Android 中自定义ContentProvider与ContentObserver的使用简单实例

package cn.testcontentprovider; 
import android.content.ContentProvider; 
import android.content.ContentUris; 
import android.content.ContentValues; 
import android.content.UriMatcher; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.net.Uri; 
/** 
 * Demo描述: 
 * 自定义ContentProvider的实现 
 * ContentProvider主要用于在不同的应用程序之间共享数据,这也是官方推荐的方式. 
 * 
 * 注意事项: 
 * 1 在AndroidManifest.xml中注册ContentProvider时的属性 
 *  android:exported="true"表示允许其他应用访问. 
 * 2 注意*和#这两个符号在Uri中的作用 
 *  其中*表示匹配任意长度的字符 
 *  其中#表示匹配任意长度的数据 
 *  所以： 
 *  一个能匹配所有表的Uri可以写成: 
 *  content://cn.bs.testcontentprovider/* 
 *  一个能匹配person表中任意一行的Uri可以写成: 
 *  content://cn.bs.testcontentprovider/person/# 
 *  
 */ 
public class ContentProviderTest extends ContentProvider { 
  private SQLiteDatabaseOpenHelper mSQLiteDatabaseOpenHelper; 
  private final static String AUTHORITY="cn.bs.testcontentprovider"; 
  private static UriMatcher mUriMatcher; 
  private static final int PERSON_DIR = 0; 
  private static final int PERSON = 1; 
   
  /** 
   * 利用静态代码块初始化UriMatcher 
   * 在UriMatcher中包含了多个Uri,每个Uri代表一种操作 
   * 当调用UriMatcher.match(Uri uri)方法时就会返回该uri对应的code; 
   * 比如此处的PERSONS和PERSON 
   */ 
  static { 
    mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH); 
    // 该URI表示返回所有的person,其中PERSONS为该特定Uri的标识码 
    mUriMatcher.addURI(AUTHORITY, "person", PERSON_DIR); 
    // 该URI表示返回某一个person,其中PERSON为该特定Uri的标识码 
    mUriMatcher.addURI(AUTHORITY, "person/#", PERSON); 
  } 
   
   
  /** 
   * 在自定义ContentProvider中必须覆写getType(Uri uri)方法. 
   * 该方法用于获取Uri对象所对应的MIME类型. 
   * 
   * 一个Uri对应的MIME字符串遵守以下三点: 
   * 1 必须以vnd开头 
   * 2 如果该Uri对应的数据可能包含多条记录,那么返回字符串应该以"vnd.android.cursor.dir/"开头 
   * 3 如果该Uri对应的数据只包含一条记录,那么返回字符串应该以"vnd.android.cursor.item/"开头 
   */ 
  @Override 
  public String getType(Uri uri) { 
    switch (mUriMatcher.match(uri)) { 
    case PERSON_DIR: 
      return "vnd.android.cursor.dir/"+AUTHORITY+".persons"; 
    case PERSON: 
      return "vnd.android.cursor.item/"+AUTHORITY+".person"; 
    default: 
      throw new IllegalArgumentException("unknown uri"+uri.toString()); 
    } 
  }   
 
   
  @Override 
  public boolean onCreate() { 
    mSQLiteDatabaseOpenHelper=new SQLiteDatabaseOpenHelper(getContext()); 
    return true; 
  } 
   
 
  /** 
   * 插入操作: 
   * 插入操作只有一种可能:向一张表中插入 
   * 返回结果为新增记录对应的Uri 
   * 方法db.insert()返回结果为新增记录对应的主键值 
   */ 
  @Override 
  public Uri insert(Uri uri, ContentValues values) { 
    SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase(); 
    switch (mUriMatcher.match(uri)) { 
    case PERSON_DIR: 
      long newId = db.insert("person", "name,phone,salary", values); 
      //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应  
      getContext().getContentResolver().notifyChange(uri, null);  
      return ContentUris.withAppendedId(uri, newId); 
    default: 
      throw new IllegalArgumentException("unknown uri" + uri.toString()); 
    } 
  } 
   
  /** 
   * 更新操作: 
   * 更新操作有两种可能:更新一张表或者更新某条数据 
   * 在更新某条数据时原理类似于查询某条数据,见下. 
   */ 
  @Override 
  public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) { 
    SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase(); 
    int updatedNum = 0; 
    switch (mUriMatcher.match(uri)) { 
    // 更新表 
    case PERSON_DIR: 
      updatedNum = db.update("person", values, selection, selectionArgs); 
      break; 
    // 按照id更新某条数据 
    case PERSON: 
      long id = ContentUris.parseId(uri); 
      String where = "personid=" + id; 
      if (selection != null && !"".equals(selection.trim())) { 
        where = selection + " and " + where; 
      } 
      updatedNum = db.update("person", values, where, selectionArgs); 
      break; 
    default: 
      throw new IllegalArgumentException("unknown uri" + uri.toString()); 
    } 
    //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应  
    getContext().getContentResolver().notifyChange(uri, null);  
    return updatedNum; 
  } 
   
  /** 
   * 删除操作: 
   * 删除操作有两种可能:删除一张表或者删除某条数据 
   * 在删除某条数据时原理类似于查询某条数据,见下. 
   */ 
  @Override 
  public int delete(Uri uri, String selection, String[] selectionArgs) { 
    SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase(); 
    int deletedNum = 0; 
    switch (mUriMatcher.match(uri)) { 
    // 删除表 
    case PERSON_DIR: 
      deletedNum = db.delete("person", selection, selectionArgs); 
      break; 
    // 按照id删除某条数据 
    case PERSON: 
      long id = ContentUris.parseId(uri); 
      String where = "personid=" + id; 
      if (selection != null && !"".equals(selection.trim())) { 
        where = selection + " and " + where; 
      } 
      deletedNum = db.delete("person", where, selectionArgs); 
      break; 
    default: 
      throw new IllegalArgumentException("unknown uri" + uri.toString()); 
    } 
    //向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应  
    getContext().getContentResolver().notifyChange(uri, null);  
    return deletedNum; 
  } 
 
  /** 
   * 查询操作: 
   * 查询操作有两种可能:查询一张表或者查询某条数据 
   * 
   * 注意事项: 
   * 在查询某条数据时要注意--因为此处是按照personid来查询 
   * 某条数据,但是同时可能还有其他限制.例如: 
   * 要求personid为2且name为xiaoming1 
   * 所以在查询时分为两步: 
   * 第一步: 
   * 解析出personid放入where查询条件 
   * 第二步: 
   * 判断是否有其他限制(如name),若有则将其组拼到where查询条件. 
   * 
   * 详细代码见下. 
   */ 
  @Override 
  public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) { 
    SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase(); 
    Cursor cursor =null; 
    switch (mUriMatcher.match(uri)) { 
    // 查询表 
    case PERSON_DIR: 
      cursor = db.query("person", projection, selection, selectionArgs,null, null, sortOrder); 
      break; 
    // 按照id查询某条数据 
    case PERSON: 
      // 第一步: 
      long id = ContentUris.parseId(uri); 
      String where = "personid=" + id; 
      // 第二步: 
      if (selection != null && !"".equals(selection.trim())) { 
        where = selection + " and " + where; 
      } 
      cursor = db.query("person", projection, where, selectionArgs, null, null, sortOrder); 
      break; 
    default: 
      throw new IllegalArgumentException("unknown uri" + uri.toString()); 
    } 
    return cursor; 
  } 
   
 
} 

package cn.testcontentprovider; 
import android.content.Context; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
public class SQLiteDatabaseOpenHelper extends SQLiteOpenHelper { 
  public SQLiteDatabaseOpenHelper(Context context) { 
    super(context, "contentprovidertest.db", null, 1); 
  } 
 
  @Override 
  public void onCreate(SQLiteDatabase db) { 
    db.execSQL("create table person(personid integer primary key autoincrement,name varchar(20),phone varchar(12),salary Integer(12))");     
  } 
 
  //当数据库版本号发生变化时调用该方法 
  @Override 
  public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) { 
    //db.execSQL("ALTER TABLE person ADD phone varchar(12) NULL"); 
    //db.execSQL("ALTER TABLE person ADD salary Integer NULL"); 
  } 
 
} 

MainActivity如下:
[java] view plain copy
package cn.testcontentprovider; 
import android.app.Activity; 
import android.os.Bundle; 
public class MainActivity extends Activity { 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
  } 
 
} 

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
  package="cn.testcontentprovider" 
  android:versionCode="1" 
  android:versionName="1.0" > 
 
  <uses-sdk 
    android:minSdkVersion="8" 
    android:targetSdkVersion="8" /> 
 
  <uses-permission android:name="android.permission.INTERNET" /> 
  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
  <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> 
   
  <application 
    android:allowBackup="true" 
    android:icon="@drawable/ic_launcher" 
    android:label="@string/app_name" 
    android:theme="@style/AppTheme" > 
    <activity 
      android:name="cn.testcontentprovider.MainActivity" 
      android:label="@string/app_name" > 
      <intent-filter> 
        <action android:name="android.intent.action.MAIN" /> 
 
        <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
    </activity> 
     
     <provider  
      android:name="cn.testcontentprovider.ContentProviderTest" 
      android:authorities="cn.bs.testcontentprovider" 
      android:exported="true" 
     /> 
  </application> 
 
</manifest> 

<RelativeLayout  
  xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  > 
 
   <Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="该应用包含一个自定义的ContentProvider" 
    android:textSize="15sp" 
   android:layout_centerInParent="true" 
  /> 
 
</RelativeLayout> 

package cn.testbaidu; 
import android.net.Uri; 
import android.os.Bundle; 
import android.os.Handler; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.app.Activity; 
import android.content.ContentResolver; 
import android.content.ContentValues; 
import android.database.ContentObserver; 
import android.database.Cursor; 
/** 
 * Demo描述: 
 * 应用A(TestBaidu)调用另外一个应用(TestContentProvider)中的自定义ContentProvider,即: 
 * 1 自定义ContentProvider的使用 
 * 2 其它应用调用该ContentProvider 
 * 3 ContentObserver的使用 
 * 
 * 备注说明: 
 * 1 该例子在以前版本的基础上整理了代码 
 * 2 该例子在以前版本的基础上融合了ContentObserver的使用 
 *  利用ContentObserver随时监听ContentProvider的数据变化. 
 *  为实现该功能需要在自定义的ContentProvider的insert(),update(),delete() 
 *  方法中调用getContext().getContentResolver().notifyChange(uri, null); 
 *  向外界通知该ContentProvider里的数据发生了变化 ,以便ContentObserver作出相应  
 * 
 * 测试方法: 
 * 1 依次测试ContentProvider的增查删改(注意该顺序)!! 
 * 2 其它应用查询该ContentProvider的数据 
 * 
 */ 
public class MainActivity extends Activity { 
  private Button mAddButton; 
  private Button mDeleteButton; 
  private Button mUpdateButton; 
  private Button mQueryButton; 
  private Button mTypeButton; 
  private long lastTime=0; 
  private ContentResolver mContentResolver; 
  private ContentObserverSubClass mContentObserverSubClass; 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    init(); 
    initContentObserver(); 
  } 
 
  private void init() { 
    mContentResolver=this.getContentResolver(); 
     
    mAddButton=(Button) findViewById(R.id.addButton); 
    mAddButton.setOnClickListener(new ClickListenerImpl()); 
     
    mDeleteButton=(Button) findViewById(R.id.deleteButton); 
    mDeleteButton.setOnClickListener(new ClickListenerImpl()); 
     
    mUpdateButton=(Button) findViewById(R.id.updateButton); 
    mUpdateButton.setOnClickListener(new ClickListenerImpl()); 
     
    mQueryButton=(Button) findViewById(R.id.queryButton); 
    mQueryButton.setOnClickListener(new ClickListenerImpl()); 
     
    mTypeButton=(Button) findViewById(R.id.typeButton); 
    mTypeButton.setOnClickListener(new ClickListenerImpl()); 
     
  } 
   
   
 
  // 注册一个针对ContentProvider的ContentObserver用来观察内容提供者的数据变化 
  private void initContentObserver() { 
    Uri uri = Uri.parse("content://cn.bs.testcontentprovider/person"); 
    mContentObserverSubClass=new ContentObserverSubClass(new Handler()); 
    this.getContentResolver().registerContentObserver(uri, true,mContentObserverSubClass); 
  } 
   
  @Override 
  protected void onDestroy() { 
    super.onDestroy(); 
    if (mContentObserverSubClass!=null) { 
      this.getContentResolver().unregisterContentObserver(mContentObserverSubClass); 
    } 
  } 
 
   
   
   
  // 自定义一个内容观察者ContentObserver 
  private class ContentObserverSubClass extends ContentObserver { 
 
    public ContentObserverSubClass(Handler handler) { 
      super(handler); 
    } 
 
    //采用时间戳避免多次调用onChange( ) 
    @Override 
    public void onChange(boolean selfChange) { 
      super.onChange(selfChange); 
      System.out.println("ContentObserver onChange() selfChange="+ selfChange); 
      if (System.currentTimeMillis()-lastTime>2000) { 
        ContentResolver resolver = getContentResolver(); 
        Uri uri = Uri.parse("content://cn.bs.testcontentprovider/person"); 
        // 获取最新的一条数据 
        Cursor cursor = resolver.query(uri, null, null, null,"personid desc limit 1"); 
        while (cursor.moveToNext()) { 
          int personid = cursor.getInt(cursor.getColumnIndex("personid")); 
          System.out.println("内容提供者中的数据发生变化,现数据中第一条数据的personid="+ personid); 
        } 
        cursor.close(); 
        lastTime=System.currentTimeMillis(); 
      }else{ 
        System.out.println("时间间隔过短,忽略此次更新"); 
      } 
       
       
    } 
     
    @Override 
    public boolean deliverSelfNotifications() { 
      return true; 
    } 
     
  } 
   
   
   
   
 
  private class ClickListenerImpl implements OnClickListener { 
    @Override 
    public void onClick(View v) { 
      switch (v.getId()) { 
      case R.id.addButton: 
        Person person = null; 
        for (int i = 0; i < 5; i++) { 
          person = new Person("xiaoming" + i, "9527" + i, (8888 + i)); 
          testInsert(person); 
        } 
        break; 
      case R.id.deleteButton: 
        testDelete(1); 
        break; 
      case R.id.updateButton: 
        testUpdate(3); 
        break; 
      case R.id.queryButton: 
        // 查询表 
        // queryFromContentProvider(-1); 
 
        // 查询personid=2的数据 
        testQuery(2); 
        break; 
      case R.id.typeButton: 
        testType(); 
        break; 
      default: 
        break; 
      } 
 
    } 
 
  } 
  private void testInsert(Person person) { 
    ContentValues contentValues=new ContentValues(); 
    contentValues.put("name", person.getName()); 
    contentValues.put("phone", person.getPhone()); 
    contentValues.put("salary",person.getSalary()); 
    Uri insertUri=Uri.parse("content://cn.bs.testcontentprovider/person"); 
    Uri returnUri=mContentResolver.insert(insertUri, contentValues); 
    System.out.println("新增数据:returnUri="+returnUri); 
  } 
   
  private void testDelete(int index){ 
    Uri uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index)); 
    mContentResolver.delete(uri, null, null); 
  } 
   
  private void testUpdate(int index){ 
    Uri uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index)); 
    ContentValues values=new ContentValues(); 
    values.put("name", "hanmeimei"); 
    values.put("phone", "1234"); 
    values.put("salary", 333); 
    mContentResolver.update(uri, values, null, null); 
  } 
 
  private void testQuery(int index) { 
    Uri uri=null; 
    if (index<=0) { 
      //查询表 
      uri=Uri.parse("content://cn.bs.testcontentprovider/person"); 
    } else { 
       //按照id查询某条数据 
      uri=Uri.parse("content://cn.bs.testcontentprovider/person/"+String.valueOf(index)); 
    } 
     
    //对应上面的:查询表 
    //Cursor cursor= mContentResolver.query(uri, null, null, null, null); 
     
    //对应上面的:查询personid=2的数据 
    //注意:因为name是varchar字段的,所以应该写作"name='xiaoming1'" 
    //   若写成"name=xiaoming1"查询时会报错 
    Cursor cursor= mContentResolver.query(uri, null, "name='xiaoming1'", null, null); 
     
    while(cursor.moveToNext()){ 
      int personid=cursor.getInt(cursor.getColumnIndex("personid")); 
      String name=cursor.getString(cursor.getColumnIndex("name")); 
      String phone=cursor.getString(cursor.getColumnIndex("phone")); 
      int salary=cursor.getInt(cursor.getColumnIndex("salary")); 
      System.out.println("查询得到:personid=" + personid+",name="+name+",phone="+phone+",salary="+salary); 
    } 
    cursor.close(); 
  } 
   
  private void testType(){ 
    Uri dirUri=Uri.parse("content://cn.bs.testcontentprovider/person"); 
    String dirType=mContentResolver.getType(dirUri); 
    System.out.println("dirType:"+dirType); 
     
    Uri itemUri=Uri.parse("content://cn.bs.testcontentprovider/person/3"); 
    String itemType=mContentResolver.getType(itemUri); 
    System.out.println("itemType:"+itemType); 
  } 
 
} 

package cn.testbaidu; 
 
public class Person { 
  private Integer id; 
  private String name; 
  private String phone; 
  private Integer salary; 
  public Person(String name, String phone,Integer salary) { 
    this.name = name; 
    this.phone = phone; 
    this.salary=salary; 
  } 
  public Person(Integer id, String name, String phone,Integer salary) { 
    this.id = id; 
    this.name = name; 
    this.phone = phone; 
    this.salary=salary; 
  } 
  public Integer getId() { 
    return id; 
  } 
  public void setId(Integer id) { 
    this.id = id; 
  } 
  public String getName() { 
    return name; 
  } 
  public void setName(String name) { 
    this.name = name; 
  } 
  public String getPhone() { 
    return phone; 
  } 
  public void setPhone(String phone) { 
    this.phone = phone; 
  } 
  public Integer getSalary() { 
    return salary; 
  } 
  public void setSalary(Integer salary) { 
    this.salary = salary; 
  } 
  @Override 
  public String toString() { 
    return "Person [id=" + id + ", name=" + name + ", phone=" + phone+ ", salary=" + salary + "]"; 
  } 
   
   
   
} 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" > 
 
  <Button 
    android:id="@+id/addButton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="30dip" 
    android:text="增加" 
    android:textSize="20sp" /> 
   
   <Button 
    android:id="@+id/queryButton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="30dip" 
     android:layout_below="@id/addButton" 
    android:text="查询" 
    android:textSize="20sp" /> 
   
 
  <Button 
    android:id="@+id/deleteButton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="30dip" 
    android:layout_below="@id/queryButton" 
    android:text="删除" 
    android:textSize="20sp" /> 
 
  <Button 
    android:id="@+id/updateButton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="30dip" 
     android:layout_below="@id/deleteButton" 
    android:text="修改" 
    android:textSize="20sp" /> 
 
  
   <Button 
    android:id="@+id/typeButton" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_centerHorizontal="true" 
    android:layout_marginTop="30dip" 
     android:layout_below="@id/updateButton" 
    android:text="类型" 
    android:textSize="20sp" /> 
 
</RelativeLayout>