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面包板与基础电路 - IoT 硬件实验的前置知识 · App Inventor 2 中文网
...只用板子不接手机，先把电路跑通
怀疑是电路问题还是 App 问题时，先甩开手机，用 Arduino 官方的三个最小例子验证硬件：
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官方例子
LED 亮不亮（数字输出）
Blink
...
Scheduling recurring task in Android
...leep as soon as your onReceive() method completes. If your alarm receiver called Context.startService(), it is possible that the phone will sleep before the requested service is launched. To prevent this, your BroadcastReceiver and Service will need to implement a separate wake lock policy to ensure...
Is System.nanoTime() completely useless?
...cific counter. Now consider the following case I use to measure time of a call:
15 Answers
...
What is the strict aliasing rule?
...n(void)
{
// Get a 32-bit buffer from the system
uint32_t* buff = malloc(sizeof(Msg));
// Alias that buffer through message
Msg* msg = (Msg*)(buff);
// Send a bunch of messages
for (int i = 0; i < 10; ++i)
{
msg->a = i;
msg->b = i+1;...
GestureDetect 手势检测扩展：识别滑动、点击和长按手势 · App Inventor 2 中文网
...势检测原理
性能优化建议
常见问题
Q: 手势检测不灵敏怎么办？
Q: 手势在按钮上不起作用？
Q: 可以在滚动排列中使用吗？
Q: 如何在同一个组件上检测多种手势？
...
Android: AsyncTask vs Service
... accomplish the same task with either an AsyncTask or a Service however usually one is better suited to a task than the other.
AsyncTasks are designed for once-off time-consuming tasks that cannot be run of the UI thread. A common example is fetching/processing data when a button is pressed.
Servi...
StatusbarTools 状态栏工具扩展 · App Inventor 2 中文网
...
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状态栏颜色、图标深浅、透明沉浸式已内置为原生组件「屏幕控制」，归入界...
Why is an int in OCaml only 31 bits?
...
This is called a tagged pointer representation, and is a pretty common optimization trick used in many different interpreters, VMs and runtime systems for decades. Pretty much every Lisp implementation uses them, many Smalltalk VMs, m...
Is there an auto increment in sqlite?
...old & italic are mine):
The AUTOINCREMENT keyword imposes extra CPU, memory, disk space, and
disk I/O overhead and should be avoided if not strictly needed. It is
usually not needed.
In SQLite, a column with type INTEGER PRIMARY KEY is an alias for the
ROWID (except in WITHOUT ROW...
LEGO EV3 机器人按键控制 · App Inventor 2 中文网
... 界面优化
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LEGO EV3 机器人按键控制
项目概述
这是一...