048): ... 11 more
答案 0 :(得分：0)
((GridView) listView).setAdapter(new ImageAdapter());
在asyncTask的onPostExecute中调用它。基本上你是在创建imageUrls字符串数组之前制作适配器
答案 1 :(得分：0)
您的imageUrls正在AsyncTask的onPostExecute()中初始化;在后台线程完成任务执行之前，可能正在从主线程调用count()函数。