Question

i have a spinner an two buttons on my Android app,

the spinner is populated dynamicaly from server-side script.

it works last time, but i don’t know why now i’m having a java.NullPointerException problem and i don’t know how to fix it, the log from LogCat said that i’m having null on my spinner

first, this is my complete script on FormPilihLokasiKelompok.class

package com.nigmagrid.jm.demo;

import java.util.ArrayList;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;
import android.widget.AdapterView.OnItemSelectedListener;

public class FormPilihLokasiKelompok extends Activity {

    ArrayList<String> content;
    ArrayAdapter<String> content_adapter;
    Button btn_save, btn_back;
    Context context;
    String selected_value, spinner_prompt, toast_failed, url_retrieval;
    Spinner spinner;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.form_pilih_lokasi_kelompok);

        btn_save = (Button) findViewById(R.id.btn_save);
        btn_back = (Button) findViewById(R.id.btn_back);
        spinner = (Spinner) findViewById(R.id.spinner);

        context = FormPilihLokasiKelompok.this;

        selected_value = "";
        spinner_prompt = "Pilih Lokasi";
        toast_failed = "Tidak ada lokasi yang terpilih";

        url_retrieval = VarsUrl.getServerAddress()+"get_list.php?table=kelompok_lokasi";

        content = new ArrayList<String>();

        btn_back.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                finish();
            }
        });

        btn_save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(selected_value.length() > 1){
                    Intent intent = new Intent(getApplicationContext(), FormPilihLokasiKm.class);
                    intent.putExtra("content", selected_value);
                    startActivity(intent);
                }else{
                    Toast.makeText(getApplicationContext(), toast_failed, Toast.LENGTH_SHORT).show();
                }
            }
        });

        spinner.setPrompt(spinner_prompt);
        spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
                String sel_val = spinner.getSelectedItem().toString();
                if(sel_val != null || sel_val.length() > 0){
                    selected_value = spinner.getSelectedItem().toString();
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {
                // do nothing
            }

        });

        new PopulateSpinner().execute(url_retrieval);

    }

    protected class PopulateSpinner extends AsyncTask<String, Void, String>{

        ProgressDialog pd = new ProgressDialog(context);

        protected void onPreExecute(){
            pd.setMessage("Mengambil data...");
        }

        @Override
        protected String doInBackground(String... arg0) {
            try{
                String response = CustomHttpClient.excecuteHttpGet(arg0[0]);
                String res = response.toString().trim();
                return res;             
            }catch (Exception e){
                return e.toString();
            }
        }

        protected void onPostExecute(String res){
            String[] datanya = res.split("#", 0);
            int jumlah_data = datanya.length;
            if(datanya[0].equals("1")){
                try{
                    content.clear();
                    for(int i = 1; i < jumlah_data; i++){
                        content.add(datanya[i]);
                    }

                    content_adapter = new ArrayAdapter<String>(context, android.R.layout.simple_spinner_item, content);
                    content_adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                    spinner.setAdapter(content_adapter);

                }catch(Exception e){
                    Toast.makeText(getApplicationContext(), "Terjadi kesalahan sistem\n"+e.toString(), Toast.LENGTH_SHORT).show();
                }
            }else{
                content.add("Tidak ada data untuk ditampilkan");                
            }

            content_adapter = new ArrayAdapter<String>(context, android.R.layout.simple_spinner_item, content);
            content_adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(content_adapter);

            pd.dismiss();
        }
    }

}

Here’s the Log

11-23 12:49:57.179: W/dalvikvm(22610): threadid=1: thread exiting with uncaught exception (group=0x40015578)
11-23 12:49:57.187: E/AndroidRuntime(22610): FATAL EXCEPTION: main
11-23 12:49:57.187: E/AndroidRuntime(22610): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nigmagrid.jm.demo/com.nigmagrid.jm.demo.FormPilihLokasiKelompok}: java.lang.NullPointerException
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.os.Looper.loop(Looper.java:123)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread.main(ActivityThread.java:3687)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at java.lang.reflect.Method.invokeNative(Native Method)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at java.lang.reflect.Method.invoke(Method.java:507)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at dalvik.system.NativeStart.main(Native Method)
11-23 12:49:57.187: E/AndroidRuntime(22610): Caused by: java.lang.NullPointerException
11-23 12:49:57.187: E/AndroidRuntime(22610):    at com.nigmagrid.jm.demo.FormPilihLokasiKelompok.onCreate(FormPilihLokasiKelompok.java:68)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-23 12:49:57.187: E/AndroidRuntime(22610):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
11-23 12:49:57.187: E/AndroidRuntime(22610):    ... 11 more

this script was on line 68 : spinner.setPrompt(spinner_prompt);

i’ve change the spinner_prompt to normal string like “test prompt” but it’s still same
so it must be the spinner (cmiiw) and i don’t know where i should fix it.

anybody knows how to fix it?
thanks

update
here’s my layout

<?xml version="1.0" encoding="utf-8"?>
<ScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">

        <TextView 
            android:text="Lokasi"
            android:padding="5dip"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />
        <Spinner
            android:id="@+id/spinner"
            android:padding="5dip"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />
        <Button
            android:id="@+id/btn_save"
            android:text="Lanjutkan"
            android:padding="5dip"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />

        <Button
            android:id="@+id/btn_back"
            android:text="Kembali"
            android:padding="5dip"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" />

    </LinearLayout>
</ScrollView>

Answer 1

perhaps you may need to regenerate your R.java file… using eclipse, go to “Project -> Clean” and select your project. Then build your project again. maybe you even need to restart eclipse during those steps.

I’ve had this issue happen when it was working just fine before and suddenly stopped working after i did some un-related thing.