java - 扫描时出现InputMismatchException

Question

我正在做一项作业，试图操作一个整数(等级)数组。它崩溃了，我不明白为什么。不知道和文件输入、输出有没有关系？错误日志似乎表明它甚至没有通过运行 onclick 方法。

主要 Activity 代码:

package com.example.brandon.lab5;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.*;
import android.content.res.*;
import java.io.*;
import java.util.*;
import java.util.Scanner;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void arrayChange(View view)
        throws IOException {
            EditText et;
            TextView tv;
            String fileName;
            tv = (TextView) findViewById(R.id.text_main);
            et = (EditText) findViewById(R.id.edit_infile);
            int n=0;

            AssetManager assetManager = getAssets();
            fileName = (et.getText().toString());
            Scanner fsc = new Scanner(assetManager.open(fileName));
            int grades[] = new int[100];
            while(fsc.hasNext()) {
                grades[n] = fsc.nextInt();
                n++;
            }
            int fromIndex = 0;
            int toIndex = grades.length;
            int size = grades.length;

            double cubicMean = 0;
            double num = 0;
            double deno = size;
            while(size>0) {
                num+=Math.pow(grades[size], 3);
                size--;
            }
            cubicMean = Math.cbrt((num/deno));

            Arrays.sort(grades, fromIndex, toIndex);

            double med = 0;
            double temp = Math.ceil(grades[(toIndex/2)]);
            if(toIndex%2==0) {
                med = ((grades[toIndex/2] + grades[(toIndex/2)+1])/2);
            }
            else {
                med = temp;
            }

            tv.append("Number of grades: " + grades.length);
            tv.append("Highest grade: " + grades[0]);
            tv.append("Cubed root of the grades: " + cubicMean);
            tv.append("Median grade: " + med);

            File outfile = new File(getExternalFilesDir(null), "out.txt");
            FileWriter fw = new FileWriter(outfile);
            BufferedWriter bw = new BufferedWriter(fw);
            PrintWriter pw = new PrintWriter(bw);
            while(size>0) {
                pw.println(grades[size]);
                size--;
            }
            pw.close();
        }
    }

list

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.brandon.lab5">

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <application

        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

XML

<?xml version="1.0" encoding="utf-8"?>

<!-- your context in the "tools:context" field below.  See YYY -->

<LinearLayout 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:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.brandon.lab5.MainActivity"
    tools:showIn="@layout/activity_main">

    <EditText
        android:id="@+id/edit_infile"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:hint="@string/edit_infile" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:onClick="arrayChange"
        android:text="Start" />

    <!-- Spacing and horizontal rule (line) to separate Button from TextView -->

    <Space
        android:layout_width="match_parent"
        android:layout_height="10dp" />

    <View
        android:layout_width="fill_parent"
        android:layout_height="0.5dp"
        android:background="#000000" />

    <Space
        android:layout_width="match_parent"
        android:layout_height="10dp" />

    <ScrollView
        android:id="@+id/SCROLLER_ID"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:scrollbars="vertical"
        android:fillViewport="true">

        <TextView
            android:id="@+id/text_main"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="..." />

    </ScrollView>

</LinearLayout>

日志猫:

       --------- beginning of crash
12-04 23:16:22.456 3056-3056/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.example.brandon.lab5, PID: 3056
                                                 java.lang.IllegalStateException: Could not execute method for android:onClick
                                                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                                                     at android.view.View.performClick(View.java:4780)
                                                     at android.view.View$PerformClick.run(View.java:19866)
                                                     at android.os.Handler.handleCallback(Handler.java:739)
                                                     at android.os.Handler.dispatchMessage(Handler.java:95)
                                                     at android.os.Looper.loop(Looper.java:135)
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at java.lang.reflect.Method.invoke(Method.java:372)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
                                                  Caused by: java.lang.reflect.InvocationTargetException
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at java.lang.reflect.Method.invoke(Method.java:372)
                                                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                                                     at android.view.View.performClick(View.java:4780) 
                                                     at android.view.View$PerformClick.run(View.java:19866) 
                                                     at android.os.Handler.handleCallback(Handler.java:739) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                     at android.os.Looper.loop(Looper.java:135) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
                                                  Caused by: java.util.InputMismatchException
                                                     at java.util.Scanner.next(Scanner.java:973)
                                                     at java.util.Scanner.nextInt(Scanner.java:1318)
                                                     at java.util.Scanner.nextInt(Scanner.java:1282)
                                                     at com.example.brandon.lab5.MainActivity.arrayChange(MainActivity.java:72)
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                                                     at android.view.View.performClick(View.java:4780) 
                                                     at android.view.View$PerformClick.run(View.java:19866) 
                                                     at android.os.Handler.handleCallback(Handler.java:739) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                     at android.os.Looper.loop(Looper.java:135) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
12-04 23:16:22.457 1514-1646/system_process W/ActivityManager: 

Answer 1

这是有问题的代码:

    while(fsc.hasNext()) {
        grades[n] = fsc.nextInt();
        n++;
    }

来自 Scanner#nextInt() 的文档:

Throws

InputMismatchException if the next token does not match the Integer regular expression, or is out of range

仔细检查您的文件内容。