publicstaticfinalUri CONTENT_URI =Uri.parse("content://com.example.codelab.transportationprovider");

其中：content是协议

      Com.exmaple.codelab.transportationprovider是类名，包含完整的包名。

Uri.parse将一个字符串转换成Uri类型。

content://com.example.codelab.transportationprovider/train 

content://com.example.codelab.transportationprovider/air/domestic 

content://com.example.codelab.transportationprovider/air/international

      public static final UriMatcher uriMatcher;  

      static {  

                     uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);  

                     uriMatcher.addURI(Book.AUTHORITY, "item", Book.ITEM);  

                     uriMatcher.addURI(Book.AUTHORITY, "item/#", Book.ITEM_ID);  

              } 

<!-- android:name是完成ContentProvider类的全称

             android:authorities是和FirstProvidermetaData中的常量AUTHORITY的值一样，否则会报错

         -->

        <provider android:name="com.bj.FirstContentProvider"

            android:authorities="com.bj.firstcontentprovider"

            />

public class Activity19Activity extends Activity {

    private Button queryButton = null;

    private Button insertButton = null;

    @Override

    public void onCreate(Bundle savedInstanceState) {

       super.onCreate(savedInstanceState);

       setContentView(R.layout.main);

       queryButton = (Button) this.findViewById(R.id.query);

       queryButton.setOnClickListener(newQueryListener());

       insertButton = (Button) this.findViewById(R.id.insert);

       insertButton.setOnClickListener(newInsertListener());

        System.out.println(getContentResolver().getType(FirstProvidermetaData.UserTableMetaData.CONTENT_URI));

    }

    class InsertListener implementsOnClickListener {

       @Override

       public void onClick(View v) {

           // TODOAuto-generated method stub

           ContentValues values = new ContentValues();

           values.put(FirstProvidermetaData.UserTableMetaData.USER_NAME,

                  “michal”);

           Uri uri = getContentResolver()

                  .insert(

                         FirstProvidermetaData.UserTableMetaData.CONTENT_URI,

                         values);

           System.out.println(“uri—>” + uri.toString());

       }

    }

    class QueryListener implementsOnClickListener {

       public void onClick(View v) {

           Cursor c = getContentResolver().query(

                  FirstProvidermetaData.UserTableMetaData.CONTENT_URI, null,

                  null, null, null);

           while (c.moveToNext()) {

              System.out.println(c.getString(c.getColumnIndex(“username”)));

           }

       }

    }

}

public class FirstContentProvider extendsContentProvider {

    // 当别的程序来访问这个ContentProvider，是通过Uri来访问的，UriMatcher检查是否符合标准

    // 给uri起一个规则，返回数字

    public static final UriMatcher uriMatcher;

    // 下面定义两个规则

    public static final int INCOMING_USER_COLLECTION = 1;

    public static final int INCOMING_USER_SINGLE = 2;

    private DatabaseHelper dh;

    static {//下面的users前面不能加/

       uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

       uriMatcher.addURI(FirstProvidermetaData.AUTHORITY, “users”,

              INCOMING_USER_COLLECTION);

       uriMatcher.addURI(FirstProvidermetaData.AUTHORITY, “users/#”,

              INCOMING_USER_SINGLE);

    }

    //有点类似于sql里面表的别名，这个也是给列其别名，必须要用

    //列的别名还是原来的名，没必要修改

    public static HashMap<String,String> userProjectionMap;

    static{

       userProjectionMap = newHashMap<String,String>();

        userProjectionMap.put(UserTableMetaData._ID, UserTableMetaData._ID );

       userProjectionMap.put(UserTableMetaData.USER_NAME, UserTableMetaData.USER_NAME);

    }

    @Override

    public int delete(Uri uri, String selection, String[] selectionArgs) {

       // TODOAuto-generated method stub

       System.out.println(“delete”);

       return 0;

    }

    // 根据传入的URI，返回该URI所表示的数据类型

    // 也就是说，我们通过URI要访问的数据，返回什么类型

    @Override

    public String getType(Uri uri) {

       // TODOAuto-generated method stub

       System.out.println(“getType”);

       switch (uriMatcher.match(uri)) {

       case INCOMING_USER_COLLECTION:

           // UserTableMetaData是FirstProvidermetaData的内部类

           return UserTableMetaData.CONTENT_TYPE;

       case INCOMING_USER_SINGLE:

           return UserTableMetaData.CONTENT_TYPE_ITEM;

       default:

           throw new IllegalArgumentException(“Unknown uri” + uri);

       }

    }

    @Override

    public Uri insert(Uri uri, ContentValues values) {

       // TODOAuto-generated method stub

       System.out.println(“insert”);

       SQLiteDatabase db = dh.getWritableDatabase();

       //返回表中自动增长的列的值，否则返回-1      

       long rowId = db.insert(UserTableMetaData.TABLE_NAME,null, values);   

       if(rowId>0){

           //将rowId追加到后面

           //contentUris：用来处理Uri的工具类

           Uri insertedUserUri = ContentUris.withAppendedId(UserTableMetaData.CONTENT_URI, rowId);

           //通知监听器，数据已经改变

           getContext().getContentResolver().notifyChange(insertedUserUri, null);

           return insertedUserUri;

       }

       throw new SQLException(“Failed to insert row into “+uri);

    }

    //是一个回调方法，所以说在ContentProvider创建的时候执行

    //也就是创建这个DatabaseHelper对象

    @Override

    public boolean onCreate() {

       // TODOAuto-generated method stub

       //getContext得到当前正在运行着的context

       dh = new DatabaseHelper(getContext(),FirstProvidermetaData.DATABASE_NAME);

       System.out.println(“on create”);

        SQLiteDatabase db = dh.getReadableDatabase();

       return true;

    }

    //projection：查询的列有哪些

    //selection:where子句的内容，可以用?

    //selectionArgs:占位符对应的参数

    //sortOrder:排序

    @Override

    public Cursor query(Uri uri, String[] projection, String selection,

           String[] selectionArgs, String sortOrder) {

       // TODOAuto-generated method stub

       System.out.println(“query”);

       //创建一个查询的语句

       SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

       switch(uriMatcher.match(uri)){

       case INCOMING_USER_COLLECTION:

           //设置查询哪张表

           qb.setTables(UserTableMetaData.TABLE_NAME);

           qb.setProjectionMap(userProjectionMap);

           break;

       case INCOMING_USER_SINGLE:

           qb.setTables(UserTableMetaData.TABLE_NAME);

           qb.setProjectionMap(userProjectionMap);

           //添加where条件，getPathSegments：得到uri的path部分content:XXX/user/1，get(1)得到1

           qb.appendWhere(UserTableMetaData._ID+“=”+uri.getPathSegments().get(1));

           break;

       }

       String orderBy;

       if(TextUtils.isEmpty(sortOrder)){

           orderBy = UserTableMetaData.DEFAULT_SORT_ORDER;

       }

       else

       {

           orderBy = sortOrder;

       }

       SQLiteDatabase db = dh.getWritableDatabase();

       //下面的query使用qb这个对象

       Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);

       //也是通知下

       c.setNotificationUri(getContext().getContentResolver(), uri);

       System.out.println(“query”);

       return c;

    }

    @Override

    public int update(Uri uri, ContentValues values, String selection,

           String[] selectionArgs) {

       // TODOAuto-generated method stub

       return 0;

    }

}

FirstProvidermetaData.java

public class FirstProvidermetaData {

    public static final String AUTHORITY=“com.bj.firstcontentprovider”; //继承了contentprovider的类的全名

    //数据库名称 

    public static final String DATABASE_NAME = “FirstProvider.db”; 

    //数据库的版本  

    public static final int DATABASE_VERSION = 1; 

    //表名  

    public static final String USERS_TABLE_NAME = “users”; 

    public static final class UserTableMetaData implements BaseColumns{

       //表名

       public static final String TABLE_NAME=“users”;

       //访问该ContentProvider的URI

       public static final Uri CONTENT_URI=Uri.parse(“content://”+AUTHORITY+“/users”);

       public static final String CONTENT_TYPE=“vnd.android.cursor.dir/vnd.firstprovider.user”;

       public static final String CONTENT_TYPE_ITEM=“vnd.android.cursor.item/vnd.firstprovider.user”;

       //列名，在users表中添加一个名为name的列    

       public static final String USER_NAME=“name”;

       //默认排序方式

       public static final String DEFAULT_SORT_ORDER=“_id desc”;

    }

}