Qt C ++; 如何解决特定的文本字段，具体取决于用户输入

Question

I'm having issues with formulating the question but this is what I want to do with my application.

A user can select one or multiple image-files (.ppm), and they are displayed in some sort of legend, with their filename underneath. The information of these images is stored in a structure. (This structure contains the image path, name, and other info).

Now I want to give the user the chance to change the name of the selected images, and uses this name in the rest of the application. So I would have to change the name in the structure.

I could do this by adding textfields in the legend, where users can type the desired name, but how can I get the input from this textfield if I don't know which one is alterred?

If the user selects 6 images, I need 6 new textfields in the legend, but how can I address the correct one?

 struct[2].name = input2.getText();

I also thought about doing it with some sort of wizard, with 6 pages where the names can be changed, but I don't know how I can adress the correct textfield.

Any help would be welcome, thanks!!

Answer 1

If you want to allow users to rename multiple files at one time, you may want to create a wizard. In the wizard you could display each picture they selected (one at a time) and allow them to rename each picture (one at a time). Otherwise it will be confusing to the user and harder for you to manage.

When generating the wizard, I would use the information structure to associate the picture with the textfield.

Answer 2

Qt, signals and slots are your friend here.

When you setup the textfields for the name, assuming you use something like a QLineEdit object, connect to a relevant signal, such as editingFinished(). Make the connection to the slot of the Object that stores the structure. The receiving slot then updates the appropriate information.

So, assuming your struct is in an object derived from QObject, you can do something like this: -

struct DataStruct // the struct storing the underlying data
{
    QString name;
    QLineEdit* linkedEditWidget; // widget for user to change text
};


class MainObject : public QObject
{
    Q_OBJECT // required for signals and slots

    public slots:
        void UpdateText();

    private:
     const int NUM_STRUCTS = 10; // initialisation in C++ 11
     DataStruct myStructs[NUM_STRUCTS]; // a number of structs
};

When you initialize the array of structs and the LineEdit widgets, store a pointer to the matching LineEdit widget in each myStruct and connect the widgets' editingFinished signals to the MainObject updateText() slot. It would be a good idea to use weak smart pointers here, but I'll use a standard pointer, to keep things simple.

When you receive notification that the text has changed, you'll need to match up the caller with the LineEdit* in the struct. Note that QObject::sender() will return the pointer to the object that sent the message: -

void MainObject::UpdateText()
{
    QObject* theSendingWidget = sender();
    for(int i=0; i<NUM_STRUCTS; ++i) // assuming NUM_STRUCTS is already defined
    {
        if(myStructs[i].linkedEditWidget == theSendingWidget)
        {
            // update the name in the data struct
            myStructs[i].name = (static_cast<QLineEdit*>(theSendingWidget))->text();
            return; // our work is done.
        }
    }
}

Finally, you'd probably make life easier for yourself by storing the data in Qt model objects, rather than using a plain struct. I suggest reading up on Model / View programming and the MVC design pattern