Android开发之ContentProvider组合LoaderManager加载数据（源代码分享）

Android开发之ContentProvider结合LoaderManager加载数据（源代码分享）

       contentprovider作为Android的四大存储方式之一，有着广泛的应用性，它暴露了数据地址，可以让其他应用访问数据，可以用于存储图片、通讯录等信息。 按照惯例我们还是看下谷歌官方文档对contentprovider的解释，contentprovider管理一个结构化的数据集。它封装了数据,并提供定义数据安全机制。contentProvider的标准接口实现多线程机制来连接数据,一般是用loadermanager异步加载数据。当你想要访问数据在一个contentprovider,我们使用ContentResolver对象在应用程序的上下文中作为沟通方法。ContentResolver用来解析请求码返还数据。

MainActivity的代码

package com.example.f14_contentprovider;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import android.net.Uri;import android.os.Bundle;import android.app.Activity;import android.app.LoaderManager;import android.app.LoaderManager.LoaderCallbacks;import android.content.ContentResolver;import android.content.ContentValues;import android.content.CursorLoader;import android.content.Loader;import android.database.Cursor;import android.view.Menu;import android.view.View;import android.widget.Button;import android.widget.ListView;import android.widget.SimpleCursorAdapter;public class MainActivity extends Activity implements LoaderCallbacks<Cursor> {	private Button button;	private ListView listView;	private LoaderManager loaderManager;	private SimpleCursorAdapter adapter;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);		button = (Button) this.findViewById(R.id.button1);		listView = (ListView) this.findViewById(R.id.listView1);		button.setOnClickListener(new View.OnClickListener() {			@Override			public void onClick(View v) {				// TODO Auto-generated method stub				ContentResolver resolver = getContentResolver();				Uri uri = Uri						.parse("content://com.example.f14_contentprovider.PersonContentProvider/person");				ContentValues values = new ContentValues();				values.put("name", "jack");				values.put("address", "hangzhou");				resolver.insert(uri, values);				loaderManager.restartLoader(1001, null, MainActivity.this);			}		});		loaderManager = getLoaderManager();		loaderManager.initLoader(1001, null, this);	}	@Override	public Loader<Cursor> onCreateLoader(int id, Bundle args) {		// TODO Auto-generated method stub		/**		 * CursorLoader该类用于加载程序,查询ContentResolver并返回一个指针。这个类实现了装载机协议查询游标的标准方法,		 * 基于AsyncTaskLoader执行游标查询在一个后台线程,以便它不会阻止应用程序的UI。		 */		CursorLoader loader = new CursorLoader(this);		Uri uri = Uri				.parse("content://com.example.f14_contentprovider.PersonContentProvider/person");		loader.setUri(uri);		loader.setProjection(new String[] { "name", "address" });		return loader;	}	@SuppressWarnings("deprecation")	@Override	public void onLoadFinished(Loader<Cursor> arg0, Cursor arg1) {		// TODO Auto-generated method stub		List<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();		// 加载数据		while (arg1.moveToNext()) {			HashMap<String, String> map = new HashMap<String, String>();			map.put("name", arg1.getString(arg1.getColumnIndex("name")));			map.put("address", arg1.getString(arg1.getColumnIndex("address")));			list.add(map);		}		adapter = new SimpleCursorAdapter(this, R.layout.item, arg1,				new String[] { "name", "address" }, new int[] { R.id.textView1,						R.id.textView2 });		listView.setAdapter(adapter);		adapter.notifyDataSetChanged();// 若内容发生变化 触发该方法	}	@Override	public void onLoaderReset(Loader<Cursor> arg0) {		// TODO Auto-generated method stub	}}

PersonContentProvider继承了ContentProvider的方法

package com.example.f14_contentprovider;import android.content.ContentProvider;import android.content.ContentResolver;import android.content.ContentUris;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.net.Uri;//要在manifest文件中注册providerpublic class PersonContentProvider extends ContentProvider {	private MyOpenHelper helper;	private static final UriMatcher matcher = new UriMatcher(			UriMatcher.NO_MATCH);// 专门用来匹配URI的类	private static final int PERSONS = 1;	private static final int PERSON = 2;	private ContentResolver resolver;	static {		matcher.addURI("com.example.f14_contentprovider.PersonContentProvider",				"person", PERSONS);		matcher.addURI("com.example.f14_contentprovider.PersonContentProvider",				"person/#", PERSON);	}	@Override	public int delete(Uri uri, String selection, String[] selectionArgs) {		// TODO Auto-generated method stub		return 0;	}	// 当您需要匹配一个URI,调用匹配(URI),用来来建立一个查询,返回类型,插入或删除一行。	@Override	public String getType(Uri arg0) {		// TODO Auto-generated method stub		int match = matcher.match(arg0);		switch (match) {		case PERSONS:			return "vnd.android.cursor.dir/person";		case PERSON:			return "vnd.android.cursor.item/person";		default:			return null;		}	}	@Override	public Uri insert(Uri uri, ContentValues values) {		// TODO Auto-generated method stub		SQLiteDatabase database = helper.getWritableDatabase();		long id = database.insert("person", null, values);		Uri rUri = ContentUris.withAppendedId(uri, id);		resolver.notifyChange(rUri, null);		return rUri;	}	@Override	public boolean onCreate() {		// TODO Auto-generated method stub		helper = new MyOpenHelper(getContext());		resolver = getContext().getContentResolver();		return true;	}	@Override	public Cursor query(Uri uri, String[] projection, String selection,			String[] selectionArgs, String sortOrder) {		// TODO Auto-generated method stub		Cursor cursor = null;		int flag = matcher.match(uri);		SQLiteDatabase database = helper.getReadableDatabase();		switch (flag) {		case PERSONS:            cursor=database.query("person", null, null, null,null, null, null);			break;		case PERSON:			long _id = ContentUris.parseId(uri);			String where_value = " _id  = " + _id;			if (selection != null && !selection.equals("")) {				where_value += selection;			}			cursor = database.query("person", projection, where_value,					selectionArgs, null, null, sortOrder);			break;		default:			break;		}		cursor.setNotificationUri(resolver, uri);		return cursor;	}	@Override	public int update(Uri arg0, ContentValues arg1, String arg2, String[] arg3) {		// TODO Auto-generated method stub		return 0;	}}

数据库创建类MyopenHelper

package com.example.f14_contentprovider;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class MyOpenHelper extends SQLiteOpenHelper {	private static final int DATABASE_VERSION = 1;	private static final String PERSON_TABLE_NAME = "person";	public MyOpenHelper(Context context) {		super(context, PERSON_TABLE_NAME, null, DATABASE_VERSION);		// TODO Auto-generated constructor stub	}	@Override	public void onCreate(SQLiteDatabase db) {		// TODO Auto-generated method stub		db.execSQL("create table "				+ PERSON_TABLE_NAME				+ "(_id integer primary key autoincrement,name varchar(64),address varchar(64))");	}	@Override	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {		// TODO Auto-generated method stub	}}

1楼u01390087518分钟前

LoaderManager的介绍好像粗略了一点