android - 首选项 api。设置摘要崩溃的方法

Question

如果我调用这个方法

（变量声明 public static SharedPreferences prefs = null;）

---

public void setManualycallResetCal(long time)
{   
    Preference calPrefCal = findPreference("callReset");
    callResetCal.setTimeInMillis(time);

    Date d = new Date(time);
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
    simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

    StringBuilder sumValue = new StringBuilder("Since :");
    sumValue.append(simpleDateFormat.format(d));
    calPrefCal.setSummary( sumValue.toString() );

    edit = prefs.edit();
    edit.putString("calDate", sumValue.toString() );
    edit.commit();
}

应用程序因空指针而崩溃是有线还是什么

错误：

        calPrefCal.setSummary( sumValue.toString() );

我的呼叫代码

if (Settings.prefs != null) {
        Calendar cal = Settings.callResetCal;
        Calendar comp = Calendar.getInstance();
        if (cal.getTimeInMillis() < comp.getTimeInMillis()) {
            int reset = Settings.callReset;
            Calendar end = Calendar.getInstance();
            end.setTimeInMillis(cal.getTimeInMillis());
            end.add(Calendar.DATE, reset);

            new Settings().setManualycallResetCal(end.getTimeInMillis());
        } // end if
    } // end if null check

---

如果我评论整个调用代码块，一切正常

---

整页代码

   package srinath.logger.app;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.os.Bundle;
import android.preference.Preference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceManager;
import android.widget.Toast;

public class Settings extends PreferenceActivity {

    private OnSharedPreferenceChangeListener listener;
    public static SharedPreferences prefs = null;
    static SharedPreferences.Editor edit = null;

    public static boolean callEnable;
    public static boolean callNotify;
    public static int callUpdate;
    public static int callReset; // sec

    // since
    public static Calendar callResetCal;
    public static int callUnits;
    public static int callLimit;
    //public static int unitPulse; // cost per unit of extra usage


    public static boolean dataEnable;
    public static boolean dataNotify;
    public static int dataUpdate;
    public static int dataReset; // sec
    public static Calendar dataResetCal;
    public static long dataUnits;
    public static long dataLimit;

    String dummy = "";

    public Settings() {
        // TODO Auto-generated constructor stub
    }

    public void setManualycallResetCal(long time)
    {   
        //
        Preference calPrefCal = findPreference("callReset");
        callResetCal.setTimeInMillis(time);

        Date d = new Date(time);
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
        simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

        StringBuilder sumValue = new StringBuilder("Since :");
        sumValue.append(simpleDateFormat.format(d));
        calPrefCal.setSummary( sumValue.toString() );

        prefs = Settings.this.getSharedPreferences("Prefs_Name", 
                MODE_WORLD_READABLE);
        edit = prefs.edit();
        edit.putString("calDate", sumValue.toString() );
        edit.commit();

        edit = prefs.edit();
        edit.putString("calDate", sumValue.toString() );
        edit.commit();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.settings);

        prefs = PreferenceManager.getDefaultSharedPreferences(this);
        Preference calPrefCal = findPreference("callReset");

        // set defaults to class variable   
        // array list stores in string format .. seems getInt cant parse

        // call

        callEnable = prefs.getBoolean("callEnable", false);
        //Log.d("callEnable","" + callEnable);

        callNotify = prefs.getBoolean("callNotify", false);
        //Log.d("notify","" + callNotify);

        dummy = prefs.getString("callUpdate", "0");
        callUpdate = Integer.parseInt(dummy);
        //Log.d("callUpdate","" + callUpdate);

        dummy = prefs.getString("callReset", "0");
        callReset = Integer.parseInt(dummy);
        //Log.d("callReset","" + callReset);

        callResetCal = Calendar.getInstance();

            if(prefs.getString("calDate", "0").equals("0")) // no pref with name calDate
            {
                Calendar cMain = Calendar.getInstance();
                cMain.setTimeInMillis(0);
                cMain.set(Calendar.DATE, callResetCal.get(Calendar.DATE));
                cMain.set(Calendar.MONTH, callResetCal.get(Calendar.MONTH));
                cMain.set(Calendar.YEAR, callResetCal.get(Calendar.YEAR));

                // set since
                callResetCal.setTimeInMillis(cMain.getTimeInMillis());

                // to print create date
                Date d = new Date(cMain.getTimeInMillis());
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
                simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

                StringBuilder sumValue = new StringBuilder("Since :");
                sumValue.append(simpleDateFormat.format(d));
                calPrefCal.setSummary( sumValue.toString() );

                edit = prefs.edit();
                edit.putString("calDate", sumValue.toString() );
                edit.commit();
            } // else set summary as of pref 
            else
            {
                calPrefCal.setSummary(prefs.getString("calDate", "0"));
            }

        dummy = prefs.getString("callUnits", "0");
        callUnits = Integer.parseInt(dummy);

        //Toast toast = Toast.makeText(getApplicationContext(), "" + dummy , Toast.LENGTH_SHORT);
        //toast.show();

        //Log.d("callUnits","" + callUnits);

        dummy = prefs.getString("callLimit", "0");
        callLimit = Integer.parseInt(dummy);
        //Log.d("callLimit","" + callLimit);

        // data

            dataEnable = prefs.getBoolean("dataEnable", false);

            dataNotify = prefs.getBoolean("dataNotify", false);

            dummy = prefs.getString("dataUpdate", "0");
            dataUpdate = Integer.parseInt(dummy);

            dummy = prefs.getString("dataReset", "0");
            dataReset = Integer.parseInt(dummy);

            dummy = prefs.getString("dataUnits", "0");
            dataUnits = Long.parseLong(dummy);

            dummy = prefs.getString("dataLimit", "0");
            dataLimit = Long.parseLong(dummy);

        // end


        // preference onChange listener

        listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
              public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {


                  //DEBUGGING ONLY

                  Toast toast = Toast.makeText(getApplicationContext(), "preferenceUpdate:DEBUG_ONLY", Toast.LENGTH_SHORT);
                  toast.show();


                    if(key.equals("callEnable"))
                    {
                        callEnable = prefs.getBoolean(key, false);
                    }
                    else if(key.equals("callNotify"))
                    {
                        callNotify = prefs.getBoolean(key, false);                      
                    }
                    else if(key.equals("callUpdate"))
                    {
                        dummy = prefs.getString(key, "0" );
                        callUpdate = Integer.parseInt(dummy);
                    }
                    else if(key.equals("callReset"))
                    {
                        Preference calPrefCal = findPreference(key);
                        dummy = prefs.getString(key, "0" );
                        callReset = Integer.parseInt(dummy);
                        callResetCal = Calendar.getInstance(); 

                        Calendar cMain = Calendar.getInstance();
                        cMain.setTimeInMillis(0);
                        cMain.set(Calendar.DATE, callResetCal.get(Calendar.DATE));
                        cMain.set(Calendar.MONTH, callResetCal.get(Calendar.MONTH));
                        cMain.set(Calendar.YEAR, callResetCal.get(Calendar.YEAR));
                        callResetCal.setTimeInMillis(cMain.getTimeInMillis());

                        // to print create date
                        Date d = new Date(cMain.getTimeInMillis());

                        SimpleDateFormat simpleDateFormat = new SimpleDateFormat();
                        simpleDateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

                        StringBuilder sumValue = new StringBuilder("Since :");
                        sumValue.append(simpleDateFormat.format(d));
                        calPrefCal.setSummary( sumValue.toString() );

                        edit = prefs.edit();
                        edit.putString("calDate", sumValue.toString() );
                        edit.commit();
                    }
                    else if(key.equals("callUnits"))
                    {
                        dummy = prefs.getString(key, "0" );
                        callUnits = Integer.parseInt(dummy);
                    }
                    else if(key.equals("callLimit"))
                    {                       
                        dummy = prefs.getString(key, "0" );
                        callLimit = Integer.parseInt(dummy);
                    }

                    // data

                    else if(key.equals("dataEnable"))
                    {
                        dataEnable = prefs.getBoolean(key, false);
                    }
                    else if(key.equals("dataNotify"))
                    {
                        dataNotify = prefs.getBoolean(key, false);                      
                    }
                    else if(key.equals("dataUpdate"))
                    {
                        dummy = prefs.getString(key, "0" );
                        dataUpdate = Integer.parseInt(dummy);
                    }
                    else if(key.equals("dataReset"))
                    {
                        dummy = prefs.getString(key, "0" );
                        dataReset = Integer.parseInt(dummy);
                        dataResetCal = Calendar.getInstance(); 
                    }
                    else if(key.equals("dataUnits"))
                    {
                        dummy = prefs.getString(key, "0" );
                        dataUnits = Long.parseLong(dummy);
                    }
                    else if(key.equals("dataLimit"))
                    {                       
                        dummy = prefs.getString(key, "0" );
                        dataLimit = Long.parseLong(dummy);
                    }


              } // end of 
        }; // end of 
        prefs.registerOnSharedPreferenceChangeListener(listener);

    }

}