非法符号Exception：无效列

Question

这是logcat：

01-15 16:06:03.622: ERROR/AndroidRuntime(22300): Uncaught handler: thread main exiting due to uncaught exception
01-15 16:06:03.657: ERROR/AndroidRuntime(22300): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mohit.geo2do/com.mohit.geo2do.activities.TaskEdit}: java.lang.IllegalArgumentException: Invalid column due_date
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.os.Looper.loop(Looper.java:123)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread.main(ActivityThread.java:4363)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at java.lang.reflect.Method.invokeNative(Native Method)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at java.lang.reflect.Method.invoke(Method.java:521)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:862)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at dalvik.system.NativeStart.main(Native Method)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300): Caused by: java.lang.IllegalArgumentException: Invalid column due_date
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.database.sqlite.SQLiteQueryBuilder.computeProjection(SQLiteQueryBuilder.java:508)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.database.sqlite.SQLiteQueryBuilder.buildQuery(SQLiteQueryBuilder.java:356)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.database.sqlite.SQLiteQueryBuilder.query(SQLiteQueryBuilder.java:309)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.database.sqlite.SQLiteQueryBuilder.query(SQLiteQueryBuilder.java:266)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at com.mohit.geo2do.provider.TasksProvider.query(TasksProvider.java:174)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.content.ContentProvider$Transport.query(ContentProvider.java:130)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.content.ContentResolver.query(ContentResolver.java:202)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at com.mohit.geo2do.activities.TaskEdit.onCreate(TaskEdit.java:105)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-15 16:06:03.657: ERROR/AndroidRuntime(22300):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)

与之相关的行是：

private Cursor task;
private Uri uri;
private String[] PROJECTION { 
    Tasks._ID, Tasks.TITLE, Tasks.COMPLETED, Tasks.DUE_DATE, Tasks.IMPORTANCE, Tasks.NOTES
};
...
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_task);
    ...
    uri = getIntent().getData();
    task = getContentResolver().query(uri, PROJECTION, null, null, null);
} 
...

可能是什么问题呢？数据库的创建正好很好。您还有其他代码需要查看吗？

更新：
我非常确定这列存在。我对数据库进行了查询：

Cursor c = db.rawQuery("SELECT * FROM tasks LIMIT 1", null);
for (int i = 0; i < c.getColumnNames().length; i++) {
    Log.v(TAG, c.getColumnNames()[i]);
}

在logcat中：

01-15 16:52:07.857: VERBOSE/TasksProvider(24325): Creating database...
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): _id
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): title
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): completed
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): due_date
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): notes
01-15 16:52:07.862: VERBOSE/TasksProvider(24325): importance

因此，列确实存在。

Answer 1

我发现了一个奇怪的解决方法。在 String[] PROJECTION. 。你所要做的：

private String[] PROJECTION { 
    Tasks._ID, 
    Tasks.TITLE, 
    Tasks.COMPLETED,
    Tasks.DUE_DATE + " as " + Tasks.DUE_DATE, 
    Tasks.IMPORTANCE + " as " + Tasks.DUE_DATE, 
    Tasks.NOTES + " as " + Tasks.NOTES
};

Answer 2

该列无疑确实存在于您的数据库中，但是如果您尚未将列添加到一个称为的事物中 投影图, ，您将看到您看到的“无效列”错误。您可以通过查询构建器对象添加投影映射，例如：

// The projection map is a hashmap of strings
HashMap<String, String> MyProjectionMap;
MyProjectionMap = new HashMap<String, String>();

// Add column mappings to the projection map
MyProjectionMap.put(Tasks._ID, Tasks._ID);
MyProjectionMap.put(Tasks.TITLE, Tasks.TITLE);
[...]

SQLiteQueryBuilder qb;
qb.setTables("tasks");
qb.setProjectionMap(MyProjectionMap)

// Then do your query
Cursor c = qb.query(db, projection, ...)

要了解发生了什么，请查看SQLiteQueryBuilder类的来源，您会看到以下内容：

private String[] computeProjection(String[] projectionIn) {
    if (projectionIn != null && projectionIn.length > 0) {
       if (mProjectionMap != null) {
          [...]
          for (int i = 0; i < length; i++) {
             String userColumn = projectionIn[i];
             String column = mProjectionMap.get(userColumn);
             [...]
             if (!mStrictProjectionMap && ( userColumn.contains(" AS ") || userColumn.contains(" as "))) {
                /* A column alias already exist */
                projection[i] = userColumn;
                continue;
             }
             throw new IllegalArgumentException("Invalid column " + projectionIn[i]);
          }
      }
[...]

基本上，它是在投影中对“允许”列列表中要求的列进行检查，并且您可以看到，如果地图不包含投影中的列，它将像您看到的那样抛出IllegalargumentException。 （我想对地图进行检查是一项安全功能，可防止滥用内容提供商的人的基于SQL的攻击，但这只是一个猜测。）

还请注意，如果您在查询构建器中设置“严格”投影映射：

qb.setStrictProjectionMap(true);

然后，在这种情况下，它希望您知道确切的列名...如果您不设置它，它将检查“ AS”列别名 - 我认为这解释了您发现的“怪异修复”。

希望这可以帮助。

Answer 3

您是否在与此列的表相对于表格提供商的投影映射中添加了此列？我希望这有帮助。