SQLiteDatabase和Contentprovider

时间：2021-11-07 21:30:29

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！

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