Question

这个问题与通过带有Java的android studio进行android开发有关。

当ListViewLoader调用getLoaderManager接受“ this”上下文时，我遇到了麻烦（扩展了ListActivity实现LoaderManager.LoaderCallbacks）。

我基本上是在以下链接中复制并粘贴代码：https://developer.android.com/guide/topics/ui/layout/listview#java。我在这里（getLoaderManager().initLoader() doesn't accept 'this' as argument though the class (ListFragment) implements LoaderManager.LoaderCallbacks<Cursor>）阅读了答案。我试图确保我的导入是正确的，并且我的最小sdk是15，所以这应该不是问题。我尝试使用getSupportLoaderManager，而android studio无法解决它。我不太了解答案对于片段的含义。但是，当我从官方文档中复制代码时，我认为不需要。

我在构建时遇到的错误如下：

error: method initLoader in class LoaderManager cannot be applied to given types;
required: int,Bundle,LoaderCallbacks<D>
found: int,<null>,ListViewLoader
reason: cannot infer type-variable(s) D
(argument mismatch; ListViewLoader cannot be converted to LoaderCallbacks<D>)
where D is a type-variable:
D extends Object declared in method <D>initLoader(int,Bundle,LoaderCallbacks<D>)

我试图强制类型转换，但这只会导致类似的运行时错误（如预期的那样）。

请参阅下面的完整代码，我要缺少什么。

package com.example.tracker2;

import android.app.ActionBar;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.BaseColumns;

import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.SimpleCursorAdapter;

public class ListViewLoader extends ListActivity implements LoaderManager.LoaderCallbacks<Cursor> {

    SimpleCursorAdapter mAdapter;

    String[] projection = {
            BaseColumns._ID,
            PriceListContract.PriceList.COLUMN1_NAME_TITLE,
            PriceListContract.PriceList.COLUMN2_NAME_TITLE
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ProgressBar progressBar = new ProgressBar(this);
        progressBar.setLayoutParams(new ActionBar.LayoutParams(ActionBar.LayoutParams.WRAP_CONTENT,
                ActionBar.LayoutParams.WRAP_CONTENT, Gravity.CENTER));
        progressBar.setIndeterminate(true);
        getListView().setEmptyView(progressBar);

        ViewGroup root = (ViewGroup) findViewById(android.R.id.content);
        root.addView(progressBar);


        String[] fromColumns = {PriceListContract.PriceList.COLUMN1_NAME_TITLE, PriceListContract.PriceList.COLUMN2_NAME_TITLE};
        int[] toViews = {android.R.id.text1, android.R.id.text2}; // The TextView in simple_list_item_1


        mAdapter = new SimpleCursorAdapter(this,
                android.R.layout.simple_list_item_2, null,
                fromColumns, toViews, 0);
        setListAdapter(mAdapter);

        // !!This following line is the issue!!
        getLoaderManager().initLoader(0, null, this);

    }


    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
        return new CursorLoader(this, PriceListContract.PriceList.CONTENT_URI,
                projection, null    , null, null);
    }


    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        mAdapter.swapCursor(data);
    }


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

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
    }
}

getLoaderManager不接受实现LoaderManger.LoaderCallbacks <cursor>

0 个答案: