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

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

示例说明:

该示例中一共包含两个工程。其中一个工程完成了自定义ContentProvider，另外一个工程用于测试该自定义ContentProvider且在该工程中使用了ContentObserver监听自定义ContentProvider的数据变化

以下代码为工程TestContentProvider

ContentProviderTest如下:

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;   }     }

SQLiteDatabaseOpenHelper如下:

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 copypackage 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);   }  }

AndroidManifest.xml如下:

<?xml version="1.0" encoding="utf-8"?>

main.xml如下:

以下代码为工程TestBaidu

MainActivity如下:

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);   }  }

Person如下:

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 + "]";   }          }

main.xml如下:

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