我试图用AutoCompleteText和SimpleCusorAdapte工作检索SQLite数据库的数据。当我输入第一个字母AutoCompleteText它的秀的println需要消息的错误和不显示结果。但与此同时，我进入第二个字母，它的显示效果。为什么它发生，我怎么能解决这个问题？

这是logcat的

  W /过滤器：performFiltering过程中发生异常（）！显示java.lang.NullPointerException：需要的println消息在android.util.Log.println_native（本机方法）在android.util.Log.v（Log.java:121）在com.example.dilanka.ypbrothers.DbAdapter.fetchCustomersByName（DbAdapter.java:178）在com.example.dilanka.ypbrothers.CreateInvoice $ 3.runQuery（CreateInvoice.java:80）在android.widget.CursorAdapter.runQueryOnBackgroundThread（CursorAdapter.java:395）在android.widget.CursorFilter.performFiltering（CursorFilter.java:49）在android.widget.Filter $ RequestHandler.handleMessage（Filter.java:234）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:135）在android.os.HandlerThread.run（HandlerThread.java:61）P.S：DbAdapter.java：178  -  Log.v（TAG，inputText的）;    CreateInvoice.java:80  - 返回dbHelper.fetchCustomersByName（（约束= NULL constraint.toString（）：空）！？）; 

这是一些DbAdapter.java的code

 公共光标fetchCustomersByName（字符串inputText的）抛出的SQLException {    Log.v（TAG，inputText的）; //这是DbAdapter.java:178线    光标mCursor = NULL;    如果（inputText的== NULL || inputText.length（）== 0）{        mCursor = mDb.query（CusDet_TABLE，新的String [] {CusDet_COL_1，CusDet_COL_2，CusDet_COL_3，                        CusDet_COL_4，CusDet_COL_5，CusDet_COL_6，CusDet_COL_7，CusDet_COL_8}，                NULL，NULL，NULL，NULL，_name COLLATE NOCASE）;    }    其他{        mCursor = mDb.query（真，CusDet_TABLE，新的String [] {CusDet_COL_1，CusDet_COL_2，CusDet_COL_3，                        CusDet_COL_4，CusDet_COL_5，CusDet_COL_6，CusDet_COL_7，CusDet_COL_8}，                CusDet_COL_3 +LIKE'％+的inputText +％'，空，                NULL，NULL，_name COLLATE NOCASE，NULL）;    }    如果（mCursor！= NULL）{        mCursor.moveToFirst（）;    }    返回mCursor;} 

这是活动的code：

 最终诠释[]为= INT新[] {} android.R.id.text1;最终的String [] =由新的String [] {_name};dbHelper =新DbAdapter（本）;dbHelper.open（）;acTextView =（AutoCompleteTextView）findViewById（R.id.autoCompleteTextView）;SimpleCursorAdapter适配器=新SimpleCursorAdapter（        本，        android.R.layout.simple_dropdown_item_1line，        空值，        从，        至）;acTextView.setAdapter（适配器）;acTextView.setOnItemClickListener（新AdapterView.OnItemClickListener（）{    @覆盖    公共无效onItemClick（适配器视图＆LT;＆GT;母公司，观景，INT位置，长的id）{        光标光标=（光标）parent.getItemAtPosition（位置）;        字符串资本= cursor.getString（cursor.getColumnIndexOrThrow（_名））;    }}）;adapter.setCursorToStringConverter（新SimpleCursorAdapter.CursorToStringConverter（）{    @覆盖    公共CharSequence的convertToString（光标光标）{        最终诠释参数：columnIndex = cursor.getColumnIndexOrThrow（_名）;        最终字符串str = cursor.getString（参数：columnIndex）;        返回海峡;    }}）;adapter.setFilterQueryProvider（新FilterQueryProvider（）{    @覆盖    公共光标runQuery（CharSequence的约束）{        返回dbHelper.fetchCustomersByName（（约束= NULL constraint.toString（）：！NULL））; //这是CreateInvoice.java:80线    }}）; 

更新：我的问题还没解决。之后，我改变Log.v（TAG，inputText的）;到Log.v（TAG的inputText：+ inputText的）;在需要的println消息错误没有显示。但是当我输入一个字母的logcast秀的inputText：空，不显示一个字母的结果。根据现在的情况，我必须输入两个或多个字符得到的结果。如何解决呢？

  Log.v（TAG，inputText的）; //这是DbAdapter.java:178线 

您正在试图登录导致此异常的空消息。

将其更改为例如。

  Log.v（TAG的inputText：+ inputText的）; 

I am trying to work with AutoCompleteText and SimpleCusorAdapte to retrieve data from sqlite database. when I input first letter to AutoCompleteText it's show "Println Needs a Message" Error and doesn't show result. but at meantime I enter the second letter and it's show result. why that it happen and how can i solve this?

this is logcat

W/Filter: An exception occured during performFiltering()!
java.lang.NullPointerException: println needs a message
at android.util.Log.println_native(Native Method)
at android.util.Log.v(Log.java:121)
at com.example.dilanka.ypbrothers.DbAdapter.fetchCustomersByName(DbAdapter.java:178)
at com.example.dilanka.ypbrothers.CreateInvoice$3.runQuery(CreateInvoice.java:80)
at android.widget.CursorAdapter.runQueryOnBackgroundThread(CursorAdapter.java:395)
at android.widget.CursorFilter.performFiltering(CursorFilter.java:49)
at android.widget.Filter$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)


P.S:DbAdapter.java:178 - Log.v(TAG, inputText);
    CreateInvoice.java:80 - return dbHelper.fetchCustomersByName((constraint != null ? constraint.toString() : null));

This is some of code of DbAdapter.java

public Cursor fetchCustomersByName(String inputText) throws SQLException {
    Log.v(TAG, inputText); //This is DbAdapter.java:178 line
    Cursor mCursor = null;
    if (inputText == null  ||  inputText.length () == 0)  {
        mCursor = mDb.query(CusDet_TABLE, new String[] {CusDet_COL_1,CusDet_COL_2, CusDet_COL_3,
                        CusDet_COL_4, CusDet_COL_5, CusDet_COL_6, CusDet_COL_7, CusDet_COL_8},
                null, null, null, null, " _name COLLATE NOCASE");

    }
    else {
        mCursor = mDb.query(true, CusDet_TABLE, new String[] {CusDet_COL_1,CusDet_COL_2, CusDet_COL_3,
                        CusDet_COL_4, CusDet_COL_5, CusDet_COL_6, CusDet_COL_7, CusDet_COL_8},
                CusDet_COL_3 + " like '%" + inputText + "%'", null,
                null, null, " _name COLLATE NOCASE",null);
    }
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;

}

This is code of Activity:

final int[] to = new int[] { android.R.id.text1 };
final String[] from = new String[] { "_name" };
dbHelper = new DbAdapter(this);
dbHelper.open();

acTextView = (AutoCompleteTextView) findViewById(R.id.autoCompleteTextView);
SimpleCursorAdapter adapter = new SimpleCursorAdapter(
        this,
        android.R.layout.simple_dropdown_item_1line,
        null,
        from,
        to);

acTextView.setAdapter(adapter);
acTextView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Cursor cursor = (Cursor) parent.getItemAtPosition(position);
        String capital = cursor.getString(cursor.getColumnIndexOrThrow("_name"));
    }
});
adapter.setCursorToStringConverter(new SimpleCursorAdapter.CursorToStringConverter() {
    @Override
    public CharSequence convertToString(Cursor cursor) {
        final int columnIndex = cursor.getColumnIndexOrThrow("_name");
        final String str = cursor.getString(columnIndex);
        return str;
    }
});
adapter.setFilterQueryProvider(new FilterQueryProvider() {
    @Override
    public Cursor runQuery(CharSequence constraint) {
        return dbHelper.fetchCustomersByName((constraint != null ? constraint.toString() : null));//This is CreateInvoice.java:80 line
    }
});

Update: My problem hasn't solved yet. After i change Log.v(TAG, inputText); to Log.v(TAG, "inputText:" + inputText); the "Println Needs a Message" error isn't show. but when I input one letter the logcast show "inputText: null" and doesn't show result for one letter. according to now situation i have to enter two or more than character to get result. how can i solve that?

Log.v(TAG, inputText); //This is DbAdapter.java:178 line

You're attempting to log a null message that causes this exception.

Change it to e.g.

Log.v(TAG, "inputText:" + inputText);