Question

我是初学者，我正在编写此代码以进行作业。

我知道这看起来像重复，但知道NullPointerException错误意味着什么，我真的不明白如何修复这个，但我认为它与我导入的库有关;我真的不确定。我真诚地感谢任何建议。

第一部分是我的代码，下面是来自堆栈跟踪的NullPointerException错误。

如果我需要指明其他任何内容，请告诉我。

代码：

import processing.video.*;
String PATH = "/Project_2_Scetch/data/video_library/img4.mp4";
Movie mov;`enter code here`

PFont f;

Capture cam;
float xin, yin;
int maxImages = 8;
int imageIndex = 0;
int value = 0;
PImage img;
PImage[] images = new PImage[maxImages]; 
float positionX = xin;
float positionY = yin;

void setup() {
  size(1000, 650);
  smooth();
  noStroke();
  img = loadImage("img0.jpg");
  rectMode(CENTER);

f = createFont("Source Sans Pro", 20, true);

if (key == 's'){
  String[] cameras = Capture.list();

  if (cameras.length == 0) {
    println("There are no cameras available for capture.");
    exit();
  } else {
    println("Available cameras:");
    for (int i = 0; i < cameras.length; i++) {
      println(cameras[i]);
    }

    // The camera can be initialized directly using an 
    // element from the array returned by list():
    cam = new Capture(this, cameras[0]);
    cam.start();     
  }      

  for (int i = 0; i < images.length; i ++ ) {
    images[i] = loadImage( "img" + i + ".jpg" );}}

}
void movieEvent(Movie m) {
  m.read();
}
void draw() {
  background(50, 20, 120);
  {
  textSize(20);
  text("In this game, there is no such thing as sleep. You will be going about my", 150, 70);
  text("endless day either procrastinating, or catching up on homework", 200, 110 );
  fill(255);
  text("To procrastinate for endless fun use Free Mode", 288, 150);
  fill(255);
  text("To catch up on my homework and experience existential terror, use Adventure Mode", 95, 190);
  fill(255);

  text("Free Mode (Press J)", 175, 338);
  fill(255);

  text("Adventure Mode (Press K)", 579, 340);
  fill(255);}




  if (key == 'j') {
    background(50, 20, 120);
    text("To take intentionally terrible selfies, press the (A) key.", 150, 300);
    fill(255);
    text("To rescue pets, press the (B) key.", 150, 350);
    fill(255);}

  if (key == 'a') {
    img = loadImage("img1.jpg");
    image(img, width/4, height/6);
    background(50, 20, 120);
    text("If you would like to continue taking terrible selfies, press the (G) key.", 125, 320);
    text("If you would like to go back and do something else, press the (J) key.", 125, 350);
  }
  if (key == 'b'){
    img = loadImage("img6.jpg");
    background(50, 20, 120);
    text("If you would like to see more animals, press the (C) key.", 175, 320);
    text("If you would like to go back and do something else, press the (J) key.", 175, 370);
  }

  if (key == 'c'){
 image(mov, 0, 0);
  }

  if (key == 'e'){
   // img = loadImage("img5.jpg");
    background(50, 20, 120);  
    text("You seem like an animal lover. If you would like to watch Animal Planet, press the (D) key.", 50, 320);
    text("If you are not an animal lover, how dare you.", 50, 360);
    text("Press the spacebar to start over and rethink your life's choices.", 50, 390);
  }
 if (key == 'g'){
   img = loadImage("img7.jpg");
   background(50, 20, 120);  
   text("You seem to like taking selfies. If you would like to take some more funky fresh selfies,", 53, 300);
   text("then please hit the (H) key.", 53, 350);
  }
 if (key == 'h'){
   background(50, 20, 120); 
   img = loadImage("img4.jpg");
   text("Are you satisfied with this selfie? Would you like to take more selfies? If so, press the (M) key.", 40, 300);
   text("If not, then that's okay too. If you'd rather work on some homework, press the (K) key instead.", 40, 335);
  }

  if (key == 'm'){
   text("Hey. You like selfies. No judgement here. Press the (S) key and take your own selfies and keep them close.", 40, 300);
   text("If not, that's alright too. If you'd rather, press (K) to start on some homework :)", 40, 330);
 }

 if (key == 'd'){
    background(50, 20, 120);
    fill(50, 60, 170);
    text("Go on, click on the box, you animal!", 250, 160);
    fill(255);
    line(470, 0, 470, 530);
    line(0, 295, 355, 295);

  }
  //this is a hot mess too, but move onto the next thing.j
  if (key == 's'){
  if(cam.available() == true) {
    cam.read();
  }
     image(cam, 0, 0);
  // The following does the same, and is faster when just drawing the image
  // without any additional resizing, transformations, or tint.
  //set(0, 0, cam);
  }
 }


void mouseClicked() {
  if (mouseX < 470 && mouseY < 295){
    fill(255);
    rect(470, 295, 500, 340);
    link("http://www.animalplanet.com/tv-shows/"); 
 } 
}

NullPointerException错误＃1：

当我执行if（key =='c'）时会显示;功能，我正在尝试播放视频。我为此功能导入了视频库。

Exception in thread "Animation Thread" java.lang.NullPointerException
    at processing.core.PGraphics.image(PGraphics.java:3765)
    at processing.core.PApplet.image(PApplet.java:12109)
    at Project_2_Scetch.draw(Project_2_Scetch.java:113)
    at processing.core.PApplet.handleDraw(PApplet.java:2399)
    at processing.awt.PSurfaceAWT$12.callDraw(PSurfaceAWT.java:1527)
    at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:316)

NullPointerException错误＃2：当我执行if（key =='s'）时会显示;功能，在这里我试图让用户的网络摄像头拉起来。我为此功能导入了IPCapture库。

Exception in thread "Animation Thread" java.lang.NullPointerException
    at Project_2_Scetch.draw(Project_2_Scetch.java:152)
    at processing.core.PApplet.handleDraw(PApplet.java:2399)
    at processing.awt.PSurfaceAWT$12.callDraw(PSurfaceAWT.java:1527)
    at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:316)

Answer 1

您有两个不能初始化的变量：mov和cam。

mov变量的初始化看起来像是你应该完成的任务。在使用该变量之前，您必须完成该部分。

您已初始化cam变量，但它在if语句中。但请注意，永远不会输入if语句，因为在setup()函数完成之后才会检测到用户输入。

另请注意，您不应该从loadImage()功能调用draw()。这将每秒加载图像60次，这将减慢你的草图速度。相反，在setup()函数中加载所有图像是草图的开头。将每个图像存储在变量中，然后在以后需要时使用这些变量。

我在Processing中有两个NullPointerException，这两个动画线程错误我都不知道如何解决

1 个答案: