Java中关于时间间隔的计算，起始时间和截止时间怎么用EditText的内容进行填充

Question

布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/rv"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/et_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="40dp"
        android:layout_marginTop="84dp"
        android:ems="10"
        android:hint="开始时间"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/et_end"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="40dp"
        android:layout_marginTop="28dp"
        android:ems="10"
        android:hint="结束时间"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline" />

    <TextView
        android:id="@+id/tv_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="92dp"
        android:layout_marginEnd="56dp"
        android:text="开始时间"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_end"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="36dp"
        android:layout_marginEnd="56dp"
        android:text="结束时间"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="157dp" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="263dp" />

    <Button
        android:id="@+id/bt_IntervalTime"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="156dp"
        android:layout_marginTop="20dp"
        android:text="计算间隔时间"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline3" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="333dp" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="64dp"
        android:text="间隔时间"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline2" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guideline4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="416dp" />

    <TextView
        android:id="@+id/tv_12_chazhi"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="84dp"
        android:layout_marginTop="40dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline4"
        tools:text="0" />

    <TextView
        android:id="@+id/textView6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp"
        android:layout_marginEnd="28dp"
        android:text="与12小时的差值"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline4" />

    <EditText
        android:id="@+id/et_IntervalTime"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginTop="12dp"
        android:ems="10"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/guideline2" />
</androidx.constraintlayout.widget.ConstraintLayout>

主程序

package com.example.test1;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.text.ParseException;
import java.text.SimpleDateFormat;

public class MainActivity extends AppCompatActivity {
    public EditText et_StartTime;
    public EditText et_EndTime;
    public EditText et_IntervalTime;
    public TextView tv_12_chazhi;
    public Button bt_IntervalTime;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_StartTime=findViewById(R.id.et_start);
        et_EndTime=findViewById(R.id.et_end);
        tv_12_chazhi=findViewById(R.id.tv_12_chazhi);
        et_IntervalTime=findViewById(R.id.et_IntervalTime);
        bt_IntervalTime=findViewById(R.id.bt_IntervalTime);
        String StartTimeET=  et_StartTime.getText().toString();
        String EndTimeET=  et_EndTime.getText().toString();
        SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        java.util.Date begin= null;
        try {
            begin = dfs.parse(StartTimeET);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        java.util.Date end = null;
        try {
            end = dfs.parse(EndTimeET);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        long between=(end.getTime()-begin.getTime())/1000;//除以1000是为了转换成秒
        long day1=between/(24*3600);
        long hour1=between%(24*3600)/3600;
        long minute1=between%3600/60;
        long second1=between%60/60;
        Toast.makeText(this, day1+"天"+hour1+"小时"+minute1+"分"+second1+"秒", Toast.LENGTH_SHORT).show();

    }
}

报错
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test1/com.example.test1.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'long java.util.Date.getTime()' on a null object reference

源码
链接：https://pan.baidu.com/s/10FlH5EZV1L72KXMe0i6KUA
提取码：dwjs
--来自百度网盘超级会员V1的分享

Answer 1

这个地方要不返回了null要不抛了异常，打断点看看