通过 LoaderManager + CursorLoader加载通讯录中所有人

通过上面4篇LoaderManager的学习，我们可能已经熟悉了LoaderManager。可能第四篇学习时，我们会感觉好有点小吃力。
所以我们现在从最基础的Demo练习。先不自定义Loader,先实现一个简单的小Demo。

通过Fragment加载通讯录中所有人

因为好长时间没用过Fragment了，今天重新练练Fragment。

1、自定义Fragment

//CursorLoaderFragment实现LoaderManager.LoaderCallbacks<Cursor>接口public class CursorLoaderFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor>{    private static final int LOADER_ID = 100;    private LoaderManager lm;    private SimpleCursorAdapter adapter;    private List<String> datas = null;    private String[] from;    private int[] to;    @Override    //在onCreate中初始化我们需要用到的数据    public void onCreate(Bundle savedInstanceState) {        // TODO Auto-generated method stub        super.onCreate(savedInstanceState);        lm = getActivity().getLoaderManager();        lm.initLoader(LOADER_ID, null, this);        from = new String[] {ContactsContract.Contacts.DISPLAY_NAME};        to = new int[]{R.id.data};        //在这里我们先把Cursor为null        adapter = new SimpleCursorAdapter(getActivity(), R.layout.simplecursor, null, from, to, 0);    }    //在onCreateView中加载自定义的Fragment的View只显示名字的ListView    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.fragment_listview, null);        ListView listView = (ListView) view.findViewById(R.id.listview);        listView.setAdapter(adapter);        return view;    }    @Override    public void onDestroy() {        // TODO Auto-generated method stub        super.onDestroy();        lm.destroyLoader(LOADER_ID);    }    @Override    //LoaderManager将会在它第一次创建Loader的时候调用该方法    public Loader<Cursor> onCreateLoader(int id, Bundle args) {        // TODO Auto-generated method stub        String[] projection = {ContactsContract.Contacts._ID,ContactsContract.Contacts.DISPLAY_NAME};        return new CursorLoader(getActivity(), ContactsContract.Contacts.CONTENT_URI, projection,                 null, null, null);    }    @Override    //Loader创建完毕将自动调用    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {        // TODO Auto-generated method stub        if(LOADER_ID == loader.getId()){            //SimpleCursorAdapter中把之前的OldCursor(null)交换为现在的data            adapter.swapCursor(data);        }    }    @Override    //当Loader中的数据被重置时，将被调用。    public void onLoaderReset(Loader<Cursor> loader) {        // TODO Auto-generated method stub        //数据被重置时，将Cursor置为null        adapter.swapCursor(null);    }}

2、Fragment的布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <ListView         android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/listview"        /></LinearLayout>

3、Adapter中添加的布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <TextView         android:layout_width="match_parent"        android:layout_height="wrap_content"        android:id="@+id/data"        /></LinearLayout>

4、Activity布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    >    <FrameLayout         android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/content"        /></LinearLayout>

5、Activity

public class MainActivity extends Activity {    private static final String TAG = "LOADER";    private FragmentManager fragmentManager;    private Fragment fragment;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        fragmentManager = getFragmentManager();        fragment = new CursorLoaderFragment();        fragmentManager.beginTransaction().replace(R.id.content, fragment, TAG).commit();    }}

通过上面的实例分析用一张图来介绍Activity/Fragment与LoaderManager、LoaderManager与Loader之间的关系：

下面我们将从源码的角度来分析Activity/Fragment是如何通过生命周期来管理Cursor。