Android System startup process

说明：  脉冲宽度调制是一种模拟控制方式，根据相应载荷的变化来调制晶体管基极或MOS管栅极的偏置，来实现晶体管或MOS管导通时间的改变，从而实现开关稳压电源输出的改变。这种方式能使电源的输出电压在工作条件变化时保持恒定，是利用微处理器的数字信号对模拟电路进行控制的一种非常有效的技术。脉冲宽度调制是利用微处理器的数字输出来对模拟电路进行控制的一种非常有效的技术，广泛应用在从测量、通信到功率控制与变换的许多领域中。(Pulse width modulation (PWM) is an analog control method, which modulates the bias of transistor base or MOS gate according to the change of load, so as to change the turn-on time of transistor or MOS and realize the change of output of switching regulated power supply. This method can keep the output voltage of the power supply constant when the working conditions change. It is a very effective technology to control the analog circuit by using the digital signal of the microprocessor. Pulse width modulation (PWM) is a very effective technology to control analog circuits by using the digital output of microprocessors. It is widely used in many fields, from measurement, communication to power control and conversion.)

单片机的按键的使用，此程序用按键控制LED的移动，按下按键一次LED移动一位，此程序能提供一点这方面的思路。(The use of key MCU, this procedure with keypad control LED of the mobile, press the button first LED moving one, this procedure can offer a few thoughts in this regard.)

介绍了andriod系统源代码的层次结构(introduce the architecture of android source code )

说明：  用Android studio配置谷歌地图，实现坐标定位并显示。(Configure Google Map with Android studio to achieve coordinate positioning and display.)

安卓手机应用开发从入门到精通，非常好的入门学习书籍(Android mobile application development from entry to the master)

一、ExpandableListView介绍 　　　　一个垂直滚动的显示两个级别（Child,Group）列表项的视图，列表项来自ExpandableListAdapter 。组可以单独展开。 　　1.重要方法 　　　　　　expandGroup(int groupPos) :在分组列表视图中展开一组，　　　　　　setSelectedGroup(int groupPosition) ：设置选择指定的组。　　　　　　setSelectedChild(int groupPosition, int childPosition, boolean shouldExpandGroup) ：设置选择指定的子项。　　　　　　getPackedPositionGroup(long packedPosition) ：返回所选择的组　　　　　　getPackedPositionForChild(int groupPosition, int childPosition) ：返回所选择的子项　　　　　　getPackedPositionType(long packedPosition) ：返回所选择项的类型（Child,Group）　　　　　　isGroupExpanded(int groupPosition) :判断此组是否展开　　2.代码：ExpandableListContextMenuInfo menuInfo=(ExpandableListContextMenuInfo)item.getMenuInfo();String title=((TextView)menuInfo.targetView).getText().toString();int type=ExpandableListView.getPackedPositionType(menuInfo.packedPosition);if (type==ExpandableListView.PACKED_POSITION_TYPE_CHILD) {int groupPos =ExpandableListView.getPackedPositionGroup(menuInfo.packedPosition);int childPos =ExpandableListView.getPackedPositionChild(menuInfo.packedPosition);二、ExpandableListAdapter　　　　一个接口，将基础数据链接到一个ExpandableListView。此接口的实施将提供访问Child的数据（由组分类），并实例化的Child和Group。 getChildId(int groupPosition, int childPosition) 获取与在给定组给予孩子相关的数据。 　　　　getChildrenCount(int groupPosition) 返回在指定Group的Child数目。

该软件实现MP3播放器的基本功能,实现播放，暂停，停止，上一曲，下一曲(The software to achieve the basic functions of MP3 player to achieve play, pause, stop, previous song, next song)

一个3D方块，在android上显示纹理映射贴图的demo(A 3D box display demo map texture mapping on android)

Android播放器源代码，源代码模式(Android.mk)编译，支持USB播放，需要手动输入视频文件的路径。(Android mediaplayer source code.)

基于android studio的蓝牙小程序，实现蓝牙连接发送和接收，简单实用(Bluetooth-based android studio small program to achieve Bluetooth connection to send and receive simple, practical)