ContentProvider简介
内容提供者( ContentProvider ) 主要用于不同应用程序之间的数据共享,并且提供CRUD,内容提供者一般提供两种用法:
1 第一种使用现有的内容提供器来读取和操作数据比如: 查询 音乐 , 视频 , 联系人等等一些信息;
2 第二种就是实现自己的内容提供器给我们的程序提供外界的接口
下面我会用一个我写好的一个类来给大家介绍基本的方法 :
package com.example.liangshaoteng.contentprovider;import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.net.Uri;
import android.support.annotation.Nullable;
import android.widget.Toast;/*** Created by liangshaoteng on 17-6-21.*/public class MyContentProvider extends ContentProvider {public static final int TABLE1_DIR = 0;public static final int TABLE1_ITEM = 1;public static final int TABLE2_DIR = 2;public static final int TABLE2_ITEM = 3;//一般都是用我们的包名public static final String uriPath = "com.example.liangshaoteng.contentprovider";private static UriMatcher uriMatcher;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(uriPath, "table1", TABLE1_DIR);uriMatcher.addURI(uriPath, "table1/#", TABLE1_ITEM);uriMatcher.addURI(uriPath, "table2", TABLE2_DIR);uriMatcher.addURI(uriPath, "table2/#", TABLE2_ITEM);}@Overridepublic boolean onCreate() {return false;}/*** @param uri //用来查询那张表* @param projection //用来查询那些列* @param selection* @param selectionArgs //用于查询那些行* @param sortOrder //用于对结果进行排序* @return*/@Nullable@Overridepublic Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {switch (uriMatcher.match(uri)) {case TABLE1_DIR:Toast.makeText(getContext(), "查询table1表中所有的数据", Toast.LENGTH_LONG).show();break;case TABLE1_ITEM:Toast.makeText(getContext(), "查询table1表中单条的数据", Toast.LENGTH_LONG).show();break;case TABLE2_DIR:Toast.makeText(getContext(), "查询table2表中所有的数据", Toast.LENGTH_LONG).show();break;case TABLE2_ITEM:Toast.makeText(getContext(), "查询table2表中单条的数据", Toast.LENGTH_LONG).show();break;default:break;}return null;}/*** @param uri //根据传来的uri返回相应的MIME* @return*/@Nullable@Overridepublic String getType(Uri uri) {switch (uriMatcher.match(uri)) {case TABLE1_DIR:return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.table1";case TABLE1_ITEM:return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.table1";case TABLE2_DIR:return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.table2";case TABLE2_ITEM:return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.table2";default:break;}return null;}/*** @param uri //确定添加到那张表* @param values //待添加的数据保存在values* @return //返回一条表示新添加数据的uri*/@Nullable@Overridepublic Uri insert(Uri uri, ContentValues values) {return null;}/*** @param uri //用来删除那张表* @param selection //用来约束删除那些行* @param selectionArgs* @return //并返回删除的行数*/@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {return 0;}/*** @param uri //用于更新那张表* @param values //新数据保存在values* @param selection* @param selectionArgs //约束更新哪一行* @return*/@Overridepublic int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {return 0;}
}
对于访问现有的内容提供器我就不多说了,就给大家看一下我写的一个CRUD的代码看着挺多其实挺简单的,有什么不懂得或者有不同意见或建议的请给出指示谢谢!
首先给大家看一下效果图:
下面我们需要创建一张表:
package com.example.liangshaoteng.contentprovider;import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;/*** Created by liangshaoteng on 17-6-21.*/public class MyDatabaseHelper extends SQLiteOpenHelper {private Context context;public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {super(context, name, factory, version);this.context = context;}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL("create table Book(_id integer primary key autoincrement,author,price,pages,name)");Toast.makeText(context, "创建成功!", Toast.LENGTH_LONG).show();}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
}
其次就是创建我们的内容提供器:
记得要在manifest里面注册!
下面我就简单的写的具体还需要你根据项目需求来写
package com.example.liangshaoteng.contentprovider;import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;public class DataContentProvider extends ContentProvider {public static final int TABLE1_DIR = 0;public static final int TABLE1_ITEM = 1;public static final int TABLE2_DIR = 2;public static final int TABLE2_ITEM = 3;public static final String AUTHORITY = "com.example.liangshaoteng.contentprovider";private static UriMatcher uriMatcher;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(AUTHORITY, "book", TABLE1_DIR);uriMatcher.addURI(AUTHORITY, "book/#", TABLE1_ITEM);uriMatcher.addURI(AUTHORITY, "category", TABLE2_DIR);uriMatcher.addURI(AUTHORITY, "category/#", TABLE2_ITEM);}private MyDatabaseHelper myDatabaseHelper;public DataContentProvider() {}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {// Implement this to handle requests to delete one or more rows.SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();int deleteRows = 0;switch (uriMatcher.match(uri)) {case TABLE1_DIR:deleteRows = writableDatabase.delete("Book", selection, selectionArgs);break;case TABLE1_ITEM:String sBook = uri.getPathSegments().get(1);deleteRows = writableDatabase.delete("Book", "id=?", new String[]{sBook});break;case TABLE2_DIR:deleteRows = writableDatabase.delete("Category", selection, selectionArgs);break;case TABLE2_ITEM:String sCategory = uri.getPathSegments().get(1);deleteRows = writableDatabase.delete("Category", "id=?", new String[]{sCategory});break;default:break;}return deleteRows;}@Overridepublic String getType(Uri uri) {// TODO: Implement this to handle requests for the MIME type of the dataswitch (uriMatcher.match(uri)) {case TABLE1_DIR:return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.book";case TABLE1_ITEM:return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.book";case TABLE2_DIR:return "vnd.android.cursor.dir/vnd.com.example.liangshaoteng.contentprovider.category";case TABLE2_ITEM:return "vnd.android.cursor.item/vnd.com.example.liangshaoteng.contentprovider.category";default:break;}return null;}@Overridepublic Uri insert(Uri uri, ContentValues values) {// TODO: Implement this to handle requests to insert a new row.SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();Uri uriReturn = null;switch (uriMatcher.match(uri)) {case TABLE1_DIR:case TABLE1_ITEM:long bookBook = writableDatabase.insert("Book", null, values);uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + bookBook);break;case TABLE2_DIR:case TABLE2_ITEM:long bookCategory = writableDatabase.insert("Category", null, values);uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + bookCategory);break;default:break;}return uriReturn;}@Overridepublic boolean onCreate() {// TODO: Implement this to initialize your content provider on startup.myDatabaseHelper = new MyDatabaseHelper(getContext(), "BookStores.db", null, 1);return true;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {// TODO: Implement this to handle query requests from clients.SQLiteDatabase readableDatabase = myDatabaseHelper.getReadableDatabase();Cursor cursor = null;switch (uriMatcher.match(uri)) {case TABLE1_DIR:cursor = readableDatabase.query("Book", projection, selection, selectionArgs, null, null, sortOrder);break;case TABLE1_ITEM:String s = uri.getPathSegments().get(1);cursor = readableDatabase.query("Book", projection, "id=?", new String[]{s}, null, null, sortOrder);break;case TABLE2_DIR:cursor = readableDatabase.query("Category", projection, selection, selectionArgs, null, null, sortOrder);break;case TABLE2_ITEM:String s1 = uri.getPathSegments().get(1);cursor = readableDatabase.query("Category", projection, "id=?", new String[]{s1}, null, null, sortOrder);break;default:break;}return cursor;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {// TODO: Implement this to handle requests to update one or more rows.SQLiteDatabase writableDatabase = myDatabaseHelper.getWritableDatabase();int updatedRows = 0;switch (uriMatcher.match(uri)) {case TABLE1_DIR:updatedRows = writableDatabase.update("Book", values, selection, selectionArgs);break;case TABLE1_ITEM:String sBook = uri.getPathSegments().get(1);updatedRows = writableDatabase.update("Book", values, "id=?", new String[]{sBook});break;case TABLE2_DIR:updatedRows = writableDatabase.update("Category", values, selection, selectionArgs);break;case TABLE2_ITEM:String sCategory = uri.getPathSegments().get(1);updatedRows = writableDatabase.update("Category", values, "id=?", new String[]{sCategory});break;default:break;}return updatedRows;}
}
好了基本上就是这样了! 不足之处还望指出 !