我正在处理异步任务，结构是主类中的实现接口，将主类作为侦听器传递给异步任务，当异步类完成时，调用监听器函数，问题是当我通过async任务的主类它返回以下错误：
02-18 19:37:43.826: E/AndroidRuntime(15928): FATAL EXCEPTION: AsyncTask #2
02-18 19:37:43.826: E/AndroidRuntime(15928): java.lang.RuntimeException: An error occured while executing doInBackground()
02-18 19:37:43.826: E/AndroidRuntime(15928): at android.os.AsyncTask$3.done(AsyncTask.java:299)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
02-18 19:37:43.826: E/AndroidRuntime(15928): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.lang.Thread.run(Thread.java:856)
02-18 19:37:43.826: E/AndroidRuntime(15928): Caused by: java.lang.ClassCastException: com.project.hkseven.Fragment.Home$1 cannot be cast to com.project.hkseven.Listener.LoginListener
02-18 19:37:43.826: E/AndroidRuntime(15928): at com.project.hkseven.Utility.APIHandler.doInBackground(APIHandler.java:69)
02-18 19:37:43.826: E/AndroidRuntime(15928): at com.project.hkseven.Utility.APIHandler.doInBackground(APIHandler.java:1)
02-18 19:37:43.826: E/AndroidRuntime(15928): at android.os.AsyncTask$2.call(AsyncTask.java:287)
02-18 19:37:43.826: E/AndroidRuntime(15928): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
02-18 19:37:43.826: E/AndroidRuntime(15928): ... 5 more
以下是我如何调用主要类（片段）并将其传递给异步任务
new APIHandler(getActivity(),tracker,"login").execute(this,session.getAccessToken());
API处理程序是一个异步任务，处理方式如下
public class APIHandler extends AsyncTask<Object, Void, JSONObject> {
private String TAG = "APIHandler";
private LoginListener loginListener;
private UploadImageListener uploadImageListener;
private UpdateProfileListener updateProfileListener;
private MyPtListener myPtListener;
public Context ctx;
public String type;
public String url;
public String formType;
public EasyTracker tracker;
public String token;
public String memId;
public APIHandler(Context _ctx,EasyTracker _tracker,String _formType) {
this.ctx = _ctx;
this.tracker = _tracker;
this.formType = _formType;
//Get access data
SharedPreferences prefs = ctx.getSharedPreferences("userInfo", 0);
token = prefs.getString("token","");
memId = prefs.getString("memId","");
}
@Override
protected JSONObject doInBackground(Object... params) {
MultipartEntityBuilder builder = MultipartEntityBuilder.create();
builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
if (formType.equals("login")){
url = Constant.loginAPI;
loginListener = (LoginListener) params[0];
Log.d(TAG, "Login API(token): " + params[1] );
builder.addTextBody("var1", (String) params[1]); //Facebook access token
builder.addTextBody("var2", "2"); //Device type 2 = android
.......................
@Override
protected void onPostExecute(JSONObject result) {
try {
if(result != null) {
if (formType.equals("login")){
if (result.getString("result").equals("ok")) {
loginListener.onLoginComplete(result.getString("member_id"),result.getString("token"));
}else {
loginListener.onLoginFailure(result.getString("error_code"));
}
更新
感谢您的回复，我已经实现了loginListener，但它仍然会出错。
界面：
public interface LoginListener {
public void onLoginComplete(String memberId, String token);
public void onLoginFailure(String errorMsg);
}
Home类片段：
public class Home extends Fragment implements LoginListener {
public View rootView;
public ImageView HomeBg;
public ImageView buttonLoginLogout;
public TextView chi;
public TextView eng;
public ColorStateList oldColor;
public SharedPreferences prefs;
public EasyTracker tracker = null;
public String[] PERMISSION_ARRAY_READ = {"email"};
public List<String> PERMISSION_LIST;
public SharedPreferences.Editor editor;
public ProgressDialog pd;
//Facebook login
private Session.StatusCallback statusCallback = new SessionStatusCallback();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
tracker = EasyTracker.getInstance(getActivity());
PERMISSION_LIST = Arrays.asList(PERMISSION_ARRAY_READ);
prefs = getActivity().getSharedPreferences("userInfo", 0);
editor = prefs.edit();
getActivity().getActionBar().hide();
rootView = inflater.inflate(R.layout.home, container, false);
buttonLoginLogout = (ImageView) rootView.findViewById(R.id.home_connectFB);
eng = (TextView) rootView.findViewById(R.id.btn_eng);
chi = (TextView) rootView.findViewById(R.id.btn_chi);
if (Utility.getLocale(getActivity()).equals("TC")) {
chi.setTextColor(getActivity().getResources().getColor(
android.R.color.white));
oldColor = eng.getTextColors();
} else {
eng.setTextColor(getActivity().getResources().getColor(
android.R.color.white));
oldColor = chi.getTextColors();
}
eng.setOnClickListener(setChangeLangListener("EN"));
chi.setOnClickListener(setChangeLangListener("TC"));
//Facebook login
Settings.addLoggingBehavior(LoggingBehavior.INCLUDE_ACCESS_TOKENS);
Session session = Session.getActiveSession();
if (session == null) {
if (savedInstanceState != null) {
session = Session.restoreSession(getActivity(), null, statusCallback, savedInstanceState);
}
if (session == null) {
session = new Session(getActivity());
}
Session.setActiveSession(session);
if (session.getState().equals(SessionState.CREATED_TOKEN_LOADED)) {
session.openForRead(new Session.OpenRequest(this).setPermissions(PERMISSION_LIST).setCallback(statusCallback));
}
}
updateView();
return rootView;
}
@Override
public void onStart() {
super.onStart();
Session.getActiveSession().addCallback(statusCallback);
tracker.set(Fields.SCREEN_NAME, "hk7app/CX/" + Utility.getLocale(getActivity()) + "/Landing Page");
tracker.send(MapBuilder.createAppView().build());
}
@Override
public void onStop() {
super.onStop();
Session.getActiveSession().removeCallback(statusCallback);
EasyTracker.getInstance(getActivity()).activityStop(getActivity());
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Session.getActiveSession().onActivityResult(getActivity(), requestCode, resultCode, data);
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Session session = Session.getActiveSession();
Session.saveSession(session, outState);
}
@SuppressWarnings("deprecation")
private void updateView() {
final Session session = Session.getActiveSession();
if (session.isOpened()) {
Request.executeMeRequestAsync(session,
new Request.GraphUserCallback() {
@Override
public void onCompleted(GraphUser user,Response response) {
// TODO Auto-generated method stub
if (user != null) {
if (!user.getId().equals(prefs.getString("fbId",""))) {
editor.putString("fbId", user.getId());
editor.putString("fName", user.getFirstName());
editor.putString("lName", user.getLastName());
editor.putString("email", user.asMap().get("email").toString());
editor.commit();
//pd = ProgressDialog.show(getActivity(), getActivity().getResources().getString(R.string.sys_info),getActivity().getResources().getString(R.string.loading));
Log.d("test1",session.getAccessToken());
new APIHandler(getActivity(),tracker,"login").execute(this,session.getAccessToken());
} else {
onLoginComplete("","");
}
}
}
});
} else {
buttonLoginLogout.setImageResource(R.drawable.landing_btn_connect_facebook);
buttonLoginLogout.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) { onClickLogin(); }
});
}
}
private void onClickLogin() {
tracker.send(MapBuilder.createEvent("menu_click","Fbconnect","connectFB_" + Utility.getLocale(getActivity()),null).build());
Session session = Session.getActiveSession();
if (!session.isOpened() && !session.isClosed()) {
session.openForRead(new Session.OpenRequest(this).setPermissions(PERMISSION_LIST).setCallback(statusCallback));
} else {
Session.openActiveSession(getActivity(), this, true, statusCallback);
}
}
private class SessionStatusCallback implements Session.StatusCallback {
@Override
public void call(Session session, SessionState state, Exception exception) {
updateView();
}
}
public OnClickListener setChangeLangListener(final String lang) {
OnClickListener changeLangListener = new OnClickListener() {
@Override
public void onClick(View arg0) {
Configuration config = new Configuration(getResources().getConfiguration());
if (Utility.getLocale(getActivity()).equals("TC") && lang.equals("EN")) {
tracker.send(MapBuilder.createEvent("menu_click","language", "switchEN", null).build());
config.locale = Locale.ENGLISH;
chi.setTextColor(oldColor);
eng.setTextColor(getActivity().getResources().getColor(
android.R.color.white));
} else if (Utility.getLocale(getActivity()).equals("EN") && lang.equals("TC")) {
tracker.send(MapBuilder.createEvent("menu_click","language", "switchTC", null).build());
config.locale = Locale.TRADITIONAL_CHINESE;
eng.setTextColor(oldColor);
chi.setTextColor(getActivity().getResources().getColor(
android.R.color.white));
}
getResources().updateConfiguration(config,getResources().getDisplayMetrics());
onConfigurationChanged(config);
}
};
return changeLangListener;
}
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
Intent intent = getActivity().getIntent();
intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
getActivity().finish();
startActivity(intent);
}
@Override
public void onResume() {
super.onResume();
AppEventsLogger.activateApp(getActivity(),getResources().getString(R.string.app_id));
}
@Override
public void onLoginComplete(String memberId, String token) {
if (pd != null)
pd.dismiss();
if (!memberId.equals("") && !token.equals("")) {
editor.putString("memId", memberId);
editor.putString("token", token);
}
buttonLoginLogout.setImageResource(R.drawable.landing_btn_take_a_selfie);
buttonLoginLogout.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
tracker.send(MapBuilder.createEvent("menu_click","TakeSelfie","Selfie_now_" + Utility.getLocale(getActivity()),null).build());
((LandingPage)getActivity()).tabHost.setCurrentTab(2);
}
});
}
@Override
public void onLoginFailure(String errorMsg) {
if (pd != null)
pd.dismiss();
Toast.makeText(getActivity(), errorMsg, Toast.LENGTH_LONG).show();
}
}
更新（2）：
我没有将Home转换为LoginListener，而是试图简单地不将其强制转换，问题是它仍然抛出异常
Caused by: java.lang.ClassCastException: com.project.hkseven.Fragment.Home$1 cannot be cast to com.project.hkseven.Fragment.Home
答案 0 :(得分：2)
我想这个问题就在于这一行，
loginListener = (LoginListener) params[0];
因为你的params [0]是这个，我指的是Home。但是，在doInBackground（）方法中，您已将其转换为LoginListener。所以@Blackbelt说，你能检查一下你的Home是否实现了LoginListener。
答案 1 :(得分：1)
可以解决您的问题的方法是替换此行
loginListener = (LoginListener) params[0];
通过
TheActivityThatYoupassedin= (TheActivityThatYoupassedin) params[0];
if(TheActivityThatYoupassedin instanceOf LoginListener){
}
else{
throw new ClassCastException("Home does not implements the loginlistener);
}
答案 2 :(得分：0)
据我了解，您使用的接口LoginListener作为CallBack侦听器。但是，不幸的是，您没有在LoginListener课程中实现Home界面。你可以查看你的班级定义......
public class Home extends Fragment implements LoginListener {
答案 3 :(得分：0)
在onCreate而不是onCreateView中获取上下文修复了问题。谢谢你的帮助