Tablayout片段的java实现接口(Android)
我不确定这是一个完美的标题,但这是我能想出的最好的
我有一个java类APIREST,它运行一些http请求,并通过接口在回调中返回结果。下面的验证方法就是一个示例:
public class ApiRequest {
private Context context;
private ApiRequestCallback api_request_callback;
public ApiRequest ( Context context ){
this.context = context;
// this can either be activity or context. Neither works in fragment
// but does in activity
this.api_request_callback = ( ApiRequestCallback ) context;
}
public interface ApiRequestCallback {
void onResponse(JSONObject response );
void onErrorResponse(JSONObject response );
}
public JsonObject authenticate(){
.... do stuff and when you get response from the server. This is some
kinda of async task usually takes a while
// after you get the response from the server send it to the callback
api_request_callback.onResponse( response );
}
现在我在tablayout中有一个fragment类,它实现了下面这个类
public class Home extends Fragment implements ApiRequest.ApiRequestCallback
{
// I have tried
@Override
public void onViewCreated(.........) {
api_request = new ApiRequest( getContext() );
}
// and this two
@Override
public void onAttach(Context context) {
super.onAttach(context);
api_request = new ApiRequest( context );
}
@Override
public void onResponse(JSONObject response) {
//I expect a response here
}
}
我得到的回应是,我无法将活动上下文强制转换为接口
Java.lang.ClassCastException: com.*****.**** cannot be cast to com.*****.****ApiRequest$ApiRequestCallback
但这是一项有规律的活动,所以它真的让我很紧张。对此的修复将不胜感激。我想说,这对我来说是一个可教的时刻。谢谢
# 1 楼答案
要构造ApiRequest对象,需要传递上下文。在构造函数中,您假设始终可以将此上下文强制转换为ApiRequestCallback(这是您正在执行的错误)。就像在片段中一样,片段没有自己的上下文,当您在片段中使用getContext()时,它将返回父活动的上下文,而ApiRequest类的构造函数中的上下文不能转换为ApiRequestCallback
将APIRESQUEST构造函数更改为以下内容:
然后在片段中使用以下内容: