clear

问题 I want to clear data through coding for my application. Right now I am Clearing Data from Settings->Applications->Manage Application->My Application-> Clear Data . But I want to do it through coding. Please help me if any one have answers. 回答1: Use Context's getFilesDir method to get the directory, and then delete all directory and data as explained here. 回答2: Using MByD's code to delete a dir, delete the folder /data/app/my.app.name ;-) 回答3: If the data is "Internal" to the application, it

问题 I defined the derivative of a function in Mathematica without defining the function itself, i.e. I have a function definition that looks like this: y'[x_] := constant * f'[x]. I can't figure out how to clear it out. If I use Clear[y'] or `ClearAll[y'], I get an error message: ClearAll::ssym: y' is not a symbol or a string. Clear[y] and ClearAll[y] do nothing to remove the definition of y' . Any ideas on how I can remove the definition of y' ? 回答1: This should do what you want: y'[x_] =. See

问题 I'm trying to draw two lines in a Canvas in Java, calling two methods separately, but when I draw the second line, the first one disapears (Java clears the screen). How can I avoid that? I want to see the two lines. I've seen paint tutorials (how to make a program like the Paint on Windows) where the user uses the mouse to draw lines and when one line is drawn, the other do not disappear. They just call the paint method and it does not clear the screen. I'll be grateful if anyone can help me.

问题 I have a streamstring in two loops and it is burning my RAM. So how to clear properly the buffer of a steamstring? It is like that to simplify : stringstream ss (stringstream::in | stringstream::out); for() { for() { val = 2; ss << 2; mystring = ss.str(); // my stuff } // Clear the buffer here } It wrote 2 then 22 then 222... I tried .clear() or .flush() but it is not that. So how I do this? 回答1: The obvious solution is to use a new stringstream each time, e.g.: for (...) { std::stringstream

问题 One can use string::clear function to empty a string, and can use empty double quotation "" to do that also. What is the difference? 回答1: When you assign an empty string, the compiler will have to store an empty C-string in the data section, and create the code to pass a pointer to it to the assignment operator. The assignment operator then has to read from the data section, just to find out, that you passed an empty string. With clear() the compiler just generates a function call without any

问题 I have an EditText field, suppose the user has already entered text into it. Then the user wants to come back to edit the text again: the feature I want for this EditText field is that if you select it after it already has text in it, it clears the text for you before you can type something new in. I tried using the EditText field's OnClick method, but this required that I select the EditText field, then click on it a second time, something that isn't obvious to anyone but me. How can I get

问题 I'm using a QPainter to get some graphics on a window. Unfortunately every time the paintEvent() function is called, the whole window is cleared. How can I draw without clearing? I.e. how do I leave the stuff from previous paint event untouched? I'm using Qt4 回答1: You need to set the backgroundMode by using the setBackgroundMode setter. The Qt::NoBackground enum is what you are searching for. 回答2: Since both replies are for Qt3 only, here is the solution for Qt4. You need to call setAttribute

问题 I have a Rails 3 based CMS that allows users to create and modify layouts and views. These layouts and views are the same ones built into the framework, only backed by a model for some additional capabilities. The problem I would like to address is that these template files are cached as soon as they are accessed on the public end, so it is not possible to see changes in the layouts or views unless the server is restarted. This does not occur in development mode where caching is disabled, but

问题 Previously, when I had floatings blocks, and i will stop the float, i used ; <div style="clear:both"></div> But now, i'm solve this problem with pseudo class : .last_floating_div:after { content: ""; display: table; clear: both; } I has always works perfectly. But today... It doesn't work... ! Look at this clear example : http://jsfiddle.net/YsueS/2/ I know my problem is a total beginner problem. I have sold this problem so many times... I really don't understand why it doesn't work here !

问题 Calling clear() on a vector will call the destructors of whatever is stored in the vector, which is a linear time operation. But is this the case when the vector contains primitive types like int or double ? 回答1: I believe the answer is implementation dependent. It takes at most linear time, but some implementations may choose to optimize this. Per 'Does clearing a vector affect its capacity?', neither MSVC nor G++ decrease the capacity of their vectors, even when .clear is called. Looking at