nw.js node-webkit系列（13）Native UI API 其它

ゞ浴缸里的玫瑰 2021-09-10 20:22 272阅读 0赞

本节主要介绍Native UI API中一些不常用的功能，包括Shell、Handling files and arguments、Screen。

# （一）Shell #

Shell主要用来处理桌面相关应用的工作。如使用默认浏览器打开一个网页地址、使用文本的方式打开一个文件、在文件资源管理器中打开文件。

// Load native UI library.
    var gui = require('nw.gui');
    
    // Open URL with default browser.
    gui.Shell.openExternal('https://github.com/rogerwang/node-webkit');
    
    // Open a text file with default text editor.
    gui.Shell.openItem('test.txt');
    
    // Open a file in file explorer.
    gui.Shell.showItemInFolder('test.txt');

# （二）NW应用处理文件和参数的方式 #

针对一些应用，例如文本编辑器和IDE，它可以绑定文件类型并指定特定的APP打开，这个功能是很重要的。

**Command line arguments**

命令行参数传输。在node-webkit中，当使用命令行去指定你的APP去打开一个文件时，如

your-app file.txt file2.txt

其中

file.txt file2.txt

将会被记录而且你能够使用App.argv的方法去获取它们，如

var gui = require('nw.gui');
    console.log(gui.App.argv);
    // Print "file.txt, file2.txt"

**Open file with existing app**

使用现有的应用打开文件。在很多时候，当你使用你的APP打开多个文件时，你更希望使用一个APP会话去打开而不是多个会话。例如，一个IDE，如果你已经打开了一个IDE实例，然后再打开一个源码文件，你会希望使用已打开的IDE实例去编辑文件而不是重新打开一个IDE实例。

对于node-webkit的应用，这个问题已经被默认解决了。当你打开一个文件，node-webkit会检测你的APP是否已经打开，如果没有打开，你的应用实例将会被打开并且文件的路径会从App.argv中获取；如果你的应用已经在打开的状态，那么整个命令行的内容将会通过open事件监听到APP对象获取。两种情况获取的打开文件的参数对象方式不同。

// Listen to `open` event
    gui.App.on('open', function(cmdline) {
      console.log('command line: ' + cmdline);
    });

注：open事件只有在你的APP是独立存在的情况下生效。例如使用这种方式进行打包：

https://github.com/nwjs/nw.js/wiki/How-to-package-and-distribute-your-apps

注：在苹果系统，如果以文件拖动到你的APP图标中的方式打开文件，open事件依然有效。

注：在苹果系统，你应该注册你的文件类型，使文件启动类型指向你的APP。操作方法参照：

https://developer.apple.com/library/ios/documentation/FileManagement/Conceptual/DocumentInteraction\_TopicsForIOS/Articles/RegisteringtheFileTypesYourAppSupports.html

注：如果你不想使用这个功能，在Windows和Linux系统下，你可以在package配置文件中设置single-instance为false。然而这个设置对苹果系统并没有效果。

# （三）Screen #

Screen是EventEmitter对象的一个实例。你可以使用Screen.on(...)去回应本地屏幕事件。

Screen是一个独立的对象，它需要被初始化当使用的时候。如gui.Screen.Init()。

**Screen.Init()**

初始化Screen实例对象，你只需要调用一次即可。

**Screen.screens**

获取Screen实例对象的数据。Screen对象有以下的结构：

screen {
    // unique id for a screen
      id: int,
    
    // physical screen resolution, can be negative, not necessarily start from 0,depending on screen arrangement
      bounds: {
        x: int,
        y: int,
        width: int,
        height: int
      },
    
    // useable area within the screen bound
      work_area: {
        x: int,
        y: int,
        width: int,
        height: int
      },
    
      scaleFactor: float,
      isBuiltIn: bool,
      rotation: int,
      touchSupport: int
    }

**Screen.chooseDesktopMedia (array of DesktopCaptureSourceType sources, function callback)**

该功能比较复杂，详细请参考：

https://github.com/nwjs/nw.js/issues/3077

更多对屏幕控制的函数，请参考

https://github.com/nwjs/nw.js/wiki/Screen

# （四）小贴士 #

**（1）Show window after page is ready**

通常情况下，node-webkit打开一个APP，需要通过以下步骤：

1）.显示浏览器

2）.解压你的APP

3）.创建渲染过程

4）.初始化webkit

5）.最后打开你的APP

这个过程需要些时间，而且这段时间用户将看到一个空的浏览器。这会导致看起来你的APP运行的非常缓慢，你应该等所有都准备就绪后才显示你的主窗口。针对这个问题，下面有些小贴士可以提供给你。

首先，你需要在package配置文件中设置窗口的显示为false，这样在node-webkit启动时便不会显示窗口。

{
      "window": {
        "show": false
      }
    }

当所有都准备就绪后，你再调用Windows API把窗口显示出来。

**（2）Minimize to tray**

在windows系统中，一种通用的窗口设计模式是最小化窗口时会到通知区域。如当点击窗口的最小化按钮时，会最小化到托盘，点击托盘将返回窗口。

为了在node-webkit中实现这种功能，你可以使用以下代码：

<html>
    <body>
      <div>Minimize to tray</div>
      <script>
        // Load library
        var gui = require('nw.gui');
    
        // Reference to window and tray
        var win = gui.Window.get();
        var tray;
    
        // Get the minimize event
        win.on('minimize', function() {
          // Hide window
          this.hide();
    
          // Show tray
          tray = new gui.Tray({ icon: 'icon.png' });
    
          // Show window and remove tray when clicked
          tray.on('click', function() {
            win.show();
            this.remove();
            tray = null;
          });
        });
      </script>
    </body>
    </html>

**（3）Preserve window state between sessions**

在多次会话中保存窗口的状态。意思是当首次打开窗口时，将窗口的位置和宽高记录在node-webkit的Local Storage中，下次打开窗口时，恢复上次窗口的显示状态。

为了实现这个功能，首先你需要把窗口的显示状态设为false：

{
      "window": {
        "show": false
      }
    }

然后你可以使用下面这段代码：

/**
     * https://github.com/nwjs/nw.js/wiki/Preserve-window-state-between-sessions
     *
     * Cross-platform window state preservation.
     * Yes this code is quite complicated, but this is the best I came up with for
     * current state of node-webkit Window API (v0.7.3 and later).
     *
     * Known issues:
     * - Unmaximization not always sets the window (x, y) in the lastly used coordinates.
     * - Unmaximization animation sometimes looks wierd.
     * - Extra height added to window, at least in linux x64 gnome-shell env. It seems that
     *   when we read height then it returns it with window frame, but if we resize window
     *   then it applies dimensions only to internal document without external frame.
     *   Need to test in other environments with different visual themes.
     *
     * Change log:
     * 2013-12-01
     * - Workaround of extra height in gnome-shell added.
     *
     * 2014-03-22
     * - Repared workaround (from 2013-12-01) behaviour when use frameless window.
     *   Now it works correctly.
     * 2014-10-02
     * - Fixed cannot set windowState of null error when attempting to set localStorage
     *
     * 2015-03-05
     * - Don't call window.show() if dev tools are already open (see initWindowState).
     *
     * 2015-06-15
     * - Don't resize the window when using LiveReload.
     */
    
    var gui = require('nw.gui');
    var win = gui.Window.get();
    var winState;
    var currWinMode;
    var resizeTimeout;
    var isMaximizationEvent = false;
    // extra height added in linux x64 gnome-shell env, use it as workaround
    var deltaHeight = gui.App.manifest.window.frame ? 0 : 'disabled';
    
    
    function initWindowState() {
    	// Don't resize the window when using LiveReload.
    	// There seems to be no way to check whether a window was reopened, so let's
    	// check for dev tools - they can't be open on the app start, so if
    	// dev tools are open, LiveReload was used.
    	if (!win.isDevToolsOpen()) {
    		winState = JSON.parse(localStorage.windowState || 'null');
    
    		if (winState) {
    			currWinMode = winState.mode;
    			if (currWinMode === 'maximized') {
    				win.maximize();
    			} else {
    				restoreWindowState();
    			}
    		} else {
    			currWinMode = 'normal';
    			dumpWindowState();
    		}
    
    		win.show();
    	}
    }
    
    function dumpWindowState() {
    	if (!winState) {
    		winState = {};
    	}
    
    	// we don't want to save minimized state, only maximized or normal
    	if (currWinMode === 'maximized') {
    		winState.mode = 'maximized';
    	} else {
    		winState.mode = 'normal';
    	}
    
    	// when window is maximized you want to preserve normal
    	// window dimensions to restore them later (even between sessions)
    	if (currWinMode === 'normal') {
    		winState.x = win.x;
    		winState.y = win.y;
    		winState.width = win.width;
    		winState.height = win.height;
    
    		// save delta only of it is not zero
    		if (deltaHeight !== 'disabled' && deltaHeight !== 0 && currWinMode !== 'maximized') {
    			winState.deltaHeight = deltaHeight;
    		}
    	}
    }
    
    function restoreWindowState() {
    	// deltaHeight already saved, so just restore it and adjust window height
    	if (deltaHeight !== 'disabled' && typeof winState.deltaHeight !== 'undefined') {
    		deltaHeight = winState.deltaHeight
    		winState.height = winState.height - deltaHeight
    	}
    
    
    	//Make sure that the window is displayed somewhere on a screen that is connected to the PC. 
    	//Imagine you run the program on a secondary screen connected to a laptop - and then the next time you start the 
    	//program the screen is not connected...
    	gui.Screen.Init();
    	var screens = gui.Screen.screens;
    	var locationIsOnAScreen = false;
    	for (var i = 0; i < screens.length; i++) {
    		var screen = screens[i];
    		if (winState.x > screen.bounds.x && winState.x < screen.bounds.x + screen.bounds.width) {
    			if (winState.y > screen.bounds.y && winState.y < screen.bounds.y + screen.bounds.height) {
    				console.debug("Location of window (" + winState.x + "," + winState.y + ") is on screen " + JSON.stringify(screen));
    				locationIsOnAScreen = true;
    			}
    		}
    	}
    
    	if (!locationIsOnAScreen) {
    		console.debug("Last saved position of windows is not usable on current monitor setup. Moving window to center!");
    		win.setPosition("center");
    	} else {
    		win.resizeTo(winState.width, winState.height);
    		win.moveTo(winState.x, winState.y);
    	}
    }
    
    function saveWindowState() {
    	dumpWindowState();
    	localStorage['windowState'] = JSON.stringify(winState);
    }
    
    initWindowState();
    
    win.on('maximize', function() {
    	isMaximizationEvent = true;
    	currWinMode = 'maximized';
    });
    
    win.on('unmaximize', function() {
    	currWinMode = 'normal';
    	restoreWindowState();
    });
    
    win.on('minimize', function() {
    	currWinMode = 'minimized';
    });
    
    win.on('restore', function() {
    	currWinMode = 'normal';
    });
    
    win.window.addEventListener('resize', function() {
    	// resize event is fired many times on one resize action,
    	// this hack with setTiemout forces it to fire only once
    	clearTimeout(resizeTimeout);
    	resizeTimeout = setTimeout(function() {
    
    		// on MacOS you can resize maximized window, so it's no longer maximized
    		if (isMaximizationEvent) {
    			// first resize after maximization event should be ignored
    			isMaximizationEvent = false;
    		} else {
    			if (currWinMode === 'maximized') {
    				currWinMode = 'normal';
    			}
    		}
    
    		// there is no deltaHeight yet, calculate it and adjust window size
    		if (deltaHeight !== 'disabled' && deltaHeight === false) {
    			deltaHeight = win.height - winState.height;
    
    			// set correct size
    			if (deltaHeight !== 0) {
    				win.resizeTo(winState.width, win.height - deltaHeight);
    			}
    		}
    
    		dumpWindowState();
    
    	}, 500);
    }, false);
    
    win.on('close', function() {
    	try {
    		saveWindowState();
    	} catch (err) {
    		console.log("winstateError: " + err);
    	}
    	this.close(true);
    });

最后，在html中导入这段代码即可

<script src="lib/winstate.js"></script>

本节内容就介绍到这，如果后续博主发现更多Native UI API的相关功能，会继续在CSDN博客中发表，至此Native UI API相关功能已经介绍完毕。