Question

今天我想在我的消息应用程序中实现一个简单的SQLite数据库来处理保存消息，遗憾的是我无法从数据库中读回数据并将它们显示到ListView中。

我在模拟器上通过ADB查看数据库，我看到数据已正确保存。

这是我的代码

使用空列初始化TABLE

db.execSQL("CREATE TABLE IF NOT EXISTS Messages(zero);");

使用聊天联系人作为列名创建列

public void addMessagetoDB(String message, String from) {
    Toast.makeText(this.getApplicationContext(), "msg msg", Toast.LENGTH_LONG).show();
    try
    {
        db.execSQL("ALTER TABLE Messages ADD COLUMN '" + from + "' TEXT");
    }
    catch (android.database.sqlite.SQLiteException e)
    {

    }
    db.execSQL("INSERT INTO Messages ('" + from + "') VALUES('" + message + "');");
}

在这里我还可以看到SQLite识别我的列名，因为当我向客户端发送多条消息时，我收到调试消息

E/SQLiteLog﹕ (1) duplicate column name: test@zapp.org

这是我的读数无效

public void updateView(String from) {
        Cursor crs = zapp.rawQuery("SELECT * FROM Messages", null);
        while (crs.moveToNext()) {
            String name = crs.getString(crs.getColumnIndex(from));
            messages.add(name);
        }
        arrayAdapter.notifyDataSetChanged();
}

这是我的例外

06-05 22:15:45.841    4926-4926/? E/SQLiteCursor﹕ requesting column name with table name -- test@zapp.org
    java.lang.Exception
            at android.database.sqlite.SQLiteCursor.getColumnIndex(SQLiteCursor.java:180)
            at org.reisacher.zapp.ChatActivity.updateView(ChatActivity.java:43)
            at org.reisacher.zapp.MainActivity$1.onItemClick(MainActivity.java:52)
            at android.widget.AdapterView.performItemClick(AdapterView.java:305)
            at android.widget.AbsListView.performItemClick(AbsListView.java:1146)
            at android.widget.AbsListView$PerformClick.run(AbsListView.java:3053)
            at android.widget.AbsListView$3.run(AbsListView.java:3860)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-05 22:15:45.841    4926-4926/? E/CursorWindow﹕ Failed to read row 0, column -1 from a CursorWindow which has 5 rows, 2 columns.
06-05 22:15:45.841    4926-4926/? D/AndroidRuntime﹕ Shutting down VM
06-05 22:15:45.841    4926-4926/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: org.reisacher.zapp, PID: 4926
    java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
            at android.database.CursorWindow.nativeGetString(Native Method)
            at android.database.CursorWindow.getString(CursorWindow.java:438)
            at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
            at org.reisacher.zapp.ChatActivity.updateView(ChatActivity.java:43)
            at org.reisacher.zapp.MainActivity$1.onItemClick(MainActivity.java:52)
            at android.widget.AdapterView.performItemClick(AdapterView.java:305)
            at android.widget.AbsListView.performItemClick(AbsListView.java:1146)
            at android.widget.AbsListView$PerformClick.run(AbsListView.java:3053)
            at android.widget.AbsListView$3.run(AbsListView.java:3860)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

正如人们可以看到SQLite正在尝试获取列名，该列名与我保存消息的列匹配，但不知何故，然后读取列-1

我找不到这种行为的解决方案

由于

Answer 1

问题是你有一个＆＃39;。＆＃39;在字段名称中，引擎将其理解为table.field分隔符。

换句话说，getColumnIndex（）正试图找到＆＃39; org＆＃39;的数字索引。在表格中测试@ zapp＆＃39; ...不在字段名称中使用该类型值的另一个原因。

提供它的线索是＆＃34; E / SQLiteCursor：请求带有表名的列名 - test@zapp.org"

我还会质疑您根据＆＃39;从＆＃39;动态添加列到表格的想法。值，水平增长你的表而不是让它垂直扩展的常规方法。随着它越来越大，越来越笨重，它变得越来越慢。

Android SQLite抛出无法从CursorWindow读取第0行，第-1列

1 个答案: