android ContentProvider实现资源共享实例

浏览数：27 / 时间：2015年06月11日

ContentProvider为存储和读取数据提供了统一的接口，使用ContentProvider，应用程序可以实现数据共享，android内置的许多数据都是使用ContentProvider形式，供开发者调用的(如视频，音频，图片，通讯录等)。

本实例将SQLite作为存储数据的方式。

Activity代码：

protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_content_provider);
		insertButton = (Button) findViewById(R.id.insertButton);
		updateButton = (Button) findViewById(R.id.updateButton);
		deleteButton = (Button) findViewById(R.id.deleteButton);
		queryButton = (Button) findViewById(R.id.queryButton);

		insertButton.setOnClickListener(new InsertListener());
		updateButton.setOnClickListener(new UpdateListener());
		deleteButton.setOnClickListener(new DeleteListener());
		queryButton.setOnClickListener(new QueryListener());
	}

	class InsertListener implements OnClickListener {
		@Override
		public void onClick(View v) {
			ContentValues[] values = new ContentValues[2];
			ContentValues value = new ContentValues();
			value.put(CPMetadata.users.NAME, "张三");
			value.put(CPMetadata.users.AGE, 12);
			values[0] = value;
			
			value = new ContentValues();
			value.put(CPMetadata.users.NAME, "李四");
			value.put(CPMetadata.users.AGE, 11);
			values[1] = value;
			//多条插入，调用DemoProvider的insert()，每条调用一次，结果返回成功行数
			int count = getContentResolver().bulkInsert(CPMetadata.users.CONTENT_URI, values);
			// 插入单条数据
			// Uri uri =
			// getContentResolver().insert(CPMetadata.users.CONTENT_URI, values);
			// Log.d("ContentProvider", "uri : " + uri);

			Log.d("ContentProvider", "count : " + count);
		}
	}

	class UpdateListener implements OnClickListener {
		@Override
		public void onClick(View v) {
			//要更新的数据
			ContentValues values = new ContentValues();
			values.put(CPMetadata.users.NAME, "赵六");
			values.put(CPMetadata.users.AGE, 22);
			//根据ID更新，ContentUris.withAppendedId() 方法在URI的结尾追加一个1
			Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 1);
			int count = getContentResolver().update(uri, values, null, null);
			Log.d("ContentProvider", "update rows : " + count);
		}
	}

	class DeleteListener implements OnClickListener {
		@Override
		public void onClick(View v) {
			//根据ID删除，ContentUris.withAppendedId() 方法在URI的结尾追加一个2
			Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 2);
			int count = getContentResolver().delete(uri, null, null);
			Log.d("ContentProvider", "delete rows : " + count);
		}
	}

	class QueryListener implements OnClickListener {
		@Override
		public void onClick(View v) {
			//根据ID查询使用此uri，ContentUris.withAppendedId() 方法在URI的结尾追加一个1
			//Uri uri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, 1);
			//更新和删除数据使用where子句方法同理
			Cursor cursor = getContentResolver().query(CPMetadata.users.CONTENT_URI, null
					, CPMetadata.users.NAME + "=?", new String[]{"张三"}, CPMetadata.users._ID + " desc");
			//根据游标打印查询结果
			while (cursor.moveToNext()) {
				String id = cursor.getString(cursor.getColumnIndex(CPMetadata.users._ID));
				String name = cursor.getString(cursor.getColumnIndex(CPMetadata.users.NAME));
				String age = cursor.getString(cursor.getColumnIndex(CPMetadata.users.AGE));
				Log.d("ContentProvider", "ID : " + id + "  NAME : " + name + "  AGE : " + age);
			}
			cursor.close();
		}
	}

CPMetadata代码：

public class CPMetadata {

	public static final String AUTHORITY = "com.example.olds1_contentprovider.DemoProvider";
	public static final String DATABASE_NAME = "DemoProviderDB";
	public static final int DATABASE_VERSION = 1;
	
	public static final int CONTENT = 1;
	public static final int CONTENT_ITEM = 2;

	public static final class users implements BaseColumns {
		public static final String TABLE_NAME = "users";
		public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/users");
		public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.demoprovider.user";
		public static final String CONTENT_TYPE_ITEM = "vnd.android.cursor.item/vnd.demoprovider.user";
		public static final String NAME = "name";
		public static final String AGE = "age";
	}
}

DBHelper代码：

public class DBHelper extends SQLiteOpenHelper{

	public DBHelper(Context context) {
		super(context, CPMetadata.DATABASE_NAME, null, CPMetadata.DATABASE_VERSION);
		// TODO Auto-generated constructor stub
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		StringBuffer sql = new StringBuffer();
		sql.append("create table " + CPMetadata.users.TABLE_NAME + "(");
		sql.append(CPMetadata.users._ID + " integer primary key autoincrement,");
		sql.append(CPMetadata.users.NAME + " varchar(20),");
		sql.append(CPMetadata.users.AGE + " integer);");
		db.execSQL(sql.toString());
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		
	}
}

public class DemoProvider extends ContentProvider {

	private DBHelper helper;
	private SQLiteDatabase db;

	private static final UriMatcher uriMatcher;
	static {
		uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
		uriMatcher.addURI(CPMetadata.AUTHORITY, CPMetadata.users.TABLE_NAME, CPMetadata.CONTENT);
		uriMatcher.addURI(CPMetadata.AUTHORITY, CPMetadata.users.TABLE_NAME + "/#",
				CPMetadata.CONTENT_ITEM);
	}

	@Override
	public boolean onCreate() {
		helper = new DBHelper(getContext());
		db = helper.getWritableDatabase();
		return true;
	}

	@Override
	public String getType(Uri uri) {
		switch (uriMatcher.match(uri)) {
		case CPMetadata.CONTENT:
			return CPMetadata.users.CONTENT_TYPE;
		case CPMetadata.CONTENT_ITEM:
			return CPMetadata.users.CONTENT_TYPE_ITEM;
		default:
			throw new IllegalArgumentException("unknown URI:" + uri);
		}
	}
	
	/**
	 * 整理where子句
	 * 条件分为有ID和无ID两种，ID为主键具有唯一性，不用添加其他条件
	 * 无ID则使用传入的条件处理
	 * @param uri
	 * @param selection
	 * @return
	 */
	public String getWhereStr(Uri uri, String selection){
		String whereStr;
		switch (uriMatcher.match(uri)) {
		case CPMetadata.CONTENT:
			whereStr = selection;
			break;
		case CPMetadata.CONTENT_ITEM:
			whereStr = CPMetadata.users._ID + "=" + uri.getPathSegments().get(1);
			break;
		default:
			throw new IllegalArgumentException("unknown URI :" + uri);
		}
		return whereStr;
	}

	@Override
	public Uri insert(Uri uri, ContentValues values) {
		long rowid = db.insert(CPMetadata.users.TABLE_NAME, null, values);
		if (rowid > 0) {
			Uri insertUri = ContentUris.withAppendedId(CPMetadata.users.CONTENT_URI, rowid);
			getContext().getContentResolver().notifyChange(insertUri, null);
			Log.d("ContentProvider", "Insert Success  :" + insertUri);
			return insertUri;
		}
		throw new IllegalArgumentException("unknown URI: " + uri);
	}

	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
		int count = 0;
		String  whereStr = getWhereStr(uri, selection);
		Log.d("ContentProvider", "Delete Where  :" + whereStr);
		count = db.delete(CPMetadata.users.TABLE_NAME, whereStr, selectionArgs);
		getContext().getContentResolver().notifyChange(uri, null);
		return count;
	}

	@Override
	public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
		int count = 0;
		String  whereStr = getWhereStr(uri, selection);
		Log.d("ContentProvider", "Update Where  :" + whereStr);
		count = db.update(CPMetadata.users.TABLE_NAME, values, whereStr, selectionArgs);
		getContext().getContentResolver().notifyChange(uri, null);
		return count;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
			String sortOrder) {
		Cursor cursor;
		String  whereStr = getWhereStr(uri, selection);
		Log.d("ContentProvider", "Query Where  :" + whereStr);
		cursor = db.query(CPMetadata.users.TABLE_NAME, projection, whereStr, selectionArgs, null, null, sortOrder);
		cursor.setNotificationUri(getContext().getContentResolver(), uri);
		
		return cursor;
	}

注册ContentProvider，红色部分表示是否允许外部应用访问，必须设置

<span style="color:#4b4b4b;"><provider
            android:name="DemoProvider"
            android:authorities="com.example.olds1_contentprovider.DemoProvider" 
            </span><span style="color:#ff0000;">android:exported="true"</span><span style="color:#4b4b4b;">>
        </provider></span>

新建一个test工程，

效果：

Activity代码如下：

private Button button;
	private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button)findViewById(R.id.button);
        textView = (TextView)findViewById(R.id.textView);
        button.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				String uriStr = "content://com.example.olds1_contentprovider.DemoProvider/users";
				Uri uri = Uri.parse(uriStr);
				Cursor cursor = getContentResolver().query(uri, null, "name=?", new String[]{"张三"}, null);
				StringBuffer show = new StringBuffer();
				//根据游标打印查询结果
				while (cursor.moveToNext()) {
					String id = cursor.getString(cursor.getColumnIndex("_id"));
					String name = cursor.getString(cursor.getColumnIndex("name"));
					String age = cursor.getString(cursor.getColumnIndex("age"));
					show.append("ID : " + id + "  NAME : " + name + "  AGE : " + age + "\n");
				}
				cursor.close();
				textView.setText(show.toString());
			}
		});
    }

完整代码下载地址：

点我下载实例

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android ContentProvider实现资源共享实例