小贝子编程

Android NullPointerException when setting ListView Adapter



我遇到了一个令人沮丧的问题，即在将自定义列表视图适配器设置为列表视图时出现空指针异常。我无法弄清楚什么是空的。我在应用程序的另一部分做了类似的事情，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？

下面是我的代码：

我正在获取数据并启动列表视图的片段类(我已经成功测试了我正在获取数据(

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)

我的代码的第 168 行导致中断：

finalUSListView.setAdapter(finalUSLVAdapter);

我似乎无法弄清楚我的适配器中什么是空的......

感谢所有帮助！谢谢！

问题似乎出在您的列表视图最终USListView上，而不是适配器上。 您确定使用正确的 id 来膨胀此视图吗？你能检查它是否已正确实例化吗？

Vinicius Sant' Ana 是对的，你的 listView 是空的，因为你使用大写 id 来绑定 id

(ListView) view.findViewById(R.id.FinalUnitStatusList);

将xml 和代码中的引用重命名为final_unit_status_list

如果您想了解更多信息，请检查这一点：

为什么在 android 中命名资源时不能使用大写？

下次要做的一件好事是在调试模式下启动您的应用程序并在错误行上添加一个断点，您将很快看到您的列表视图为 null

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