QT（4）信号、SLOT和QMap - Addressbook例子2

　　在之前的MeeGo开发者（五）：QT（3）对象和继承小例子基础上，我们增加三个button，参考http://doc.qt.nokia.com/latest/tutorials-addressbook-part2.html 、http://doc.qt.nokia.com/latest/tutorials-addressbook-part3.html和http://doc.qt.nokia.com/latest/tutorials-addressbook-part4.html，学习下面三个内容：

1. 这三个button放置在layout上，然后摆放在GuidLayout。
2. 当按这些button的时候，释放signal，这些信号将触发某些slot的函数。这是本次学习的重点。
3. 学习QMap的使用方法。

　　最后的UI如图所示。我们在GuidLayou的（1,2）上摆放一个layout，layout上有三个button，按Add这进入增加新的联系人，按submit表示确定增加该联系人，按Cancel表示取消增加该联系人。在图的右边我们还看到一种三个button的摆放方式，我们会在程序中进行说明。

　　用户的信息存放在QMap中，QMap适合存放带索引的数据，在这个例子中，以name为索引，address为该人名对应的信息。QMap是不使用外置数据库的情况下存储数据库的很好的方式。

　　当button click后，释放一个signal，我们需要将这个signal和某个函数，在QT上称为slot函数。 在这个例子中，我们需要建立三个对应关心，如图所示。方式为：connect(addButton/*发出信号的对象*/, SIGNAL(clicked())/*捕抓的信号*/, this,SLOT(addContact())/*监测到信号后触发的slot函数*/);

　　main.cpp无需修改，addressbook.h如下所示：

#ifndef COM_WEI_ADDRESSBOOK_H
#define COM_WEI_ADDRESSBOOK_H

#include
#include

class QLineEdit;
class QLabel;
class QTextEdit;
class QPushButton;

class AddressBook : public QWidget
{
    Q_OBJECT

public:
    AddressBook(QWidget * parent = NULL);

/* A slot is a function that responds to a particular signal.  */
public slots:
    void addContact();
    void submitContact();
    void cancel();

private:
    QPushButton * addButton, * submitButton, * cancelButton;
    QLineEdit * nameLine;
    QTextEdit * addressText;

    /* contacts用于存储联系人信息，是QMap对象，是存储key-value：这里联系人名字作为key，联系人地址作为value. */
    QMap contacts;
    QString oldName,oldAddress;
};

#endif

addressbook.cpp如下所示

/* addressbook.cpp - the implementation file for the AddressBook class */

#include
#include "addressbook.h"

AddressBook :: AddressBook(QWidget * parent) : QWidget(parent)
{
    QLabel * nameLabel = new QLabel(tr("Name:"));
    nameLine = new QLineEdit();
    nameLine->setReadOnly(true); // not editable

    QLabel * addressLabel = new QLabel(tr("Address:"));
    addressText = new QTextEdit();
    addressText->setReadOnly(true);

    addButton = new QPushButton("&Add");
    addButton->show();
    submitButton = new QPushButton("&Submit");
    submitButton->hide();
    cancelButton = new QPushButton("&Cancel");
    cancelButton->hide();

    QVBoxLayout * buttonLayout1 = new QVBoxLayout;
    buttonLayout1->addWidget(addButton,Qt::AlignTop);
    buttonLayout1->addWidget(submitButton);
    buttonLayout1->addWidget(cancelButton);
    buttonLayout1->addStretch(); //紧凑排列,否则按三等分布局，即上面UI图中的右图。

    connect(addButton, SIGNAL(clicked()),this,SLOT(addContact()));
    connect(submitButton, SIGNAL(clicked()),this,SLOT(submitContact()));
    connect(cancelButton, SIGNAL(clicked()),this,SLOT(cancel()));

    QGridLayout * mainLayout = new QGridLayout();
    mainLayout->addWidget(nameLabel,0,0);
    mainLayout->addWidget(nameLine,0,1);
    mainLayout->addWidget(addressLabel,1,0,Qt::AlignTop);
    mainLayout->addWidget(addressText,1,1);
    mainLayout->addLayout(buttonLayout1,1,2);

    setLayout(mainLayout);
    setWindowTitle(tr("Simple Address Book"));
}

void AddressBook::addContact()
{
    printf("Line %d: %s/n",__LINE__,__FUNCTION__);
    oldName = nameLine->text();
    oldAddress = addressText->toPlainText();

    nameLine->clear();
    addressText->clear();

    nameLine->setReadOnly(false);
    nameLine->setFocus(Qt::OtherFocusReason);
    addressText->setReadOnly(false);

    addButton->setEnabled(false);
    submitButton->show();
    cancelButton->show();
}

void AddressBook::submitContact()
{
    printf("Line %d: %s/n",__LINE__,__FUNCTION__);
    QString name = nameLine->text();
    QString address = addressText->toPlainText();
    if(name.isEmpty() || address.isEmpty()){
        QMessageBox::information(this,tr("Empty Field"), tr("Please enter a name and address"));
        return;
    }

    if(contacts.contains(name)){
        QMessageBox::information(this,tr("Add Unsuccessful!"), tr("Sorry,/"%1/" is already in your address book").arg(name));
        return;
    }

    contacts.insert(name, address); //QMap的用法
    QMessageBox::information(this, tr("Add Successful!"),
     tr("<%1,%2> has been added to your address book.").arg(name,address)); //%1,%2表示arg中的参数顺序，图见下
 
    nameLine -> setReadOnly(true);
    addressText -> setReadOnly(true);
    addButton -> setEnabled(true);
    submitButton->hide();
    cancelButton->hide();
}

void AddressBook::cancel()
{
    printf("Line %d: %s/n",__LINE__,__FUNCTION__);
    nameLine->setText(oldName);
    nameLine->setReadOnly(true);
    addressText->setText(oldAddress);
    addressText->setReadOnly(true);

    addButton->setEnabled(true);
    submitButton->hide();
    cancelButton->hide();
}

　　QMessageBox的截图如下

　　我们在这个基础上做进一步处理。我们增加一个两个button，用于向前查看或者向后查看，再次实践布局，并且学习一个QMap这个存储。QMap是的entry是，key的排列具体是否安hash值不清楚，但是在试验中，我们可以看到如果我们一次读取QMap的元素，将是按顺序（字母大小顺序）进行读出。begin是第一个元素，但是end不是最后一个元素，end可能是NULL，因此end-1才是最后一个有效元素。QMap的元素iterator是可以简单进行++和--操作的。

　　数据的基础操作是增/删/改/查，我们增加删/改两个功能，其中submit和cancel按键通用，在不同的功能要求下各组建的editabled/disenditabled，enabled/disenable，show/hide的显示要求不一样，我们采用一个函数updateUI来统计进行处理，利用一个enum区分不同的模式。将UI独立与功能也是开发的原则之一。

　　对于addressbook.h，我们增加相关的button定义和SLOT函数。

... ...
class AddressBook : public QWidget
{
... ...
public:
    ... ...
    enum Mode {NavigationMode,AddingMode, EditingMode};//设置枚举方式

public slots:
    ... ...
    void next();
    void previous();
    void editContact();
    void removeContact();

private:
    ... ...
    QPushButton * nextButton, * previousButton;
    QPushButton * editButton, * removeButton;
    Mode currentMode;
    void updateUI(Mode mode); //用于专门处理UI的函数
};
... ...

　　对于addressbook.cpp文件，我们修改如下，并让程序看起来更为优雅：

... ...
AddressBook :: AddressBook(QWidget * parent) : QWidget(parent)
{
    ... ...
    editButton = new QPushButton(tr("&Edit"));
    editButton->setEnabled(false);
    removeButton = new QPushButton(tr("&Remove"));
    removeButton->setEnabled(false);
    ... ...
    buttonLayout1->addWidget(editButton); //将edit和remove两个button放置在sumbit和calcel前面
    buttonLayout1->addWidget(removeButton);
    buttonLayout1->addWidget(submitButton);
    buttonLayout1->addWidget(cancelButton);
    ... ...
    connect(editButton, SIGNAL(clicked()),this,SLOT(editContact()));
    connect(removeButton, SIGNAL(clicked()),this,SLOT(removeContact()));
    ... ...
    nextButton = new QPushButton(tr("&Next"));
    nextButton->setEnabled(false);
    previousButton = new QPushButton(tr("&Previous"));
    previousButton->setEnabled(false);
    connect(nextButton,SIGNAL(clicked()),this,SLOT(next()));
    connect(previousButton,SIGNAL(clicked()),this,SLOT(previous()));
    QHBoxLayout * buttonLayout2 = new QHBoxLayout;
    buttonLayout2->addWidget(nextButton);
    buttonLayout2->addWidget(previousButton);
    ... ...
    mainLayout->addLayout(buttonLayout1,1,2);
    mainLayout->addLayout(buttonLayout2,2,1);
    ... ...
}

void AddressBook::updateUI(Mode mode){
    currentMode = mode;
    switch(mode){
    case AddingMode:
    case EditingMode:
        if(mode == AddingMode)
            editButton->hide();
        else if(mode == EditingMode)
            addButton->hide();
        removeButton->hide();

        nameLine->setReadOnly(false);
        nameLine->setFocus(Qt::OtherFocusReason);
        addressText -> setReadOnly(false);

        addButton->setEnabled(false);
        editButton->setEnabled(false);
        removeButton->setEnabled(false);
        nextButton->setEnabled(false);
        previousButton->setEnabled(false);

        submitButton->show();
        cancelButton->show();
        break;
    case NavigationMode: //浏览模式：任何功能完成后都进入浏览模式，如果有一个元素，则next和previous有效，并在此模式下可以进入功能操作
        nameLine->setReadOnly(true);
        addressText -> setReadOnly(true);
        if(contacts.isEmpty()){
            nameLine->clear();
            addressText->clear();
        }
        addButton->setEnabled(true);
        editButton->setEnabled(!contacts.isEmpty());
        removeButton -> setEnabled(!contacts.isEmpty());
        nextButton -> setEnabled(!contacts.isEmpty());
        previousButton -> setEnabled(!contacts.isEmpty());
        addButton->show();
        editButton->show();
        removeButton->show();
        submitButton->hide();
        cancelButton->hide();
        break;
    default:
        break;
    }   
}

void AddressBook::addContact()
{
    oldName = nameLine->text();
    oldAddress = addressText->toPlainText();
    nameLine->clear();
    addressText->clear();
    updateUI(AddingMode);
}

void AddressBook::editContact(){
    oldName = nameLine->text();
    oldAddress = addressText->toPlainText();
    updateUI(EditingMode);
}

void AddressBook::removeContact(){
    QString name = nameLine->text();
    QString address = addressText->toPlainText();
   
    if(contacts.contains(name)){
        if(QMessageBox::question(this,tr("Confirm Remove"), tr("Are you sure you want to remove %1").arg(name),
         QMessageBox ::Yes | QMessageBox :: No) == QMessageBox :: Yes){
            previous();
            contacts.remove(name);//QMap操作
            if(contacts.isEmpty()){
                nameLine->clear();
                addressText->clear();
            }
            QMessageBox::information(this,tr("Remove successful!"),
             tr("/"%1/" is already removed from your address book").arg(name));
        }
    }
    updateUI(NavigationMode);
}

void AddressBook::submitContact()
{
    QString name = nameLine->text();
    QString address = addressText->toPlainText();
  
    if(name.isEmpty() || address.isEmpty()){
        QMessageBox::information(this,tr("Empty Field"),
         tr("Please enter a name and address"));
        return;
    }

    switch(currentMode){
    case AddingMode:
        if(contacts.contains(name)){
            QMessageBox::information(this,tr("Add Unsuccessful!"), tr("Sorry,/"%1/" is already in your address book").arg(name));
            return;
        }else{
            contacts.insert(name, address);//QMap的使用：增加
            QMessageBox::information(this, tr("Add Successful!"),  tr("<%1,%2> has been added.").arg(name,address));
        }
        break;
    case EditingMode:
        if(oldName != name){
            if(!contacts.contains(name)){
                QMessageBox::information(this, tr("Edit successful!"), tr("Sorry,<%1> has been edited.").arg(name));
                contacts.remove(oldName);//QMap使用：删除
                contacts.insert(name,address); //QMap的使用：增加
            }else{
                QMessageBox::information(this, tr("Edit Unsuccessful!"), tr("Sorry,<%1> already in your addressbook.").arg(name));
                cancel();
            }
        } else if(oldAddress != address){
            QMessageBox::information(this, tr("Edit successful!"), tr("Sorry,<%1> has been edited.").arg(name));
            contacts[name] = address; //可以采用类似数组的方法对QMap[key]进行赋值
            cancel();
        }break;
    default:
        break;
    }
    updateUI(NavigationMode);
}

void AddressBook::cancel()
{
    nameLine->setText(oldName);
    addressText->setText(oldAddress);
    updateUI(NavigationMode);
}

void AddressBook::next()
{
    QString name = nameLine->text();
    QMap::iterator i = contacts.find(name); //QMap的查找和interator

    i ++; //可通过i++，将元素移到下一个元素

    if(i == contacts.end()) //由于最后一个元素为NULL，并不实际存在，需要设为第一个元素
        i = contacts.begin();

    nameLine->setText(i.key()); //获取key的值
    addressText->setText(i.value()); //获取value的值
}

void AddressBook::previous()
{
    QString name = nameLine->text();
    QMap::iterator i = contacts.find(name);

    if(i == contacts.begin()){ //如果是第一元素，需要移为实际的最后一个元素，即end-1
        i = contacts.end()-1;
    }else{
        i --;
    }

    nameLine->setText(i.key());
    addressText->setText(i.value());
}

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