Question

我在设备上运行代码时遇到这些错误

FATAL EXCEPTION: main
Process: com.androidapp.restart, PID: 9401
java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ListView
    at com.androidapp.restart.Events.onCreateView(Events.java:46)
    at android.app.Fragment.performCreateView(Fragment.java:2508)
    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1279)
    at android.app.FragmentManagerImpl.addAddedFragments(FragmentManager.java:2407)
    at android.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2186)
    at android.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2142)
    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2043)
    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:719)
    at android.os.Handler.handleCallback(Handler.java:790)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

现在基于我在这里看到的代码库，它在错误中说明。请帮助我初学者 Events.java

package com.androidapp.restart;

import android.app.Fragment;
import android.app.LoaderManager;
import android.app.ProgressDialog;
import android.content.ContentUris;
import android.content.CursorLoader;
import android.content.Intent;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import android.app.FragmentManager;

import com.getbase.floatingactionbutton.FloatingActionButton;


/**
 * Created by aa215995 on 3/2/2018.
 */

public class Events extends Fragment implements 
LoaderManager.LoaderCallbacks<Cursor> {

    private FloatingActionButton mAddEventButton;
    private Toolbar mToolbar;
    EventCursorAdapter mCursorAdapter;
    EventDbHelper eventDbHelper = new EventDbHelper(getActivity());
    ListView eventListView;
    ProgressDialog prgDialog;



    private static final int VEHICLE_LOADER = 0;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup 
container, Bundle savedInstanceState) {
        eventListView = (ListView) inflater.inflate(R.layout.nav_events, 
container, false);


        mToolbar = (Toolbar) getView().findViewById(R.id.toolbar);
        ((AppCompatActivity)getActivity()).setSupportActionBar(mToolbar);
        mToolbar.setTitle("Events");


        eventListView = (ListView) getView().findViewById(R.id.list);
        View emptyView = getView().findViewById(R.id.empty_view);
        eventListView.setEmptyView(emptyView);


        mCursorAdapter = new EventCursorAdapter(getActivity(), null);
        eventListView.setAdapter(mCursorAdapter);

        eventListView.setOnItemClickListener(new 
AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View 
view, int position, long id) {

                Intent intent = new Intent(view.getContext(), 
AddEvent.class);


                Uri currentVehicleUri = 
ContentUris.withAppendedId(EventContract.EventEntry.CONTENT_URI, id);

                // Set the URI on the data field of the intent
                intent.setData(currentVehicleUri);

                startActivity(intent);

            }
        });


        mAddEventButton = (FloatingActionButton) 
getView().findViewById(R.id.fab);

        mAddEventButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                 Intent intent = new Intent(v.getContext(), 
AddEvent.class);
                startActivity(intent);
            }
        });

        getLoaderManager().initLoader(VEHICLE_LOADER, null, this);
        return eventListView;


    }

    @Override
    public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
        String[] projection = {
                EventContract.EventEntry._ID,
                EventContract.EventEntry.KEY_TITLE,
                EventContract.EventEntry.KEY_DATE,
                EventContract.EventEntry.KEY_TIME,
                EventContract.EventEntry.KEY_REPEAT,
                EventContract.EventEntry.KEY_REPEAT_NO,
                EventContract.EventEntry.KEY_REPEAT_TYPE,
                EventContract.EventEntry.KEY_ACTIVE

        };

        return new CursorLoader(getActivity(),   // Parent activity 
context
                EventContract.EventEntry.CONTENT_URI,   // Provider 
content URI to query
                projection,             // Columns to include in the 
resulting Cursor
                null,                   // No selection clause
                null,                   // No selection arguments
                null);                  // Default sort order

    }

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
        mCursorAdapter.swapCursor(cursor);

    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        mCursorAdapter.swapCursor(null);

    }
}

片段Java（它说我在这里得到一个错误：

 if (mFragmentManager != null) {
        writer.print(prefix); writer.print("mFragmentManager=");
        writer.println(mFragmentManager);
    }
    if (mHost != null) {
        writer.print(prefix); writer.print("mHost=");
        writer.println(mHost);
    }
    if (mParentFragment != null) {
        writer.print(prefix); writer.print("mParentFragment=");
        writer.println(mParentFragment);

总之，我正在尝试运行应用程序，但每次我进入某个部分，在这种情况下，Events.java是nav_events.xml布局，我不断收到错误，不知道如何解决它< / p>

Answer 1

您的错误可在Events.java文件的第46行找到。

当你的视图中的一个LinearLayout似乎是XML文件中的一个LinearLayout时，你正在给视图充气并在Java中声明它是一个ListView（第46行）。

此后，您正在使用getView（）。只有在onCreateView（）返回一个View后才能正确使用该函数，绝对不在其中。

评论后编辑：您还没有返回View，因为您无法在return语句后执行任何代码。现在没有你的布局文件，我只能推测，但可能会替换

eventListView = (ListView) inflater.inflate(R.layout.nav_events, container, false);

与

View rootView = (LinearLayout) inflater.inflate(R.layout.nav_events, container, false);

然后用rootView替换该代码块中出现的所有getView（）。最后

return rootView;

我在设备上运行应用程序时出现此错误

1 个答案: