从其他活动中调用时，Android中的Sharedpreferences返回null [英] Sharedpreferences in Android returns null when called from another activity

问题描述

我进行了两项活动，一项用于小部件，另一项用于设置活动.

I made two activities, one for the widget and one for the settings activity.

有两个变量"strSavedMem1"&在设置活动中初始化的"strSavedMem1" ...是通过sharedPreference方法创建的.

There are two variables "strSavedMem1" & "strSavedMem1" initialised in the settings activity... and are made via sharedPreference method.

但是当我尝试在小部件活动中使用该变量时，该变量返回一个空"值.

But when I try to use the variable in widget activity, the variable return a "null" value.

小部件活动:

package com.eightbitcloud.example.widget;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Calendar;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Handler;
import android.preference.PreferenceManager;
import android.util.Log;
import android.widget.RemoteViews;

import com.shashank.pingwidget.R;

public class ExampleAppWidgetProvider extends AppWidgetProvider {
private static final String LOG_TAG = "Ping_Widget";
private static Handler handler;
static String currentTime = null ;
public String strSavedMem1;
public String strSavedMem2;
public static final String PREFS_NAME="LocalePrefs";



/**
 * Custom Intent name that is used by the AlarmManager to tell us to update the               clock once per second.
 */
public static String PING_WIDGET_UPDATE =    "com.eightbitcloud.example.widget.8BITCLOCK_WIDGET_UPDATE";

@Override
public void onReceive(Context context, Intent intent) {
    super.onReceive(context, intent);


    if (PING_WIDGET_UPDATE.equals(intent.getAction())) {
        Log.d(LOG_TAG, "Clock update");
        // Get the widget manager and ids for this widget provider, then call the shared
        // clock update method.
        ComponentName thisAppWidget = new        ComponentName(context.getPackageName(), getClass().getName());
        AppWidgetManager appWidgetManager =   AppWidgetManager.getInstance(context);
        int ids[] = appWidgetManager.getAppWidgetIds(thisAppWidget);
        for (int appWidgetID: ids) {
            updateAppWidget(context, appWidgetManager, appWidgetID);

        }
    }
}

private PendingIntent createClockTickIntent(Context context) {
    Intent intent = new Intent(PING_WIDGET_UPDATE);
    PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent,     PendingIntent.FLAG_UPDATE_CURRENT);

    return pendingIntent;
}

@Override
public void onDisabled(Context context) {
    super.onDisabled(context);
    Log.d(LOG_TAG, "Widget Provider disabled. Turning off timer");
    AlarmManager alarmManager = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
    alarmManager.cancel(createClockTickIntent(context));    
}

@Override 
public void onEnabled(Context context) {
    super.onEnabled(context);


SharedPreferences sharedPreferences = context.getSharedPreferences(PREFS_NAME,0);
    strSavedMem1 = sharedPreferences.getString("MEM1", null);
    if (strSavedMem1 == null) {
        strSavedMem1="google.com";
          Log.d(getClass().getSimpleName(),"MEM1 name is: "+ strSavedMem1);
    } 


    strSavedMem2 = sharedPreferences.getString("MEM1", null);
    if (strSavedMem2 == null) {
        strSavedMem2 = "1";
        Log.d(getClass().getSimpleName(),"MEM2 name is: "+ strSavedMem2);
    } 


    Log.d(LOG_TAG, "Widget Provider enabled.  Starting timer to update widget every second");
    AlarmManager alarmManager = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());
    calendar.add(Calendar.SECOND, 30);
    alarmManager.setRepeating(AlarmManager.RTC, calendar.getTimeInMillis(), 50000, createClockTickIntent(context));
}


@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
    final int N = appWidgetIds.length;


    Log.d(LOG_TAG, "Updating Example Widgets.");

    // Perform this loop procedure for each App Widget that belongs to this
    // provider
    for (int i = 0; i < N; i++) {
        int appWidgetId = appWidgetIds[i];

        // Create an Intent to launch ExampleActivity
        Intent intent = new Intent(context, WidgetExampleActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);

        // Get the layout for the App Widget and attach an on-click listener
        // to the button
        RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.widget1);
        views.setOnClickPendingIntent(R.id.button, pendingIntent);
        // Tell the AppWidgetManager to perform an update on the current app
        // widget
        appWidgetManager.updateAppWidget(appWidgetId, views);


        // Update The clock label using a shared method
        updateAppWidget(context, appWidgetManager, appWidgetId);
    }
}

public  void updateAppWidget(final Context context, final AppWidgetManager appWidgetManager, final int appWidgetId) {
    //String currentTime =  df.format(new Date());
    handler = new Handler();




    Runnable runnable = new Runnable() {

        @Override
        public void run() {


            try {
                String pingCmd = "ping -c 3 " + "google.com";
                String pingResult = "";
                Runtime r = Runtime.getRuntime();
                Process p = r.exec(pingCmd);
                BufferedReader in = new BufferedReader(new
                InputStreamReader(p.getInputStream()));
                String inputLine;
                while ((inputLine = in.readLine()) != null) {
                System.out.println(inputLine);
                currentTime = inputLine + "\n";
                pingResult += inputLine+ "\n";
                currentTime = pingResult ;
                }
                in.close();
                }//try
                catch (IOException e) {
                System.out.println(e);
                }


                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        //progress.setProgress(value);
                        RemoteViews updateViews = new RemoteViews(context.getPackageName(), R.layout.widget1);
                        updateViews.setTextViewText(R.id.widget1label, currentTime+"\n"+ strSavedMem1+"\n"+strSavedMem2);
                        appWidgetManager.updateAppWidget(appWidgetId, updateViews); 


                    }
                });
        }

    };
    new Thread(runnable).start();

    }
}

设置活动为:

package com.eightbitcloud.example.widget;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.shashank.pingwidget.R;

public class WidgetExampleActivity extends Activity {
public static final String PREFS_NAME="LocalePrefs";
public Context ctx = null;
EditText editText1, editText2;
TextView textSavedMem1, textSavedMem2;
Button buttonSaveMem1, buttonSaveMem2;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

     textSavedMem1 = (TextView)findViewById(R.id.savedmem1);
       textSavedMem2 = (TextView)findViewById(R.id.savedmem2);
       editText1 = (EditText)findViewById(R.id.edittext1);
       editText2 = (EditText)findViewById(R.id.edittext2);
       buttonSaveMem1 = (Button)findViewById(R.id.save_mem1);
       buttonSaveMem2 = (Button)findViewById(R.id.save_mem2);

       buttonSaveMem1.setOnClickListener(buttonSaveMem1OnClickListener);
       buttonSaveMem2.setOnClickListener(buttonSaveMem2OnClickListener);

       LoadPreferences();
   }

   Button.OnClickListener buttonSaveMem1OnClickListener
    = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   SavePreferences("MEM1", editText1.getText().toString());
   LoadPreferences();
  }

   };

   Button.OnClickListener buttonSaveMem2OnClickListener = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   SavePreferences("MEM2", editText2.getText().toString());
   LoadPreferences();
  }

   };


  private void SavePreferences(String key, String value){

    SharedPreferences sharedPreferences = getSharedPreferences(PREFS_NAME,MODE_WORLD_READABLE);


        /*SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putString(key, value);
        editor.commit();*/

        //SharedPreferences sharedPreferences =PreferenceManager.getDefaultSharedPreferences(WidgetExampleActivity.this);

      //SharedPreferences sharedPreferences = getSharedPreferences(PREFS_NAME,  MODE_WORLD_READABLE);


        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putString(key, value);
        editor.commit();
       }

       public void LoadPreferences(){

    //  SharedPreferences sharedPreferences = ctx.getSharedPreferences(PREFS_NAME, MODE_WORLD_READABLE);
        SharedPreferences sharedPreferences = getSharedPreferences(PREFS_NAME,  MODE_WORLD_READABLE);

        String strSavedMem1 = sharedPreferences.getString("MEM1", "google.com");
        String strSavedMem2 = sharedPreferences.getString("MEM2", "1");
        textSavedMem1.setText(strSavedMem1);
        textSavedMem2.setText(strSavedMem2);

        strSavedMem1 = sharedPreferences.getString("MEM1", null);
        if (strSavedMem1 == null) {
            strSavedMem1="google.com";
              Log.d(getClass().getSimpleName(),"Wallpaper name is: "+ strSavedMem1);
        } 


        strSavedMem2 = sharedPreferences.getString("MEM1", null);
        if (strSavedMem2 == null) {
            strSavedMem2 = "1";
            Log.d(getClass().getSimpleName(),"Wallpaper name is: "+ strSavedMem2);
        }

       }

}

推荐答案

您应该

• 检查提交是否有效并返回true.
• 使用MODE_PRIVATE(作为常量而不是其值)以相同的方式打开两个SharedPreferences

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