java - 在 Java 中创建并迭代字符串列表

Question

我正在尝试创建大小动态的数组列表，添加元素并在完成后迭代它们。目前我的代码是:

    String activities = "SELECT DISTINCT phoneactivity from ContextTable030313";
    ArrayList<String> myActivities = new ArrayList();

    Cursor cursor2 = db.rawQuery(activities, null);
    // looping through all rows and adding to list
    if (cursor2.moveToFirst()) {
        do {
            myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));

        } while (cursor2.moveToNext());
    }

但是它无法在 do 循环中运行。我相信我声明了一些错误的内容，并且收到以下警告:

- ArrayList is a raw type. References to generic type ArrayList<E> should be parameterized
    - Avoid object allocations during draw/layout operations (preallocate and reuse instead)
    - Type safety: The expression of type ArrayList needs unchecked conversion to conform to 
     ArrayList<String>

但我不明白为什么这不起作用。

Answer 1

问题似乎是这样的:

Type safety: The expression of type ArrayList needs unchecked conversion to conform to ArrayList

这指出了这行代码:

ArrayList<String> myActivities = new ArrayList();

您应该将该行更改为:

ArrayList<String> myActivities = new ArrayList<String>();

换句话来说，您可以替换此代码段:

  if (cursor2.moveToFirst()) {
        do {
            myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));

        } while (cursor2.moveToNext());
    }

这样:

  while (cursor2.moveToFirst()) {       
        myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));       
    }