java.lang.NullPointerException：尝试在空对象引用上调用虚方法'java.lang.String android.net.Uri.getScheme（）'

Question

java.lang.NullPointerException：尝试在空对象引用上调用虚方法'java.lang.String android.net.Uri.getScheme（）'

我想知道如何在列表视图中只删除一个元素我添加alertDialog，当用户在列表中的元素上单击long时，会出现alertdialog

delete方法中的错误

private void deleteAlert() {

        int rowsDeleted = getActivity().getContentResolver().delete(mCurrentPetUri, null, null); //error
        if (rowsDeleted == 0) {
            Toast.makeText(getActivity(), getString(R.string.editor_delete_alert_failed),
                    Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(getActivity(), getString(R.string.editor_delete_alert_successful),
                    Toast.LENGTH_SHORT).show();
        }

}

而这个片段

package com.amira.amira.amira.ChatCalendarProfile.Calendar;


import android.app.AlertDialog;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListView;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.support.v4.widget.CursorAdapter;
import android.content.ContentUris;
import android.content.ContentValues;
import android.widget.Toast;

import com.amira.amira.amira.R;

import static com.amira.amira.amira.ChatCalendarProfile.Calendar.data.AlertContract.*;


public class CalendarFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor> {
    private static final int ALERT_LOADER = 0;
    AlertCursorAdapter mCursorAdapter;
    private Uri mCurrentPetUri;

    public CalendarFragment() {
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.activity_calendar_fragment, container, false);

        com.github.clans.fab.FloatingActionButton addAlert = rootView.findViewById(R.id.add_alert);
        addAlert.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getActivity(), EditorActivity.class);
                startActivity(intent);
            }
        });
        ListView AlertListView = (ListView) rootView.findViewById(R.id.list);
        View emptyView = rootView.findViewById(R.id.empty);
        AlertListView.setEmptyView(emptyView);
        Intent intent = getActivity().getIntent();
        mCurrentPetUri = intent.getData();

        AlertListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> arg0, final View arg1, final int pos, long id) {
                showDeleteConfirmationDialog();
                return true;
            }
        });

        mCursorAdapter = new AlertCursorAdapter(getActivity(), null);
        AlertListView.setAdapter(mCursorAdapter);
        AlertListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                Intent intent = new Intent(getActivity(), EditorActivity.class);
                Uri currentAlertUri = ContentUris.withAppendedId(AlertEntry.CONTENT_URI, id);
                intent.setData(currentAlertUri);
                startActivity(intent);
            }
        });

        getLoaderManager().initLoader(ALERT_LOADER, null, this);


        return rootView;
    }

    private void showDeleteConfirmationDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(R.string.delete_dialog_msg);
        builder.setPositiveButton(R.string.delete, new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                deletePet();
            }
        });
        builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                if (dialog != null) {
                    dialog.dismiss();
                }
            }
        });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    @Override
    public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
        String[] projection = {
                AlertEntry._ID,
                AlertEntry.COLUMN_ALERT_TITLE,
                AlertEntry.COLUMN_ALERT_LOCATION,
                AlertEntry.COLUMN_ALERT_OCCASION_DATE,
                AlertEntry.COLUMN_ALERT_OCCASION_TIME};
        return new CursorLoader(getActivity(),   // Parent activity context
                AlertEntry.CONTENT_URI,   // Provider content URI to query
                projection,             // Columns to include in the resulting Cursor
                null,                   // No selection clause
                null,                   // No selection arguments
                null);
    }
    private void deletePet() {

            int rowsDeleted = getActivity().getContentResolver().delete(mCurrentPetUri, null, null);
            if (rowsDeleted == 0) {
                Toast.makeText(getActivity(), getString(R.string.editor_delete_alert_failed),
                        Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(getActivity(), getString(R.string.editor_delete_alert_successful),
                        Toast.LENGTH_SHORT).show();
            }

    }

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

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

Answer 1

当你开始你的活动时，检查你用setData方法设置的数据，因为intent.getData()现在是null