SQLiteDatabase和Contentprovider

SQLiteDatabase和Contentprovider这两个数据库,我一般是用前面一个,喜欢它的操作数据库的语句,简单明了,可惜有时遇到数据库同步的问题,有时我们需要在一个数据库下建立多个表,多个Activity都要访问到数据库。最近就遇到过这个问题,虽然应用没有死掉,但有时报错也不太爽,报的警告如下

A SQLiteConnection object for database '/storage/sdcard0/vpnmsgdb.db' was leaked!  Please fix your application to end transactions in progress properly and to close the database when it is no longer needed.

不过虽然警告是报了,我暂时也没有改,虽然Contentprovider这个接口可以解决同步的问题,也许是一直都是用SQLiteDatabase的原因吧,个人觉得只要应用不死掉应该问题不大,

在网上找到有Contentprovider的例子。

原文在http://www.cnblogs.com/chenglong/articles/1892029.html

贴上原文

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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<application android:icon= "@drawable/icon" android:label= "@string/app_name" >
                 <activity android:name= ".TestWebviewDemo" android:label= "@string/app_name" >
                         <intent-filter>
                                 <action android:name= "android.intent.action.MAIN" />
                                 <category android:name= "android.intent.category.LAUNCHER" />
                         </intent-filter>
                         <intent-filter>
                                 <data android:mimeType= "vnd.android.cursor.dir/vnd.ruixin.login" />
                         </intent-filter>
                         <intent-filter>
                                 <data android:mimeType= "vnd.android.cursor.item/vnd.ruixin.login" />
                         </intent-filter>
                         
                 </activity>
                 <provider android:name= "MyProvider" android:authorities= "com.ruixin.login" />
         </application>

需要在<application></application>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!


posted on 2013-08-30 18:09  you Richer  阅读(1001)  评论(0编辑  收藏  举报