handler | 易学教程

Check if Android handler has callbacks

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问题 I have some code which sets a timer, but if a user sets the timer while it is in use I need to remove the runnable which runs the timer and start it again. But when no handler callback runnable exists and this code is called it crashes my application. So I need to check if a handler is running, if so then end it and restart it, but looking through the documentation and other Stackoverflow questions, I cannot see if this is possible. Here is my code, I have commented around the code which

How to create multiple timer handler in vb.net

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问题 I have to create multiple timer "n" times with handler. Which will be stored for a row in my DataGrid. For each row there will be a timer that works seperately. What I thought of looks like: Private Sub CreateTimer() Dim tmr As New Timer tmr.Interval = 1000 '1 Second tmr.Enabled = True AddHandler tmr.Tick, AddressOf GlobalTimerTick End Sub 'A timer tick handler that would work for each timer I add with the sub above 'All timers I created should work seperately Private Sub GlobalTimerTick

Accessing UI view in another thread does not cause a crash. Why?

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问题 All: I really don't grok handlers yet. I thought that the code below -- modified so that, instead of using a handler, the UI widget (progress bar) was accessed directly -- would cause a cross-threading exception. But it doesn't. So, my question is, shouldn't this code crash? And if it doesn't, then when do I need to use a handler? public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); progress = 0; progressBar = (ProgressBar)

Passing context to Handler

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问题 Is it possible to pass arguments to an Android Handler?? I have two pieces of code. new Thread(){ public void run(){ for(;;){ uiCallback.sendEmptyMessage(0); Thread.sleep(2000); //sleep for 2 seconds } } }.start(); private Handler uiCallback = new Handler(){ public void handleMessage(Message msg){ //add a new blossom to the blossom ArrayList!! blossomArrayList.add(new Blossom(context, R.drawable.blossom)); } }; I of course get an error because the Handler method cannot see my context. This is

Android中的Handler, Looper, MessageQueue和Thread

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前几天，和同事探讨了一下 Android 中的消息机制，探究了消息的发送和接收过程以及与线程之间的关系。虽然我们经常使用这些基础的东西，但对于其内部原理的了解，能使我们更加容易、合理地架构系统，并避免一些低级错误。对于这部分的内容，将分成 4 小节来描述： 1.职责与关系 2.消息循环 3.线程与更新 4.几点小结 -------------------------------------------------------------------------------------------------- 1 ）接下来，我们开始这部分的内容，首先了解一下各自的职责及相互之间的关系。职责 Message ：消息，其中包含了消息 ID ，消息处理对象以及处理的数据等，由 MessageQueue 统一列队，终由 Handler 处理。 Handler ：处理者，负责 Message 的发送及处理。使用 Handler 时，需要实现 handleMessage(Message msg) 方法来对特定的 Message 进行处理，例如更新 UI 等。 MessageQueue ：消息队列，用来存放 Handler 发送过来的消息，并按照 FIFO 规则执行。当然，存放 Message 并非实际意义的保存，而是将 Message 以链表的方式串联起来的，等待 Looper 的抽取。

Does the memory get released when I throw an exception?

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问题 I was debating with some colleagues about what happens when you throw an exception in a dynamically allocated class. I know that malloc gets called, and then the constructor of the class. The constructor never returns, so what happens to the malloc ? Consider the following example: class B { public: B() { cout << "B::B()" << endl; throw "B::exception"; } ~B() { cout << "B::~B()" << endl; } }; void main() { B *o = 0; try { o = new B; } catch(const char *) { cout << "ouch!" << endl; } } What

python模块 ---logging模块

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摘要by crazyhacking：与log4cxx一样，分为三个部分，logger, handler,formatter. 详细内容参考：1官网 http://docs.python.org/2/howto/logging.html#formatters 2 log4cxx http://blog.csdn.net/crazyhacking/article/category/1536605 一简单示例 import logging logger = logging.getLogger() # 生成一个日志对象 # logfile是一个全局变量，它就是一个文件名，如：'crawl.log' logfile = 'test.log' # 生成一个Handler。logging支持许多Handler， # 象FileHandler, SocketHandler, SMTPHandler等，我由于要写 # 文件就使用了FileHandler。 hdlr = logging.FileHandler('sendlog.txt') # 成一个格式器，用于规范日志的输出格式。如果没有这行代码，那么缺省的 # 格式就是："%(message)s"。也就是写日志时，信息是什么日志中就是什么， # 没有日期，没有信息级别等信息。logging支持许多种替换值，详细请看 #

Android postDelayed Handler Inside a For Loop?

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问题 Is there any way of running a handler inside a loop? I have this code but is not working as it does not wait for the loop but executes the code right way: final Handler handler = new Handler(); final Runnable runnable = new Runnable() { public void run() { // need to do tasks on the UI thread Log.d(TAG, "runn test"); // for (int i = 1; i < 6; i++) { handler.postDelayed(this, 5000); } } }; // trigger first time handler.postDelayed(runnable, 0); Of course when I move the post delayed outside

事件兼容函数

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Android Async, Handler or Timer?

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问题 Every 5 seconds, I want to call my webservice and get text (not images), then display it in my ImageAdapter. What would be the best way to accomplish this? 回答1: It depends if you want to use a different thread or not. Do you want the user to be able to interact with the application on the UI Thread while the images are downloading? If so, then I would definitely use an AsyncTask with a small ProgressBar ( style="@android:style/Widget.ProgressBar.Small" ) If you don't care about threading then