我遇到一个令人沮丧的问题，我在将自定义listview适配器设置为listview时遇到空指针异常。我无法弄清楚什么是null。我在应用程序的另一部分做了类似的事情，并没有任何问题。我不确定这个问题是否与这次使用图像有关？
以下是我的代码：
我正在获取数据并启动listview的片段类，（我已经成功测试了我的数据）
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Base64;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
public class FinalUnitStatusFragment extends Fragment {
Context finalUnitStatusContext;
Activity finalUnitStatusActivity;
ProgressDialog progressDialog;
//FinalUnitStatusListViewAdapter finalUnitStatusLVAdapter;
String ReadOnly;
String LexaUser;
String Password;
String SearchValue;
String finalResultFinalUS;
String HttpURLFinalUS = "https://[my/path/to/page]/getFinalUnitStatus.php";
HashMap<String, String> hashMapFinalUS = new HashMap<>();
HttpParse httpParseFinalUS = new HttpParse();
String[] Uid;
String[] Ustatus;
String[] Uqastandard;
String[] Ufinaloutcome;
String[] Ugencause;
String[] Uspeccause;
String[] Usurface;
String[] Uorigin;
String[] Ulexauser;
String[] Ulexausercomment;
String[] Urejphoto1String;
Bitmap[] Urejphoto1;
String[] Ulexausertimestamp;
String[] Uqauser;
String[] Uqacomment;
String[] Urejphoto2String;
Bitmap[] Urejphoto2;
String[] Uqausertimestamp;
ListView finalUSListView;
public FinalUnitStatusFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_siblings, container, false);
finalUSListView = (ListView) view.findViewById(R.id.FinalUnitStatusList);
finalUnitStatusContext = getContext();
finalUnitStatusActivity = getActivity();
if (getArguments() != null) {
SearchValue = getArguments().getString("SearchValue");
LexaUser = getArguments().getString("LexaUser");
getFinalUnitStatus(SearchValue, LexaUser);
} else {
Toast.makeText(finalUnitStatusContext, "Arguments Null", Toast.LENGTH_LONG).show();
}
return view;
}
public void getFinalUnitStatus(String searchInput, String lexaUser) {
class FinalUnitStatusClass extends AsyncTask<String,Void,String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = ProgressDialog.show(finalUnitStatusContext, "Loading Data", null, true, true);
}
@Override
protected void onPostExecute(String httpResponseMsg) {
super.onPostExecute(httpResponseMsg);
if (httpResponseMsg != null) {
try {
JSONArray json = new JSONArray(httpResponseMsg);
Uid = new String[json.length()];
Ustatus = new String[json.length()];
Uqastandard = new String[json.length()];
Ufinaloutcome = new String[json.length()];
Ugencause = new String[json.length()];
Uspeccause = new String[json.length()];
Usurface = new String[json.length()];
Uorigin = new String[json.length()];
Ulexauser = new String[json.length()];
Ulexausercomment = new String[json.length()];
Urejphoto1String = new String[json.length()];
Urejphoto1 = new Bitmap[json.length()];
Ulexausertimestamp = new String[json.length()];
Uqauser = new String[json.length()];
Uqacomment = new String[json.length()];
Urejphoto2String = new String[json.length()];
Urejphoto2 = new Bitmap[json.length()];
Uqausertimestamp = new String[json.length()];
for (int i = 0; i < json.length(); i++) {
JSONObject object = json.getJSONObject(i);
Uid[i] = object.getString("statusID");
Ustatus[i] = object.getString("unitStatus");
Uqastandard[i] = object.getString("qaStandard");
Ufinaloutcome[i] = object.getString("finalOutcome");
Ugencause[i] = object.getString("genCause");
Uspeccause[i] = object.getString("specCause");
Usurface[i] = object.getString("surface");
Uorigin[i] = object.getString("origin");
Ulexauser[i] = object.getString("lexaUser");
Ulexausercomment[i] = object.getString("initComment");
Urejphoto1String[i] = object.getString("rejImage1");
Ulexausertimestamp[i] = object.getString("addDate");
Uqauser[i] = object.getString("qaUser");
Uqacomment[i] = object.getString("qaComment");
Urejphoto2String[i] = object.getString("rejImage2");
Uqausertimestamp[i] = object.getString("qaAddDate");
if (Urejphoto1String.equals("Could not find image.")) {
String placeholder = "";
} else {
byte[] decodedString = Base64.decode(Urejphoto1String[i], Base64.DEFAULT);
Urejphoto1[i] = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);
}
if (Urejphoto2String.equals("Could not find image.")) {
String placeholder = "";
} else {
byte[] decodedString2 = Base64.decode(Urejphoto2String[i], Base64.DEFAULT);
Urejphoto2[i] = BitmapFactory.decodeByteArray(decodedString2, 0, decodedString2.length);
}
}
FinalUnitStatusListViewAdapter finalUSLVAdapter = new FinalUnitStatusListViewAdapter(finalUnitStatusActivity, Uid, Ustatus, Uqastandard, Ufinaloutcome, Ugencause, Uspeccause, Usurface, Uorigin, Ulexauser, Ulexausercomment, Urejphoto1, Ulexausertimestamp, Uqauser, Uqacomment, Urejphoto2, Uqausertimestamp);
if (finalUSLVAdapter != null) {
finalUSListView.setAdapter(finalUSLVAdapter);
} else {
Toast.makeText(finalUnitStatusContext, "Error: ListView Adapter is null", Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
Log.e("JSONException", "Error: " + e.toString());
Toast.makeText(finalUnitStatusContext, "Error: " + e.toString(), Toast.LENGTH_LONG).show();
} // catch (JSONException e)
progressDialog.dismiss();
} else {
progressDialog.dismiss();
Toast.makeText(finalUnitStatusContext, "HttpResponseMsg is null.", Toast.LENGTH_LONG).show();
}
}
@Override
protected String doInBackground(String... params) {
hashMapFinalUS.put("searchinput", params[0]);
hashMapFinalUS.put("lexauser", params[1]);
finalResultFinalUS = httpParseFinalUS.postRequest(hashMapFinalUS, HttpURLFinalUS);
return finalResultFinalUS;
}
}
FinalUnitStatusClass finalUnitStatusClass = new FinalUnitStatusClass();
finalUnitStatusClass.execute(searchInput, lexaUser);
}
}
我的自定义适配器：
package com.ltiws.www.lexaapp;
import android.app.Activity;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class FinalUnitStatusListViewAdapter extends BaseAdapter {
Activity context;
String Uid[];
String Ustatus[];
String Uqastandard[];
String Uresolution[];
String Ugencause[];
String UspecCause[];
String Usurface[];
String Uorigin[];
String Ulexauser[];
String Uinitcomment[];
Bitmap Urejphoto1[];
String Ulexausertimestamp[];
String Uqauser[];
String Uqacomment[];
Bitmap Urejphoto2[];
String Uqausertimestamp[];
public FinalUnitStatusListViewAdapter(Activity context, String[] Uid, String[] Ustatus, String[] Uqastandard, String[] Uresolution, String[] Ugencause, String[] UspecCause, String[] Usurface, String[] Uorigin, String[] Ulexauser, String[] Uinitcomment, Bitmap[] Urejphoto1, String[] Ulexausertimestamp, String[] Uqauser, String[] Uqacomment, Bitmap[] Urejphoto2, String[] Uqausertimestamp) {
super();
this.context = context;
this.Uid = Uid;
this.Ustatus = Ustatus;
this.Uqastandard = Uqastandard;
this.Uresolution = Uresolution;
this.Ugencause = Ugencause;
this.UspecCause = UspecCause;
this.Usurface = Usurface;
this.Uorigin = Uorigin;
this.Ulexauser = Ulexauser;
this.Uinitcomment = Uinitcomment;
this.Urejphoto1 = Urejphoto1;
this.Ulexausertimestamp = Ulexausertimestamp;
this.Uqauser = Uqauser;
this.Uqacomment = Uqacomment;
this.Urejphoto2 = Urejphoto2;
this.Uqausertimestamp = Uqausertimestamp;
}
public int getCount() {
// TODO Auto-generated method stub
return Uid.length;
}
public Object getItem(int position) {
// TODO Auto-generated method stub
return null;
}
public long getItemId(int position) {
// TODO Auto-generated method stub
return 0;
}
private class ViewHolder {
TextView txtViewUid;
TextView txtViewStatus;
TextView txtViewQAStandard;
TextView txtViewResolution;
TextView txtViewGenCause;
TextView txtViewSpecCause;
TextView txtViewSurface;
TextView txtViewOrigin;
TextView txtViewLexaUser;
TextView txtViewInitComment;
ImageView imageViewRejPhoto1;
TextView txtViewLexaUserTimestamp;
TextView txtViewQAUser;
TextView txtViewQAComment;
ImageView imageViewRejPhoto2;
TextView txtViewQAUserTimestamp;
}
public View getView(int position, View convertView2, ViewGroup parent)
{
// TODO Auto-generated method stub
FinalUnitStatusListViewAdapter.ViewHolder holder2;
LayoutInflater inflater = context.getLayoutInflater();
if (convertView2 == null)
{
convertView2 = inflater.inflate(R.layout.finalunitstatus_list, null);
holder2 = new FinalUnitStatusListViewAdapter.ViewHolder();
holder2.txtViewUid = (TextView) convertView2.findViewById(R.id.FinalStatusID);
holder2.txtViewStatus = (TextView) convertView2.findViewById(R.id.FinalStatus);
holder2.txtViewQAStandard = (TextView) convertView2.findViewById(R.id.FinalQAStandard);
holder2.txtViewResolution = (TextView) convertView2.findViewById(R.id.FinalResolution);
holder2.txtViewGenCause = (TextView) convertView2.findViewById(R.id.FinalGenCause);
holder2.txtViewSpecCause = (TextView) convertView2.findViewById(R.id.FinalSpecCause);
holder2.txtViewSurface = (TextView) convertView2.findViewById(R.id.FinalSurface);
holder2.txtViewOrigin = (TextView) convertView2.findViewById(R.id.FinalOrigin);
holder2.txtViewLexaUser = (TextView) convertView2.findViewById(R.id.FinalLexaUser);
holder2.txtViewInitComment = (TextView) convertView2.findViewById(R.id.FinalLexaUserComment);
holder2.imageViewRejPhoto1 = (ImageView) convertView2.findViewById(R.id.FinalLexaUserPhoto);
holder2.txtViewLexaUserTimestamp = (TextView) convertView2.findViewById(R.id.FinalLexaUserTimestamp);
holder2.txtViewQAUser = (TextView) convertView2.findViewById(R.id.FinalQAUser);
holder2.txtViewQAComment = (TextView) convertView2.findViewById(R.id.FinalQAUserComment);
holder2.imageViewRejPhoto2 = (ImageView) convertView2.findViewById(R.id.FinalQAUserPhoto);
holder2.txtViewQAUserTimestamp = (TextView) convertView2.findViewById(R.id.FinalQAUserTimestamp);
convertView2.setTag(holder2);
}
else
{
holder2 = (FinalUnitStatusListViewAdapter.ViewHolder) convertView2.getTag();
}
holder2.txtViewUid.setText(Uid[position]);
holder2.txtViewStatus.setText(Ustatus[position]);
holder2.txtViewQAStandard.setText(Uqastandard[position]);
holder2.txtViewResolution.setText(Uresolution[position]);
holder2.txtViewGenCause.setText(Ugencause[position]);
holder2.txtViewSpecCause.setText(UspecCause[position]);
holder2.txtViewSurface.setText(Usurface[position]);
holder2.txtViewOrigin.setText(Uorigin[position]);
holder2.txtViewLexaUser.setText(Ulexauser[position]);
holder2.txtViewInitComment.setText(Uinitcomment[position]);
holder2.imageViewRejPhoto1.setImageBitmap(Urejphoto1[position]);
holder2.txtViewLexaUserTimestamp.setText(Ulexausertimestamp[position]);
holder2.txtViewQAUser.setText(Uqauser[position]);
holder2.txtViewQAComment.setText(Uqacomment[position]);
holder2.imageViewRejPhoto2.setImageBitmap(Urejphoto2[position]);
holder2.txtViewQAUserTimestamp.setText(Uqausertimestamp[position]);
return convertView2;
}
}
我的堆栈跟踪：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: [package], PID: 25971
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.ltiws.www.lexaapp.FinalUnitStatusFragment$1FinalUnitStatusClass.onPostExecute(FinalUnitStatusFragment.java:168)
at com.ltiws.www.lexaapp.FinalUnitStatusFragment$1FinalUnitStatusClass.onPostExecute(FinalUnitStatusFragment.java:92)
at android.os.AsyncTask.finish(AsyncTask.java:660)
at android.os.AsyncTask.-wrap1(AsyncTask.java)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:677)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:159)
at android.app.ActivityThread.main(ActivityThread.java:6097)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
我的代码第168行导致中断：
finalUSListView.setAdapter(finalUSLVAdapter);
我似乎无法弄清楚我的适配器中的null是什么......
感谢所有帮助！谢谢！
答案 0 :(得分：3)
问题似乎是你的listview finalUSListView而不是适配器。 您确定使用正确的ID来夸大此视图吗？你能检查一下它是否被正确实例化了吗？
答案 1 :(得分：1)
Vinicius Sant'Ana是对的，你的listView为null，因为你使用大写的id绑定id
(ListView) view.findViewById(R.id.FinalUnitStatusList);
将xml中的引用和代码重命名为final_unit_status_list而不是
如果您想了解更多信息，请选中此项：
Why is it not possible to use uppercase in naming resources in android?
下次好的做法是在调试模式下启动应用程序并在错误行上添加断点，您将很快看到列表视图为空