Android EditText 在光标处插入，删除内容（例如可用于表情文字输入控件）

1.获取光标位置

[java]
int index = editText.getSelectionStart();

2.在光标处插入字符

[java]
int index = editText.getSelectionStart();
Editable editable = editText.getText();
editable.insert(index, "aaaa");

3.删除光标前字符

[java]
int index = editText.getSelectionStart();
Editable editable = editText.getText();
editable.delete(index-1, index);