Android验证码页面如何比对结果？

题目描述

使用计算题的验证方式，验证成功则跳转到新页面，否则提示验证失败

题目来源及自己的思路

通过比对正确结果和用户输入的答案来进行下一步操作

相关代码

粘贴代码文本（请勿用截图）package com.example.goout;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;import android.os.Bundle;import android.view.View;import android.widget.EditText;import android.widget.TextView;

import java.util.Random;

public class VerifyActivity extends AppCompatActivity {

TextView tv_num;
TextView tv_num2;
TextView tv_info;
int result;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_verify);
    tv_num=findViewById(R.id.num1);
    tv_info=findViewById(R.id.textView6);
    //用户输入
    tv_num2=findViewById(R.id.number2);

    //生成随机数（计算）
    Random random=new Random();
    int a=(int)(Math.random()*(100-50+1));
    int b=(int)(Math.random()*(50-1+1));
    result=a-b;
    int swit=(int)(Math.random()*(3-1+1));
    switch (swit){
        case 1:tv_num.setText(a+"+"+b+"=");break;
        case 2:tv_num.setText(a+"-"+b+"=");break;
    }

}
//验证步骤
public void varifyAc(View v){
    //获取到用户输入的结果
      int num2=Integer.valueOf(tv_num2.getText().toString());
      //比较结果
    if (result==num2){
        Intent intent=new Intent(this,PriceActivity.class);
        startActivity(intent);
    }else{
        tv_info.setText("false");
    }
}
//跳回页面1
public void gotoMain(View v){
    Intent intent=new Intent(this,MainActivity.class);
    startActivity(intent);

}

}

你期待的结果是什么？实际看到的错误信息又是什么？

点击验证按钮时程序闪退

    --------- beginning of crash
2022-09-18 20:59:03.431 19260-19260/com.example.goout E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.goout, PID: 19260
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.goout/com.example.goout.PriceActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
        at com.example.goout.PriceActivity.onCreate(PriceActivity.java:19)
        at android.app.Activity.performCreate(Activity.java:6975)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6541) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)