ContentProvider的简单实现 + ContentObserver加听数据库

有时候我们需要动态的刷新页面，比如收到短信的时候，短信页面动态刷新，显示最新的短信状态。

一般我们会采用监听数据库的方法来实现，但是监听数据库要有uri，也就是要tigongContentProvider才行。

这里就是一个简单里的例子，输入姓名，点插入按钮就会插入数据，然后动态更新下面的TextView，点击删除按钮也会更新TextView。

不多说了，让代码来说话。

DBInfo.java：

public class DBInfo implements BaseColumns{private DBInfo() {}public static final String AUTHORITY = "droid.provider.mycontentprovider";    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/my_tbl");            public static final String CONTENT_TYPE = "vnd.Android.cursor.dir/vnd.droid.my_tbl";    public static final String CONTENT_ITEM_TYPE = "vnd.Android.cursor.item/vnd.droid.my_tbl";    public static final String TABLE_NAME = "my_tbl";    public static final int VERSION = 1;        public static final String NAME = "name";    }

DatabaseHelper.java：

public class DatabaseHelper extends SQLiteOpenHelper {public static String DATABASE_NAME = "mydatabase.db";public static int version = 1;public DatabaseHelper(Context context) {super(context, DATABASE_NAME, null, version);}@Overridepublic void onOpen(SQLiteDatabase db) {super.onOpen(db);}@Overridepublic void onCreate(SQLiteDatabase db) {String s = "CREATE TABLE " + DBInfo.TABLE_NAME + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT)";db.execSQL(s);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("DROP TABLE IF EXISTS notes");onCreate(db);}}

上面两个类定义了一些数据库的结构，和一些常量等。

下面是ContentProvider（没有实现完全，只是先部分方法）：

public class MyContentProvider extends ContentProvider {private static final int ALL_ROWS = 1;private static final int SINGLE_ROW = 2;private static UriMatcher uriMatcher = null;private DatabaseHelper dbHelper = null;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(DBInfo.AUTHORITY, "my_tbl", ALL_ROWS);uriMatcher.addURI(DBInfo.AUTHORITY, "my_tbl/#", SINGLE_ROW);}@Overridepublic boolean onCreate() {System.out.println("MyContentProvider ---> onCreate()");dbHelper = new DatabaseHelper(getContext());return false;}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {SQLiteDatabase db = dbHelper.getWritableDatabase();int resultCode = db.delete(DBInfo.TABLE_NAME, selection, selectionArgs);getContext().getContentResolver().notifyChange(uri, null);return resultCode;}@Overridepublic String getType(Uri uri) {switch (uriMatcher.match(uri)) {case ALL_ROWS:return DBInfo.CONTENT_TYPE;case SINGLE_ROW:return DBInfo.CONTENT_ITEM_TYPE;default:throw new IllegalArgumentException("Unknown URI: " + uri);}}@Overridepublic Uri insert(Uri uri, ContentValues values) {SQLiteDatabase db = dbHelper.getWritableDatabase();db.insert(DBInfo.TABLE_NAME, null, values);getContext().getContentResolver().notifyChange(uri, null);return null;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {SQLiteDatabase db = dbHelper.getReadableDatabase();Cursor cursor = db.query(DBInfo.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);return cursor;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {// TODO Auto-generated method stubreturn 0;}}

Activity：

public class Activity01 extends Activity {private static final int INSERT_TAG = 1;private static final int DELETE_TAG = 2;private Uri uri = Uri.parse("content://droid.provider.mycontentprovider/my_tbl");private EditText name_input;private Button insertBtn;private Button deleteBtn;private TextView display;private MyObserver observer;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                name_input = (EditText) findViewById(R.id.name_input);        insertBtn = (Button) findViewById(R.id.insertBtn);        deleteBtn = (Button) findViewById(R.id.deleteBtn);        insertBtn.setOnClickListener(new ButtonListener());        deleteBtn.setOnClickListener(new ButtonListener());        insertBtn.setTag(INSERT_TAG);        deleteBtn.setTag(DELETE_TAG);        display = (TextView) findViewById(R.id.display);                observer = new MyObserver(new Handler());this.getContentResolver().registerContentObserver(uri, true, observer);query();    }        private class ButtonListener implements OnClickListener {@Overridepublic void onClick(View v) {int tag = (Integer) v.getTag();switch(tag) {case INSERT_TAG:insert();break;case DELETE_TAG:delete();break;}}        }        private void insert() {    ContentValues cv = new ContentValues();    String nameStr = name_input.getText().toString();    if(nameStr == null || "".equals(nameStr)) {    return;    }    cv.put("name", nameStr);    this.getContentResolver().insert(uri, cv);    }        private void delete() {    String nameStr = name_input.getText().toString();    int i = this.getContentResolver().delete(uri, "name=?", new String[]{nameStr});    System.out.println("--- delete() i--->" + i);    }        private void query() {    String[] projection = {"_id", "name"};    StringBuffer sb = new StringBuffer();;    Cursor cursor = getContentResolver().query(uri, projection, null, null, null);    if(cursor != null && cursor.getCount() > 0) {    cursor.moveToFirst();    for(int i=0; i<cursor.getCount(); i++) {    cursor.moveToPosition(i);    String id = cursor.getString(cursor.getColumnIndex("_id"));    String name = cursor.getString(cursor.getColumnIndex("name"));    sb.append("id: " + id + " ;    name: " + name + "\n");    }    }    display.setText(sb.toString());    sb.delete(0, sb.length());    }        public class MyObserver extends ContentObserver {public MyObserver(Handler handler) {super(handler);}@Overridepublic void onChange(boolean selfChange) {super.onChange(selfChange);System.out.println(" ----- MyObserver -----> onChange() --- selfChange: " + selfChange);query();}        }    }

一定记得，contentProvider要在配置文件中声明：

<provider android:authorities="droid.provider.mycontentprovider"android:name=".MyContentProvider" />

布局很简单，这里就不在贴布局文件了。ContentProvider提供的不够完整。