java - 错误的第三个论点，但应该通过视频教程工作

Question

我正在关注 tutorial但是当我到达要制作的部分时:

getLoaderManager().initLoader(0, null, this);

this 造成了问题。它引用了 MainActivity 但它不会接受实现。

它的具体信息是:

Wrong 3rd argument type. Found: 'com.example.plainolnotes.MainActivity', required: 'android.app.LoaderManager.LoaderCallbacks

package com.example.plainolnotes;

import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
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.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity
        implements LoaderManager.LoaderCallbacks<Cursor>
{
    private CursorAdapter cursorAdapter;

    // @TargetApi(Build.VERSION_CODES.JELLY_BEAN) //Not a good long term solution

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        insertNote("New_note");
        /*
        Cursor cursor = getContentResolver().query(NotesProvider.CONTENT_URI,
                DBOpenHelper.ALL_COLUMNS, null, null, null, null);
                */
        String[] from = {DBOpenHelper.NOTE_TEXT};
        int[] to = {android.R.id.text1};

        cursorAdapter = new SimpleCursorAdapter(this,
                android.R.layout.simple_list_item_1, null, from, to, 0);
        ListView list = (ListView) findViewById(android.R.id.list);
        list.setAdapter(cursorAdapter);

        //getLoaderManager().initLoader(0, null, this);
        getLoaderManager().initLoader(0, null, this);

        /*
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        */
    }

    private void insertNote(String noteText) {
        ContentValues values = new ContentValues();
        values.put(DBOpenHelper.NOTE_TEXT, noteText);
        Uri noteUri = getContentResolver().insert(NotesProvider.CONTENT_URI,
                values);
        Log.d("MainActivity", "Inserted note " + noteUri.getLastPathSegment());
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        //Loaded when data is needed for the contentProvider
        return new CursorLoader(this, NotesProvider.CONTENT_URI,
                null, null, null, null);
    }

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

    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        //data needs to be wiped out
        cursorAdapter.swapCursor(null);

    }
}

Answer 1

问题出在导入语句上

import android.support.v4.app.LoaderManager;

而需要的是

android.app.LoaderManager.LoaderCallbacks

替换它来解决你的问题