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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \example network/qftp |
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44 \title FTP Example |
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45 |
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46 The FTP example demonstrates a simple FTP client that can be used |
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47 to list the available files on an FTP server and download them. |
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48 |
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49 \image ftp-example.png |
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50 |
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51 The user of the example can enter the address or hostname of an |
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52 FTP server in the \gui {Ftp Server} line edit, and then push the |
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53 \gui Connect button to connect to it. A list of the server's |
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54 top-level directory is then presented in the \gui {File List} tree |
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55 view. If the selected item in the view is a file, the user can |
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56 download it by pushing the \gui Download button. An item |
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57 representing a directory can be double clicked with the mouse to |
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58 show the contents of that directory in the view. |
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59 |
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60 The functionality required for the example is implemented in the |
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61 QFtp class, which provides an easy, high-level interface to the |
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62 file transfer protocol. FTP operations are requested through |
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63 \l{QFtp::Command}s. The operations are asynchronous. QFtp will |
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64 notify us through signals when commands are started and finished. |
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65 |
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66 We have one class, \c FtpWindow, which sets up the GUI and handles |
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67 the FTP functionality. We will now go through its definition and |
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68 implementation - focusing on the code concerning FTP. The code for |
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69 managing the GUI is explained in other examples. |
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70 |
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71 \section1 FtpWindow Class Definition |
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72 |
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73 The \c FtpWindow class displays a window, in which the user can |
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74 connect to and browse the contents of an FTP server. The slots of |
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75 \c FtpWindow are connected to its widgets, and contain the |
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76 functionality for managing the FTP connection. We also connect to |
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77 signals in QFtp, which tells us when the |
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78 \l{QFtp::Command}{commands} we request are finished, the progress |
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79 of current commands, and information about files on the server. |
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80 |
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81 \snippet examples/network/qftp/ftpwindow.h 0 |
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82 |
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83 We will look at each slot when we examine the \c FtpWindow |
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84 implementation in the next section. We also make use of a few |
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85 private variables: |
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86 |
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87 \snippet examples/network/qftp/ftpwindow.h 1 |
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88 |
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89 The \c isDirectory hash keeps a history of all entries explored on |
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90 the FTP server, and registers whether an entry represents a |
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91 directory or a file. We use the QFile object to download files |
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92 from the FTP server. |
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93 |
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94 \section1 FtpWindow Class Implementation |
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95 |
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96 We skip the \c FtpWindow constructor as it only contains code for |
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97 setting up the GUI, which is explained in other examples. |
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98 |
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99 We move on to the slots, starting with \c connectOrDisconnect(). |
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100 |
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101 \snippet examples/network/qftp/ftpwindow.cpp 0 |
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102 |
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103 If \c ftp is already pointing to a QFtp object, we QFtp::Close its |
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104 FTP connection and delete the object it points to. Note that we do |
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105 not delete the object using standard C++ \c delete as we need it |
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106 to finish its abort operation. |
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107 |
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108 \dots |
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109 \snippet examples/network/qftp/ftpwindow.cpp 1 |
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110 |
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111 If we get here, \c connectOrDisconnect() was called to establish a |
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112 new FTP connection. We create a new QFtp for our new connection, |
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113 and connect its signals to slots in \c FtpWindow. The |
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114 \l{QFtp::}{listInfo()} signal is emitted whenever information |
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115 about a single file on the sever has been resolved. This signal is |
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116 sent when we ask QFtp to \l{QFtp::}{list()} the contents of a |
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117 directory. Finally, the \l{QFtp::}{dataTransferProgress()} signal |
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118 is emitted repeatedly during an FTP file transfer, giving us |
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119 progress reports. |
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120 |
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121 \snippet examples/network/qftp/ftpwindow.cpp 2 |
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122 |
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123 The \gui {Ftp Server} line edit contains the IP address or |
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124 hostname of the server to which we want to connect. We first check |
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125 that the URL is a valid FTP sever address. If it isn't, we still |
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126 try to connect using the plain text in \c ftpServerLineEdit. In |
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127 either case, we assume that port \c 21 is used. |
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128 |
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129 If the URL does not contain a user name and password, we use |
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130 QFtp::login(), which will attempt to log into the FTP sever as an |
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131 anonymous user. The QFtp object will now notify us when it has |
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132 connected to the FTP server; it will also send a signal if it |
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133 fails to connect or the username and password were rejected. |
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134 |
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135 We move on to the \c downloadFile() slot: |
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136 |
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137 \snippet examples/network/qftp/ftpwindow.cpp 3 |
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138 \dots |
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139 \snippet examples/network/qftp/ftpwindow.cpp 4 |
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140 |
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141 We first fetch the name of the file, which we find in the selected |
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142 item of \c fileList. We then start the download by using |
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143 QFtp::get(). QFtp will send progress signals during the download |
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144 and a signal when the download is completed. |
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145 |
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146 \snippet examples/network/qftp/ftpwindow.cpp 5 |
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147 |
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148 QFtp supports canceling the download of files. |
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149 |
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150 \snippet examples/network/qftp/ftpwindow.cpp 6 |
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151 |
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152 The \c ftpCommandFinished() slot is called when QFtp has |
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153 finished a QFtp::Command. If an error occurred during the |
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154 command, QFtp will set \c error to one of the values in |
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155 the QFtp::Error enum; otherwise, \c error is zero. |
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156 |
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157 \snippet examples/network/qftp/ftpwindow.cpp 7 |
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158 |
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159 After login, the QFtp::list() function will list the top-level |
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160 directory on the server. addToList() is connected to |
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161 QFtp::listInfo(), and will be invoked for each entry in that |
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162 directory. |
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163 |
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164 \snippet examples/network/qftp/ftpwindow.cpp 8 |
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165 |
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166 When a \l{QFtp::}{Get} command is finished, a file has finished |
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167 downloading (or an error occurred during the download). |
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168 |
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169 \snippet examples/network/qftp/ftpwindow.cpp 9 |
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170 |
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171 After a \l{QFtp::}{List} command is performed, we have to check if |
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172 no entries were found (in which case our \c addToList() function |
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173 would not have been called). |
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174 |
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175 Let's continue with the \c addToList() slot: |
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176 |
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177 \snippet examples/network/qftp/ftpwindow.cpp 10 |
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178 |
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179 When a new file has been resolved during a QFtp::List command, |
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180 this slot is invoked with a QUrlInfo describing the file. We |
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181 create a separate row for the file in \c fileList. If \c fileList |
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182 does not have a current item, we set the new item to be the |
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183 current item. |
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184 |
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185 \snippet examples/network/qftp/ftpwindow.cpp 11 |
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186 |
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187 The \c processItem() slot is called when an item is double clicked |
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188 in the \gui {File List}. If the item represents a directory, we |
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189 want to load the contents of that directory with QFtp::list(). |
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190 |
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191 \snippet examples/network/qftp/ftpwindow.cpp 12 |
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192 |
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193 \c cdToParent() is invoked when the user requests to go to the |
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194 parent directory of the one displayed in the file list. After |
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195 changing the directory, we QFtp::List its contents. |
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196 |
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197 \snippet examples/network/qftp/ftpwindow.cpp 13 |
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198 |
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199 The \c updateDataTransferProgress() slot is called regularly by |
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200 QFtp::dataTransferProgress() when a file download is in progress. |
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201 We use a QProgressDialog to show the download progression to the |
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202 user. |
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203 |
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204 \snippet examples/network/qftp/ftpwindow.cpp 14 |
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205 |
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206 The \c enableDownloadButton() is called whenever the current item |
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207 in \c fileList changes. If the item represents a file, the \gui |
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208 {Enable Download} Button should be enabled; otherwise, it is |
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209 disabled. |
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210 */ |
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211 |