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getting null pointer exception?

由 。_饼干妹妹 提交于 2019-12-18 09:47:35

问题


I am trying to have name of contacts in one array and their types in another array,but can't get through with null pointer exception.here is my code.I have pointed out the line where I am getting null pointer exception.please help..thanks in advance.

package application.test;
import android.app.Activity;
import android.content.ContentResolver;
import android.database.Cursor;
import android.database.SQLException;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.provider.ContactsContract.CommonDataKinds.Phone;  
import android.provider.ContactsContract.Contacts.Data;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.RelativeLayout;

public final class TestActivity extends Activity {
String[] name;
String[] phoneType;
ListView lv;
ListViewAdapter lva;


    public static final String TAG = "ContactManager";
@Override
public void onCreate(Bundle savedInstanceState)
{
    Log.v(TAG, "Activity State: onCreate()");
    super.onCreate(savedInstanceState);
    LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.WRAP_CONTENT);        
    LinearLayout mainLayout=new LinearLayout(this);
    mainLayout.setOrientation(LinearLayout.VERTICAL);               
    LayoutInflater layoutInflater = getLayoutInflater();        
    mainLayout.addView(layoutInflater.inflate(R.layout.main,null));
    mainLayout.addView(layoutInflater.inflate(R.layout.extra,null));

    this.addContentView(mainLayout, params);

      lv = (ListView)findViewById(android.R.id.list);
     lva = new ListViewAdapter(this,name,phoneType); 
    lv.setAdapter(lva);
    testGetContacts();
}


private void testGetContacts() { 

        ContentResolver cr = getContentResolver();

        String[] projection = new String[] { Data._ID,
                ContactsContract.Contacts.DISPLAY_NAME, Phone.TYPE}; 

        Cursor cur = cr.query(ContactsContract.Data.CONTENT_URI,
                projection, null, null, null); 


        if (cur != null && cur.moveToFirst()) { 

        try {

            int indexID =  cur.getColumnIndexOrThrow(ContactsContract.Contacts._ID);
            int indexName = cur.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME);
             int indexPhoneType = cur.getColumnIndexOrThrow(Phone.TYPE);

          while (cur.moveToNext()) {
             int  i=1;
              String id = cur.getString(indexID);    
 //HERE LIES NULL POINTER EXCEPTION   name[i] = cur.getString(indexName);  
 //HERE TOO              phoneType[i] =  cur.getString(indexPhoneType);

             i++;


              System.out.println(id + "\n");
              System.out.println(name + "\n");
              System.out.println(phoneType + "\n");


          }


        } catch (SQLException sqle) {
           //handling exception       
        } finally { 
         if (!cur.isClosed()) {
             cur.close();
         }     
     }

        }

}
}

回答1:


Initialize String[] name before using it. You can do that like:

name=new String[cur.getCount()];
String s="";
while (cur.moveToNext()) {

     int  i=1;
     String id = cur.getString(indexID);    
     name[i] = cur.getString(indexName);  
     phoneType[i] =  cur.getString(indexPhoneType);         

     //System.out.println(id + "\n");
     //System.out.println(name + "\n");
     //System.out.println(phoneType + "\n");

     s=s+"id="+id+" name="+name[i]+" phoneType="+phoneType[i]+"\n";
     i++;
}
Toast.makeText(getApplicationContext(),i+" - "+s).show();

Edit :

Create an xml file in layout folder.

main.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical" >    

    <ListView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/listview"
        android:cacheColorHint="#0000"
        />
</LinearLayout>

now in your TestActivity.class:

public final class TestActivity extends Activity {

String[] name;
String[] phoneType;
ListView lv;
String s[];
public static final String TAG = "ContactManager";

@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.id.main);        

    testGetContacts();

    lv = (ListView)findViewById(R.id.listview);
    ArrayAdapter<String> sa=new ArrayAdapter<String>(context, android.R.layout.simple_list_item_1,s);
    lv.setAdapter(sa);        
}


private void testGetContacts() { 

    ContentResolver cr = getContentResolver();    
    String[] projection = new String[] { Data._ID,
                ContactsContract.Contacts.DISPLAY_NAME, Phone.TYPE};     
    Cursor cur = cr.query(ContactsContract.Data.CONTENT_URI,
                projection, null, null, null);     

    if (cur != null && cur.moveToFirst()) { 

        try {

            int indexID =  cur.getColumnIndexOrThrow(ContactsContract.Contacts._ID);
            int indexName = cur.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME);
             int indexPhoneType = cur.getColumnIndexOrThrow(Phone.TYPE);

          name=new String[cur.getCount()];
          s=new String[cur.getCount()];

          while (cur.moveToNext()) {

               int  i=1;
               String id = cur.getString(indexID);    
               name[i-1] = cur.getString(indexName);  
               phoneType[i-1] =  cur.getString(indexPhoneType);       


              String temp="id="+id+"-name="+name[i-1]+"-phoneType="+phoneType[i-1];
              s[i-1]=temp;
              i++;
}

}




回答2:


You're not initializing your String[] name, so when you try to access it, you get a null pointer exception. I would suggest using more meaningful variable names. 'name' is very ambiguous.




回答3:


Your name and phone arrays have not been initialized.

String[] name = new String[EXPECTED_SIZE];
String[] phoneType = new String[EXPECTED_SIZE];

Any proper IDE should tell you that before you try to run it. Are you using Eclipse or IntelliJ? You should!




回答4:


You are getting null pointer because you are accessing wrong index.

try this:

s=new String[cur.getCount()];
int  i=1;
while (cur.moveToNext()) {    

                   String id = cur.getString(indexID);    
                   name[i-1] = cur.getString(indexName);  
                   phoneType[i-1] =  cur.getString(indexPhoneType);       


                  String temp="id="+id+"-name="+name[i-1]+"-phoneType="+phoneType[i-1];
                  s[i-1]=temp;
                  i++;
    }

and also lv=(ListView)findViewById(R.id.listview); instead of lv=(ListView)findViewById(android.R.id.list);

You should add a condition here:

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);      
       testGetContacts();

if(s.length()>0)
{
    lv = (ListView)findViewById(R.id.listview);
    ArrayAdapter<String> sa=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,s);
    lv.setAdapter(sa);
}
else
{
   Toast.makeText(getApplicationContext(),"Nothing Found",Toast.LENGTH_SHORT).show();
}



回答5:


Try this and tell me i it helped: 

  @Override
        public void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);        

            lv = (ListView)findViewById(R.id.listview);
            testGetContacts();
            ArrayAdapter<String> sa=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,s);
              lv.setAdapter(sa);        

        }//method


        private void testGetContacts() { 

            ContentResolver cr = getContentResolver();    
            String[] projection = new String[] { Data._ID,
                        ContactsContract.Contacts.DISPLAY_NAME, Phone.TYPE};     
            Cursor cur = cr.query(ContactsContract.Data.CONTENT_URI,
                        projection, null, null, null);     

            if (cur != null && cur.moveToFirst()) { 

                try {

                    int indexID =  cur.getColumnIndexOrThrow(ContactsContract.Contacts._ID);
                    int indexName = cur.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME);
                     int indexPhoneType = cur.getColumnIndexOrThrow(Phone.TYPE);

                  name=new String[cur.getCount()];
                  phoneType=new String[cur.getCount()];
                  s=new String[cur.getCount()];
                  int  i=1;
                  while (cur.moveToNext()) {

                       String id = cur.getString(indexID);    
                       name[i] = cur.getString(indexName);  
                       phoneType[i] =  cur.getString(indexPhoneType);       


                      String temp="id="+id+"-name="+name[i]+"-phoneType="+phoneType[i];
                      s[i-1]=temp;
                      i++;                  
                   }//while
             ArrayAdapter<String> sa=new ArrayAdapter<String>(getApplicationContext(),               android.R.layout.simple_list_item_1,s);
             lv.setAdapter(sa);
             }catch(Exception e){

        e.printStackTrace();    
            }//catch

            }//if

        }//method


来源：https://stackoverflow.com/questions/8036850/getting-null-pointer-exception

标签
android
nullpointerexception
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