您code说：

如果输入的字符串长度为0 ...大写字母，然后检查这个词与它启动，但输入的字符串长度为0，为什么你会想这样做这两件事情？

if the input string length is 0 ... uppercase it and then check that the word starts with it, but the input string is length 0 so why would you want to do these two things?

你应该有你的方法的顶部的第一件事是：

The first thing you should have at the top of your method is:

input = autocomplete.getText().toString();

if(input == null || input.isEmpty()) {
      return; // user hasn't done anything or has cleared the box
}

修改的

您应该改变你的方法输入变量名，以帮助您：

You should change your method input variable names to help you:

 onItemClick(AdapterView<?> parent, View view, int position, long id);

您数组下标越界是在这里，你需要检查你的铸造和你正在做一个拿到就行了。确保它拥有您的​​项目。

Your array index out of bounds is in here, you need to check what your casting and the list that you are doing a get on. Ensure it holds your items.