android之StrictMode介绍

Android 2.3起,新增加了一个新的类,叫StrictMode(android.os.StrictMode)。这个类可以用来帮助开发者改进他们编写的应用,并且提供了各种的策略,这些策略能随时检查报告开发者开发应用中存在的问题,比如可以监视那些本不应该在主线程中完成的工作或者其他的一些不规范和不好的代码。

StrictMode的策略和规则

  目前,有两大类的策略可供使用

一类是关于常用的监控方面的

Disk Reads 磁盘读

Disk Writes 磁盘写

Network access 网络访问

Custom Slow Code 自定义的运行速度慢的代码分析

前面三种的意思读者应该很清楚,就是正如它们的名字所示,分别对磁盘的读和写,网络访问进行监控。而第四种的自定义慢代码分析,是仅当访问调用类的时后才触发的,可以通过这种

方法去监视运行缓慢的代码。当在主线程中调用时,这些验证规则就会起作用去检查你的代码。比如,当你的应用在下载或者解析大量的数据时,你可以触发自定义运行速度慢代码的查询分、

析,作用很大。StrictMode可以用于捕捉发生在应用程序主线程中耗时的磁盘、网络访问或函数调用,可以帮助开发者使其改进程序,使主线程处理UI和动画在磁盘读写和网络操作时变得更平

滑,避免主线程被阻塞的发生。

另一类是关于VM虚拟机等方面的策略

内存泄露的Activity对象

内存泄露的SQLite对象

内存泄露的释放的对象

其中,内存泄露的Activity对象和内存泄露的SQLite对象都比较好理解,而所谓对关闭对象的检查,主要是去监那些本该释放的对象,比如应该调用close()方法的对象

相关的违反情况可以记录在LogCat中或者存储在DropBox中(android.os.DropBox)服务中

  如何使用:

  放在activity的周期onCreate方法中

 

XCode 无法显示Size Inspector

XCode 升级到4.5 以后,在View的设置界面中就再也找不到Size Inspector  的踪迹了,找了很长时间,才知道原来 到 4.5 的时候,引入了“Autolayout”功能来简化设计,可是,当需要手动配置某些复杂控件的时候,这个就不怎么智能了。

找到下面的方法禁止掉其自动的功能。只是所有的都要手动设置了。

在Interface Builder中选中View,然后在Attributes Builder中去掉“Use Autolayout”前面的钩,如下图:

1352635874_6561

Ubuntu 12 以及 13 清除Dash主页及电影播放器(视频)历史记录的方法

1.清除Dash主页中历史记录的方法。

系统设置-隐私-清除历史记录

也可在“应用程序”选项卡中,设置哪些应用软件不启用历史记录。

2.电影播放器用文本编辑器历史记录的清除方法。

ctrl+alt+t,打开命令行

Android 源代码 error: Exited sync due to fetch errors…

希望各位不要出现这个错误,出现这个错误就要折腾一会了

首先继续repo sync,若是一直提示这个错误,那么就按照下面的方法来做吧:

关于这个问题其实google是有说明的http://source.android.com/source/downloading.html,为了防止连接数过多,每个ip都需要认证。。。

第一步:从这里 the password generator 获取用户名和密码,前提是你在之前填写了你的真实姓名和邮箱

第二步:将上面的页面上以machine开头的两行复制到 ~/.netrc文件中

第三步:

多了个“/a”,并且指定 “--config-name”

参数,很多时候会用以前配置过的用户名密码,指定这个参数会重新设置用户名

然后就可以repo sync了

特别注意.netrc文件是在用户的根目录下,root用户就是/目录下,如果没有的话就自己建一个,把权限改为 777 好了

Install the Arduino IDE in Ubuntu 12.04

转自http://blog.markloiseau.com/2012/05/install-arduino-ubuntu/

Install the Arduino IDE in Ubuntu 12.04

Installing the Arduino IDE in Ubuntu only takes a few minutes. As usual, it’s a better idea to install the Arduino straight from the source, instead of relying on the version in Ubuntu’s repository. While it wasn’t hard to install the Arduino IDE, I noticed that the Arduino GUI was really slow and laggy. This is because the startup script tells Java to use Ubuntu’s GTK look and feel, which makes everything run slowly. It’s easily fixed by changing a single line in the startup script.

Update: In the Arduino 1.0.1 update, “Serial Port” is greyed out. The fix is outlined in the troubleshooting section.

Install the Arduino IDE in Ubuntuarduino_logo

  1. Install gcc-avr, avr-libc and openjdk-6-jre if you don’t have it already.
  2. Plug in the board, see where it’s connected
  3. Download and unpack the Arduino IDEtarball
  4. Run the IDE
  5. Select your board model and serial port
  6. Run a sample program
  7. Fix the buggy interface (optional)
  8. Troubleshooting

Everything worked out of the box, other than the interface.

Install gcc-avr and avr-libc

Gcc-avr and avr-libc give your system the tools it needs to compile c into AVR machine code:

If you don’t have openjdk-6-jre already, install and configure that too:

Once those are installed plug in your board and type  $ dmesg . It will print the kernel’s ring buffer and show you what USB port your Arduino is plugged into:

According to dmesg, our board is plugged into ttyACM0.

Download and Run the Arduino IDE

Go to the downloads page on Arduino’s download page to get the latest Arduino IDE tarball (.tgz file) for your architecture. My laptop is 64-bit, so I chose accordingly. Once the file was finished downloading, I unzipped and ran it with the following command:

Select your board model and serial port

I’m using an Arduino MEGA 2560, so I went to Tools>Board>”Arduino Mega 2560 or Mega ADK.” At this point, I noticed that the GUI was really slow and hard to use. If you want to fix it before proceeding, exit the IDE and skip to the  ”Fixing the Interface” section before proceeding.

The IDE flashed an error about how my board wasn’t accessible over the COM1 port. COM1 usually refers to a 9-pin serial port, and my laptop doesn’t even have one. I went to Tools>Serial Port and selected /dev/ttyACM0, which reflected the output I saw when I checked dmesg.

The errors went away, and I went to File>Examples>Basics>Blink and clicked upload. Sure enough, the LED started blinking. You should be ready to start writing and running Arduino programs!

Fix the Arduino IDE to make it run more smoothly in Ubuntu

Exit the Arduino IDE and go to the installation folder (the folder you unzipped from the .tgz file). Edit the “arduino” script in your favorite text editor. To make Arduino use the native Swing windowing instead of forcing the GTK look and feel, which is the cause of the bugginess, change the following line:

Just delete the -D flag and its argument. Personally, I get nostalgic about the old-school Swing look and feel, but either way, it fixed all of the lagginess issues I was experiencing.arduino_ide_ubuntu

My Arduino IDE, running in Ubuntu (using SWT instead of GTK)

Troubleshooting USB and the grayed out Serial Port

When I got the Arduino 1.0.1 update, “Serial Port” was grayed out in the tools menu. Running arduino as root ( sudo ./arduino) resolved the issue, but it’s not an acceptable solution. In my case, serial port was grayed out because my user didn’t have permission to read and write to the device.

I added my user to the dialout group with the command  sudo usermod -a -G dialout mark . Usually, that would have fixed it but iserial port was still grayed out.

Changing the permissions on /dev/ttyACM0 to world readable and writeable fixed the grayed out serial port. I ran  sudo chmod a+rw /dev/ttyACM0 and the serial port menu worked again.

I’ve noticed that running programs that send lots of data over USB can cause issues with the arduino programming software, making it give errors while uploading code. Holding down the reset button fixed my upload and USB errors in most cases.

Further Reading

If you read nothing else before you start writing programs, look at the official Arduino Reference page. It might be the most concise, complete language reference I’ve ever seen.