QFileSelector provides a convenient way of selecting file variants. 更多...
| 頭： | #include <QFileSelector> |
| qmake: | QT += core |
| Since: | Qt 5.2 |
| 繼承： | QObject |
| QFileSelector (QObject * parent = Q_NULLPTR) | |
| ~QFileSelector () | |
| QStringList | allSelectors () const |
| QStringList | extraSelectors () const |
| QString | select (const QString & filePath ) const |
| QUrl | select (const QUrl & filePath ) const |
| void | setExtraSelectors (const QStringList & list ) |
QFileSelector provides a convenient way of selecting file variants.
QFileSelector is a convenience for selecting file variants based on platform or device characteristics. This allows you to develop and deploy one codebase containing all the different variants more easily in some circumstances, such as when the correct variant cannot be determined during the deploy step.
If you always use the same file you do not need to use QFileSelector .
考慮以下範例用法，若希望在不同區域設置使用不同設置文件。可以在區域設置之間選擇代碼，像這樣：
QString defaultsBasePath = "data/"; QString defaultsPath = defaultsBasePath + "defaults.conf"; QString localizedPath = defaultsBasePath + QString("%1/defaults.conf").arg(QLocale().name()); if (QFile::exists(localizedPath)) defaultsPath = localizedPath; QFile defaults(defaultsPath);
同樣，若想要基於目標平颱拾取不同數據文件，代碼可能看起來像這樣：
QString defaultsPath = "data/defaults.conf";
#if defined(Q_OS_ANDROID)
defaultsPath = "data/android/defaults.conf";
#elif defined(Q_OS_IOS)
defaultsPath = "data/ios/defaults.conf";
#endif
QFile defaults(defaultsPath);
QFileSelector provides a convenient alternative to writing such boilerplate code, and in the latter case it allows you to start using an platform-specific configuration without a recompile. QFileSelector also allows for chaining of multiple selectors in a convenient way, for example selecting a different file only on certain combinations of platform and locale. For example, to select based on platform and/or locale, the code is as follows:
QFileSelector selector; QFile defaultsFile(selector.select("data/defaults.conf"));
要選擇的文件放在的目錄命名采用
'+'
和選擇器名稱。在以上範例中，通過將它們放置在以下位置選擇平颱配置：
data/defaults.conf data/+android/defaults.conf data/+ios/+en_GB/defaults.conf
To find selected files, QFileSelector looks in the same directory as the base file. If there are any directories of the form +<selector> with an active selector, QFileSelector will prefer a file with the same file name from that directory over the base file. These directories can be nested to check against multiple selectors, for example:
images/background.png images/+android/+en_GB/background.png
有瞭這些文件，可以在 Android 平颱選擇不同文件，但前提是語言環境為 en_GB。
對於不存在有效選擇器的錯誤處理，推薦在基文件位置下存在默認文件或錯誤處理文件，即使期望所有部署都存在選擇器。
在未來版本中，某些可能會被標記為部署時靜態，並在部署步驟期間因優化而移動。由於選擇器自帶性能開銷，推薦避免將它們用於涉及性能關鍵代碼的情況。
選擇器通常可用於的
進一步，選擇器將添加自
QT_FILE_SELECTORS
環境變量，設置時應該是以逗號分隔的一組選擇器。注意，隻會讀取此變量一次；選擇器可能不更新，若變量在應用程序運行時改變。僅在首次使用時，評估初始選擇器集一次。
還可以在運行時，為自定義行為添加額外選擇器。這些將用於任何將來調用 select ()。若額外選擇器列錶已改變，調用 select () 將使用新列錶，且可能以不同方式返迴。
當可以把多個選擇器應用於同一文件時，選擇第一匹配選擇器。選擇器的校驗次序：
QT_FILE_SELECTORS
環境變量，從左到右
這裏是涉及多個選擇器的同時匹配範例。它使用平颱選擇器，加由應用程序基於用戶證書設置的名為 admin 的額外選擇器。範例有排序以便選取最低匹配文件，若所有選擇器存在：
images/background.png images/+linux/background.png images/+windows/background.png images/+admin/background.png images/+admin/+linux/background.png
由於額外選擇器的校驗，先於平颱
+admin/background.png
將在 Windows 被選取當有設置 admin 選擇器時，和
+windows/background.png
將在 Windows 被選取當未設置 admin 選擇器時。在 Linux，
+admin/+linux/background.png
將被選取當有設置 admin 時，和
+linux/background.png
當不是它時。
創建 QFileSelector instance. This instance will have the same static selectors as other QFileSelector instances, but its own set of extra selectors.
若提供，它將擁有給定 QObject parent .
銷毀此選擇器實例。
返迴用於此實例的完整、有序選擇器列錶
返迴以編程方式被添加到此實例的額外選擇器列錶。
另請參閱 setExtraSelectors ().
This function returns the selected version of the path, based on the conditions at runtime. If no selectable files are present, returns the original filePath .
If the original file does not exist, the original filePath is returned. This means that you must have a base file to fall back on, you cannot have only files in selectable sub-directories.
See the class overview for the selection algorithm.
This is a convenience version of select operating on QUrl objects. If the scheme is not file or qrc, filePath is returned immediately. Otherwise selection is applied to the path of filePath 和 QUrl is returned with the selected path and other QUrl parts the same as filePath .
See the class overview for the selection algorithm.
設置 list of extra selectors which have been added programmatically to this instance.
These selectors have priority over any which have been automatically picked up.
另請參閱 extraSelectors ().