Java ClassCastException:使用DialogFragment时应用程序崩溃_Java_Android_Android Fragments_Classcastexception

Java ClassCastException:使用DialogFragment时应用程序崩溃

java android android-fragments

Java ClassCastException:使用DialogFragment时应用程序崩溃,java,android,android-fragments,classcastexception,Java,Android,Android Fragments,Classcastexception,我的MainActivity.java中有一个RecyclerView。在每个RecyclerView行中，我都有一个按钮，当按下它时，它应该会打开一个自定义的片段对话框，其中包含RecyclerView列表（这是一个多选对话框）在我的SecondActivity.java，这是我的另一个活动，我也有同样的按钮，它应该做同样的事情（这就是为什么我需要模态作为片段对话框）。在我的SecondActivity.java中，没有RecyclerView，只有一篇文章（详细信息页）我的问题： 10-

我的

MainActivity.java

中有一个

RecyclerView

。在每个RecyclerView行中，我都有一个按钮，当按下它时，它应该会打开一个自定义的片段对话框，其中包含RecyclerView列表（这是一个多选对话框）

在我的

SecondActivity.java

，这是我的另一个活动，我也有同样的按钮，它应该做同样的事情（这就是为什么我需要模态作为片段对话框）。在我的

SecondActivity.java

中，没有RecyclerView，只有一篇文章（详细信息页）

我的问题：

10-06 14:35:12.353 21683-21683/com.example.appname E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.appname, PID: 21683
java.lang.ClassCastException: com.example.appname.MainActivity@e06db1e
    at adapters.MultiDialogAdapter.<init>(MultiDialogAdapter.java:40)
    at fragments.CustomDialogFragment.onViewCreated(CustomDialogFragment.java:60)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1430)
    at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
    at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
    at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
    at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
    at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)
    at android.os.Handler.handleCallback(Handler.java:751)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6776)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

当我单击

SecondActivity.java

上弹出窗口的按钮时，它会正常打开对话框片段弹出窗口。当我对RecyclerView（位于

MainActivity.java

中）中的任何一行执行相同操作时，我会得到一个

ClassCastException

错误：

java.lang.ClassCastException: com.example.appname.MainActivity cannot be cast to interfaces.DialogCommunicator$Communicator

我的代码：

10-06 14:35:12.353 21683-21683/com.example.appname E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.appname, PID: 21683
java.lang.ClassCastException: com.example.appname.MainActivity@e06db1e
    at adapters.MultiDialogAdapter.<init>(MultiDialogAdapter.java:40)
    at fragments.CustomDialogFragment.onViewCreated(CustomDialogFragment.java:60)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1430)
    at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
    at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
    at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
    at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
    at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)
    at android.os.Handler.handleCallback(Handler.java:751)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6776)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

SecondActivity.java

//*****************//
// THIS CODE WORKS //
//*****************//

// This code will run when the button is clicked.
// postOptions is a string array of menu items.
Bundle args = new Bundle();
args.putStringArray("displaymenu", postOptions);
mDialogFragment = new CustomDialogFragment();
mDialogFragment.setArguments(args);
mDialogFragment.show(getSupportFragmentManager(), "title");

//***************************//
// THIS CODE CRASHES THE APP //
//***************************//

// This code is planted in onClick method listener in onBindViewHolder
// for the button that's supposed to open the fragment dialog.
FragmentManager fm = ((MainActivity) mContext).getSupportFragmentManager();
String[] items = mContext.getResources().getStringArray(R.array.post_options);
CustomDialogFragment customDialogFragment = CustomDialogFragment.newInstance(items);
customDialogFragment.show(fm, "title");

public class CustomDialogFragment extends DialogFragment {

    private RecyclerView mRecyclerView;

    public CustomDialogFragment() {
        // Empty constructor is required for DialogFragment
        // Make sure not to add arguments to the constructor
        // Use `newInstance` instead as shown below
    }

    public static CustomDialogFragment newInstance(String[] items) {
        CustomDialogFragment customDialogFragment = new CustomDialogFragment();
        Bundle args = new Bundle();
        args.putStringArray("displaymenu", items);
        customDialogFragment.setArguments(args);
        return customDialogFragment;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.layout_multiselect_dialog, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Bundle args = getArguments();
        String[] items = args.getStringArray("displaymenu");
        List<String> itemsList = Arrays.asList(items);

        // THIS LINE CRASHES ON POSTSLISTADAPTER!!!
        MultiDialogAdapter adapter = new MultiDialogAdapter(getActivity(), itemsList);

        mRecyclerView = (RecyclerView) view.findViewById(R.id.items_recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mRecyclerView.setAdapter(adapter);

        getDialog().setTitle(null);
    }

}

public class MultiDialogAdapter extends RecyclerView.Adapter<MultiDialogViewHolder> {

    private List<String> mItems;
    private LayoutInflater mInflater;
    private CustomFonts mCustomFont;
    private DialogCommunicator.Communicator mCommunicator;

    public MultiDialogAdapter(Context context, List<String> items) {
        this.mInflater = LayoutInflater.from(context);
        this.mItems = items;
        this.mCustomFont = new CustomFonts(context);

        try {
            mCommunicator = (DialogCommunicator.Communicator) context;
        } catch (ClassCastException e) {
            // THIS IS WHERE THE CLASSCASTEXCEPTION HAPPENS!
            throw new ClassCastException(context.toString());
        }
    }

    @Override
    public MultiDialogViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.layout_multiselect_dialog_row, parent, false);
        return new MultiDialogViewHolder(view);
    }

    @Override
    public void onBindViewHolder(MultiDialogViewHolder holder, int position) {
        final String item = mItems.get(position);
        holder.getItemTextView().setText(item);
        holder.getItemTextView().setTypeface(mCustomFont.getPrimaryFontMedium());
        holder.getItemTextView().setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCommunicator.onDialogButtonResponse(item);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mItems.size();
    }

}

class MultiDialogViewHolder extends RecyclerView.ViewHolder {

    private TextView mItemTextView;

    public MultiDialogViewHolder(View rootView) {
        super(rootView);
        mItemTextView = (TextView) rootView.findViewById(R.id.item_text_view);
    }

    public TextView getItemTextView() {
        return mItemTextView;
    }

}

public class DialogCommunicator {

    public interface Communicator {
        public void onDialogButtonResponse(String responseMessage);
    }

}

PostsListAdapter.java

//*****************//
// THIS CODE WORKS //
//*****************//

// This code will run when the button is clicked.
// postOptions is a string array of menu items.
Bundle args = new Bundle();
args.putStringArray("displaymenu", postOptions);
mDialogFragment = new CustomDialogFragment();
mDialogFragment.setArguments(args);
mDialogFragment.show(getSupportFragmentManager(), "title");

//***************************//
// THIS CODE CRASHES THE APP //
//***************************//

// This code is planted in onClick method listener in onBindViewHolder
// for the button that's supposed to open the fragment dialog.
FragmentManager fm = ((MainActivity) mContext).getSupportFragmentManager();
String[] items = mContext.getResources().getStringArray(R.array.post_options);
CustomDialogFragment customDialogFragment = CustomDialogFragment.newInstance(items);
customDialogFragment.show(fm, "title");

public class CustomDialogFragment extends DialogFragment {

    private RecyclerView mRecyclerView;

    public CustomDialogFragment() {
        // Empty constructor is required for DialogFragment
        // Make sure not to add arguments to the constructor
        // Use `newInstance` instead as shown below
    }

    public static CustomDialogFragment newInstance(String[] items) {
        CustomDialogFragment customDialogFragment = new CustomDialogFragment();
        Bundle args = new Bundle();
        args.putStringArray("displaymenu", items);
        customDialogFragment.setArguments(args);
        return customDialogFragment;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.layout_multiselect_dialog, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Bundle args = getArguments();
        String[] items = args.getStringArray("displaymenu");
        List<String> itemsList = Arrays.asList(items);

        // THIS LINE CRASHES ON POSTSLISTADAPTER!!!
        MultiDialogAdapter adapter = new MultiDialogAdapter(getActivity(), itemsList);

        mRecyclerView = (RecyclerView) view.findViewById(R.id.items_recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mRecyclerView.setAdapter(adapter);

        getDialog().setTitle(null);
    }

}

public class MultiDialogAdapter extends RecyclerView.Adapter<MultiDialogViewHolder> {

    private List<String> mItems;
    private LayoutInflater mInflater;
    private CustomFonts mCustomFont;
    private DialogCommunicator.Communicator mCommunicator;

    public MultiDialogAdapter(Context context, List<String> items) {
        this.mInflater = LayoutInflater.from(context);
        this.mItems = items;
        this.mCustomFont = new CustomFonts(context);

        try {
            mCommunicator = (DialogCommunicator.Communicator) context;
        } catch (ClassCastException e) {
            // THIS IS WHERE THE CLASSCASTEXCEPTION HAPPENS!
            throw new ClassCastException(context.toString());
        }
    }

    @Override
    public MultiDialogViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.layout_multiselect_dialog_row, parent, false);
        return new MultiDialogViewHolder(view);
    }

    @Override
    public void onBindViewHolder(MultiDialogViewHolder holder, int position) {
        final String item = mItems.get(position);
        holder.getItemTextView().setText(item);
        holder.getItemTextView().setTypeface(mCustomFont.getPrimaryFontMedium());
        holder.getItemTextView().setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCommunicator.onDialogButtonResponse(item);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mItems.size();
    }

}

class MultiDialogViewHolder extends RecyclerView.ViewHolder {

    private TextView mItemTextView;

    public MultiDialogViewHolder(View rootView) {
        super(rootView);
        mItemTextView = (TextView) rootView.findViewById(R.id.item_text_view);
    }

    public TextView getItemTextView() {
        return mItemTextView;
    }

}

public class DialogCommunicator {

    public interface Communicator {
        public void onDialogButtonResponse(String responseMessage);
    }

}

CustomDialogFragment.java

//*****************//
// THIS CODE WORKS //
//*****************//

// This code will run when the button is clicked.
// postOptions is a string array of menu items.
Bundle args = new Bundle();
args.putStringArray("displaymenu", postOptions);
mDialogFragment = new CustomDialogFragment();
mDialogFragment.setArguments(args);
mDialogFragment.show(getSupportFragmentManager(), "title");

//***************************//
// THIS CODE CRASHES THE APP //
//***************************//

// This code is planted in onClick method listener in onBindViewHolder
// for the button that's supposed to open the fragment dialog.
FragmentManager fm = ((MainActivity) mContext).getSupportFragmentManager();
String[] items = mContext.getResources().getStringArray(R.array.post_options);
CustomDialogFragment customDialogFragment = CustomDialogFragment.newInstance(items);
customDialogFragment.show(fm, "title");

public class CustomDialogFragment extends DialogFragment {

    private RecyclerView mRecyclerView;

    public CustomDialogFragment() {
        // Empty constructor is required for DialogFragment
        // Make sure not to add arguments to the constructor
        // Use `newInstance` instead as shown below
    }

    public static CustomDialogFragment newInstance(String[] items) {
        CustomDialogFragment customDialogFragment = new CustomDialogFragment();
        Bundle args = new Bundle();
        args.putStringArray("displaymenu", items);
        customDialogFragment.setArguments(args);
        return customDialogFragment;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.layout_multiselect_dialog, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Bundle args = getArguments();
        String[] items = args.getStringArray("displaymenu");
        List<String> itemsList = Arrays.asList(items);

        // THIS LINE CRASHES ON POSTSLISTADAPTER!!!
        MultiDialogAdapter adapter = new MultiDialogAdapter(getActivity(), itemsList);

        mRecyclerView = (RecyclerView) view.findViewById(R.id.items_recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mRecyclerView.setAdapter(adapter);

        getDialog().setTitle(null);
    }

}

public class MultiDialogAdapter extends RecyclerView.Adapter<MultiDialogViewHolder> {

    private List<String> mItems;
    private LayoutInflater mInflater;
    private CustomFonts mCustomFont;
    private DialogCommunicator.Communicator mCommunicator;

    public MultiDialogAdapter(Context context, List<String> items) {
        this.mInflater = LayoutInflater.from(context);
        this.mItems = items;
        this.mCustomFont = new CustomFonts(context);

        try {
            mCommunicator = (DialogCommunicator.Communicator) context;
        } catch (ClassCastException e) {
            // THIS IS WHERE THE CLASSCASTEXCEPTION HAPPENS!
            throw new ClassCastException(context.toString());
        }
    }

    @Override
    public MultiDialogViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.layout_multiselect_dialog_row, parent, false);
        return new MultiDialogViewHolder(view);
    }

    @Override
    public void onBindViewHolder(MultiDialogViewHolder holder, int position) {
        final String item = mItems.get(position);
        holder.getItemTextView().setText(item);
        holder.getItemTextView().setTypeface(mCustomFont.getPrimaryFontMedium());
        holder.getItemTextView().setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCommunicator.onDialogButtonResponse(item);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mItems.size();
    }

}

class MultiDialogViewHolder extends RecyclerView.ViewHolder {

    private TextView mItemTextView;

    public MultiDialogViewHolder(View rootView) {
        super(rootView);
        mItemTextView = (TextView) rootView.findViewById(R.id.item_text_view);
    }

    public TextView getItemTextView() {
        return mItemTextView;
    }

}

public class DialogCommunicator {

    public interface Communicator {
        public void onDialogButtonResponse(String responseMessage);
    }

}

崩溃日志：

10-06 14:35:12.353 21683-21683/com.example.appname E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.appname, PID: 21683
java.lang.ClassCastException: com.example.appname.MainActivity@e06db1e
    at adapters.MultiDialogAdapter.<init>(MultiDialogAdapter.java:40)
    at fragments.CustomDialogFragment.onViewCreated(CustomDialogFragment.java:60)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1430)
    at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
    at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
    at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
    at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
    at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)
    at android.os.Handler.handleCallback(Handler.java:751)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6776)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

10-06 14:35:12.353 21683-21683/com.example.appname E/AndroidRuntime:FATAL EXCEPTION:main
进程：com.example.appname，PID:21683
java.lang.ClassCastException:com.example.appname。MainActivity@e06db1e
MultiDialogAdapter.java:40）
在fragments.CustomDialogFragment.onViewCreated（CustomDialogFragment.java:60）
位于android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1430）
位于android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState（FragmentManager.java:1740）
位于android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1809）
位于android.support.v4.app.BackStackRecord.executeOps（BackStackRecord.java:799）
位于android.support.v4.app.FragmentManagerImpl.executeOps（FragmentManager.java:2580）
在android.support.v4.app.FragmentManagerImpl.executeOpsTogether（FragmentManager.java:2367）
在android.support.v4.app.FragmentManagerImpl.removedandtoperationsandexecute（FragmentManager.java:2322）
位于android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:2229）
位于android.support.v4.app.FragmentManagerImpl$1.run（FragmentManager.java:700）
位于android.os.Handler.handleCallback（Handler.java:751）
位于android.os.Handler.dispatchMessage（Handler.java:95）
位于android.os.Looper.loop（Looper.java:154）
位于android.app.ActivityThread.main（ActivityThread.java:6776）
位于java.lang.reflect.Method.invoke（本机方法）
在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:1520）上
位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1410）

我有一个在

PostsListAdapter.java

和

SecondActivity.java

中实现的接口。这是一个回调方法，因此我可以响应每个单独的操作，并知道在片段对话框弹出窗口中单击了哪些项

因此，我正确地构建了对话框片段，因为它在列表之外的正常活动中工作，但是对于RecyclerView列表中的每一行，该对话框片段会因为

ClassCastException

而使应用程序崩溃。为什么？

您可以使用

parent.getContext（）在onCreateViewHolder中获取构造函数，而不是将上下文作为对象传递。

此外，在onBindViewholder中，您忘了键入Cast viewholder。添加

MultiDialogViewHolder viewholder=(MultiDialogViewHolder)holder;

然后访问

viewholder.getItemTextView（）.setText（item）
同样，在转换适配器中的上下文之前，对话框片段应实现DialogCommunicator
。在对话框片段中添加DialogCommunicator
的实现
public class CustomDialogFragment extends DialogFragment implements DialogCommunicator {

 //override the method
}

编辑：
发生错误的另一个主要问题是由于上下文。
这里传递multi-dialogadapter=new-multi-dialogadapter（getContext（），itemsList）

如果要将getActivity（）传递给适配器，则相应的activity必须实现接口DialogCommunicator
，回调将转到activity，而不是CustomDialogFragment

因此，传递getContext（）
而不是getActivity（）
，因为CustomDialogFragment实现的是接口而不是活动。
而不是将上下文作为对象传递，您可以使用parent.getContext（）在onCreateViewHolder中获取构造函数。

此外，在onBindViewholder中，您忘了键入Cast viewholder。添加
MultiDialogViewHolder viewholder=(MultiDialogViewHolder)holder;

然后访问viewholder.getItemTextView（）.setText（item）
同样，在转换适配器中的上下文之前，对话框片段应实现DialogCommunicator
。在对话框片段中添加DialogCommunicator
的实现
public class CustomDialogFragment extends DialogFragment implements DialogCommunicator {

 //override the method
}

编辑：
发生错误的另一个主要问题是由于上下文。
这里传递multi-dialogadapter=new-multi-dialogadapter（getContext（），itemsList）

如果要将getActivity（）传递给适配器，则相应的activity必须实现接口DialogCommunicator
，回调将转到activity，而不是CustomDialogFragment

因此，请传递getContext（）
而不是getActivity（）
，因为CustomDialogFragment正在实现接口而不是活动。
您的崩溃非常明显：
MainActivity
无法转换为DialogCommunicator$Communicator

根据您发布的内容，您尚未在MainActivity
中实现此接口。你说：
我有一个在PostsListAdapter.java
和SecondActivity.java
中实现的接口
从postslistatadapterimplements DialogCommunicator.Communicator
行的可能性非常大