ContentObserver的使用完整詳細示例

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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:   * 自定義ContentProvider的實現   * ContentProvider主要用於在不同的應用程序之間共享數據,這也是官方推薦的方式.   *   * 注意事項:   * 1 在AndroidManifest.xml中注冊ContentProvider時的屬性   *   android:exported=true表示允許其他應用訪問.   * 2 注意*和#這兩個符號在Uri中的作用   *   其中*表示匹配任意長度的字符   *   其中#表示匹配任意長度的數據   *   所以：   *   一個能匹配所有表的Uri可以寫成:   *   content://cn.bs.testcontentprovider/*   *   一個能匹配person表中任意一行的Uri可以寫成:   *   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 ;            /**       * 利用靜態代碼塊初始化UriMatcher       * 在UriMatcher中包含了多個Uri,每個Uri代表一種操作       * 當調用UriMatcher.match(Uri uri)方法時就會返回該uri對應的code;       * 比如此處的PERSONS和PERSON       */      static {          mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);          // 該URI表示返回所有的person,其中PERSONS為該特定Uri的標識碼          mUriMatcher.addURI(AUTHORITY, person, PERSON_DIR);          // 該URI表示返回某一個person,其中PERSON為該特定Uri的標識碼          mUriMatcher.addURI(AUTHORITY, person/#, PERSON);      }                  /**       * 在自定義ContentProvider中必須覆寫getType(Uri uri)方法.       * 該方法用於獲取Uri對象所對應的MIME類型.       *       * 一個Uri對應的MIME字符串遵守以下三點:       * 1  必須以vnd開頭       * 2  如果該Uri對應的數據可能包含多條記錄,那么返回字符串應該以vnd.android.cursor.dir/開頭       * 3  如果該Uri對應的數據只包含一條記錄,那么返回字符串應該以vnd.android.cursor.item/開頭       */      @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:       * 插入操作只有一種可能:向一張表中插入       * 返回結果為新增記錄對應的Uri       * 方法db.insert()返回結果為新增記錄對應的主鍵值       */      @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);              //向外界通知該ContentProvider里的數據發生了變化 ,以便ContentObserver作出相應              getContext().getContentResolver().notifyChange(uri, null );               return ContentUris.withAppendedId(uri, newId);          default :              throw new IllegalArgumentException(unknown uri + uri.toString());          }      }            /**       * 更新操作:       * 更新操作有兩種可能:更新一張表或者更新某條數據       * 在更新某條數據時原理類似於查詢某條數據,見下.       */      @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更新某條數據          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());          }          //向外界通知該ContentProvider里的數據發生了變化 ,以便ContentObserver作出相應          getContext().getContentResolver().notifyChange(uri, null );           return updatedNum;      }            /**       * 刪除操作:       * 刪除操作有兩種可能:刪除一張表或者刪除某條數據       * 在刪除某條數據時原理類似於查詢某條數據,見下.       */      @Override      public int delete(Uri uri, String selection, String[] selectionArgs) {          SQLiteDatabase db = mSQLiteDatabaseOpenHelper.getWritableDatabase();          int deletedNum = 0 ;          switch (mUriMatcher.match(uri)) {          // 刪除表          case PERSON_DIR:              deletedNum = db.delete(person, selection, selectionArgs);              break ;          // 按照id刪除某條數據          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());          }          //向外界通知該ContentProvider里的數據發生了變化 ,以便ContentObserver作出相應          getContext().getContentResolver().notifyChange(uri, null );           return deletedNum;      }        /**       * 查詢操作:       * 查詢操作有兩種可能:查詢一張表或者查詢某條數據       *       * 注意事項:       * 在查詢某條數據時要注意--因為此處是按照personid來查詢       * 某條數據,但是同時可能還有其他限制.例如:       * 要求personid為2且name為xiaoming1       * 所以在查詢時分為兩步:       * 第一步:       * 解析出personid放入where查詢條件       * 第二步:       * 判斷是否有其他限制(如name),若有則將其組拼到where查詢條件.       *       * 詳細代碼見下.       */      @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)) {          // 查詢表          case PERSON_DIR:              cursor = db.query(person, projection, selection, selectionArgs, null , null , sortOrder);              break ;          // 按照id查詢某條數據          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:

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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 )));          }        //當數據庫版本號發生變化時調用該方法      @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:

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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);      }   }

AndroidManifest.xml如下:

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<!--?xml version= 1.0 encoding=utf- 8 ?--> <manifest android:versioncode= "1" android:versionname= "1.0" package = "cn.testcontentprovider" xmlns:android= "http://schemas.android.com/apk/res/android" >        <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" >                                    <intent-filter>                                      <category android:name= "android.intent.category.LAUNCHER" >              </category></action></intent-filter>          </activity>                     <provider android:authorities= "cn.bs.testcontentprovider" android:exported= "true" android:name= "cn.testcontentprovider.ContentProviderTest" >      </provider></application>   </uses-permission></uses-permission></uses-permission></uses-permission></uses-sdk></manifest>

 

 

main.xml如下:

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<relativelayout android:layout_height= "match_parent" android:layout_width= "match_parent" xmlns:android= "http://schemas.android.com/apk/res/android" xmlns:tools= "http://schemas.android.com/tools" ><button android:layout_centerinparent= "true" android:layout_height= "wrap_content" android:layout_width= "wrap_content" android:text= "該應用包含一個自定義的ContentProvider" android:textsize= "15sp" ></button></relativelayout>

 

 

以下代碼為工程TestBaidu

 

MainActivity如下:

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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:   * 應用A(TestBaidu)調用另外一個應用(TestContentProvider)中的自定義ContentProvider,即:   * 1 自定義ContentProvider的使用   * 2 其它應用調用該ContentProvider   * 3 ContentObserver的使用   *   * 備注說明:   * 1 該例子在以前版本的基礎上整理了代碼   * 2 該例子在以前版本的基礎上融合了ContentObserver的使用   *   利用ContentObserver隨時監聽ContentProvider的數據變化.   *   為實現該功能需要在自定義的ContentProvider的insert(),update(),delete()   *   方法中調用getContext().getContentResolver().notifyChange(uri, null);   *   向外界通知該ContentProvider里的數據發生了變化 ,以便ContentObserver作出相應    *   * 測試方法:   * 1 依次測試ContentProvider的增查刪改(注意該順序)!!   * 2 其它應用查詢該ContentProvider的數據   *   */ 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());                }                    // 注冊一個針對ContentProvider的ContentObserver用來觀察內容提供者的數據變化      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);          }      }                          // 自定義一個內容觀察者ContentObserver      private class ContentObserverSubClass extends ContentObserver {            public ContentObserverSubClass(Handler handler) {              super (handler);          }            //采用時間戳避免多次調用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);                  // 獲取最新的一條數據                  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(內容提供者中的數據發生變化,現數據中第一條數據的personid=+ personid);                  }                  cursor.close();                  lastTime=System.currentTimeMillis();              } else {                  System.out.println(時間間隔過短,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:                  // 查詢表                  // queryFromContentProvider(-1);                    // 查詢personid=2的數據                  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(新增數據: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 ) {              //查詢表              uri=Uri.parse(content: //cn.bs.testcontentprovider/person);          } else {               //按照id查詢某條數據              uri=Uri.parse(content: //cn.bs.testcontentprovider/person/+String.valueOf(index));          }                    //對應上面的:查詢表          //Cursor cursor= mContentResolver.query(uri, null, null, null, null);                    //對應上面的:查詢personid=2的數據          //注意:因為name是varchar字段的,所以應該寫作name='xiaoming1'          //     若寫成name=xiaoming1查詢時會報錯          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(查詢得到: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:

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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 + ];      }                   }