Question

我一直在完成一个教程，但我的代码中有7个错误需要解决，我完全不知道如何解决手中的错误。

package com.example.youdothemath;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View.OnClickListener;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Random;

public class PlayGame extends Activity implements OnClickListener 
{
    private SharedPreferences gamePrefs;
    public static final String GAME_PREFS = "ArithmeticFile";

    //class content
    private int level = 0, answer = 0, operator = 0, operand1 = 0, operand2 = 0;
    private final int ADD_OPERATOR = 0, SUBTRACT_OPERATOR = 1, MULTIPLY_OPERATOR = 2, DIVIDE_OPERATOR = 3;
    private String[] operators = {"+", "-", "x", "/"};
    private int[][] levelMin = {
            {1, 11, 21},
            {1, 5, 10},
            {2, 5, 10},
            {2, 3, 5}};
        private int[][] levelMax = {
            {10, 25, 50},
            {10, 20, 30},
            {5, 10, 15},
            {10, 50, 100}};

        private Random random;

        private TextView question, answerTxt, scoreTxt;
        private ImageView response;
        private Button btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9, btn0, enterBtn, clearBtn;


    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        gamePrefs = getSharedPreferences(GAME_PREFS, 0);

        question =  (TextView)findViewById(R.id.question);
        answerTxt = (TextView)findViewById(R.id.answer);
        response =  (ImageView)findViewById(R.id.response);
        scoreTxt =  (TextView)findViewById(R.id.score);

        response.setVisibility(View.INVISIBLE);

        btn1 = (Button)findViewById(R.id.btn1);
        btn2 = (Button)findViewById(R.id.btn2);
        btn3 = (Button)findViewById(R.id.btn3);
        btn4 = (Button)findViewById(R.id.btn4);
        btn5 = (Button)findViewById(R.id.btn5);
        btn6 = (Button)findViewById(R.id.btn6);
        btn7 = (Button)findViewById(R.id.btn7);
        btn8 = (Button)findViewById(R.id.btn8);
        btn9 = (Button)findViewById(R.id.btn9);
        btn0 = (Button)findViewById(R.id.btn0);
        enterBtn = (Button)findViewById(R.id.enter);
        clearBtn = (Button)findViewById(R.id.clear);

        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
        btn3.setOnClickListener(this);
        btn4.setOnClickListener(this);
        btn5.setOnClickListener(this);
        btn6.setOnClickListener(this);
        btn7.setOnClickListener(this);
        btn8.setOnClickListener(this);
        btn9.setOnClickListener(this);
        btn0.setOnClickListener(this);
        enterBtn.setOnClickListener(this);
        clearBtn.setOnClickListener(this);

        if(savedInstanceState!=null)
        {
            //restore state
        }

        else
        {
            Bundle extras = getIntent().getExtras();
            if(extras !=null)
            {
                int passedLevel = extras.getInt("level", -1);
                if(passedLevel>=0) level = passedLevel;
                level=savedInstanceState.getInt("level");
                int exScore = savedInstanceState.getInt("score");
                scoreTxt.setText("Score: "+exScore);
            }
        }

        random = new Random();
        chooseQuestion();
    }

    private void chooseQuestion()
    {
        //get a question
        answerTxt.setText("= ?");
        operator = random.nextInt(operators.length);
        operand1 = getOperand();
        operand2 = getOperand();

        if(operator == SUBTRACT_OPERATOR)
        {
            while(operand2>operand1)
            {
                operand1 = getOperand();
                operand2 = getOperand();
            }
        }

        else if(operator==DIVIDE_OPERATOR)
        {
            while((((double)operand1/(double)operand2)%1 > 0) || (operand1==operand2))
            {
                operand1 = getOperand();
                operand2 = getOperand();
            }
        }

        switch(operator)
        {
            case ADD_OPERATOR:
                answer = operand1+operand2;
                break;
            case SUBTRACT_OPERATOR:
                answer = operand1-operand2;
                break;
            case MULTIPLY_OPERATOR:
                answer = operand1*operand2;
                break;
            case DIVIDE_OPERATOR:
                answer = operand1/operand2;
                break;
            default:
                break;
        }

        question.setText(operand1+" "+operators[operator]+" "+operand2);
    }

    private int getOperand()
    {
        //return operand number
        return random.nextInt(levelMax[operator][level] - levelMin[operator][level] + 1) 
                + levelMin[operator][level];
    }

    @Override
    public void onClick(View view) 
    {
        //button clicked
        if(view.getId()==R.id.enter)
        {
            //enter button
            String answerContent = answerTxt.getText().toString();
            if(!answerContent.endsWith("?"))
            {
                //we have an answer
                int enteredAnswer = Integer.parseInt(answerContent.substring(2));
                int exScore = getScore();
            }

            if(enteredAnswer==answer) // error: enteredAnswer cannot be resolved to a variable
            {
                //correct
                scoreTxt.setText("Score: "+(exScore+1)); //error: exScore cannot be resolved to a variable
                response.setImageResource(R.drawable.tick);
                response.setVisibility(View.VISIBLE);
            }

            else
            {
                //incorrect
                scoreTxt.setText("Score: 0");
                response.setImageResource(R.drawable.cross);
                response.setVisibility(View.VISIBLE);
                setHighScore();
            }
            chooseQuestion();

        }

        else if(view.getId()==R.id.clear)
        {
            //clear button
            answerTxt.setText("= ?");
            response.setVisibility(View.INVISIBLE);

            int enteredNum = Integer.parseInt(view.getTag().toString());
            if(answerTxt.getText().toString().endsWith("?"))
                answerTxt.setText("= "+enteredNum);
            else
                answerTxt.append(""+enteredNum);
        }

        else 
        {
            //number button
        }
    }

    private int getScore()
    {
        String scoreStr = scoreTxt.getText().toString();
        return Integer.parseInt(scoreStr.substring(scoreStr.lastIndexOf(" ")+1));
    }

    private void setHighScore()
    {
        //set high score
        int exScore = getScore();

        if(exScore>0)
        {
            //we have a valid score
            SharedPreferences.Editor scoreEdit = gamePrefs.edit();
            DateFormat dateForm = new SimpleDateFormat("dd MMMM yyyy");
            String dateOutput = dateForm.format(new Date());
            String scores = gamePrefs.getString("highScores", "");

            if(scores.length()>0)
            {
                //we have existing scores
            }
            else
            {
                //no existing scores
                scoreEdit.putString("highScores", ""+dateOutput+" - "+exScore);
                scoreEdit.commit();
            }
        }

        List<Score> scoreStrings = new ArrayList<Score>();
        String[] exScores = scores.split("\\|"); // error: scores cannot be resolved
        for(String eSc : exScores)
        {
            String[] parts = eSc.split(" - ");
            scoreStrings.add(new Score(parts[0], Integer.parseInt(parts[1])));
        }

        Score newScore = new Score(dateOutput, exScore); // error: dateOutput cannot be resolved to a variable
        scoreStrings.add(newScore);
        Collections.sort(scoreStrings);

        StringBuilder scoreBuild = new StringBuilder("");
        for(int s=0; s<scoreStrings.size(); s++)
        {
            if(s>=10) break;//only want ten
            if(s>0) scoreBuild.append("|");//pipe separate the score strings
            scoreBuild.append(scoreStrings.get(s).getScoreText());
        }
        //write to prefs

        scoreEdit.putString("highScores", scoreBuild.toString()); //error: scoreEdit cannot be resolved
        scoreEdit.commit(); //error: scoreEdit cannot be resolved
    }

    protected void onDestroy()
    {
        setHighScore();
        super.onDestroy();
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) 
    {
        //save state
        int exScore = getScore();
        savedInstanceState.putInt("score", exScore);
        savedInstanceState.putInt("level", level);
        super.onSaveInstanceState(savedInstanceState);
    }


}

我评论了问题所在的代码以及问题所在。代码的特色来自PlayGame.java代码。任何帮助将不胜感激。

Answer 1

试试这个..

第一部分

        if(!answerContent.endsWith("?"))
        {
            //we have an answer
            int enteredAnswer = Integer.parseInt(answerContent.substring(2));
            int exScore = getScore();

            if(enteredAnswer==answer) // error: enteredAnswer cannot be resolved to a variable
            {
            //correct
            scoreTxt.setText("Score: "+(exScore+1)); //error: exScore cannot be resolved to a variable
            response.setImageResource(R.drawable.tick);
            response.setVisibility(View.VISIBLE);
            }
        } else
        {
            //incorrect
            scoreTxt.setText("Score: 0");
            response.setImageResource(R.drawable.cross);
            response.setVisibility(View.VISIBLE);
            setHighScore();
        }

第二部分

private void setHighScore()
{
    //set high score
    int exScore = getScore();

    if(exScore>0)
    {
        //we have a valid score
        SharedPreferences.Editor scoreEdit = gamePrefs.edit();
        DateFormat dateForm = new SimpleDateFormat("dd MMMM yyyy");
        String dateOutput = dateForm.format(new Date());
        String scores = gamePrefs.getString("highScores", "");

        if(scores.length()>0)
        {
            //we have existing scores
        }
        else
        {
            //no existing scores
            scoreEdit.putString("highScores", ""+dateOutput+" - "+exScore);
            scoreEdit.commit();

            List<Score> scoreStrings = new ArrayList<Score>();
    String[] exScores = scores.split("\\|"); // error: scores cannot be resolved
    for(String eSc : exScores)
    {
        String[] parts = eSc.split(" - ");
        scoreStrings.add(new Score(parts[0], Integer.parseInt(parts[1])));
    }

    Score newScore = new Score(dateOutput, exScore); // error: dateOutput cannot be resolved to a variable
    scoreStrings.add(newScore);
    Collections.sort(scoreStrings);

    StringBuilder scoreBuild = new StringBuilder("");
    for(int s=0; s<scoreStrings.size(); s++)
    {
        if(s>=10) break;//only want ten
        if(s>0) scoreBuild.append("|");//pipe separate the score strings
        scoreBuild.append(scoreStrings.get(s).getScoreText());
    }
    //write to prefs

    scoreEdit.putString("highScores", scoreBuild.toString()); //error: scoreEdit cannot be resolved
    scoreEdit.commit(); //error: scoreEdit cannot be resolved
        }
    }
}

Answer 2

大多数错误都与变量的范围有关。例如，在if块之外声明的变量未在该块之外定义：

if (thisOrThat == true) {
    int value = 10;
    Log.d("YourApp", "Value is: " + value);
}

Log.d("YourApp", "Value is: " + value); //value is cannot be resolved to a variable

将标记if块之外的日志记录行，因为未在if块之外定义值。

Answer 3

您的所有问题都与范围相关：

以此为例：

if(!answerContent.endsWith("?"))
{
    //we have an answer
    int enteredAnswer = Integer.parseInt(answerContent.substring(2));
    int exScore = getScore();
}

enteredAnswer仅在if子句的语句中可见，并且不能在其外部访问。如果要在if语句之外访问它，请在范围之外声明它。像这样：

int enteredAnswer = 0;
int exScore = 0;
if(!answerContent.endsWith("?"))
{
    //we have an answer
    enteredAnswer = Integer.parseInt(answerContent.substring(2));
    exScore = getScore();
}

代码中的错误 - 无法解决

3 个答案: