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！