Android项目报错package R does not exist，求解决方案

我是应用开发新手，正在开发一款拼写测验游戏项目。最初在IntelliJ Idea中创建该项目，使用Gradle 4.2，迁移到Android Studio后升级Gradle至7.4，但项目从未成功运行。尝试修改AndroidManifest.xml来解决问题，但无任何效果。

报错信息 #

C:\Users\admin\Desktop\Educational App\app\src\main\java\com\example\funspelling\GameActivity.java:48: error: package R does not exist setContentView(R.layout.activity_game

AndroidManifest.xml代码 #

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

    <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>
        <activity
            android:name=".SettingsActivity"
            android:label="@string/title_activity_settings"
            android:parentActivityName=".MainActivity"
            android:theme="@style/AppTheme.NoActionBar">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.sinanli.funspelling.MainActivity" />
        </activity>
        <activity
            android:name=".GameActivity"
            android:label="@string/title_activity_game"
            android:parentActivityName=".MainActivity"
            android:theme="@style/AppTheme.NoActionBar">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.sinanli.funspelling.MainActivity" />
        </activity>
        <activity
            android:name=".ScoreActivity"
            android:label="@string/title_activity_score"
            android:parentActivityName=".MainActivity"
            android:theme="@style/AppTheme.NoActionBar">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.sinanli.funspelling.MainActivity" />
        </activity>
    </application>

</manifest>

GameActivity.java代码 #

package com.example.funspelling;

import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.preference.PreferenceManager;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
import android.R;

import java.util.Collections;
import java.util.List;

public class GameActivity extends AppCompatActivity {

    private TextView questionT;
    private ImageView foodImage;
    private TextView timeT;
    private EditText inputT;
    private Button buttonC;

    private CountDownTimer count;
    private SharedPreferences prefs;
    private AssetManager assetManager;
    private SoundManager soundManager;
    private int clap;

    private String rightAnswer;
    private String alertTitle;
    private int rightAnswerCount;
    private int quizCount = 1;
    private List<String> foodNames;
    private String difOption;
    private String musicOption;

    static private final int QUIZ_COUNT = 5;

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

        questionT = (TextView) findViewById(R.id.questionText);
        foodImage = (ImageView) findViewById(R.id.foodImage);
        timeT = (TextView) findViewById(R.id.timeText);
        inputT = (EditText) findViewById(R.id.inputText);
        buttonC = (Button) findViewById(R.id.button);

        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
        difOption = prefs.getString("difSelection","1");
        assetManager = new AssetManager(this, difOption);
        foodNames = assetManager.allFoodNames(difOption);

        soundManager = new SoundManager(this);
        clap = soundManager.addSound(R.raw.clap);

        musicOption = prefs.getString("musicSelection", "On");


        showNextQuiz();
        count = new CountDownTimer(10 * 1000, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                timeT.setText("Seconds Remaining: " + millisUntilFinished / 1000);
            }

            @Override
            public void onFinish() {
                timeT.setText("Done");
                buttonC.performClick();
            }
        };
        count.start();
    }

    public void showNextQuiz () {
        questionT.setText("Question " + quizCount + " Out of " + QUIZ_COUNT);

        Collections.shuffle(foodNames);
        foodImage.setImageDrawable(assetManager.imageForFood(foodNames.get(0)));
        rightAnswer = foodNames.get(0);

        foodNames.remove(0);
        Collections.shuffle(foodNames);
    }

    public void checkAnswer(View view) {
        String answer = inputT.getText().toString();
        inputT.setText("");

        if (answer.equals(rightAnswer)){
            alertTitle = "Correct!";
            rightAnswerCount++;
            if (musicOption.equals("On")){
                soundManager.play(clap);
            }
        } else {
            alertTitle = "Wrong...";
        }

        prefs = getSharedPreferences("value", MODE_PRIVATE);
        prefs.edit().putInt("Score", rightAnswerCount * 10).apply();

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        if (quizCount == QUIZ_COUNT) {
            count.cancel();
            builder.setTitle("Game Over");
            builder.setMessage("Score: " + rightAnswerCount * 10);
            builder.setPositiveButton("Close", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    Intent intent = new Intent(getApplicationContext(), MainActivity.class);
                    startActivity(intent);
                }
            });
        } else {
            count.cancel();
            builder.setTitle(alertTitle);
            builder.setMessage("Answer : " + rightAnswer);
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    quizCount++;
                    showNextQuiz();
                    count = new CountDownTimer(10 * 1000, 1000) {
                        @Override
                        public void onTick(long millisUntilFinished) {
                            timeT.setText("Seconds Remaining: " + millisUntilFinished / 1000);
                        }

                        @Override
                        public void onFinish() {
                            timeT.setText("Done");
                            buttonC.performClick();
                        }
                    };
                    count.start();
                }
            });
        }
        builder.setCancelable(false);
        builder.show();
    }
}

解决方法 #

• 移除错误的R类导入：GameActivity中导入了系统的android.R，这会覆盖项目自动生成的自定义R类。删除这行代码：

  import android.R;
  

  确保使用项目自身的R类（Android Studio通常会自动导入com.example.funspelling.R，如果没有可手动添加）。

• 统一包名：Manifest中的包名是com.example.sinanli.funspelling，但GameActivity的包声明是com.example.funspelling，两者不一致会导致R类生成异常，二选一修改：

  1. 修改GameActivity的包声明为package com.example.sinanli.funspelling;
  2. 修改Manifest的根标签package属性为com.example.funspelling，同时将所有<meta-data>中的android:value改为com.example.funspelling.MainActivity

• 清理重建项目：执行Android Studio菜单栏的Build > Clean Project，随后执行Build > Rebuild Project，强制重新生成R类文件。

• 检查布局文件：确认activity_game.xml存在于app/src/main/res/layout目录下，且xml代码无语法错误（如标签未闭合、无效资源引用等），这类错误会阻止R类生成。

内容的提问来源于stack exchange，提问作者setupspawn