processing出现nullpointerException要怎么解决呀?

想通过arduino的超声波传感器来控制processing播放视频,但是运行的时候一直不出现视频画面,屏幕为白色 ,有声音 但是过几秒就卡住
请问这个程序有什么问题嘛??
import processing.serial.;
import processing.video.
;

Serial port;
Serial serial;
Movie mp4;
int jumpTime=60;

void setup(){
//fullScreen();
size(640,360);
background(0);
port=new Serial(this,"COM3",9600);
mp4=new Movie(this,"2.mp4");
mp4.loop();
frameRate(30);
}

void movieEvent(Movie mp4) {

mp4.read();
}

void draw(){

String inString=serial.readString().trim();
if(inString!=null){
if("1".equals(inString)){
mp4.jump(jumpTime);
}
}

}