初探PApplet窗口打开方式（Processing程序）

使用Processing快6年了，是时候回过头来看看它的"main"方法了，也就是它从哪出生的？~~~

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源码学习

  //////////////////////////////////////////////////////////////

  // MAIN

  /**
   * main() method for running this class from the command line.
   * <p>
   * Usage: PApplet [options] &lt;class name&gt; [sketch args]
   * <ul>
   * <li>The [options] are one or several of the parameters seen below.
   * <li>The class name is required. If you're running outside the PDE and
   * your class is in a package, this should include the full name. That means
   * that if the class is called Sketchy and the package is com.sketchycompany
   * then com.sketchycompany.Sketchy should be used as the class name.
   * <li>The [sketch args] are any command line parameters you want to send to
   * the sketch itself. These will be passed into the args[] array in PApplet.
   * <p>
   * The simplest way to turn and sketch into an application is to
   * add the following code to your program:
   * <PRE>static public void main(String args[]) {
   *   PApplet.main("YourSketchName");
   * }</PRE>
   * That will properly launch your code from a double-clickable .jar
   * or from the command line.
   * <PRE>
   * Parameters useful for launching or also used by the PDE:
   *
   * --location=x,y         Upper-lefthand corner of where the applet
   *                        should appear on screen. If not used,
   *                        the default is to center on the main screen.
   *
   * --present              Presentation mode: blanks the entire screen and
   *                        shows the sketch by itself. If the sketch is
   *                        smaller than the screen, the background around it
   *                        will use the --window-color setting.
   *
   * --hide-stop            Use to hide the stop button in situations where
   *                        you don't want to allow users to exit. also
   *                        see the FAQ on information for capturing the ESC
   *                        key when running in presentation mode.
   *
   * --stop-color=#xxxxxx   Color of the 'stop' text used to quit an
   *                        sketch when it's in present mode.
   *
   * --window-color=#xxxxxx Background color of the window. The color used
   *                        around the sketch when it's smaller than the
   *                        minimum window size for the OS, and the matte
   *                        color when using 'present' mode.
   *
   * --sketch-path          Location of where to save files from functions
   *                        like saveStrings() or saveFrame(). defaults to
   *                        the folder that the java application was
   *                        launched from, which means if this isn't set by
   *                        the pde, everything goes into the same folder
   *                        as processing.exe.
   *
   * --display=n            Set what display should be used by this sketch.
   *                        Displays are numbered starting from 1. This will
   *                        be overridden by fullScreen() calls that specify
   *                        a display. Omitting this option will cause the
   *                        default display to be used.
   *
   * Parameters used by Processing when running via the PDE
   *
   * --external             set when the applet is being used by the PDE
   *
   * --editor-location=x,y  position of the upper-lefthand corner of the
   *                        editor window, for placement of applet window
   *
   * All parameters *after* the sketch class name are passed to the sketch
   * itself and available from its 'args' array while the sketch is running.
   *
   * @see PApplet#args
   * </PRE>
   */
  static public void main(final String[] args) {
    runSketch(args, null);
  }

  /**
   * Convenience method so that PApplet.main(YourSketch.class)
   * launches a sketch, rather than having to call getName() on it.
   */
  static public void main(final Class<?> mainClass, String... args) {
    main(mainClass.getName(), args);
  }

  /**
   * Convenience method so that PApplet.main("YourSketch") launches a sketch,
   * rather than having to wrap it into a single element String array.
   * @param mainClass name of the class to load (with package if any)
   */
  static public void main(final String mainClass) {
    main(mainClass, null);
  }

  /**
   * Convenience method so that PApplet.main("YourSketch", args) launches a
   * sketch, rather than having to wrap it into a String array, and appending
   * the 'args' array when not null.
   * @param mainClass name of the class to load (with package if any)
   * @param sketchArgs command line arguments to pass to the sketch's 'args'
   *             array. Note that this is <i>not</i> the same as the args passed
   *             to (and understood by) PApplet such as --display.
   */
  static public void main(final String mainClass, final String[] sketchArgs) {
    String[] args = new String[] { mainClass };
    if (sketchArgs != null) {
      args = concat(args, sketchArgs);
    }
    runSketch(args, null);
  }

还有一个超长，也是最重要的runSketch()我这就不贴了。。。

可以看到，主要有两种方法运行PApplet对象，即JFrame窗口。如下：

PApplet.main()

下面是默认的pde输出程序自动生成的.java文件中的main方法：

  static public void main(String[] passedArgs) {
    String[] appletArgs = new String[] { "test4run" };
    if (passedArgs != null) {
      PApplet.main(concat(appletArgs, passedArgs));
    } else {
      PApplet.main(appletArgs);
    }
  }

一般只需调用PApplet.main()即可，参数为一个字符串数组，如果只填一个也可，填类名，必须一致，不然会报错！如果标准填法，如下：

    String[] appletArgs = new String[] { "--present", "--window-color=#FFFFFF", "--stop-color=#cccccc", "Appname" };

这些字符串都是作为参数传给runSketch(),把相应的开关打开配置参数，简单看一下：

/*
   * --location=x,y         窗口的悬浮位置，相对于桌面窗口坐标系，默认是居中
   *
   * --present              展示模式，全屏，有个底色，即window-color,只要size尺寸小于屏幕大小未填充区域则显示底色
   *
   * --hide-stop            展示模式中是否隐藏stop按钮，当然即使隐藏ESC仍旧有效
   *
   * --stop-color=#xxxxxx   stop按钮颜色，主要是防止和底色相近难以辨别
   *
   * --window-color=#xxxxxx 底色
   *
   * --sketch-path          项目目录，针对保存帧等写操作的路径参数
   *
   * --display=n            显示的窗口索引，这和实际的显示设备和系统标定的显示标号相挂钩
   *
   * --external             扩展的一些方法判断依据（一般作为一个布尔值使用）[待研究]
   *
   * --editor-location=x,y  编辑器窗口位置，方便定义应用窗口位置[待研究]
*/

PApplet.runSketch()

这一种方法比较灵活，入口函数启动如下（kotlin）：

fun main(args: Array<String>) {
    var app = ShowApp()
    PApplet.runSketch(arrayOf("show"),app)
}

注意需要new一个PApplet对象，然后作为第二参数传入，第一参数类型为String[]。当然也可以在此拓展，我们可以任意创建窗口，实现多窗口开发或展示（kotlin）：

    var bsapp = BoardShowApp()
    var bsapp2 = BoardShowApp()
    PApplet.runSketch(arrayOf("BoardShow1"),bsapp)
    PApplet.runSketch(arrayOf("BoardShow2"),bsapp2)

如果读者细心学习Processing官方示例，有个多窗口应用的范例(MultipleWindows)：

你会发现它就创建了一个PApplet类ChildApplet，作为子窗口，然后在构造器中使用了上述开启窗口的方法----PApplet.runSketch()。

笔者发现不再构造器中运行runSketch是无效的，因此如果在运行时想要打开第二个或多个窗口，必须在子类构造时执行这个方法。至于子窗口的种种参数那么跟surface对象有关了，我们往后再聊。

附件

下面是完整代码的参考：

import processing.core.*;
import processing.data.*;
import processing.event.*;
import processing.opengl.*; 

import java.util.HashMap;
import java.util.ArrayList;
import java.io.File;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException; 

public class Test4run extends PApplet {

public void setup() {

}

public void draw() {

}

public void settings() {
     size(400, 400);
}

  static public void main(String[] passedArgs) {
    String[] appletArgs = new String[] { "Test4run" };
    if (passedArgs != null) {
      PApplet.main(concat(appletArgs, passedArgs));
    } else {
      PApplet.main(appletArgs);
    }
  }
}

import processing.core.PApplet

class ChildApp : PApplet() {
    override fun settings() {
        size(400, 400)
        smooth()
    }

    override fun setup() {
        surface.setTitle("Child sketch")
    }

    override fun draw() {
        background(0)

    }

    override fun mousePressed() {
    }

    override fun mouseDragged() {
    }

    //JFrame frame;
    init {
        runSketch(arrayOf(this.javaClass.name), this)
    }
}

class ShowApp : PApplet(){

    val childapp = ChildApp()
    override fun settings() {
        size(800,400)
    }

    override fun setup() {
    }

    override fun draw() {
        background(20)
    }

}

fun main(args: Array<String>) {
    var sapp = ShowApp()
    var sapp2 = ShowApp()

    PApplet.runSketch(arrayOf("Show1"),sapp)
    PApplet.runSketch(arrayOf("Show2"),sapp2)
}

有哪里出现遗漏的或是错误的讲解，请指正，感谢您的阅读！