光标数据在数据库中添加了两次

Question

在Android应用程序中，我想获取我正在使用内容观察者的调用日志。点击按钮我想看到通话记录。但是当我第一次运行此程序并在模拟器上进行调用时，记录会成功添加并显示在listview中。但是当我再次拨打电话时，最新的记录被插入两次，同样listview显示2次最新记录和一次旧记录。

请指导我哪里出错？真的需要尽快完成它。 感谢名单！

    package com.callloglist;



import static com.callloglist.Constants.KEY_ContactName;
import static com.callloglist.Constants.KEY_ContactNum;
import static com.callloglist.Constants.KEY_CurrTime;
import static com.callloglist.Constants.KEY_Date;
import static com.callloglist.Constants.KEY_Duration;
import static com.callloglist.Constants.KEY_NumType;
import static com.callloglist.Constants.TABLE_NAME;

import java.text.SimpleDateFormat;

import java.util.Date;

import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.content.ContentValues;
import android.database.ContentObserver;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;

public class MainActivity extends Activity {

    private Helper helper  = new Helper(this);
    private SimpleCursorAdapter dataAdapter; 
    private ListView listview;

     SQLiteDatabase db;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main); this.getApplicationContext()
        .getContentResolver()
        .registerContentObserver(
                android.provider.CallLog.Calls.CONTENT_URI, true,
                new CallLogObserver(new Handler()));




     Button Btn = (Button) findViewById(R.id.button1);


     Btn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View view) {
            // TODO Auto-generated method stub



    SQLiteDatabase db = helper.getReadableDatabase();


    Cursor c = db.query(TABLE_NAME, null, null, null, null, null, KEY_Date + " DESC");


    final   String[] columns = new String[]{KEY_ContactName,KEY_Date,KEY_Duration,};
    final    int[] to = new int[]{R.id.textView1,R.id.textView2,R.id.textView3};

 dataAdapter= new SimpleCursorAdapter(getApplicationContext(), R.layout.log_layout, c,    columns, to);

listview = (ListView) findViewById(R.id.list_view1);
      // Assign adapter to ListView11
      listview.setAdapter(dataAdapter);
        }
    });
    }



public void addLog() {




    db = helper.getWritableDatabase();

        Cursor cursor = getContentResolver().query(
                android.provider.CallLog.Calls.CONTENT_URI, null, null, null,
                android.provider.CallLog.Calls.DATE + " DESC ");

         cursor.moveToFirst();

        // TODO Auto-generated method stub


    int numberColumnId = cursor.getColumnIndex(android.provider.CallLog.Calls.NUMBER);
    int durationId = cursor.getColumnIndex(android.provider.CallLog.Calls.DURATION);
    int contactNameId = cursor.getColumnIndex(android.provider.CallLog.Calls.CACHED_NAME);
    int dateId = cursor.getColumnIndex(android.provider.CallLog.Calls.DATE);
   int numTypeId = cursor.getColumnIndex(android.provider.CallLog.Calls.CACHED_NUMBER_TYPE);

    Date dt = new Date();
    int hours = dt.getHours();
    int minutes = dt.getMinutes();
    int seconds = dt.getSeconds();
    String currTime = hours + ":" + minutes + ":" + seconds;


            String contactNumber = cursor.getString(numberColumnId);
            String contactName = cursor.getString(contactNameId);
            String duration = cursor.getString(durationId);
            String callDate = cursor.getString(dateId);

            SimpleDateFormat formatter = new SimpleDateFormat(
                    "dd-MMM-yyyy HH:mm");
            String dateString = formatter.format(new Date(Long
                    .parseLong(callDate)));
           String numType = cursor.getString(numTypeId);

            ContentValues values = new ContentValues();
            values.put(KEY_ContactName, contactName);
       values.put(KEY_NumType, numType);
            values.put(KEY_ContactNum, contactNumber);
            values.put(KEY_Duration, duration);
            values.put(KEY_Date, dateString);
          values.put(KEY_CurrTime, currTime);

        db.insert(TABLE_NAME, null, values);
             cursor.close();   
          db.close();

    Toast.makeText(getBaseContext(), "Inserted!", Toast.LENGTH_LONG).show();


    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }


    public class CallLogObserver extends ContentObserver
    {



        public CallLogObserver(Handler handler) {
            super(handler);
            // TODO Auto-generated constructor stub
        }


          @Override
            public boolean deliverSelfNotifications() {
                return true;
            }

            @Override
            public void onChange(boolean selfChange) {
                Log.d("LOG_TAG", "MyContentObserver.onChange( " + selfChange
                        + ")");
                super.onChange(selfChange);
                addLog();


            }

}
}