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);
	}

	@Override
	public void onOpen(SQLiteDatabase db) {
		super.onOpen(db);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		String s = "CREATE TABLE " + DBInfo.TABLE_NAME + 
		" (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT)";
		db.execSQL(s);
	}

	@Override
	public 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);
	}
	

	@Override
	public boolean onCreate() {
		System.out.println("MyContentProvider ---> onCreate()");
		dbHelper = new DatabaseHelper(getContext());
		return false;
	}
	
	@Override
	public 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;
	}

	@Override
	public 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);
		}
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
		SQLiteDatabase db = dbHelper.getWritableDatabase();
		db.insert(DBInfo.TABLE_NAME, null, values);
		getContext().getContentResolver().notifyChange(uri, null);
		return null;
	}

	@Override
	public 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;
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {
		// TODO Auto-generated method stub
		return 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 {

		@Override
		public 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);
		}

		@Override
		public 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。