一个有关Content Provider的有关问题

package com.chk.cp;import android.app.Activity;import android.content.ContentResolver;import android.database.Cursor;import android.os.Bundle;import android.provider.ContactsContract;import android.provider.ContactsContract.PhoneLookup;import android.widget.TextView;public class ContentProviderTestActivity extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        TextView tv = new TextView(this);        String string = "";        super.onCreate(savedInstanceState);        // 得到ContentResolver对象        ContentResolver cr = getContentResolver();        // 取得电话本中开始一项的光标        Cursor cursor = cr.query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null);        // 向下移动一下光标        while (cursor.moveToNext()) {            // 取得联系人名字            int nameFieldColumnIndex = cursor.getColumnIndex(PhoneLookup.DISPLAY_NAME);            String contact = cursor.getString(nameFieldColumnIndex);            // 取得电话号码            int numberFieldColumnIndex = cursor.getColumnIndex(PhoneLookup.NUMBER);            String number = cursor.getString(numberFieldColumnIndex);            string += (contact + ":" + number + "\n");        }        cursor.close();        // 设置TextView显示的内容        tv.setText(string);        // 显示到屏幕        setContentView(tv);    }}

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.chk.cp"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk android:minSdkVersion="15" /> <uses-permission     android:name="android.permission.READ_CONTACTS">    </uses-permission>    <application        android:icon="@drawable/ic_launcher"        android:label="@string/app_name" >        <activity            android:name=".ContentProviderTestActivity"            android:label="@string/app_name" >            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>

03-03 21:45:47.649: E/AndroidRuntime(883): FATAL EXCEPTION: main03-03 21:45:47.649: E/AndroidRuntime(883): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.chk.cp/com.chk.cp.ContentProviderTestActivity}: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread.access$600(ActivityThread.java:123)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.os.Handler.dispatchMessage(Handler.java:99)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.os.Looper.loop(Looper.java:137)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread.main(ActivityThread.java:4424)03-03 21:45:47.649: E/AndroidRuntime(883):     at java.lang.reflect.Method.invokeNative(Native Method)03-03 21:45:47.649: E/AndroidRuntime(883):     at java.lang.reflect.Method.invoke(Method.java:511)03-03 21:45:47.649: E/AndroidRuntime(883):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)03-03 21:45:47.649: E/AndroidRuntime(883):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)03-03 21:45:47.649: E/AndroidRuntime(883):     at dalvik.system.NativeStart.main(Native Method)03-03 21:45:47.649: E/AndroidRuntime(883): Caused by: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.03-03 21:45:47.649: E/AndroidRuntime(883):     at android.database.CursorWindow.nativeGetString(Native Method)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.database.CursorWindow.getString(CursorWindow.java:442)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.database.CursorWrapper.getString(CursorWrapper.java:114)03-03 21:45:47.649: E/AndroidRuntime(883):     at com.chk.cp.ContentProviderTestActivity.onCreate(ContentProviderTestActivity.java:29)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.Activity.performCreate(Activity.java:4465)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)03-03 21:45:47.649: E/AndroidRuntime(883):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)