安卓开发_深入理解Content Provider

 1 package com.example.mycontentprovider;
 2 
 3 import android.content.Context;
 4 import android.database.sqlite.SQLiteDatabase;
 5 import android.database.sqlite.SQLiteOpenHelper;
 6 
 7 public class DBhelper extends SQLiteOpenHelper{
 8     public DBhelper(Context context) {
 9         super(context, "users.db", null, 1);
10     }
11 
12     @Override
13     public void onCreate(SQLiteDatabase db) {
14         // TODO 初始化数据库
15         db.execSQL("create table t_user(_id integer primary key,uname,upass,money)");
16         
17         db.execSQL("create table t_order(_id integer primary key,user_id,price,productname)");
18         
19         db.execSQL("insert into t_user(uname,upass,money) values('lisi','123',200)");
20         
21         db.execSQL("insert into t_user(uname,upass,money) values('zhangsi','1234',2000)");
22         
23         
24     }
25 
26     @Override
27     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
28         // TODO 数据库升级时执行该方法
29         if(newVersion>oldVersion)
30         {
31             db.execSQL("drop table if exists t_user");
32             db.execSQL("drop table if exists t_order");
33             
34             onCreate(db);
35         }
36         
37     }
38 
39     
40 
41 }

  1 package com.example.mycontentprovider;
  2 
  3 import android.content.ContentProvider;
  4 import android.content.ContentUris;
  5 import android.content.ContentValues;
  6 import android.content.UriMatcher;
  7 import android.database.Cursor;
  8 import android.database.sqlite.SQLiteDatabase;
  9 import android.net.Uri;
 10 
 11 public class UserContentProvider extends ContentProvider{
 12     /*
 13      * 这里有两个数据表t_user t_order 
 14      * 给t_user Code标识1
 15      * 给t_order Code标识2
 16      * 假设当前只对表t_user操作
 17      * 
 18      */
 19     
 20     //声明该ContentProvider的唯一标识
 21     public static final String AUTHORITY="com.xqx_mydatabase";
 22     //为该组件中可以被外界访问 数据库中的资源定义Code标识
 23     public static final int CODE_USER = 1;
 24     public static final int CODE_ORDER = 2;
 25     //定义访问资源的URI匹配器，使用该类生成被访问的资源的URI
 26     private static UriMatcher uriMather;
 27     private DBhelper dbhelper;
 28     static {
 29         uriMather = new UriMatcher(UriMatcher.NO_MATCH);
 30         //CODE_USER(1)对应的URI：content://com.xqx_mydatabase/user
 31         uriMather.addURI(AUTHORITY, "user", CODE_USER);
 32         //CODE_USER(2)对应的URI：content://com.xqx_mydatabase/order
 33         uriMather.addURI(AUTHORITY, "order", CODE_ORDER);
 34     }
 35     
 36     //删除返回删除成功记录的条数
 37     @Override
 38     public int delete(Uri uri, String selection, String[] selectionArgs) {
 39         // TODO Auto-generated method stub
 40         SQLiteDatabase db = dbhelper.getWritableDatabase();
 41         if(uriMather.match(uri)==CODE_USER)
 42         {
 43             //删除t_user表中的数据,返回删除记录的条数
 44              int num = db.delete("t_user", selection, selectionArgs);
 45              return num;
 46         }
 47         return 0;
 48     }
 49 
 50     @Override
 51     public String getType(Uri uri) {
 52         // TODO Auto-generated method stub
 53         return null;
 54     }
 55     
 56     //插入记录
 57     @Override
 58     public Uri insert(Uri uri, ContentValues values) {
 59         // TODO Auto-generated method stub
 60         SQLiteDatabase db = dbhelper.getWritableDatabase();
 61         if(uriMather.match(uri)==CODE_USER)
 62         {
 63             //得到插入记录的ID
 64             long id = db.insert("t_user", null, values);
 65             //返回新插入记录的URI
 66             return ContentUris.withAppendedId(uri, id);
 67         }
 68         return null;
 69     }
 70     
 71     //创建DBhelper对象
 72     @Override
 73     public boolean onCreate() {
 74         // TODO Auto-generated method stub
 75         dbhelper = new DBhelper(getContext());
 76         return false;
 77     }
 78     
 79     //查询，返回Cursor对象
 80     @Override
 81     public Cursor query(Uri uri, String[] projection, String selection,
 82             String[] selectionArgs, String sortOrder) {
 83         // TODO Auto-generated method stub
 84         SQLiteDatabase db = dbhelper.getReadableDatabase();
 85         //得到uri对应的Code
 86         int code = uriMather.match(uri);
 87         Cursor cursor = null;
 88         switch (code) {
 89         //如果匹配CODE_USER 操作数据表t_user
 90         case CODE_USER:
 91             //查询数据表t_user
 92             cursor = db.query("t_user", projection, selection, selectionArgs, null, null, sortOrder);
 93             break;
 94         case CODE_ORDER:
 95             break;
 96         default:
 97             break;
 98         }
 99         
100         return cursor;
101     }
102 
103     //修改数据表中的数据,返回修改记录的条数
104     @Override
105     public int update(Uri uri, ContentValues values, String selection,
106             String[] selectionArgs) {
107         // TODO Auto-generated method stub
108         SQLiteDatabase db = dbhelper.getWritableDatabase();
109         if(uriMather.match(uri)==CODE_USER)
110         {
111             return db.update("t_user", values, selection, selectionArgs);
112         }
113         
114         return 0;
115     }
116 
117 }