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38 ** $QT_END_LICENSE$ |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \example webkit/domtraversal |
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44 \title DOM Traversal Example |
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45 |
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46 The DOM Traversal example shows how to use the QWebElement class to access |
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47 the structure of a Web page. |
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48 |
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49 \image webkit-domtraversal.png |
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50 |
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51 The QWebElement class provides an API that can be used to examine the structure |
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52 and content of a Web page via a Document Object Model (DOM) interface. It can be |
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53 used for basic traversal of the document structure, to search for particular |
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54 elements (see the \l{Simple Selector Example}), and to modify content in-place. |
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55 |
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56 This example uses a QWebView widget to display the Web page, and a dock widget |
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57 holds the QTreeWidget that shows the document structure. These widgets are |
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58 placed in an instance of the \c Window class, which we describe below. |
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59 |
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60 \section1 Window Class Definition |
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61 |
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62 The \c Window class is derived from QMainWindow and its user interface is created |
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63 using \l{Qt Designer}. As a result, the class is also derived from the user |
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64 interface class created by \l uic: |
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65 |
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66 \snippet examples/webkit/domtraversal/window.h Window class definition |
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67 |
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68 Two important functions to note are the \c on_webView_loadFinished() slot and |
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69 the \c examineChildElements() function. The former is automatically called |
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70 when the QWebView widget finishes loading a page \mdash see the |
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71 \l{#Further Reading}{Further Reading} section for more information on this |
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72 mechanism. |
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73 |
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74 The \c examineChildElements() function is used to traverse the document structure |
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75 and add items to the QTreeWidget. |
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76 |
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77 \section1 Window Class Implementation |
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78 |
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79 In the \c Window class constructor, we call the \l{QWidget::}{setupUi()} function |
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80 to set up the user interface described in the \c{window.ui} file: |
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81 |
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82 \snippet examples/webkit/domtraversal/window.cpp Window constructor |
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83 |
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84 When the Web page is loaded, the \c on_webView_loadFinished() slot is called. Here, |
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85 we clear the tree widget and begin inspection of the document by obtaining the |
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86 document element from the page's main frame: |
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87 |
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88 \snippet examples/webkit/domtraversal/window.cpp begin document inspection |
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89 |
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90 At this point, we call the \c examineChildElements() function to traverse the |
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91 document, starting with the child elements of the document element for which we |
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92 will create top level items in the tree widget. |
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93 |
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94 The \c examineChildElements() function accepts a parent element and a parent item. |
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95 Starting with the first child element, which we obtain with the element's |
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96 \l{QWebElement::}{firstChild()} function, we examine each child element of the |
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97 parent item. For each valid (non-null) element, which we check by calling its |
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98 \l{QWebElement::}{isNull()} function, we create a new QTreeWidgetItem instance with |
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99 the element name and add it to the parent item. |
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100 |
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101 \snippet examples/webkit/domtraversal/window.cpp traverse document |
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102 |
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103 We recursively examine the child elements for each element by calling |
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104 \c examineChildElements() with the current child element and the newly-created item. |
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105 To obtain the next element at the same level in the document, we call its |
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106 \l{QWebElement::}{nextSibling()} function. |
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107 |
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108 This recursive approach to reading the document makes it easy to create a simple |
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109 representation of the document structure in a tree widget. |
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110 |
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111 For completeness, we show the \c setUrl() function, which is provided to allow the |
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112 document URL to be set from the example's \c main() function. |
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113 |
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114 \snippet examples/webkit/domtraversal/window.cpp set URL |
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115 |
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116 \section1 Starting the Example |
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117 |
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118 We set up the application, create |
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119 a \c Window instance, set its URL, and show it: |
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120 |
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121 \snippet examples/webkit/simpleselector/main.cpp main program |
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122 |
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123 When the application's event loop is run, the Qt home page will load, and the |
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124 tree widget will be updated to show the document structure. Navigating to another |
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125 page will cause the tree widget to be updated to show the document structure of |
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126 the new page. |
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127 |
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128 \section1 Further Reading |
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129 |
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130 The QWebElement documentation contains more information about DOM access for the |
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131 QtWebKit classes. |
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132 |
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133 In this example, we take advantage of Qt's |
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134 \l{Using a Designer UI File in Your Application#Automatic Connections}{auto-connection} |
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135 feature to avoid explicitly connecting signals to slots. The user interface |
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136 contains a QWebView widget called \c webView whose \l{QWebView::}{loadFinished()} |
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137 signal is automatically connected to the \c on_webView_loadFinished() slot when |
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138 we call \l{QWidget::}{setupUi()} in the \c Window constructor. |
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139 */ |