Android源码学习(一) 数据集观察者
查看Android源码发现这个,决定记下下来。
1.在android.database这个包下面,存在这样一个抽象类DataSetObserver,里面包括onChanged()和onInvalidated()这个两个方法,用来监听数据的改变,在方法内要执行的操作。
/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.database; /** * Receives call backs when a data set has been changed, or made invalid. The typically data sets * that are observed are {@link Cursor}s or {@link android.widget.Adapter}s. * DataSetObserver must be implemented by objects which are added to a DataSetObservable. */ public abstract class DataSetObserver { /** * This method is called when the entire data set has changed, * most likely through a call to {@link Cursor#requery()} on a {@link Cursor}. */ public void onChanged() { // Do nothing } /** * This method is called when the entire data becomes invalid, * most likely through a call to {@link Cursor#deactivate()} or {@link Cursor#close()} on a * {@link Cursor}. */ public void onInvalidated() { // Do nothing } }
2.同级目录中存在Observable这样一个类,如果将上面的DataSetObserver作为这个类的泛型参数。
/* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.database; import java.util.ArrayList; /** * Provides methods for registering or unregistering arbitrary observers in an {@link ArrayList}. * * This abstract class is intended to be subclassed and specialized to maintain * a registry of observers of specific types and dispatch notifications to them. * * @param T The observer type. */ public abstract class Observable<T> { /** * The list of observers. An observer can be in the list at most * once and will never be null. */ protected final ArrayList<T> mObservers = new ArrayList<T>(); /** * Adds an observer to the list. The observer cannot be null and it must not already * be registered. * @param observer the observer to register * @throws IllegalArgumentException the observer is null * @throws IllegalStateException the observer is already registered */ public void registerObserver(T observer) { if (observer == null) { throw new IllegalArgumentException("The observer is null."); } synchronized(mObservers) { if (mObservers.contains(observer)) { throw new IllegalStateException("Observer " + observer + " is already registered."); } mObservers.add(observer); } } /** * Removes a previously registered observer. The observer must not be null and it * must already have been registered. * @param observer the observer to unregister * @throws IllegalArgumentException the observer is null * @throws IllegalStateException the observer is not yet registered */ public void unregisterObserver(T observer) { if (observer == null) { throw new IllegalArgumentException("The observer is null."); } synchronized(mObservers) { int index = mObservers.indexOf(observer); ) { throw new IllegalStateException("Observer " + observer + " was not registered."); } mObservers.remove(index); } } /** * Remove all registered observers. */ public void unregisterAll() { synchronized(mObservers) { mObservers.clear(); } } }
Android源码学习(一) 数据集观察者的更多相关文章
- Android源码学习之装饰模式应用
首先得了解最基础的装饰器模式 参考 设计模式之八 --- 装饰模式(Decorator) 参考链接:http://blog.csdn.net/cjjky/article/details/7478788 ...
- Android源码-学习随笔
在线代码网站1:http://grepcode.com/project/repository.grepcode.com/java/ext/com.google.android/android/ 书籍: ...
- Android源码学习之模板方法模式应用
一.模板方法模式定义 模板方法模式定义: defines the skeleton of an algorithm in a method, deferring some steps to subcl ...
- Android 源码学习
工具篇:如何使用 Visual Studio Code 阅读 Android 源码:https://jekton.github.io/2018/05/11/how-to-read-android-so ...
- 【转】Android源码学习(2)使用Git和Repo进行版本管理
原文网址:http://blog.chinaunix.net/uid-26074270-id-2458828.html Android项目采用Git和Repo进行版本管理.在大多数情况下,Git都可以 ...
- Android源码学习
http://android-wheel.googlecode.com/svn/trunk/android-wheel-read-only 在github上面有一个叫做 android-wheel 的 ...
- Android学习系列(38)--Android源码下载和编译
前面多篇文章介绍到如何下载和编译Android或者CM源码,不过一直都是放在<拓展系列>里.随着学习的深入,android源码是非常有参考和学习价值,强烈推荐大家都去下载,编译,学习,所以 ...
- (转)Android学习进阶路线导航线路(Android源码分享)
转载请注明出处:http://blog.csdn.net/qinjuning 前言:公司最近来了很多应届实习生,看着他们充满信心但略带稚气的脸庞上,想到了去年的自己,那是的我是不是也和 现在的他们一 ...
- Android事件分发详解(三)——ViewGroup的dispatchTouchEvent()源码学习
package cc.aa; import android.os.Environment; import android.view.MotionEvent; import android.view.V ...
随机推荐
- (译)"usermod"命令使用完全指导---15个练习例程截图
"usermod"命令使用完全指导---15个练习例程截图 By Babin Lonston Under: Linux Commands On: November 11, 2014 ...
- STL入门
STL入门 STL的组成 六大组件 容器container 算法algorithm 迭代器iterator 仿函数function object 适配器adaptors 空间配制器allocator ...
- hdu 5605 geometry(几何,数学)
Problem Description There is a point P at coordinate (x,y). A line goes through the point, and inter ...
- UVA 11212 Editing a Book
题意: 有一篇由n个自然段组成的文章.希望将他们排成递增序列.只能剪贴和粘贴交替进行,剪贴时可以剪贴一段连续的自然段. 分析: 用IDA*算法求解.当3*d+h>maxd时剪枝. 代码: #in ...
- (四)Android中Context的理解与使用
一.Context的作用 Context可用于访问全局资源. public class MainActivity extends Activity { private TextView tv; @Ov ...
- ZOJ 3261 - Connections in Galaxy War ,并查集删边
In order to strengthen the defense ability, many stars in galaxy allied together and built many bidi ...
- effective c++ 条款06 不想自动生成函数,就明确拒绝
编辑器会主动的生成三个/五个函数,如果不需要我们应该主动拒绝 使用私有属性来拒绝 ``` include int main() { return 0; } ``` 使用继承的方式来拒绝
- linux下的gdb调试工具--内存调试
接着上一节的代码,在while(1)的循环里面增加代码:sum=0 #include <stdio.h> int main(void) { int sum = 0, i = 0; char ...
- Qt编程学习网站
http://blog.csdn.net/k122769836/article/details/8637677 QT - little_su - 博客频道 - CSDN.NET Qt - 1+1=2 ...
- mysql学习(八)数据表类型-字符集
数据存储引擎: MyISAM:强化快速读取操作. 也有缺点.一些功能不支持 InnoDB:支持一些MyIASM一些不支持的功能 缺点:占用空间大 对比 ...