android答题系统（二）：实现主界面入口和查询数据

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_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"
    tools:context="com.mytest.exam.MainActivity" >


    <Button
        android:id="@+id/btn_exam"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="52dp"
        android:text="开始答题" />

</RelativeLayout>

package com.mytest.exam;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {

    private Button btnExam;

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

        loadDB();

        btnExam = (Button) this.findViewById(R.id.btn_exam);
        btnExam.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, ExamActivity.class);
                startActivity(intent);

            }
        });
    }

    /**
     * 加载数据库
     */
    private void loadDB() {
        File file = new File(DBService.DB_PATH + DBService.DB_NAME);
        if (file.exists() == false) {
            File dir = new File(DBService.DB_PATH);
            dir.mkdir();
        }

        try {
            InputStream is = getBaseContext().getAssets().open(DBService.DB_NAME);
            OutputStream os = new FileOutputStream(file);

            byte[] buff = new byte[1024];
            int len = 0;
            while ((len = is.read(buff)) > 0) {
                os.write(buff, 0, len);
            }
            os.flush();// 必须调用
            os.close();
            is.close();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

package com.mytest.exam;

import java.util.ArrayList;
import java.util.List;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class DBService {

    public static final String DB_PATH = "/data/data/com.mytest.exam/databases/";
    public static final String DB_NAME = "question.db";

    private SQLiteDatabase db;

    public DBService() {
        this.db = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.OPEN_READWRITE);
    }

    public List<Question> getQuestions() {
        List<Question> list = new ArrayList<Question>();

        Cursor cursor = db.rawQuery("select * from question ", null);
        if (cursor != null && cursor.getCount() > 0) {
            int count = cursor.getCount();
            for (int i = 0; i < count; i++) {
                cursor.moveToPosition(i);
                Question question = new Question();
                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.ID = cursor.getInt(cursor.getColumnIndex("ID"));
                question.explain = cursor.getString(cursor.getColumnIndex("explaination"));
                question.selectedAnswer = -1;
                list.add(question);
            }
        }
        return list;

    }

}

package com.mytest.exam;

public class Question {
    public String question;
    public String answerA;
    public String answerB;
    public String answerC;
    public String answerD;
    public int answer;
    public String explain;
    public int ID;
    public int selectedAnswer;
    
    public String getQuestion() {
        return question;
    }

    public void setQuestion(String question) {
        this.question = question;
    }

    public String getAnswerA() {
        return answerA;
    }

    public void setAnswerA(String answerA) {
        this.answerA = answerA;
    }

    public String getAnswerB() {
        return answerB;
    }

    public void setAnswerB(String answerB) {
        this.answerB = answerB;
    }

    public String getAnswerC() {
        return answerC;
    }

    public void setAnswerC(String answerC) {
        this.answerC = answerC;
    }

    public String getAnswerD() {
        return answerD;
    }

    public void setAnswerD(String answerD) {
        this.answerD = answerD;
    }

    public int getAnswer() {
        return answer;
    }

    public void setAnswer(int answer) {
        this.answer = answer;
    }

    public String getExplain() {
        return explain;
    }

    public void setExplain(String explain) {
        this.explain = explain;
    }

    public int getID() {
        return ID;
    }

    public void setID(int iD) {
        ID = iD;
    }

    public int getSelectedAnswer() {
        return selectedAnswer;
    }

    public void setSelectedAnswer(int selectedAnswer) {
        this.selectedAnswer = selectedAnswer;
    }


}