Android开始之 内容提供

1.什么Content Provider内容提供者：管理被访问的结构化数据——数据库
底层封装的是数据库的操作，操作数据库A应用中将本地数据库的数据分享给B的应用，必须要使用内容提供者
内容提供者就是提供数据的数据源，给客户端访问。

2.内容 提供者提供了一套对外接口的访问规则——————跨应用
query 查询
insert 插入
update修改
delete删除

清单文件中加入：

<provider
android:name=".PersonContentProvider"
android:authorities="com.example.android.PersonContentProvider" >
</provider>

---------------------------------------DBHelper---------------------------------------------------

public class DBHelper extends SQLiteOpenHelper {
    private static String name = "mydb.db";
    private static int version = 1;

    public DBHelper(Context context) {
        super(context, name, null, version);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        String sql = "create table person(_id integer primary key autoincrement,name varchar(64),address varchar(64))";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

}

-----------------------------------PersonContentProvider------------------------------------

public class PersonContentProvider extends ContentProvider {
    private DBHelper helper;
    private final static UriMatcher URI_MATCHER = new UriMatcher(
            UriMatcher.NO_MATCH);
    private final static int PERSONS = 1;// 操作多条记录
    private final static int PERSON = 2;// 操作单行记录
    static {
        // 表示往UriMatcher添加匹配规则
        // *:字符#：数字
        // authority:清单文件中的authorities； path：表名, code

        URI_MATCHER.addURI("com.example.android.PersonContentProvider",
                "person", PERSONS);
        // com.example.android.PersonContentProvider/person/张"
        URI_MATCHER.addURI("com.example.android.PersonContentProvider",
                "person/#", PERSON);
        // com.example.android.PersonContentProvider/person/1"

    }

    @Override
    public boolean onCreate() {
        // TODO Auto-generated method stub
        helper = new DBHelper(getContext());
        return false;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        // TODO Auto-generated method stub
        // SQLiteDatabase database=helper.getReadableDatabase();
        // database.query(table, columns, selection, selectionArgs, groupBy,
        // having, orderBy);
        Cursor cursor = null;
        int flag = URI_MATCHER.match(uri);
        SQLiteDatabase database = helper.getReadableDatabase();

        switch (flag) {
        case PERSON:
            long _id = ContentUris.parseId(uri);
            String where_value = "_id  =" + _id;
            if (selection != null && !selection.equals("")) {
                where_value += selection;
            }
            cursor = database.query("person", projection, where_value,
                    selectionArgs, null, null, sortOrder);
            break;

        case PERSONS:
            cursor = database.query("person", projection, selection,
                    selectionArgs, null, null, sortOrder);
            break;
        }
        return cursor;
    }

    @Override
    public String getType(Uri uri) {
        // TODO Auto-generated method stub
        // 解析uri,判断mime类型
        int flag = URI_MATCHER.match(uri);
        switch (flag) {
        case PERSON:

            return "vnd.android.cursor.item/person";

        case PERSONS:
            return "vnd.android.cursor.dir/persons";
        }
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // TODO Auto-generated method stub
        Uri result = null;
        // 解析uri
        int flag = URI_MATCHER.match(uri);
        switch (flag) {
        case PERSONS:
            // 调用数据库的访问方法
            SQLiteDatabase database = helper.getReadableDatabase();
            long id = database.insert("person", null, values);
            result = ContentUris.withAppendedId(uri, id);// 生成的uri返回
            System.out.println("--->>" + result.toString());
            break;

        }

        return result;
    }

    // delete from person where _id=? and name=?
    // content://com.example.android.PersonContentProvider/person/1
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // TODO Auto-generated method stub
        int flag = URI_MATCHER.match(uri);
        SQLiteDatabase database = helper.getWritableDatabase();
        int count = 0;// 影响数据库的行数
        switch (flag) {
        case PERSON:
            long _id = ContentUris.parseId(uri);
            String where_value = "_id= " + _id;
            if (selection != null && !selection.equals("")) {
                where_value += selection;

            }
            count = database.delete("person", where_value, selectionArgs);
            break;

        case PERSONS:
            count = database.delete("person", selection, selectionArgs);
            break;
        }
        return count;
    }

    // update person set name=? and address=? where _id=?
    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        // TODO Auto-generated method stub
        int flag = URI_MATCHER.match(uri);
        int count = 0;// 影响数据库行数
        SQLiteDatabase database = helper.getWritableDatabase();
        switch (flag) {
        case PERSON:
            long _id = ContentUris.parseId(uri);
            String where_value = "_id=" + _id;
            if (selection != null && !selection.equals("")) {
                where_value += selection;
            }
            count = database.update("person", values, where_value,
                    selectionArgs);
            break;

        }
        return count;
    }

}

------------------------------------- MyTest------------------------------

public class MyTest extends AndroidTestCase {

    public MyTest() {
        // TODO Auto-generated constructor stub
    }

    public void add() {
        // 使用内容解析者访问
        ContentResolver contentResolver = getContext().getContentResolver();
        ContentValues values = new ContentValues();
        values.put("name", "xx");
        values.put("address", "xxx");
        // content://authorities/person
        Uri uri = Uri
                .parse("content://com.example.android.PersonContentProvider/person");
        contentResolver.insert(uri, values);

    }

    public void del() {
        ContentResolver contentResolver = getContext().getContentResolver();
        // Uri
        // 删掉单条：
        // uri=Uri.parse("content://com.example.android.PersonContentProvider/person/1");
        Uri uri = Uri
                .parse("content://com.example.android.PersonContentProvider/person");
        Uri new_uri = ContentUris.withAppendedId(uri, 1);
        contentResolver.delete(new_uri, null, null);
        // delect from person where _id=1 and name=xx,and address=xxx
        // contentResolver.delete(new_uri, "and name=? and address=?", new
        // String[]{"xx","xxx"});//如果_id不是主键

        // 全删
        Uri uri2 = Uri
                .parse("content://com.example.android.PersonContentProvider/person");

        contentResolver.delete(uri2, null, null);
    }
    

    public void qurey() {
        ContentResolver contentResolver = getContext().getContentResolver();
        Uri uri = Uri
                .parse("content://com.example.android.PersonContentProvider/person");
        Uri new_uri = ContentUris.withAppendedId(uri, 2);
        
        Cursor cursor = contentResolver.query(new_uri, null, null, null, null);
        while(cursor.moveToNext()){
            
                System.out.println("-->>"
                        + cursor.getString(cursor.getColumnIndex("name")));
        }
    }

}