2

嗨，这是我从用户词典中获取单词的代码。这是我的代码，但我无法运行它... 

private String getwordlist() {

        String[] mSelectionArgs={""};


    String[] mProjection ={UserDictionary.Words._ID, UserDictionary.Words.WORD, UserDictionary.Words.FREQUENCY};
    String mSelectionClause = null;

    String mSortOrder = null;

     mCursor = getContentResolver().query(
            UserDictionary.Words.CONTENT_URI,  // The content URI of the words table
            mProjection,                       // The columns to return for each row
            mSelectionClause,                // Either null, or the word the user entered
            mSelectionArgs,                    // Either empty, or the string the user entered
            mSortOrder);                      // The sort order for the returned rows


     if (mCursor.moveToFirst()) {            
            do {             
               String id = mCursor.getString(mCursor.getColumnIndex(UserDictionary.Words._ID));          
               String word = mCursor.getString(mCursor.getColumnIndex(UserDictionary.Words.WORD));
               String freq= mCursor.getString(mCursor.getColumnIndex(UserDictionary.Words.FREQUENCY));
               str=str+" id: "+id+"  word: "+"  frequency: "+freq+"\n";
               System.out.println(str);
            } while(mCursor.moveToNext());
            return str;
     }
     return null;        
}

我收到错误

12-06 18:49:58.586: E/AndroidRuntime(17174): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.ScrollView}: java.lang.IllegalArgumentException: Cannot bind argument at index 1 because the index is out of range.  The statement has 0 parameters.

这是什么错误..

4

2 回答 2

2

似乎当 mSelectionClause 为空时， mSelectionArgs 也需要为空。

// If the word is the empty string, gets everything
if (TextUtils.isEmpty(searchWord)) {
    // Setting the selection clause to null will return all words
    mSelectionClause = null;
    mSelectionArgs = null;
} else {
    // Constructs a selection clause that matches the word that the user entered
    mSelectionClause = UserDictionary.Words.WORD + " = ?";
    // Moves the user's input to the selection arguments
    mSelectionArgs = new String[] {searchWord};
}

// Does a query against the table and returns a Cursor object
Cursor cursor = getContentResolver().query(
    UserDictionary.Words.CONTENT_URI, // The content URI of the words table
    mProjection,                      // The columns to return for each row
    mSelectionClause,                 // Either null, or the word the user entered
    mSelectionArgs,                   // Either empty, or the string the user entered
    null);
于 2013-03-01T07:58:54.217 回答
0

我认为您的 do while 循环有缺陷。Content Provider 的开发人员文档 ( http://developer.android.com/guide/topics/providers/content-provider-basics.html#AltForms ) 提供了以下示例代码：

/*
 * Only executes if the cursor is valid. The User Dictionary Provider returns null if
 * an internal error occurs. Other providers may throw an Exception instead of returning null.
 */

if (mCursor != null) {
    /*
     * Moves to the next row in the cursor. Before the first movement in the cursor, the
     * "row pointer" is -1, and if you try to retrieve data at that position you will get an
     * exception.
     */
     while (mCursor.moveToNext()) {

        // Gets the value from the column.
        newWord = mCursor.getString(index);

        // Insert code here to process the retrieved word.

        ...

        // end of while loop
    }
} else {

    // Insert code here to report an error if the cursor is null or the provider threw an exception.
}

你能试着用这个逻辑来修改你的代码吗？

于 2014-10-17T16:28:32.903 回答