Question

大家好，我在使用NULL POINTER EXCEPTION时遇到了一些麻烦。只有当我第一次将小部件放在主屏幕上时才会出现错误。每次小部件都能正常工作。窗口小部件具有配置活动。此活动不会启动，而是调用窗口小部件提供程序中的onReceive并调用NULL POINTER EXCEPTION。任何人都能为我的问题提供一个好的解决方案吗？

我附加了配置活动和小部件提供程序类的代码。

小部件配置类：

public class SingleNoteConfigure extends ListActivity  {


private NotesDbAdapter mDbHelper;
int mAppWidgetId = AppWidgetManager.INVALID_APPWIDGET_ID;
public static String ACTION_WIDGET_LIST = "ActionReceiverList";
public static String ACTION_WIDGET_NEW = "ActionReceiverNew";



@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //set the result to canceled to allow the user
    //to change their mind mid widget configure
    setResult(RESULT_CANCELED);
    Log.d("MYTAG", "in the onCreate of of the widget configure");

    //set the layout file for the widget configure
    setContentView(R.layout.notes_list_config);

    //using the action bar title for user instruction
    setTitle("Select note to display on the wodget");

    // Find the widget id from the intent. 
    Intent intent = getIntent();
    Bundle extras = intent.getExtras();
    if (extras != null) {
        mAppWidgetId = extras.getInt(
                AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
    }
    Log.d("MYTAG", "in the onCreate");
    //stuff to get the database to open
    mDbHelper = new NotesDbAdapter(this);
    mDbHelper.open();

    //call the method that fills the list view
    fillData();

}

 @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        Cursor note = mDbHelper.fetchNote(id);
        startManagingCursor(note);
        String title = note.getString(note.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE));
        String text = note.getString(note.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY));



        RemoteViews views = new RemoteViews(this.getPackageName(), R.layout.singlenote_widget);
        AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this); 
        appWidgetManager.updateAppWidget(mAppWidgetId, views);    



        Log.d("MYTAG", "in the onListItemClick....");

        loadData(title, text, id);//here id is the row id of the selection;it is returned by the onListItemSelect 

        Intent resultValue = new Intent();
        resultValue.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, mAppWidgetId);            
        setResult(RESULT_OK,resultValue);   
        finish();
 }



 void loadData(String title, String text, Long Id) {

    AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(this); 
    Log.d("MYTAG", "in the load data....");
    SingleNote.updateWidget(this, appWidgetManager, mAppWidgetId, title, text);
    NotesDbAdapter.updateWidgetId(mAppWidgetId,Id);

}

private void fillData() {
    Cursor notesCursor = mDbHelper.fetchAllNotes();
    startManagingCursor(notesCursor);
    Log.d("MYTAG", "in the fill data  of the widget configure");
    // Create an array to specify the fields we want to display in the list (TITLE and DATE)
    String[] from = new String[]{NotesDbAdapter.KEY_TITLE,NotesDbAdapter.KEY_DATE};


    // and an array of the fields we want to bind those fields to (title and date)
    int[] to = new int[]{R.id.title,R.id.date};


    // Now create a simple cursor adapter and set it to display
    SimpleCursorAdapter notes = new SimpleCursorAdapter(this, R.layout.notes_row1, notesCursor, from, to);

    setListAdapter(notes);


}  
}

小部件提供类：

public class SingleNote extends AppWidgetProvider {

public static String UPDATE_ACTION = "ActionUpdateSinglenoteWidget";

private static NotesDbAdapter mDbHelper;



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

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

        Log.d("MYTAG", "in the onUpdate");

        Intent intent = new Intent(context, Notepadv3.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
        RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.singlenote_widget);
        views.setOnClickPendingIntent(R.id.single_note_text, pendingIntent);  

        // Push update for this widget to the home screen

        ComponentName thisWidget = new ComponentName(context, SingleNote.class);
        AppWidgetManager manager = AppWidgetManager.getInstance(context);
        manager.updateAppWidget(thisWidget, views);

    }
}

@Override 
public void onReceive(Context context, Intent intent) { 
    Log.d("MYTAG", "in the onReceive....");
        String action = intent.getAction(); 
        Log.d("MYTAG", "in the onReceive....line 2");
        Bundle extras = intent.getExtras(); 
        Log.d("MYTAG", "in the onReceive....after bundle");//THis gets in the log 
        String title = extras.getString("title");
        Log.d("MYTAG", "in the onReceive....after title");//Non of the other log entry's
                                                          // make it in 
        String text = extras.getString("body");
        Log.d("MYTAG", "in the onReceive....after text");
        Log.d("MYTAG", "@ the point of int");
        int id = extras.getInt("widget_id");

        Log.d("MYTAG", action+ title + text + id);

        if (action != null && action.equals(UPDATE_ACTION)) { 
            final AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context); 

            if (id > 0)
            {
                updateWidget(context, appWidgetManager, id ,title ,text);
            }
            else {
                return;

            }
    } 

    else { 
            super.onReceive(context, intent); 
    } 


}

static void updateWidget(Context context, AppWidgetManager appWidgetManager, int appWidgetId, String title, String text){

    Log.d("MYTAG", "in the updatewidget method in the siglenote widget....");
    RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.singlenote_widget);
    views.setTextViewText(R.id.single_note_title, title);
    views.setTextViewText(R.id.single_note_text, text);
    appWidgetManager.updateAppWidget(appWidgetId, views);



}
}

正如您所看到的，我在整个地方都有日志条目，并且我在日志条目结束时进行了评论。

此方法属于其中一个活动，我将其称为根据需要更新我的小部件。我在方法结尾处有一个“if（！null）”，这样就不会得到NULL POINTER EXCEPTION，但它似乎没有帮助

private void updateWidget() { 
    Cursor note = mDbHelper.fetchWidgetId(mRowId);
    startManagingCursor(note);
    Log.d("MYTAG", "in the updatewidget method in edit note");
    int id = note.getInt(note.getColumnIndexOrThrow(NotesDbAdapter.KEY_WIDGET_ID));//here id is the widget id we get out of the database
    Intent i = new Intent(this, SingleNote.class); 
    i.setAction(SingleNote.UPDATE_ACTION); 
    i.putExtra("title", mTitleText.getText().toString());
    i.putExtra("body", mBodyText.getText().toString());
    i.putExtra("widget_id",id);
    String title = mTitleText.getText().toString();
    //String body =  mBodyText.getText().toString();
    if(title != null){ 
    sendBroadcast(i); 
    }

编辑堆栈跟踪：

    07-12 04:08:36.473: E/STACKTRACE_TAG(2615): STACKTRACE
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615): java.lang.NullPointerException
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at drkstr.yan.SingleNote.onReceive(SingleNote.java:58)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.handleReceiver(ActivityThread.java:1994)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.access$2400(ActivityThread.java:132)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1093)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.os.Handler.dispatchMessage(Handler.java:99)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.os.Looper.loop(Looper.java:143)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.main(ActivityThread.java:4196)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at java.lang.reflect.Method.invokeNative(Native Method)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at java.lang.reflect.Method.invoke(Method.java:507)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    07-12 04:08:36.483: E/STACKTRACE_TAG(2615):     at dalvik.system.NativeStart.main(Native Method)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615): STACKTRACE
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615): java.lang.NullPointerException
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at drkstr.yan.SingleNote.onReceive(SingleNote.java:58)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.handleReceiver(ActivityThread.java:1994)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.access$2400(ActivityThread.java:132)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1093)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.os.Handler.dispatchMessage(Handler.java:99)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.os.Looper.loop(Looper.java:143)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at android.app.ActivityThread.main(ActivityThread.java:4196)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at java.lang.reflect.Method.invokeNative(Native Method)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at java.lang.reflect.Method.invoke(Method.java:507)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    07-12 04:08:45.483: E/STACKTRACE_TAG(2615):     at dalvik.system.NativeStart.main(Native Method)

以下是我的主要问题： 1.为什么只有在我全新安装应用程序后第一次放置小部件时才会发生这种情况？ 2.为什么在小部件配置之前调用onRecieve？ 3.最后我该如何解决它。

感谢您花时间阅读本文以及您可以提供的任何帮助。

Answer 1

您应注意的主要事项是NullPointerException位于SingleNote.java:58。

根据您对日志中显示哪些语句的评论，我猜extras为空，这意味着有no extras in the Intent。如果它只是第一次发生，这是有道理的。在使用之前检查额外内容。

首次启动Widget时Widget提供程序类中的NULL POINTER EXCEPTION

1 个答案: