Android实现简单的答题系统

package com.example.lenovo.exam;  /**  * Created by lenovo on 2017/12/4.  */ //保存从数据库中读取的记录 public class Question {  public String question;  public String answerA;  public String answerB;  public String answerC;  public String answerD;  public int answer;  public String explaination;  public int ID ;  //用户选择的答案  public int selectedAnswer; } 

package com.example.lenovo.exam;  import android.database.Cursor; import android.database.sqlite.SQLiteDatabase;  import java.util.ArrayList; import java.util.List;  /**  * Created by lenovo on 2017/12/4.  */ //连接数据库，并从数据库中获取所需数据 public class DBService {  private SQLiteDatabase db;  //在构造函数中打开指定数据库，并把它的引用指向db  public DBService(){   db=SQLiteDatabase.openDatabase("/data/data/com.example.lenovo.exam/databases/question.db" +     "",null,SQLiteDatabase.OPEN_READWRITE);  }  //获取数据库中的问题  public List<Question> getQuestion(){   List<Question> list=new ArrayList<Question>();   /*     Cursor是结果集游标，用于对结果集进行随机访问,其实Cursor与JDBC中的ResultSet作用很相似。     rawQuery()方法的第一个参数为select语句；第二个参数为select语句中占位符参数的值，如果select语句没有使用占位符，该参数可以设置为null。*/   Cursor cursor =db.rawQuery("select * from question",null);   if(cursor.getCount()>0){    cursor.moveToFirst();//将cursor移动到第一个光标上    int count=cursor.getCount();    //将cursor中的每一条记录生成一个question对象，并将该question对象添加到list中    for(int i=0;i<count;i++){     cursor.moveToPosition(i);     Question question =new Question();     question.ID=cursor.getInt(cursor.getColumnIndex("ID"));     question.question=cursor.getString(cursor.getColumnIndex("question"));     question.answerA=cursor.getString(cursor.getColumnIndex("answerA"));     question.answerB=cursor.getString(cursor.getColumnIndex("answerB"));     question.answerC=cursor.getString(cursor.getColumnIndex("answerC"));     question.answerD=cursor.getString(cursor.getColumnIndex("answerD"));     question.answer=cursor.getInt(cursor.getColumnIndex("answer"));      question.explaination=cursor.getString(cursor.getColumnIndex("explanation"));     //表示没有选择任何选项     question.selectedAnswer=-1;     list.add(question);    }   }   return list;  }  } 

package com.example.lenovo.exam;  import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.RadioButton; import android.widget.RadioGroup; import android.widget.TextView;  import java.util.ArrayList; import java.util.List;  /**  * Created by lenovo on 2017/12/4.  */  public class ExamActivity extends Activity {   private int count;  private int current;  private boolean wrongMode;//标志变量，判断是否进入错题模式   protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_exam);    DBService dbService = new DBService();   final List<Question> list = dbService.getQuestion();    count = list.size();   current = 0;   wrongMode=false;//默认情况    final TextView tv_question = findViewById(R.id.question);   final RadioButton[] radioButtons = new RadioButton[4];   radioButtons[0] = findViewById(R.id.answerA);   radioButtons[1] = findViewById(R.id.answerB);   radioButtons[2] = findViewById(R.id.answerC);   radioButtons[3] = findViewById(R.id.answerD);   Button btn_previous = findViewById(R.id.btn_previous);   Button btn_next = findViewById(R.id.btn_next);   final TextView tv_explaination = findViewById(R.id.explaination);   final RadioGroup radioGroup = findViewById(R.id.radioGroup);   //为控件赋值   Question q = list.get(0);   tv_question.setText(q.question);   tv_explaination.setText(q.explaination);   radioButtons[0].setText(q.answerA);   radioButtons[1].setText(q.answerB);   radioButtons[2].setText(q.answerC);   radioButtons[3].setText(q.answerD);    btn_next.setOnClickListener(new View.OnClickListener() {     @Override    public void onClick(View view) {     if (current < count - 1) {//若当前题目不为最后一题，点击next按钮跳转到下一题；否则不响应      current++;      //更新题目      Question q = list.get(current);      tv_question.setText(q.question);      radioButtons[0].setText(q.answerA);      radioButtons[1].setText(q.answerB);      radioButtons[2].setText(q.answerC);      radioButtons[3].setText(q.answerD);      tv_explaination.setText(q.explaination);       //若之前已经选择过，则应记录选择      radioGroup.clearCheck();      if (q.selectedAnswer != -1) {       radioButtons[q.selectedAnswer].setChecked(true);      }      }     //错题模式的最后一题     else if(current==count-1&& wrongMode==true){      new AlertDialog.Builder(ExamActivity.this)        .setTitle("提示")        .setMessage("已经到达最后一题，是否退出？")        .setPositiveButton("确定", new DialogInterface.OnClickListener() {         @Override         public void onClick(DialogInterface dialogInterface, int i) {          ExamActivity.this.finish();         }        })        .setNegativeButton("取消",null)        .show();      }     else{      //当前题目为最后一题时，告知用户作答正确的数量和作答错误的数量，并询问用户是否要查看错题      final List<Integer> wrongList=checkAnswer(list);      //作对所有题目      if(wrongList.size()==0){       new AlertDialog.Builder(ExamActivity.this)         .setTitle("提示")         .setMessage("恭喜你全部回答正确！")         .setPositiveButton("确定", new DialogInterface.OnClickListener() {          @Override          public void onClick(DialogInterface dialogInterface, int i) {           ExamActivity.this.finish();          }         }).show();       }      else       new AlertDialog.Builder(ExamActivity.this)         .setTitle("提示")         .setMessage("您答对了"+(list.size()-wrongList.size())+           "道题目；答错了"+wrongList.size()+"道题目。是否查看错题？")         .setPositiveButton("确定", new DialogInterface.OnClickListener() {          @Override          public void onClick(DialogInterface dialogInterface, int which) {            //判断进入错题模式           wrongMode=true;           List<Question> newList=new ArrayList<Question>();           //将错误题目复制到newList中           for(int i=0;i< wrongList.size();i++){            newList.add(list.get(wrongList.get(i)));           }           //将原来的list清空           list.clear();           //将错误题目添加到原来的list中           for(int i=0;i<newList.size();i++){            list.add(newList.get(i));           }           current=0;           count=list.size();           //更新显示时的内容           Question q = list.get(current);           tv_question.setText(q.question);           radioButtons[0].setText(q.answerA);           radioButtons[1].setText(q.answerB);           radioButtons[2].setText(q.answerC);           radioButtons[3].setText(q.answerD);           tv_explaination.setText(q.explaination);           //显示解析           tv_explaination.setVisibility(View.VISIBLE);          }         })         .setNegativeButton("取消", new DialogInterface.OnClickListener() {          @Override          public void onClick(DialogInterface dialogInterface, int which) { //点击取消时，关闭当前activity           ExamActivity.this.finish();          }         }).show();     }    }   });   btn_previous.setOnClickListener(new View.OnClickListener() {    @Override    public void onClick(View view) {     if (current > 0)//若当前题目不为第一题，点击previous按钮跳转到上一题；否则不响应     {      current--;      Question q = list.get(current);      tv_question.setText(q.question);      radioButtons[0].setText(q.answerA);      radioButtons[1].setText(q.answerB);      radioButtons[2].setText(q.answerC);      radioButtons[3].setText(q.answerD);      tv_explaination.setText(q.explaination);        //若之前已经选择过，则应记录选择      radioGroup.clearCheck();      if (q.selectedAnswer != -1) {       radioButtons[q.selectedAnswer].setChecked(true);      }      }     }   });   //选择选项时更新选择   radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {    @Override    public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {     for (int i = 0; i < 4; i++) {      if (radioButtons[i].isChecked() == true) {       list.get(current).selectedAnswer = i;       break;      }     }     }   });  }   /* 判断用户作答是否正确，并将作答错误题目的下标生成list,返回给调用者  */  private List<Integer> checkAnswer(List<Question> list) {   List<Integer> wrongList = new ArrayList<Integer>();   for(int i=0;i<list.size();i++)   {    if(list.get(i).answer!=list.get(i).selectedAnswer){     wrongList.add(i);    }   }   return wrongList;  } } 

package com.example.lenovo.exam;  import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button;   import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;  public class MainActivity extends AppCompatActivity {   @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);   String DB_PATH = "/data/data/com.example.lenovo.exam/databases/";   String DB_NAME = "question.db";   //应用启动时，判断数据库是否存在，不存在则将提前打包好的数据库文件复制到数据库目录下   //数据库目录不存在时，创建数据库目录   if ((new File(DB_PATH + DB_NAME).exists()) == false) {    File dir = new File(DB_PATH);    if (!dir.exists()) {     dir.mkdir();    }   } //定义输入输出流，用于复制文件   try {    InputStream is = getBaseContext().getAssets().open(DB_NAME);    OutputStream os = new FileOutputStream(DB_PATH + DB_NAME);    byte[] buffer = new byte[1024];    int length;    while ((length = is.read(buffer)) > 0) {     os.write(buffer, 0, length);    }    //刷新输出流，关闭输入输出流    os.flush();    os.close();    os.close();     } catch (IOException e) {    e.printStackTrace();   }     Button btn = findViewById(R.id.button);   btn.setOnClickListener(new View.OnClickListener()    {    public void onClick(View v) {     Intent intent = new Intent(MainActivity.this, ExamActivity.class);     startActivity(intent);      }   });    } }