创建列表大小 >1 以传递到列表视图时崩溃(索引越界)

Question

我试图创建一个掷骰子工具作为更大应用程序的一部分。但是，如果我尝试在我的掷骰子功能中掷出超过 1 个骰子，应用程序就会崩溃。作为 Java 的新手，我似乎找不到索引越界错误的原因。

DiceActvity.Java

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RadioButton;
import java.util.ArrayList;
import java.util.List;

public class DiceActivity extends AppCompatActivity
{
    ListView LVDiceList;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dice);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        //Radio button
        final RadioButton rbGreater = (RadioButton) findViewById(R.id.greaterThanRadioB);
        final RadioButton rbLess = (RadioButton) findViewById(R.id.lessThanRadioB);
        //Edit boxes
        final EditText txtDiceType = (EditText) findViewById(R.id.diceTypeEdTxt);
        final EditText txtNumberDice = (EditText) findViewById(R.id.numDiceEdTxt);
        final EditText txtFilterNum = (EditText) findViewById(R.id.filterNumEdTxt);
        //Buttons
        Button btnRoll = (Button) findViewById(R.id.rollButton);
        Button btnDiscard = (Button) findViewById(R.id.discardButton);
        //Display Array
        final List<Integer> diceList = new ArrayList<Integer>(10);
        //Array Adapter
        final ArrayAdapter<Integer> adapter = new ArrayAdapter<Integer>(this, android.R.layout.simple_spinner_item, diceList);
        //Set adapter
        LVDiceList = (ListView) findViewById(R.id.diceResultListV);
        LVDiceList.setAdapter(adapter);
        //Roll the dice
        btnRoll.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                //Hide soft keyboard
                Utils.hideKeyboard(DiceActivity.this);
                //Validation of fields
                //If both fields >0
                if (Integer.valueOf(txtDiceType.getText().toString()) > 0 && Integer.valueOf(txtNumberDice.getText().toString()) > 0)
                {
                    int number =  Integer.valueOf(txtNumberDice.getText().toString());
                    int sides = Integer.valueOf(txtDiceType.getText().toString());
                    //Populate array
                    for (int i=0;i <number; i++)
                    {
                        diceList.add(i, rollDice(sides,number).get(i));
                    }
                    //Update the list view
                    adapter.notifyDataSetChanged();
                }
                return;
            }
        });
        //Clear the list of results
        btnDiscard.setOnClickListener(new View.OnClickListener()
         {
             @Override
             public void onClick(View v)
             {
                 diceList.clear();
                 adapter.notifyDataSetChanged();
             }
          });
        //Radio Button Validation
        rbGreater.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                if(rbGreater.isChecked() == true)
                {
                    rbLess.setChecked(false);
                }
            }
        });
        rbLess.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                if(rbLess.isChecked() == true)
                {
                    rbGreater.setChecked(false);
                };
            }
        });
    }
    //Returns a list of rolled dice results
    private List<Integer> rollDice(int chance, int amount)
    {
        final List<Integer> rollArray = new ArrayList<Integer>(amount);
        int result;
        //Gives a random number between 1 and X,Y number of times
        {
            //BASE Equation||Min + (int)(Math.random() * ((Max - Min) + 1))
            //1 = minimum roll
            result = 1 + (int) (Math.random() * ((chance - 1) + 1));
            rollArray.add(result);
        }
        return rollArray;
    }
}

content_dice.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="garethgriffiths.tabletopcompanion.DiceActivity"
    tools:showIn="@layout/activity_dice">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/textView_NumDice"
        android:id="@+id/numDiceTextV"
        android:layout_alignBottom="@+id/numDiceEdTxt"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:textSize="25dp"
        android:textStyle="bold"
        android:textAlignment="gravity"/>
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="4"
        android:id="@+id/numDiceEdTxt"
        android:maxLength="3"
        android:text="@string/edText_NumDice"
        android:gravity="right"
        android:selectAllOnFocus="true"
        android:layout_alignParentTop="true"
        android:layout_toRightOf="@+id/numDiceTextV"
        android:layout_toEndOf="@+id/numDiceTextV"
        android:numeric="integer"/>
    <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="@string/textView_DiceType"
    android:id="@+id/diceTypeTextV"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/numDiceTextV"
    android:layout_alignBottom="@+id/diceTypeEdTxt"
    android:layout_toLeftOf="@+id/diceTypeEdTxt"
    android:layout_toStartOf="@+id/diceTypeEdTxt"
    android:textSize="25dp"
    android:textStyle="bold"
    android:textAlignment="gravity"/>

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="4"
        android:id="@+id/diceTypeEdTxt"
        android:maxLength="2"
        android:text="@string/edText_DiceType"
        android:layout_below="@+id/numDiceEdTxt"
        android:layout_alignLeft="@+id/numDiceEdTxt"
        android:layout_alignStart="@+id/numDiceEdTxt"
        android:gravity="right"
        android:selectAllOnFocus="true"
        android:numeric="integer"/>
    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/radioB_LessThan"
        android:id="@+id/lessThanRadioB"
        android:layout_above="@+id/discardButton"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="36dp"/>
    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/radioB_GreaterThan"
        android:id="@+id/greaterThanRadioB"
        android:layout_alignTop="@+id/lessThanRadioB"
        android:layout_toRightOf="@+id/lessThanRadioB"
        android:layout_toEndOf="@+id/lessThanRadioB"/>
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="4"
        android:maxLength="3"
        android:id="@+id/filterNumEdTxt"
        android:layout_alignTop="@+id/greaterThanRadioB"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:text="@string/edText_NumFilter"
        android:gravity="center"
        android:selectAllOnFocus="true"
        android:numeric="integer"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_Discard"
        android:id="@+id/discardButton"
        android:layout_alignTop="@+id/rollButton"
        android:layout_toLeftOf="@+id/rollButton"
        android:layout_toStartOf="@+id/rollButton"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_Roll"
        android:id="@+id/rollButton"
        android:layout_marginTop="108dp"
        android:layout_below="@+id/diceTypeTextV"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"/>
    <ListView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/diceResultListV"
        android:scrollIndicators="right"
        android:visibility="visible"
        android:layout_below="@+id/discardButton"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"/>
</RelativeLayout>

这是一个用于隐藏在 DiceActivity 中调用的软键盘的小类

import android.app.Activity;
import android.content.Context;
import android.view.View;
import android.view.inputmethod.InputMethodManager;
/**
 * http://stackoverflow.com/questions/1109022/close-hide-the-android-soft-keyboard
 * Used to close soft keyboard
 */
public class Utils
{
    public static void hideKeyboard(Activity activity)
    {
        // Check if no view has focus:
        View view = activity.getCurrentFocus();
        if (view != null)
        {
            InputMethodManager inputManager = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
            inputManager.hideSoftInputFromWindow(view.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
        }
    }
}

Answer 1

您的方法private List<Integer> rollDice(int chance, int amount)返回Integer的列表。根据您在方法中的注释，它应该有多个数字。

但是此方法始终只返回一个数字。

现在，您在此处调用此方法：

for (int i=0;i <number; i++)
{
    diceList.add(i, rollDice(sides,number).get(i));
}

您正在循环中调用此方法。将结果存储在新列表中。

您得到一个异常，因为在第二个循环中 get（i） 为 1，并且此列表中索引 0 上只有 1 个条目。

要更正这一点，应改为：.get(0)

这种实现也非常混乱。请拿一张纸和一支铅笔来弄清楚。