一、ContentProvider保存数据介绍
一个程序可以通过实现一个ContentProvider的抽象接口将自己的数据完全暴露出去，而且ContentProvider是以类似数据库中表的方式将数据暴露的。那么外界获取其提供的数据，也就应该与从数据库中获取数据的操作基本一样，只不过是采用URL来表示外界需要访问的“数据库”。
ContentProvider提供了一种多应用间数据共享的方式。
ContentProvider是个实现了一组用于提供其他应用程序存取数据的标准方法的类。应用程序可以在ContentProvider中执行如下操作：查询数据、修改数据、添加数据、删除数据。
标准的ContentProvider：Android提供了一些已经在系统中实现的标准ContentProvider，比如联系人信息，图片库等等，可以用这些ContentProvider来访问设备上存储的联系人信息、图片等等。
在ContentProvider中使用的查询字符串有别于标准的SQL查询，很多诸如select、add、delete、modify等操作都使用一种特殊的URL进行，这种URL由3部分组成，“content://”，代表数据的路径和一个可选的表示数据的ID。
content://media/internal/images 这个URL将返回设备上存储的所有图片
content://contacts/people/ 这个URL将返回设备上的所有联系人信息
content://contacts/people/45 这个URL返回单个结果（联系人信息中ID为45的联系人记录）
如果想要存储字节型数据，比如位图文件等，那保存该数据的数据列其实是一个表示实际保存保存文件的URL字符串，客户端通过它来读取对应的文件数据，处理这种数据类型的ContentProvider需要实现一个名为_data的字段，_data字段列出了该文件在Android文件系统上的精确路径。这个字段不仅是供客户端使用，而且也可以供ContentResolver使用。客户端可以调用ContentResolver.openOutputStream()方法来处理该URL指向的文件资源，如果是ContentResolver本身的话，由于其持有的权限比客户端要高，所以它能直接访问该数据文件。
二、使用方法
大多数ContentProvider使用Android文件系统或者SQLite数据库来保持数据，但是也可以以任何方式来存储。本例用SQLite数据库来保持数据。
1.创建一个接口，定义了一个名为CONTENT_URL，并且是public static final的Uri类型的类变量，必须为其指定一个唯一的字符串值，最好的方案是类的全称，和数据列的名称。
public interface IProivderMetaData {public static final String AUTHORITY = "com.zhangmiao.datastoragedemo";public static final String DB_NAME = "book.db";public static final int VERSION = 1;public interface BookTableMetaData extends BaseColumns {public static final String TABLE_NAME = "book";public static final Uri CONTENT_URI = Uri.parse("content://"+ AUTHORITY + "/" + TABLE_NAME);public static final String BOOK_ID = "_id";public static final String BOOK_NAME = "name";public static final String BOOK_PUBLISHER = "publisher";public static final String SORT_ORDER = "_id desc";public static final String CONTENT_LIST = "vnd.android.cursor.dir/vnd.bookprovider.book";public static final String CONTENT_ITEM = "vnd.android.cursor.item/vnd.bookprovider.book";}}
2.实现SQLiteOpenHelper
public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProivderMetaData {private static final String TAG = "ContentProviderDBHelper";public ContentProviderDBHelper(Context context) {super(context, DB_NAME, null, VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {...}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {...}}
3.创建一个继承了ContentProvider父类的类
public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProivderMetaData {public ContentProviderDBHelper(Context context) {super(context, DB_NAME, null, VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {...}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {...}}
4.在AndroidManifest.xml中使用标签来设置调用ContentProvider。
<providerandroid:authorities="com.zhangmiao.datastoragedemo"android:name=".BookContentProvider"/>
5.增加数据
mContentResolver = getContentResolver();String[] bookNames = new String[]{"Chinese", "Math", "English", "Sports"};String[] bookPublishers = new String[]{"XinHua", "GongXin", "DianZi", "YouDian"};for (int i = 0; i < bookNames.length; i++) {ContentValues values = new ContentValues();values.put(IProivderMetaData.BookTableMetaData.BOOK_NAME, bookNames[i]);values.put(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER, bookPublishers[i]);mContentResolver.insert(IProivderMetaData.BookTableMetaData.CONTENT_URI, values);}
6.删除数据
String bookId = "1";if (!"".equals(bookId)) {ContentValues values1 = new ContentValues();values1.put(IProivderMetaData.BookTableMetaData.BOOK_ID,bookId);mContentResolver.delete(Uri.withAppendedPath(
IProivderMetaData.BookTableMetaData.CONTENT_URI,bookId),
"_id = ?",new String[]{bookId}
);} else {mContentResolver.delete(IProivderMetaData.BookTableMetaData.CONTENT_URI,null,null
);}
7.查询数据
Cursor cursor = mContentResolver.query(IProivderMetaData.BookTableMetaData.CONTENT_URI,
null, null, null, null);String text = "";if (cursor != null) {while (cursor.moveToNext()) {String bookIdText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_ID));String bookNameText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_NAME));String bookPublisherText =
cursor.getString(cursor.getColumnIndex(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER));text += "id = " + bookIdText + ",name = " + bookNameText +
",publisher = " + bookPublisherText + "\n";}cursor.close();mTableInfo.setText(text);}
8.更新数据
String bookId1 = "2";String bookName = "Art";String bookPublisher = "TieDao";ContentValues values2 = new ContentValues();values2.put(IProivderMetaData.BookTableMetaData.BOOK_NAME,bookName);values2.put(IProivderMetaData.BookTableMetaData.BOOK_PUBLISHER,bookPublisher);if ("".equals(bookId1)) {mContentResolver.update(IProivderMetaData.BookTableMetaData.CONTENT_URI,values2, null, null);} else {mContentResolver.update(Uri.withAppendedPath(IProivderMetaData.BookTableMetaData.CONTENT_URI, bookId1),values2, "_id = ? ", new String[]{bookId1}
);}
三、小案例
1.添加strings.xml文件
<string name="content_provider">ContentProvider</string><string name="add_data">增加数据</string><string name="delete_data">删除数据</string><string name="update_data">更改数据</string><string name="query_data">查询数据</string>
2.修改activity_main.xml文件
<?xml version="1.0" encoding="utf-8"?><android.support.design.widget.CoordinatorLayout xmlns:android="/apk/res/android"xmlns:tools="/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:fitsSystemWindows="true"tools:context="com.zhangmiao.datastoragedemo.MainActivity"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center_horizontal"android:text="@string/content_provider" /><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginBottom="@dimen/fab_margin"android:layout_marginTop="@dimen/fab_margin"android:orientation="horizontal"><Buttonandroid:id="@+id/provider_add"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="@string/add_data" /><Buttonandroid:id="@+id/provider_delete"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="@string/delete_data" /><Buttonandroid:id="@+id/provider_update"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="@string/update_data" /><Buttonandroid:id="@+id/provider_query"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:text="@string/query_data" /></LinearLayout><TextViewandroid:id="@+id/table_info"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="@string/app_name" /></LinearLayout></android.support.design.widget.CoordinatorLayout>
3.添加IProviderMetaData接口
package com.zhangmiao.datastoragedemo;import .Uri;import android.provider.BaseColumns;/*** Created by zhangmiao on /12/20.*/public interface IProviderMetaData {public static final String AUTHORITY = "com.zhangmiao.datastoragedemo";public static final String DB_NAME = "book.db";public static final int VERSION = 1;public interface BookTableMetaData extends BaseColumns {public static final String TABLE_NAME = "book";public static final Uri CONTENT_URI = Uri.parse("content://"+ AUTHORITY + "/" + TABLE_NAME);public static final String BOOK_ID = "_id";public static final String BOOK_NAME = "name";public static final String BOOK_PUBLISHER = "publisher";public static final String SORT_ORDER = "_id desc";public static final String CONTENT_LIST = "vnd.android.cursor.dir/vnd.bookprovider.book";public static final String CONTENT_ITEM = "vnd.android.cursor.item/vnd.bookprovider.book";}}
4.添加ContentProviderDBHelper类
package com.zhangmiao.datastoragedemo;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;/*** Created by zhangmiao on /12/20.*/public class ContentProviderDBHelper extends SQLiteOpenHelper implements IProviderMetaData {private static final String TAG = "ContentProviderDBHelper";public ContentProviderDBHelper(Context context) {super(context, DB_NAME, null, VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {String TABLESQL = "CREATE TABLE IF NOT EXISTS "+ BookTableMetaData.TABLE_NAME + " ("+ BookTableMetaData.BOOK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"+ BookTableMetaData.BOOK_NAME + " VARCHAR,"+ BookTableMetaData.BOOK_PUBLISHER + " VARCHAR)";db.execSQL(TABLESQL);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {Log.w(TAG, "Upgrading database from version " + oldVersion + "to"+ newVersion + ", which will destroy all old data");db.execSQL("DROP TABLE IF EXISTS " + DB_NAME);onCreate(db);}}
5.添加BookContentProvider类
package com.zhangmiao.datastoragedemo;import android.content.ContentProvider;import android.content.ContentUris;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import .Uri;import android.support.annotation.Nullable;import android.util.Log;/*** Created by zhangmiao on /12/21.*/public class BookContentProvider extends ContentProvider {private static final String TAG = "BookContentProvider";private static UriMatcher uriMatcher = null;private static final int BOOKS = 1;private static final int BOOK = 2;private ContentProviderDBHelper dbHelper;private SQLiteDatabase db;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(IProviderMetaData.AUTHORITY,IProviderMetaData.BookTableMetaData.TABLE_NAME, BOOKS);uriMatcher.addURI(IProviderMetaData.AUTHORITY,IProviderMetaData.BookTableMetaData.TABLE_NAME + "/#",BOOK);}@Overridepublic boolean onCreate() {dbHelper = new ContentProviderDBHelper(getContext());return (dbHelper == null) ? false : true;}@Nullable@Overridepublic String getType(Uri uri) {switch (uriMatcher.match(uri)) {case BOOKS:return IProviderMetaData.BookTableMetaData.CONTENT_LIST;case BOOK:return IProviderMetaData.BookTableMetaData.CONTENT_ITEM;default:throw new IllegalArgumentException("This is a unKnow Uri"+ uri.toString());}}@Nullable@Overridepublic Uri insert(Uri uri, ContentValues values) {switch (uriMatcher.match(uri)) {case BOOKS:db = dbHelper.getWritableDatabase();long rowId = db.insert(IProviderMetaData.BookTableMetaData.TABLE_NAME,IProviderMetaData.BookTableMetaData.BOOK_ID,values);Uri insertUri = Uri.withAppendedPath(uri, "/" + rowId);Log.i(TAG, "insertUri:" + insertUri.toString());getContext().getContentResolver().notifyChange(uri, null);return insertUri;case BOOK:default:throw new IllegalArgumentException("This is a unKnow Uri"+ uri.toString());}}@Nullable@Overridepublic Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {db = dbHelper.getReadableDatabase();switch (uriMatcher.match(uri)) {case BOOKS:return db.query(IProviderMetaData.BookTableMetaData.TABLE_NAME,projection, selection, selectionArgs, null, null,sortOrder);case BOOK:long id = ContentUris.parseId(uri);String where = "_id=" + id;if (selection != null && !"".equals(selection)) {where = selection + " and " + where;}return db.query(IProviderMetaData.BookTableMetaData.TABLE_NAME,projection, where, selectionArgs, null, null, sortOrder);default:throw new IllegalArgumentException("This is a unKnow Uri"+ uri.toString());}}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {db = dbHelper.getWritableDatabase();switch (uriMatcher.match(uri)) {case BOOKS:return db.delete(IProviderMetaData.BookTableMetaData.TABLE_NAME,selection, selectionArgs);case BOOK:long id = ContentUris.parseId(uri);String where = "_id=" + id;if (selection != null && !"".equals(selection)) {where = selection + " and " + where;}return db.delete(IProviderMetaData.BookTableMetaData.TABLE_NAME,selection, selectionArgs);default:throw new IllegalArgumentException("This is a unKnow Uri"+ uri.toString());}}@Overridepublic int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {db = dbHelper.getWritableDatabase();switch (uriMatcher.match(uri)) {case BOOKS:return db.update(IProviderMetaData.BookTableMetaData.TABLE_NAME,values, null, null);case BOOK:long id = ContentUris.parseId(uri);String where = "_id=" + id;if (selection != null && !"".equals(selection)) {where = selection + " and " + where;}return db.update(IProviderMetaData.BookTableMetaData.TABLE_NAME,values, selection, selectionArgs);default:throw new IllegalArgumentException("This is a unKnow Uri"+ uri.toString());}}}
6.修改AndroidManifest.xml文件
<providerandroid:authorities="com.zhangmiao.datastoragedemo"android:name=".BookContentProvider"/>
7.修改MainActivity
package com.zhangmiao.datastoragedemo;import android.content.ContentResolver;import android.content.ContentValues;import android.database.Cursor;import .*;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.TextView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity implements View.OnClickListener {private ContentResolver mContentResolver;private BookContentProvider mBookContentProvider;private TextView mTableInfo;@Overrideprotected void onCreate(Bundle savedInstanceState) {Log.v("MainActivity", "onCreate");super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button cpAdd = (Button) findViewById(R.id.provider_add);Button cpDelete = (Button) findViewById(R.id.provider_delete);Button cpUpdate = (Button) findViewById(R.id.provider_update);Button cpQuery = (Button) findViewById(R.id.provider_query);mTableInfo = (TextView) findViewById(R.id.table_info);cpAdd.setOnClickListener(this);cpDelete.setOnClickListener(this);cpQuery.setOnClickListener(this);cpUpdate.setOnClickListener(this);}@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.provider_add:mContentResolver = getContentResolver();String[] bookNames = new String[]{"Chinese", "Math", "English", "Sports"};String[] bookPublishers = new String[]{"XinHua", "GongXin", "DianZi", "YouDian"};for (int i = 0; i < bookNames.length; i++) {ContentValues values = new ContentValues();values.put(IProviderMetaData.BookTableMetaData.BOOK_NAME, bookNames[i]);values.put(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER, bookPublishers[i]);mContentResolver.insert(IProviderMetaData.BookTableMetaData.CONTENT_URI, values);}break;case R.id.provider_delete:String bookId = "1";if (!"".equals(bookId)) {ContentValues values1 = new ContentValues();values1.put(IProviderMetaData.BookTableMetaData.BOOK_ID,bookId);mContentResolver.delete(Uri.withAppendedPath(IProviderMetaData.BookTableMetaData.CONTENT_URI,bookId), "_id = ?",new String[]{bookId});} else {mContentResolver.delete(IProviderMetaData.BookTableMetaData.CONTENT_URI,null,null);}break;case R.id.provider_query:Cursor cursor = mContentResolver.query(IProviderMetaData.BookTableMetaData.CONTENT_URI, null, null, null, null);String text = "";if (cursor != null) {while (cursor.moveToNext()) {String bookIdText =cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_ID));String bookNameText =cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_NAME));String bookPublisherText =cursor.getString(cursor.getColumnIndex(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER));text += "id = " + bookIdText + ",name = " + bookNameText + ",publisher = " + bookPublisherText + "\n";}cursor.close();mTableInfo.setText(text);}break;case R.id.provider_update:String bookId1 = "2";String bookName = "Art";String bookPublisher = "TieDao";ContentValues values2 = new ContentValues();values2.put(IProviderMetaData.BookTableMetaData.BOOK_NAME,bookName);values2.put(IProviderMetaData.BookTableMetaData.BOOK_PUBLISHER,bookPublisher);if ("".equals(bookId1)) {mContentResolver.update(IProviderMetaData.BookTableMetaData.CONTENT_URI,values2, null, null);} else {mContentResolver.update(Uri.withAppendedPath(IProviderMetaData.BookTableMetaData.CONTENT_URI, bookId1),values2, "_id = ? ", new String[]{bookId1});}break;default:Log.v("MainActivity", "default");break;}}}
代码下载地址：/ZhangMiao147/DataStorageDemo
参考文章：/p/562.html
