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Android ContentProvider总结[转]

原创 Linux操作系统 作者:bartfj 时间:2011-12-09 15:35:13 0 删除 编辑
一、ContentProvider简介
       当应用继承ContentProvider类,并重写该类用于提供数据和存储数据的方法,就可以向其他应用共享其数据。虽然使用其他方法也可以对外共享数据,但数据访问方式会因数据存储的方式而不同,如:采用文件方式对外共享数据,需要进行文件操作读写数据;采用sharedpreferences共享数据,需要使用sharedpreferences API读写数据。而使用ContentProvider共享数据的好处是统一了数据访问方式。

二、Uri类简介
       Uri代表了要操作的数据,Uri主要包含了两部分信息:1.需要操作的ContentProvider ,2.对ContentProvider中的什么数据进行操作,一个Uri由以下几部分组成:

       1.scheme:ContentProvider(内容提供者)的scheme已经由Android所规定为:content://。
       2.主机名(或Authority):用于唯一标识这个ContentProvider,外部调用者可以根据这个标识来找到它。
       3.路径(path):可以用来表示我们要操作的数据,路径的构建应根据业务而定,如下:
•         要操作contact表中id为10的记录,可以构建这样的路径:/contact/10
•         要操作contact表中id为10的记录的name字段:/contact/10/name
•         要操作contact表中的所有记录,可以构建这样的路径:/contact
要操作的数据不一定来自数据库,也可以是文件等他存储方式,如下:
要操作xml文件中contact节点下的name节点,可以构建这样的路径:/contact/name
如果要把一个字符串转换成Uri,可以使用Uri类中的parse()方法,如下:
Uri uri = Uri.parse("content://com.changcheng.provider.contactprovider/contact")

三、UriMatcher、ContentUrist和ContentResolver简介
       因为Uri代表了要操作的数据,所以我们很经常需要解析Uri,并从Uri中获取数据。Android系统提供了两个用于操作Uri的工具类,分别为UriMatcher 和ContentUris 。掌握它们的使用,会便于我们的开发工作。

       UriMatcher:用于匹配Uri,它的用法如下:
       1.首先把你需要匹配Uri路径全部给注册上,如下:
       //常量UriMatcher.NO_MATCH表示不匹配任何路径的返回码(-1)。
       UriMatcher  uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
       //如果match()方法匹配content://com.changcheng.sqlite.provider.contactprovider/contact路径,返回匹配码为1
       uriMatcher.addURI(“com.changcheng.sqlite.provider.contactprovider”, “contact”, 1);//添加需要匹配uri,如果匹配就会返回匹配码
       //如果match()方法匹配   content://com.changcheng.sqlite.provider.contactprovider/contact/230路径,返回匹配码为2
       uriMatcher.addURI(“com.changcheng.sqlite.provider.contactprovider”, “contact/#”, 2);//#号为通配符
      
       2.注册完需要匹配的Uri后,就可以使用uriMatcher.match(uri)方法对输入的Uri进行匹配,如果匹配就返回匹配码,匹配码是调用 addURI()方法传入的第三个参数,假设匹配 content://com.changcheng.sqlite.provider.contactprovider/contact路径,返回的匹配 码为1。

       ContentUris:用于获取Uri路径后面的ID部分,它有两个比较实用的方法:
•         withAppendedId(uri, id)用于为路径加上ID部分
•         parseId(uri)方法用于从路径中获取ID部分

       ContentResolver:当外部应用需要对ContentProvider中的数据进行添加、删除、修改和查询操作时,可以使用 ContentResolver 类来完成,要获取ContentResolver 对象,可以使用Activity提供的getContentResolver()方法。 ContentResolver使用insert、delete、update、query方法,来操作数据。



四、ContentProvider示例程序
Manifest.xml中的代码

 

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需要在中为provider进行注册!!!!
首先定义一个数据库的工具类:

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public class RuiXin {
 
        public static final String DBNAME = "ruixinonlinedb";
        public static final String TNAME = "ruixinonline";
        public static final int VERSION = 3;
         
        public static String TID = "tid";
        public static final String EMAIL = "email";
        public static final String USERNAME = "username";
        public static final String DATE = "date";
        public static final String SEX = "sex";
         
         
        public static final String AUTOHORITY = "com.ruixin.login";
        public static final int ITEM = 1;
        public static final int ITEM_ID = 2;
         
        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.ruixin.login";
        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.ruixin.login";
         
        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTOHORITY + "/ruixinonline");
}

 

  1. 然后创建一个数据库:
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    public class DBlite extends SQLiteOpenHelper {
            public DBlite(Context context) {
                    super(context, RuiXin.DBNAME, null, RuiXin.VERSION);
                    // TODO Auto-generated constructor stub
            }
            @Override
            public void onCreate(SQLiteDatabase db) {
                    // TODO Auto-generated method stub
                            db.execSQL("create table "+RuiXin.TNAME+"(" +
                                    RuiXin.TID+" integer primary key autoincrement not null,"+
                                    RuiXin.EMAIL+" text not null," +
                                    RuiXin.USERNAME+" text not null," +
                                    RuiXin.DATE+" interger not null,"+
                                    RuiXin.SEX+" text not null);");
            }
            @Override
            public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                    // TODO Auto-generated method stub
            }
            public void add(String email,String username,String date,String sex){
                    SQLiteDatabase db = getWritableDatabase();
                    ContentValues values = new ContentValues();
                    values.put(RuiXin.EMAIL, email);
                    values.put(RuiXin.USERNAME, username);
                    values.put(RuiXin.DATE, date);
                    values.put(RuiXin.SEX, sex);
                    db.insert(RuiXin.TNAME,"",values);
            }
    }
  1. 接着创建一个Myprovider.java对数据库的接口进行包装:
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    public class MyProvider extends ContentProvider{
     
            DBlite dBlite;
            SQLiteDatabase db;
             
            private static final UriMatcher sMatcher;
            static{
                    sMatcher = new UriMatcher(UriMatcher.NO_MATCH);
                    sMatcher.addURI(RuiXin.AUTOHORITY,RuiXin.TNAME, RuiXin.ITEM);
                    sMatcher.addURI(RuiXin.AUTOHORITY, RuiXin.TNAME+"/#", RuiXin.ITEM_ID);
     
            }
            @Override
            public int delete(Uri uri, String selection, String[] selectionArgs) {
                    // TODO Auto-generated method stub
                    db = dBlite.getWritableDatabase();
                    int count = 0;
                    switch (sMatcher.match(uri)) {
                    case RuiXin.ITEM:
                            count = db.delete(RuiXin.TNAME,selection, selectionArgs);
                            break;
                    case RuiXin.ITEM_ID:
                            String id = uri.getPathSegments().get(1);
                            count = db.delete(RuiXin.TID, RuiXin.TID+"="+id+(!TextUtils.isEmpty(RuiXin.TID="?")?"AND("+selection+')':""), selectionArgs);
                        break;
                    default:
                            throw new IllegalArgumentException("Unknown URI"+uri);
                    }
                    getContext().getContentResolver().notifyChange(uri, null);
                    return count;
            }
     
            @Override
            public String getType(Uri uri) {
                    // TODO Auto-generated method stub
                    switch (sMatcher.match(uri)) {
                    case RuiXin.ITEM:
                            return RuiXin.CONTENT_TYPE;
                    case RuiXin.ITEM_ID:
                        return RuiXin.CONTENT_ITEM_TYPE;
                    default:
                            throw new IllegalArgumentException("Unknown URI"+uri);
                    }
            }
     
            @Override
            public Uri insert(Uri uri, ContentValues values) {
                    // TODO Auto-generated method stub
                     
                    db = dBlite.getWritableDatabase();
                    long rowId;
                    if(sMatcher.match(uri)!=RuiXin.ITEM){
                            throw new IllegalArgumentException("Unknown URI"+uri);
                    }
                    rowId = db.insert(RuiXin.TNAME,RuiXin.TID,values);
                       if(rowId>0){
                               Uri noteUri=ContentUris.withAppendedId(RuiXin.CONTENT_URI, rowId);
                               getContext().getContentResolver().notifyChange(noteUri, null);
                               return noteUri;
                       }
                       throw new IllegalArgumentException("Unknown URI"+uri);
            }
     
            @Override
            public boolean onCreate() {
                    // TODO Auto-generated method stub
                    this.dBlite = new DBlite(this.getContext());
    //                db = dBlite.getWritableDatabase();
    //                return (db == null)?false:true;
                    return true;
            }
     
            @Override
            public Cursor query(Uri uri, String[] projection, String selection,
                            String[] selectionArgs, String sortOrder) {
                    // TODO Auto-generated method stub
                    db = dBlite.getWritableDatabase();               
                    Cursor c;
                    Log.d("-------", String.valueOf(sMatcher.match(uri)));
                    switch (sMatcher.match(uri)) {
                    case RuiXin.ITEM:
                            c = db.query(RuiXin.TNAME, projection, selection, selectionArgs, null, null, null);
                     
                            break;
                    case RuiXin.ITEM_ID:
                            String id = uri.getPathSegments().get(1);
                            c = db.query(RuiXin.TNAME, projection, RuiXin.TID+"="+id+(!TextUtils.isEmpty(selection)?"AND("+selection+')':""),selectionArgs, null, null, sortOrder);
                        break;
                    default:
                            Log.d("!!!!!!", "Unknown URI"+uri);
                            throw new IllegalArgumentException("Unknown URI"+uri);
                    }
                    c.setNotificationUri(getContext().getContentResolver(), uri);
                    return c;
            }
            @Override
            public int update(Uri uri, ContentValues values, String selection,
                            String[] selectionArgs) {
                    // TODO Auto-generated method stub
                    return 0;
            }
    }


    最后创建测试类:
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    public class Test extends Activity {
        /** Called when the activity is first created. */
       private DBlite dBlite1 = new DBlite(this);;
            private ContentResolver contentResolver;
                        public void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.main);
                    //先对数据库进行添加数据
                dBlite1.add(email,username,date,sex);
                //通过contentResolver进行查找
                 contentResolver = TestWebviewDemo.this.getContentResolver();
                Cursor cursor = contentResolver.query(
                      RuiXin.CONTENT_URI, new String[] {
                      RuiXin.EMAIL, RuiXin.USERNAME,
                      RuiXin.DATE,RuiXin.SEX }, null, null, null);
                    while (cursor.moveToNext()) {
                         Toast.makeText(
                        TestWebviewDemo.this,
                        cursor.getString(cursor.getColumnIndex(RuiXin.EMAIL))
                                + " "
                                + cursor.getString(cursor.getColumnIndex(RuiXin.USERNAME))
                                + " "
                                + cursor.getString(cursor.getColumnIndex(RuiXin.DATE))
                                + " "
                                + cursor.getString(cursor.getColumnIndex(RuiXin.SEX)),
                               Toast.LENGTH_SHORT).show();
                         }
                       startManagingCursor(cursor);  //查找后关闭游标
                }
            }

    注:上面是在一个程序中进行的测试,也可以再新建一个工程来模拟一个新的程序,然后将上面查询的代码加到新的程序当中!这样就模拟了contentprovider的数据共享功能了!
    新建个工程:TestProvider
    创建一个测试的activity
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    public class Test extends Activity {
        /** Called when the activity is first created. */
            private ContentResolver contentResolver;
                        public void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.main);
                   
                //通过contentResolver进行查找
                  contentResolver = TestWebviewDemo.this.getContentResolver();                    
                 Cursor cursor = contentResolver.query(
                    RuiXin.CONTENT_URI, new String[] {
                    RuiXin.EMAIL, RuiXin.USERNAME,
                    RuiXin.DATE,RuiXin.SEX }, null, null, null);
                while (cursor.moveToNext()) {
                   Toast.makeText(TestWebviewDemo.this,
                           cursor.getString(cursor.getColumnIndex(RuiXin.EMAIL))
                           + " "
                           + cursor.getString(cursor.getColumnIndex(RuiXin.USERNAME))
                           + " "
                           + cursor.getString(cursor.getColumnIndex(RuiXin.DATE))
                           + " "
                           + cursor.getString(cursor.getColumnIndex(RuiXin.SEX)),
                           Toast.LENGTH_SHORT).show();
                       }
                       startManagingCursor(cursor);  //查找后关闭游标
                }
            }
    运行
    此程序就能实现共享数据查询了!

    注:新建的程序中的manifest.xml中不需要对provider进行注册,直接运行就行,否则会报错!

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