您好我从服务器获取数据并存储在sqlite中并显示内部滑动选项卡是动态的。我有时会收到错误，有时候它会正常工作。我不明白为什么会发生崩溃。我试图调试但找不到问题。需要帮助来解决这个问题。
这里是异步任务代码。
class JSONAsyncTask extends AsyncTask<String, Void, Boolean> implements
OnClickListener {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected Boolean doInBackground(String... urls) {
InputStream inputStream = null;
HttpURLConnection urlConnection = null;
try {
// ------------------>>
URL url = new URL(urls[0]);
urlConnection = (HttpURLConnection) url.openConnection();
/* optional request header */
urlConnection.setRequestProperty("Content-Type",
"application/json");
/* optional request header */
urlConnection.setRequestProperty("Accept", "application/json");
/* for Get request */
urlConnection.setRequestMethod("GET");
int statusCode = urlConnection.getResponseCode();
if (statusCode == 200) {
inputStream = new BufferedInputStream(
urlConnection.getInputStream());
String response = convertInputStreamToString(inputStream);
JSONObject jsono = new JSONObject(response);
JSONArray jarray = jsono.getJSONArray("product");
for (int i = 0; i < jarray.length(); i++) {
JSONObject feedObj = jarray.getJSONObject(i);
// Actors actor = new Actors();
CartItem item = new CartItem();
item.setQuantity("0");
item.setProductName(feedObj.optString("post_title"));
item.setPrice(feedObj.optString("post_excerpt"));
item.setProductPrice(feedObj.optString("meta_value"));
item.setProductId(ids);
item.setProdId(feedObj.optString("ID"));
item.setProductTotalPrice("0");
item.setImage(feedObj.optString("image_url"));
mHelper.addProduct(item);
System.out.println("Database price : "+item.getProductPrice());
}
return true;
}
// ------------------>>
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return false;
}
protected void onPostExecute(Boolean result) {
if (result == false) {
recyclerView.setVisibility(View.GONE);
fhfgh.setVisibility(View.VISIBLE);
} else {
listAdapter = new FeedListAdapter(getActivity(), mHelper.getAllProducts(ids));// Error on this line.
recyclerView.setAdapter(listAdapter);
listAdapter.setOnAddNum(this);
listAdapter.setOnSubNum(this);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(
getActivity()));
}
}
这是logcat
05-20 12:08:26.308: E/AndroidRuntime(8564): FATAL EXCEPTION: main
05-20 12:08:26.308: E/AndroidRuntime(8564): java.lang.NullPointerException
05-20 12:08:26.308: E/AndroidRuntime(8564): at com.grotap.adapter.FeedListAdapter.<init>(FeedListAdapter.java:47)
05-20 12:08:26.308: E/AndroidRuntime(8564): at com.grotap.activity.MyFragment$JSONAsyncTask.onPostExecute(MyFragment.java:350)
05-20 12:08:26.308: E/AndroidRuntime(8564): at com.grotap.activity.MyFragment$JSONAsyncTask.onPostExecute(MyFragment.java:1)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.os.AsyncTask.finish(AsyncTask.java:631)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.os.AsyncTask.access$600(AsyncTask.java:177)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.os.Handler.dispatchMessage(Handler.java:99)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.os.Looper.loop(Looper.java:137)
05-20 12:08:26.308: E/AndroidRuntime(8564): at android.app.ActivityThread.main(ActivityThread.java:5283)
05-20 12:08:26.308: E/AndroidRuntime(8564): at java.lang.reflect.Method.invokeNative(Native Method)
05-20 12:08:26.308: E/AndroidRuntime(8564): at java.lang.reflect.Method.invoke(Method.java:511)
05-20 12:08:26.308: E/AndroidRuntime(8564): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
05-20 12:08:26.308: E/AndroidRuntime(8564): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
05-20 12:08:26.308: E/AndroidRuntime(8564): at dalvik.system.NativeStart.main(Native Method)
这是适配器类
public class FeedListAdapter extends
RecyclerView.Adapter<FeedListAdapter.ViewHolder> {
private Activity activity;
private LayoutInflater inflater;
private ArrayList<CartItem> feedItems;
private ArrayList<CartItem> filteredfeedItems;
ImageView plus;
ImageView minus;
String result;
String formattedDate;
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
int id;
private TextView prices;
private View.OnClickListener onAddNum;
private View.OnClickListener onSubNum;
public FeedListAdapter(Activity activity, ArrayList<CartItem> feedItems) {
this.activity = activity;
this.feedItems = feedItems;
this.filteredfeedItems = feedItems;
inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void setOnAddNum(View.OnClickListener onAddNum) {
this.onAddNum = onAddNum;
}
public void setOnSubNum(View.OnClickListener onSubNum) {
this.onSubNum = onSubNum;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(
R.layout.feed_item, parent, false);
prices = (TextView) v.findViewById(R.id.timestamp2);
ViewHolder viewHolder = new ViewHolder(v);
if (imageLoader == null)
imageLoader = AppController.getInstance().getImageLoader();
// setupClickableViews(v, viewHolder);
return viewHolder;
}
@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
CartItem item = (CartItem) filteredfeedItems.get(position);
holder.name.setText(item.getProductName());
holder.assignTo.setText(item.getPrice());
String rupee = activity.getResources().getString(R.string.Rs);
holder.price.setText(rupee+" "+item.getProductPrice());
holder.location.setText((String.valueOf(item.getQuantity())) + "");
holder.plus.setTag(item.getId());
holder.plus.setFocusable(true);
holder.plus.setClickable(true);
holder.plus.setOnClickListener(onAddNum);
holder.minus.setTag(item.getId());
holder.minus.setOnClickListener(onSubNum);
holder.profilePic.setImageUrl(item.getImage(), imageLoader);
holder.profilePic.setDefaultImageResId(R.mipmap.ic_launcher);
holder.profilePic.setErrorImageResId(R.mipmap.ic_launcher);
//Picasso.with(activity).load(item.getImage()).into(holder.profilePic);
}
/*private void displayImage(int adapterPosition) {
// TODO Auto-generated method stub
LayoutInflater inflater = activity.getLayoutInflater();
View offer = inflater.inflate(R.layout.prompts, null);
AlertDialog.Builder alert = new AlertDialog.Builder(activity);
alert.setView(offer);
alert.setCancelable(true);
final AlertDialog dialog = alert.create();
int width = (int)(activity.getResources().getDisplayMetrics().widthPixels*0.80);
int height = (int)(activity.getResources().getDisplayMetrics().heightPixels*0.50);
dialog.show();
dialog.getWindow().setLayout(width, height);
dialog.setCanceledOnTouchOutside(true);
dialog.setCancelable(true);
CartItem item = (CartItem) filteredfeedItems.get(adapterPosition);
NetworkImageView viewOffer = (NetworkImageView)offer.findViewById(R.id.viewOffer);
viewOffer.setImageUrl(item.getImage(),imageLoader);
viewOffer.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
dialog.dismiss();
}
});
}*/
@Override
public int getItemCount() {
return filteredfeedItems.size();
}
public long getItemId(int position) {
return position;
}
class ViewHolder extends RecyclerView.ViewHolder {
ImageView plus;
ImageView minus;
NetworkImageView profilePic;
TextView name;
TextView price;
TextView assignTo;
TextView location;
public ViewHolder(View vi) {
super(vi);
name = (TextView) vi.findViewById(R.id.name);
price = (TextView) vi.findViewById(R.id.price);
assignTo = (TextView) vi.findViewById(R.id.timestamp);
location = (TextView) vi.findViewById(R.id.timestamp2);
plus = (ImageView) vi.findViewById(R.id.btnAddToCart1);
profilePic = (NetworkImageView) vi.findViewById(R.id.profilePic);
minus = (ImageView) vi.findViewById(R.id.btnAddToCart5);
}
}
}
这是getAllProducts
public ArrayList<CartItem> getAllProducts(String ids) {
SQLiteDatabase db = this.getReadableDatabase();
ArrayList<CartItem> cityList = null;
try{
cityList = new ArrayList<CartItem>();
String QUERY = "SELECT * FROM "+TABLE_NAME+ " WHERE " +KEY_PRODUCT_ID
+ " = '" + ids + "'";
Cursor cursor = db.rawQuery(QUERY, null);
if(!cursor.isLast())
{
while (cursor.moveToNext())
{
CartItem city = new CartItem();
city.setId(cursor.getInt(0));
city.setQuantity(cursor.getString(1));
city.setProductName(cursor.getString(2));
city.setPrice(cursor.getString(3));
city.setProductPrice(cursor.getString(4));
city.setProductId(cursor.getString(5));
city.setProductTotalPrice(cursor.getString(6));
city.setImage(cursor.getString(7));
city.setProdId(cursor.getString(8));
cityList.add(city);
}
}
db.close();
}catch (Exception e){
Log.e("error",e+"");
}
return cityList;
}
答案 0 :(得分：1)
在onPostExecute()方法中，您拨打getActivity()。此方法返回null，因为您的片段尚未附加到活动。确保仅在片段调用getActivity()后才能调用onAttach()。