列表视图中的空指针异常？
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【中文标题】列表视图中的空指针异常？【英文标题】：null pointer exception in list view? 【发布时间】：2011-12-24 07:23:00 【问题描述】：你好，我正在尝试检索联系人姓名及其类型。我想将它们放在列表视图中，但在名称和电话类型数组以及列表视图中获取空值。任何帮助都会很重要。谢谢提前。
package application.test;
import android.app.Activity;
import android.content.ContentResolver;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.provider.ContactsContract.CommonDataKinds.Phone;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public final class TestActivity extends Activity
String[] name;
String[] phoneType;
ListView lv;
String s[];
@Override
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
testGetContacts();
lv = (ListView)findViewById(R.id.listview);
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[] ContactsContract.Contacts._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()];
while (cur.moveToNext())
int i=0;
String id = cur.getString(indexID);
null--> name[i] = cur.getString(indexName);
null--> phoneType[i] = cur.getString(indexPhoneType);
String temp="id="+id+"-name="+name[i]+"-phoneType="+phoneType[i];
s[i]=temp;
i++;
//while
catch(Exception e)
e.printStackTrace();
//catch
//if
//method
Logcat：
11-08 15:21:45.250: WARN/System.err(1049): java.lang.NullPointerException
11-08 15:21:45.250: WARN/System.err(1049): at application.test.TestActivity.testGetContacts(TestActivity.java:60)
11-08 15:21:45.270: WARN/System.err(1049): at application.test.TestActivity.onCreate(TestActivity.java:23)
11-08 15:21:45.270: WARN/System.err(1049): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-08 15:21:45.270: WARN/System.err(1049): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
11-08 15:21:45.270: WARN/System.err(1049): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-08 15:21:45.270: WARN/System.err(1049): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-08 15:21:45.270: WARN/System.err(1049): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-08 15:21:45.279: WARN/System.err(1049): at android.os.Handler.dispatchMessage(Handler.java:99)
11-08 15:21:45.290: WARN/System.err(1049): at android.os.Looper.loop(Looper.java:123)
11-08 15:21:45.290: WARN/System.err(1049): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-08 15:21:45.290: WARN/System.err(1049): at java.lang.reflect.Method.invokeNative(Native Method)
11-08 15:21:45.290: WARN/System.err(1049): at java.lang.reflect.Method.invoke(Method.java:521)
11-08 15:21:45.290: WARN/System.err(1049): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-08 15:21:45.290: WARN/System.err(1049): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-08 15:21:45.300: WARN/System.err(1049): at dalvik.system.NativeStart.main(Native Method)
11-08 15:21:45.300: DEBUG/AndroidRuntime(1049): Shutting down VM
11-08 15:21:45.300: WARN/dalvikvm(1049): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): FATAL EXCEPTION: main
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): java.lang.RuntimeException: Unable to start activity ComponentInfoapplication.test/application.test.TestActivity: java.lang.NullPointerException
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.os.Handler.dispatchMessage(Handler.java:99)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.os.Looper.loop(Looper.java:123)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at java.lang.reflect.Method.invokeNative(Native Method)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at java.lang.reflect.Method.invoke(Method.java:521)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at dalvik.system.NativeStart.main(Native Method)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): Caused by: java.lang.NullPointerException
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at java.util.Arrays$ArrayList.<init>(Arrays.java:49)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at java.util.Arrays.asList(Arrays.java:171)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:125)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at application.test.TestActivity.onCreate(TestActivity.java:26)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
11-08 15:21:45.349: ERROR/AndroidRuntime(1049): ... 11 more
11-08 15:21:45.380: WARN/ActivityManager(58): Force finishing activity application.test/.TestActivity
11-08 15:21:45.911: WARN/ActivityManager(58): Activity pause timeout for HistoryRecord44f48960 application.test/.TestActivity
11-08 15:21:47.029: DEBUG/SntpClient(58): request time failed: java.net.SocketException: Address family not supported by protocol
11-08 15:21:56.575: WARN/ActivityManager(58): Activity destroy timeout for HistoryRecord44f48960 application.test/.TestActivity
【问题讨论】：
在你的 main.xml 布局中是 R.id.listview 吗？ 请附上您的堆栈跟踪。 是的，我的 xml 文件中有这个。schemas.android.com/apk/res/android" android:orientation= "垂直" android:layout_ android:layout_> 什么是堆栈跟踪。你在说日志猫吗。 正确检查您在 indexName 和 indexphonetype 中获得的整数值。这些值可能为空，因此 cur.getString(indexName) 值为空...请发布您的堆栈跟踪以回答更多.. 【参考方案1】：移动
int i = 0;
在循环之外（在它之前）
【讨论】：
是的，那是我想的错误。现在获取列表，但是当我在下拉列表时用完联系人时，应用程序会强制关闭【参考方案2】：如下初始化String数组名和phoneType
String[] name=new String[5];//5 is size of String array
String[] phoneType=new String[5]; //5 is size of String array
【讨论】：
【参考方案3】：尝试使用：
String[] projection = new String[] Data._ID,
ContactsContract.Contacts.DISPLAY_NAME, Phone.TYPE;
Cursor cur = cr.query(ContactsContract.Data.CONTENT_URI,
projection, null, null, null);
编辑：我刚刚意识到这与this one...
您可以尝试以下方法：
1) 创建一个类来表示 1 个条目：
public class ContactsEntry
String contactId;
String contactName;
String phoneType;
public String getContactId()
return contactId;
public void setContactId(String contactId)
this.contactId = contactId;
public String getContactName()
return contactName;
public void setContactName(String contactName)
this.contactName = contactName;
public String getPhoneType()
return phoneType;
public void setPhoneType(String phoneType)
this.phoneType = phoneType;
比你的代码：
while (cur.moveToNext())
String id = cur.getString(indexID);
String name = cur.getString(indexName);
String phoneType = cur.getString(indexPhoneType);
ContactsEntry entry = new ContactsEntry();
entry.setContactId(id);
entry.setContactName(name);
entry.setPhoneType(phoneType);
//// do some logging or whatever.
【讨论】：
我试过了，但在这两行中都获取了联系人姓名：Log.d("name",entry.getContactName()); Log.d("phoneType",entry.getPhoneType()); 如果您使用了错误的设置方法或错误的列索引，请检查您的代码。我已经在我的 CallLogs 电话数据库上对此进行了测试，它正确地获取了所有数据字段。 我需要问一件事，做 indexId、indexName 和 indexPhoneType，需要有一个值，因为它们在初始化时分别获取值 0,1,2.. 这些是包含在光标中的列索引号（它们应该具有不同的值）。这些数字意味着，包含您的 ID 的列的索引为 0，包含名称的列的索引为 1，依此类推。 知道为什么 setter 和 getter 方法运行 20 次，尽管我的 AVD 中只存储了 10 个联系人.....【参考方案4】： private void testGetContacts()
ContentResolver cr = getContentResolver();
String[] projection = new String[] ContactsContract.Contacts._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);
int count = cur.getCount();
name = new String[count];
phoneType = new String[count];
s = new String[count];
int i = 0;
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] = temp;
i = i + 1;
// while
catch (Exception e)
e.printStackTrace();
// catch
// if
// method
-
您忘记初始化字符串数组
你的计数不正确
【讨论】：
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