Question

我想查看SQLite数据库中存在数据的所有以前的用户滚动网后很多都无法实现任何目标

我为.setThreshold()

尝试了各种值

Android / java代码：

        dbHandler = new MyDBHandler(this, null, null, 1);
        mEmailView = (AutoCompleteTextView) findViewById(R.id.email);

        String[] previousUsers = dbHandler.getUseremails();

        ArrayAdapter<String> arrayAdapter1 = new ArrayAdapter<String>(this, android.R.layout.select_dialog_item, previousUsers);
        mEmailView.setThreshold(1);
        mEmailView.setAdapter(arrayAdapter1);

xml代码：

<AutoCompleteTextView
                    android:id="@+id/email"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="@string/prompt_email"
                    android:inputType="textEmailAddress"
                    android:maxLines="1"
                    android:singleLine="true" />

myDBHandler.java：

public class MyDBHandler extends SQLiteOpenHelper{

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "LoginDetails.db";
    private Context context;

    public static final String TABLE_PRODUCTS = "People";
    public static final String COLUME_ID = "_id";
    public static final String COLUME1_NAME = "_email";
    public static final String COLUME2_NAME = "_password";

    public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version)
    {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String query = "CREATE TABLE " + TABLE_PRODUCTS + "(" +
                COLUME_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUME1_NAME + " TEXT Unique, " +COLUME2_NAME + " TEXT " +
                ");";
        db.execSQL(query);
    }

    public String[] getUseremails()
    {
        String returnString[] = new String[20];
        String dbString = "";
        SQLiteDatabase db = getWritableDatabase();
        String query = "SELECT " + COLUME1_NAME +" FROM " + TABLE_PRODUCTS + ";";
        Cursor c = db.rawQuery(query, null);
        int i=0;
        if(c.moveToFirst())
        {
            do {
                dbString = String.format("%s", c.getString(c.getColumnIndex("_email")));
                returnString[i] = dbString;
                ++i;
                dbString = "";
            } while (c.moveToNext());
        }
        c.close();
        return returnString;
    }

加上奇怪的是，当我使用文本观察器填写密码时，只要自动填充条目与数据库中的密码相匹配，它就会从DB填充正确的密码。暗示DB中存在数据。

我希望单击文本框时列表会下拉。我也尝试使用onClickListener，但无法得到任何东西。

Answer 1

我认为，您的问题是，您正在将字符串数组传递给可能包含 null＆＃39; 的ArrayAdapter以及ArrayAdpater对此例外。除非你在人员表中有正好20行，否则20个定义的元素中的一些将不会被设置，因此为空。< / p>

如果您查看日志，很可能会发现类似的内容（这实际上并未使应用程序崩溃，因此您可能没有注意到它）： -

06-03 11:03:53.910 10422-10532/mjt.testvcsuse W/Filter: An exception occured during performFiltering()!
                                                        java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
                                                            at android.widget.ArrayAdapter$ArrayFilter.performFiltering(ArrayAdapter.java:480)
                                                            at android.widget.Filter$RequestHandler.handleMessage(Filter.java:234)
                                                            at android.os.Handler.dispatchMessage(Handler.java:102)
                                                            at android.os.Looper.loop(Looper.java:135)
                                                            at android.os.HandlerThread.run(HandlerThread.java:61)

其中一个解决方案是将字符串数组 returnString 设置为具有正确数量的元素，即元素数量与光标中的行数匹配。

这是 getUseremails 方法的修改版本，旧代码留在评论中（ PS我太懒了，无法包含格式< / em>的）。问题的真正关键在于使用 String returnString[] = new String[c.getCount()]; 来解决，它将数组元素的数量设置为行数（请注意，您应该检查一下如何处理行（或者只是采取行数）我的话，它是hanlded OK））： -

public String[] getUseremails() { //String returnString[] = new String[20]; //MUST BE 20 rows else nulls String dbString = ""; SQLiteDatabase db = getWritableDatabase(); String query = "SELECT " + COLUME1_NAME + " FROM " + TABLE_PRODUCTS + ";"; Cursor c = db.rawQuery(query, null); String returnString[] = new String[c.getCount()]; // # elements = rows int i = 0; while (c.moveToNext()) { returnString[i++] = c.getString( c.getColumnIndex(COLUME1_NAME) ); } /* OLD int i = 0; if (c.moveToFirst()) { do { dbString = String.format("%s", c.getString(c.getColumnIndex("_email"))); returnString[i] = dbString; ++i; dbString = ""; } while (c.moveToNext()); } */ c.close(); return returnString; }

自动填充功能下拉不起作用

1 个答案: