android cursor 空指针异常，大神帮帮忙啊！！！毕设时间要截止了，如果愿意帮忙的话，可以发整个项目过去。。

05-11 16:34:46.221: E/AndroidRuntime(9331): FATAL EXCEPTION: main
05-11 16:34:46.221: E/AndroidRuntime(9331): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.my.call_guard/com.my.call_guard.ui.SecretInboxActivity}: java.lang.NullPointerException
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.os.Handler.dispatchMessage(Handler.java:99)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.os.Looper.loop(Looper.java:137)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-11 16:34:46.221: E/AndroidRuntime(9331): at java.lang.reflect.Method.invokeNative(Native Method)
05-11 16:34:46.221: E/AndroidRuntime(9331): at java.lang.reflect.Method.invoke(Method.java:511)
05-11 16:34:46.221: E/AndroidRuntime(9331): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-11 16:34:46.221: E/AndroidRuntime(9331): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-11 16:34:46.221: E/AndroidRuntime(9331): at dalvik.system.NativeStart.main(Native Method)
05-11 16:34:46.221: E/AndroidRuntime(9331): Caused by: java.lang.NullPointerException
05-11 16:34:46.221: E/AndroidRuntime(9331): at com.my.call_guard.ui.SecretInboxActivity.onCreate(SecretInboxActivity.java:36)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.Activity.performCreate(Activity.java:5104)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-11 16:34:46.221: E/AndroidRuntime(9331): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-11 16:34:46.221: E/AndroidRuntime(9331): ... 11 more



package com.my.call_guard.ui;

import com.my.call_guard.R;
import com.my.call_guard.dao.SecretSMSDao;
import com.my.call_guard.observer.SMSObserver;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;

public class SecretInboxActivity extends ListActivity {

private ItemAdapter adapter;
private ListView lv;
private Cursor cursor;
private Handler handler;
private SMSObserver sObserver;
private SecretSMSDao secretsmsdao;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listsmsinbox);
lv = (ListView) this.findViewById(android.R.id.list);
cursor = secretsmsdao.getAllSms();
adapter = new ItemAdapter(this);
lv.setAdapter(adapter);
lv.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
cursor.moveToPosition(arg2);
String body = cursor.getString(cursor.getColumnIndexOrThrow("body")).toString();
String address = cursor.getString(cursor.getColumnIndexOrThrow("address")).toString();
String time = cursor.getString(cursor.getColumnIndexOrThrow("address")).toString();

Bundle b = new Bundle();
b.putString("body", body);
b.putString("address", address);

Intent intent = new Intent(SecretInboxActivity.this,SMSDetailsActivity.class);
intent.putExtras(b);
startActivity(intent);
}

});

// register SMSObserve
handler = new Handler(){
public void handleMessage(Message msg){
if(msg.what == SMSObserver.SMS_CHANGE){
cursor = getContentResolver().query(Uri.parse("content://sms/inbox"), null, null, null, null);
adapter.notifyDataSetChanged();
}

}
};
sObserver = new SMSObserver(handler);
this.getContentResolver().registerContentObserver(Uri.parse("content://sms"), true, sObserver);}

public class ItemAdapter extends BaseAdapter {
Activity activity;

public ItemAdapter(Activity a) {
activity = a;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return cursor.getCount();
}

@Override
public Object getItem(int arg0) {
// TODO Auto-generated method stub
return cursor.getString(arg0);
}

@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return arg0;
}

@Override
public View getView(int arg0, View arg1, ViewGroup arg2) {
// TODO Auto-generated method stub
return composeItem(arg0);
}

private View composeItem(int position) {
cursor.moveToPosition(position);
String body = cursor
.getString(cursor.getColumnIndexOrThrow("body")).toString();
String number = cursor.getString(
cursor.getColumnIndexOrThrow("number")).toString();

LinearLayout item = (LinearLayout) activity.getLayoutInflater()
.inflate(R.layout.listsms_item, null);

LinearLayout l1 = (LinearLayout) item.getChildAt(0);

TextView tbody = (TextView) item.getChildAt(1);
if (tbody != null) {
tbody.setText(body);
}

TextView tnum = (TextView) l1.getChildAt(1);
if (tnum != null) {
tnum.setText(number);
}

ImageView image = (ImageView) l1.getChildAt(0);
image.setImageResource(R.drawable.message);

return item;
}

}
}

注意这两个地方，我能看出的错。。：
1:异常中说到的出错地点：05-11 16:34:46.221: E/AndroidRuntime(9331): at com.my.call_guard.ui.SecretInboxActivity.onCreate(SecretInboxActivity.java:36)
就是下面这句：
cursor = secretsmsdao.getAllSms();
2:以下是数据接口的方法，用于获得隐私空间数据库所有短信的cursor:
public Cursor getAllSms() {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor;
if (db.isOpen()) {
cursor=db.rawQuery("select number,body from secret_sms_table", null);
if(cursor.moveToFirst()){
Log.i(TAG,"OKLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL");
return cursor;
}else {
return null;
}
}else{
return null;}
}