内容提供者

内容提供者是Android中的四大组件之一，可以将应用中的数据对外进行共享

　　  内容提供者中数据更改可被监听

内容提供者类  ContentProvider

通过Context获得ContentResolver对象

调用ContentResolver对象的方法即可访问内容提供者

package com.heima.proveders;

import com.heima.sqlitedemo.db.personSQLITEOpenHelper;

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 android.net.Uri;
//内容提供者是四大主键    所以都需要在配置清单里面配置
public class provedersCase extends ContentProvider {

	private static final String AUTHORITY="com.heima.proveders.provedersCase";
	private static final int PERSON_INSERT_CODE = 0;//操作person表添加的操作的uri匹配码
	private static final int PERSON_QUERY_ALL_CODE = 3;
	private static final int PERSON_UPDATE_CODE = 2;
	private static final int PERSON_DELETE_CODE = 1;
	private static final int PERSON_QUERY_ITEM_CODE = 4;

	//UriMatcher类用于匹配Uri
	private static UriMatcher ruiMatcher;
	private personSQLITEOpenHelper mOpenHelper = null;
	static{
		//常量UriMatcher.NO_MATCH表示不匹配任何路径的返回码
		ruiMatcher = new UriMatcher(UriMatcher.NO_MATCH);//参数是不匹配时返回值的类型

		//添加一些uri（分机号）
		//1唯一标识   手机号
		//要干的事     分机号	person/insert是要在person这个表进行insert操作
		ruiMatcher.addURI(AUTHORITY, "person/insert", PERSON_INSERT_CODE);
		ruiMatcher.addURI(AUTHORITY, "person/delete", PERSON_DELETE_CODE);
		ruiMatcher.addURI(AUTHORITY, "person/update", PERSON_UPDATE_CODE);
		ruiMatcher.addURI(AUTHORITY, "person/queryAll", PERSON_QUERY_ALL_CODE);

		//特殊的符号   #
		ruiMatcher.addURI(AUTHORITY, "person/query/#", PERSON_QUERY_ITEM_CODE);

	}

	@Override
	public boolean onCreate() {
		// TODO Auto-generated method stub
		//刚创建的时候就把数据库操作帮助类给实例化出来
		mOpenHelper = new personSQLITEOpenHelper(getContext());
		return true;
	}

	@Override
	public int delete(Uri arg0, String arg1, String[] arg2) {
		// TODO Auto-generated method stub
		int sign = ruiMatcher.match(arg0);
		switch (sign) {
		case PERSON_DELETE_CODE:
			SQLiteDatabase db = mOpenHelper.getWritableDatabase();
			if(db.isOpen()){

				int count = db.delete("person", arg1, arg2);

				db.close();
				return count;
			}
			break;

		default:
			throw new IllegalArgumentException("uri不匹配: " + arg1);
		}
		return 0;
	}

	@Override
	public String getType(Uri uri) {  //这个方法只是为了方便系统的调用，完全不管也是可以的
		// TODO Auto-generated method stub
		int sign = ruiMatcher.match(uri);
		switch (sign) {
		case PERSON_QUERY_ALL_CODE: //返回多条的MIME-type
			return "vnd.android.cursor.dir/person";
		case PERSON_QUERY_ITEM_CODE: //查询单个的方法
			return "vnd.android.cursor.item/person";
		default:
			//这里不能抛出异常   直接break就可以了
			break;
		}
		return null;
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
		// TODO Auto-generated method stub
		//ruiMatcher不仅可以添加uri	还可以匹配uri
		int sign = ruiMatcher.match(uri);

		switch (sign) {
		case PERSON_INSERT_CODE:
			SQLiteDatabase db = mOpenHelper.getWritableDatabase();
			if(db.isOpen()){
				//执行操作
				long id = db.insert("person", null, values);

				db.close();
				//ContentUris	获取和添加Uri信息
				return ContentUris.withAppendedId(uri, id);//往uri后面再加上一个id
			}
			break;

		default:
			throw new IllegalArgumentException("uri不匹配: " + uri);
		}

		return null;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {
		// TODO Auto-generated method stub

		int sign = ruiMatcher.match(uri);
		SQLiteDatabase db = mOpenHelper.getReadableDatabase();
		switch (sign) {
		case PERSON_QUERY_ALL_CODE:

			if(db.isOpen()){

				Cursor cursor = db.query("person", projection, selection, selectionArgs, null, null, sortOrder);
				return cursor;
//				db.close(); 这里的cursor不能关闭   一关闭结果集就没了，返回去也就没用了
			}
			break;
		case PERSON_QUERY_ITEM_CODE:  //查询单个值的情况
			if(db.isOpen()){

				long id = ContentUris.parseId(uri);
				Cursor cursor = db.query("person", projection, "_id = ?", new String[]{"id"}, null, null, sortOrder);
				return cursor;
			}
			break;
		default:
			throw new IllegalArgumentException("uri不匹配: " + uri);
		}

		return null;
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {
		// TODO Auto-generated method stub
		int sign = ruiMatcher.match(uri);
		switch (sign) {
		case PERSON_UPDATE_CODE:
			SQLiteDatabase db = mOpenHelper.getWritableDatabase();
			if(db.isOpen()){

				int count = db.update("person", values, selection, selectionArgs);

				db.close();
				return count;
			}
			break;

		default:
			throw new IllegalArgumentException("uri不匹配: " + uri);
		}
		return 0;
	}

}

内容提供者是四大组件之一，需要在配置清单进行配置

<provider android:name="com.heima.proveders.provedersCase"
     android:authorities="com.heima.proveders.provedersCase">
</provider>