删除List元素异常

现象

List<String> requestPermission = Arrays.asList(permissions);

for (String p : permissions) {
    if (checkPermissionGranted(p)) {
        requestPermission.remove(p);
    }
}

运行抛出以下异常

Caused by: java.lang.UnsupportedOperationException
  at java.util.AbstractList.remove(AbstractList.java:161)
  at java.util.AbstractList$Itr.remove(AbstractList.java:374)
  at java.util.AbstractCollection.remove(AbstractCollection.java:293)
  at com.tencent.edu.demo.BaseActvity.checkPermissions(BaseActvity.java:70)

原因剖析

Arrays.asList返回的是固定大小的List

1	Returns a fixed-size list backed by the specified array.

不能增删数据，不能改变改List的结构；

解决办法

可以先创建ArrayList，然后在通过addAll接口赋值；

List<String> requestPermission = new ArrayList<>();
requestPermission.addAll(Arrays.asList(permissions));

for (String p : requestPermission) {
    if (checkPermissionGranted(p)) {
        requestPermission.remove(p);
    }
}

ArrayList也可以是LinkedList

至此，问题可解。