Java Object[] 不能在 AsyncTask 中转换为 Void[]
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Object[] cannot be cast to Void[] in AsyncTask
提问by Luca Vitucci
I'm getting this error inside an extended asynctask, but i'm really sure that Object[] IS a Void[].
我在扩展的异步任务中收到此错误，但我非常确定 Object[] 是一个 Void[]。
This is my custom AsyncTask:
这是我的自定义 AsyncTask：
public abstract class RepeatableAsyncTask<A, B, C> extends AsyncTask<A, B, C> {
private static final String TAG = "RepeatableAsyncTask";
public static final int DEFAULT_MAX_RETRY = 5;
private int mMaxRetries = DEFAULT_MAX_RETRY;
private Exception mException = null;
/**
* Default constructor
*/
public RepeatableAsyncTask() {
super();
}
/**
* Constructs an AsyncTask that will repeate itself for max Retries
* @param retries Max Retries.
*/
public RepeatableAsyncTask(int retries) {
super();
mMaxRetries = retries;
}
/**
* Will be repeated for max retries while the result is null or an exception is thrown.
* @param inputs Same as AsyncTask's
* @return Same as AsyncTask's
*/
protected abstract C repeatInBackground(A...inputs);
@Override
protected final C doInBackground(A...inputs) {
int tries = 0;
C result = null;
/* This is the main loop, repeatInBackground will be repeated until result will not be null */
while(tries++ < mMaxRetries && result == null) {
try {
result = repeatInBackground(inputs);
} catch (Exception exception) {
/* You might want to log the exception everytime, do it here. */
mException = exception;
}
}
return result;
}
/**
* Like onPostExecute but will return an eventual Exception
* @param c Result same as AsyncTask
* @param exception Exception thrown in the loop, even if the result is not null.
*/
protected abstract void onPostExecute(C c, Exception exception);
@Override
protected final void onPostExecute(C c) {
super.onPostExecute(c);
onPostExecute(c, mException);
}
And this is the SubClass that gives the problem:
这是给出问题的子类：
public class ListPalinasAsynkTask extends RepeatableAsyncTask<Void, Void, List<Palina>>{
private static final String TAG = "ListPalinasAsynkTask";
private static final boolean D = SystemConstants.ACTIVE_DEBUG;
private ApiRequest.ListPalinasCallback mCallback;
public ListPalinasAsynkTask(ApiRequest.ListPalinasCallback callback) {
if(D) Log.d(TAG, "Called: ListPalinasAsynkTask([callback])");
mCallback = callback;
}
@Override
protected List<Palina> repeatInBackground(Void... voids) {
/* Here i send request to get palinas */
return Api.getPalinasNearMe();
}
@Override
protected void onPostExecute(List<Palina> palinas, Exception exception) {
if(exception != null)
Logging.e(TAG, "Received exception in Asynk Task", exception);
if(palinas != null)
mCallback.result(palinas);
else
mCallback.result(new ArrayList<Palina>());
}
}
Finally, this is the error:
最后，这是错误：
E/ListPalinasAsynkTask﹕ Received exception in Asynk Task
java.lang.ClassCastException: java.lang.Object[] cannot be cast to java.lang.Void[]
at ListPalinasAsynkTask.repeatInBackground(ListPalinasAsynkTask.java:19)
at RepeatableAsyncTask.doInBackground(RepeatableAsyncTask.java:43)
at android.os.AsyncTask.call(AsyncTask.java:288)
I can't explain this exception because i'm giving Void as a parameter! That should not be an Object. Do you have solutions?
我无法解释这个异常，因为我给 Void 作为参数！那不应该是一个对象。你有解决方案吗？
Edit: ListPalinasAsyncTask.java:19 refers to:
编辑：ListPalinasAsyncTask.java:19 指的是：
public class ListPalinasAsynkTask extends RepeatableAsyncTask<Void, Void, List<Palina>> {
RepeatableAsyncTask.java:43:
RepeatableAsyncTask.java:43:
result = repeatInBackground(inputs);
EDIT 2:
编辑2：
I'm calling execute this way:
我通过这种方式调用执行：
AsyncTask mAsyncTask = new ListPalinasAsynkTask(callback);
....
mAsyncTask.execute();
采纳答案by Luca Vitucci
Solution found:
找到的解决方法：
the problem was this:
问题是这样的：
AsyncTask mAsyncTask = new ListPalinasAsynkTask(callback);
....
mAsyncTask.execute();
I'm using generic AsyncTask to call execute, that class would pass Void as a parameter and will never call .execute() on ListPalinasAsynkTask, instead it will call ListPalinasAsynkTask.execute(Void). That gives the error.
我使用通用 AsyncTask 来调用 execute，该类将 Void 作为参数传递，并且永远不会在 ListPalinasAsynkTask 上调用 .execute()，而是调用 ListPalinasAsynkTask.execute(Void)。这给出了错误。
Solutions:
解决方案：
- Use ListPalinasAsynkTask instead of generic AsyncTask
- Better one: Create a new class VoidRepeatableAsyncTask and make other Void AsyncTasks extend that one.
- 使用 ListPalinasAsyncTask 而不是通用的 AsyncTask
- 更好的方法：创建一个新类 VoidRepeatableAsyncTask 并使其他 Void AsyncTask 扩展该类。
Like this:
像这样：
public abstract class VoidRepeatableAsyncTask<T> extends RepeatableAsyncTask<Void, Void, T> {
public void execute() {
super.execute();
}
}
Then you can easily use something like this to call execute:
然后你可以很容易地使用这样的东西来调用执行：
VoidRepeatableAsyncTask mAsyncTask = new ListPalinasAsynkTask(callback);
....
mAsyncTask.execute();
This will call the no-parameters execute method of AsyncTask.
这将调用 AsyncTask 的无参数执行方法。
回答by Raghav Sood
Try using:
尝试使用：
result = repeatInBackground((Void) inputs);
instead of
代替
result = repeatInBackground(inputs);
回答by Diolor
An alternative way with which I solved it is to pass Objectin parameters, even if you don't use the parameters.
我解决它的另一种方法是传入Object参数，即使您不使用参数。
new AsyncTask<Object, Void, MergeAdapter>()
and the override:
和覆盖：
@Override
protected ReturnClass doInBackground(Object... params) {
//...
}
The above applies (in my case) if you want to pass different types of AsyncTasks to a method and of course you do not care about the parameters.
如果您想将不同类型的 AsyncTasks 传递给方法，并且当然您不关心参数，则上述内容适用（在我的情况下）。
回答by marco
The solution is much simpler as I see it. Just create the subclass object in this way:
在我看来，解决方案要简单得多。只需以这种方式创建子类对象：
AsyncTask<Void, Void, List<Palina> mAsyncTask = new ListPalinasAsynkTask(callback);
....
mAsyncTask.execute();
回答by Amit
If this problem is occurring then you might have created a Derived class object and added its the base class variable (AsyncTask). So this error is occurring.
AsyncTask mAsyncTask = new ListPalinasAsynkTask(callback);
如果发生此问题，那么您可能已经创建了派生类对象并添加了其基类变量 (AsyncTask)。所以这个错误正在发生。
AsyncTask mAsyncTask = new ListPalinasAsynkTask(callback);
Lint also gives a warning when you do like this "Unchecked call to execute. Params ...."
当您这样做时，Lint 也会发出警告“未经检查的执行调用。参数......”
The solution is ListPalinasAsynkTask mAsyncTask = new ListPalinasAsynkTask(callback); Then call execute on it. It will work fine
解决方法是 ListPalinasAsynkTask mAsyncTask = new ListPalinasAsynkTask(callback); 然后调用执行它。它会正常工作
