在下面的课程中，我创建了创建和操作数据库的方法
package com.ashish.testquiz2;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class QuestionAdapter {
static final String KEY_ID = "id";
static final String KEY_OPTION1 = "option1";
static final String KEY_OPTION2 = "option2";
static final String KEY_OPTION3 = "option3";
static final String KEY_OPTION4 = "option4";
static final String KEY_QUE = "question";
static final String KEY_ANS = "answer";
static final String TAG = "DBAdapter";
static final String DATABASE_NAME = "quizdb2";
static final String DATABASE_TABLE = "quiztb2";
static final int DATABASE_VERSION = 1;
static final String DATABASE_CREATE = "create table " + DATABASE_TABLE + "
(" + KEY_ID + " integer(10) not null primary key, " + KEY_QUE + "
varchar(150) not null, " + KEY_OPTION1 + " varchar(50) not null, " +
KEY_OPTION2 + " varchar(50) not null, " + KEY_OPTION3 + " varchar(50) not
null, " + KEY_OPTION4 + " varchar(50) not null," + KEY_ANS + " varchar(50)
not null);";
final Context context;
DatabaseHelper DBHelper;
SQLiteDatabase db;
public QuestionAdapter(Context ctx){
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
public static class DatabaseHelper extends SQLiteOpenHelper{
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
try {
//db.execSQL("drop table if already exists " + DATABASE_TABLE);
//db.execSQL(DATABASE_CREATE);
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "upgrading database from version " + oldVersion + " to
version " + newVersion + " which will destroy all old data");
//db.execSQL("drop table if already exists " + DATABASE_TABLE);
onCreate(db);
}
}
//opens the database
public QuestionAdapter open() throws Exception{
db = DBHelper.getWritableDatabase();
return this;
}
//closes the database
public void close() {
DBHelper.close();
}
//insert into database
public void insertitem() {
db = DBHelper.getWritableDatabase();
db.execSQL("drop table " + DATABASE_TABLE);
db.execSQL(DATABASE_CREATE);
String sql1 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(1,'Nobel prize is awarded for which of the following
disciplines:', 'Literature,Peace and Economics','Medicine and
Physiology','Chemistry and Physics','All of the above','All of the
above');";
String sql2 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(2,'Galileo was an astronomer who:', 'developed the
telescope','discovered four satellites of Jupiter','discovered that the
movement of pendulum produces a regular time interval','All of the
above','discovered four satellites of Jupiter');";
String sql3 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(3,'Who is the father of geometry:',
'Aristotle','Euclid','Pythagoras','Kepler','Euclid');";
String sql4 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(4,'Who is popularly called as Iron Man of India:',
'Subhash Chandra Bose','Sardar Vallabhai Patel','Tony Stark','Govind Vallabh
Pant','Sardar Vallabhai Patel');";
String sql5 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(5,'Ball-point pen, used in day-to-day life was
invented by:', 'Waterman brothers','Write brothers','Biro brothers','Bicc
brothers','Biro brothers');";
String sql6 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(6,'The metal whose salts are sensitive to light is:',
'Zinc','Silver','Copper','Aluminium','Silver');";
String sql7 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(7,'Worlds largest desert is:',
'Thar','Kalahari','Sahara','Sonoran','Sahara');";
String sql8 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(8,'Black soil is best suited foe the cultivation
of:', 'Cotton','Rice','Cereals','Sugarcane','Cotton');";
String sql9 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(9,'The first chairman of Atomic Energy Comission
was:', 'Dr. C.V. Raman','Dr. H.J. Bhabha','Dr. A.P.J. Abdul Kalam','Dr.
Vikram Sarabhai','Dr. H.J. Bhabha');";
String sql10 = "insert into " + DATABASE_TABLE + " (" + KEY_ID + " , " +
KEY_QUE + " , " + KEY_OPTION1 + " , " + KEY_OPTION2 + " , " + KEY_OPTION3 +
" , " + KEY_OPTION4 + " , " + KEY_ANS +
" ) values(10,'Which is considered the biggest port of India:',
'Kolkata','Coachin','Chennai','Mumbai','Mumbai');";
try {
Log.i("sql1", sql1);
Log.i("sql2", sql2);
db.execSQL(sql1);
db.execSQL(sql2);
db.execSQL(sql3);
db.execSQL(sql4);
db.execSQL(sql5);
db.execSQL(sql6);
db.execSQL(sql7);
db.execSQL(sql8);
db.execSQL(sql9);
db.execSQL(sql10);
} catch (Exception e) {
e.printStackTrace();
}
}
//retrieve question
public Cursor getQuestion() {
Cursor cursor = db.query(DATABASE_TABLE, new String[] {KEY_ID,KEY_QUE,
KEY_OPTION1, KEY_OPTION2, KEY_OPTION3, KEY_OPTION4, KEY_ANS}, null, null,
null, null, null);
if(cursor!=null){
cursor.moveToFirst();
}
return cursor;
}
//retrieve first question
public Cursor getFirstQue() throws Exception{
Cursor cursor = db.query(true, DATABASE_TABLE, new String[]
{KEY_ID,KEY_QUE, KEY_OPTION1, KEY_OPTION2, KEY_OPTION3, KEY_OPTION4,
KEY_ANS}, KEY_ID + " = 1", null, null, null, null, null);
return cursor;
}
}
我删除了该表，并在insert方法中再次创建了该表，因为该表以前没有用。使用上面的代码，它可以在模拟器上运行，但不能在设备上运行。 上面的代码在下面的类中使用
package com.ashish.testquiz2;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;
public class NewActivity extends Activity{
TextView tvNextQue;
RadioGroup rg1;
RadioButton rbOption1,rbOption2,rbOption3,rbOption4;
Button bNextQue,bPreQue;
QuestionAdapter qa;
Cursor cur = null;
Cursor cur1 = null;
int score =0,id;
String answer = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.newactivity);
tvNextQue = (TextView) findViewById(R.id.tvNextQue);
rg1 = (RadioGroup) findViewById(R.id.radioGroup1);
rbOption1 = (RadioButton) findViewById(R.id.rbOption1);
rbOption2 = (RadioButton) findViewById(R.id.rbOption2);
rbOption3 = (RadioButton) findViewById(R.id.rbOption3);
rbOption4 = (RadioButton) findViewById(R.id.rbOption4);
bNextQue = (Button) findViewById(R.id.bNextQue);
bPreQue = (Button) findViewById(R.id.bPreQue);
qa = new QuestionAdapter(NewActivity.this);
try {
qa.open();
cur1 = qa.getFirstQue();
cur1.moveToNext();
tvNextQue.setText("Q. " +
cur1.getString(cur1.getColumnIndex("question")));
rbOption1.setText("" +
cur1.getString(cur1.getColumnIndex("option1")));
rbOption2.setText("" +
cur1.getString(cur1.getColumnIndex("option2")));
rbOption3.setText("" +
cur1.getString(cur1.getColumnIndex("option3")));
rbOption4.setText("" +
cur1.getString(cur1.getColumnIndex("option4")));
id = cur1.getInt(cur1.getColumnIndex("id"));
answer = cur1.getString(cur1.getColumnIndex("answer"));
} catch (Exception e) {
e.printStackTrace();
}
cur1.close();
try {
qa.open();
cur = qa.getQuestion();
} catch (Exception e) {
e.printStackTrace();
}
cur.moveToPosition(1);
bNextQue.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if(!cur.isAfterLast()){
tvNextQue.setText("Q. " +
cur.getString(cur.getColumnIndex("question")));
rbOption1.setText("" +
cur.getString(cur.getColumnIndex("option1")));
rbOption2.setText("" +
cur.getString(cur.getColumnIndex("option2")));
rbOption3.setText("" +
cur.getString(cur.getColumnIndex("option3")));
rbOption4.setText("" +
cur.getString(cur.getColumnIndex("option4")));
id = cur.getInt(cur.getColumnIndex("id"));
answer = cur.getString(cur.getColumnIndex("answer"));
cur.moveToNext();
rbOption1.setChecked(false);
rbOption2.setChecked(false);
rbOption3.setChecked(false);
rbOption4.setChecked(false);
}
else {
Intent i = new Intent(NewActivity.this,
EndActivity.class);
i.putExtra("score", score);
startActivity(i);
}
qa.close();
}
});
rg1.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup group, int id) {
if(rbOption1.isChecked() || rbOption2.isChecked() ||
rbOption3.isChecked() || rbOption4.isChecked()){
String ans = "";
switch (id) {
case R.id.rbOption1:
ans = rbOption1.getText().toString();
break;
case R.id.rbOption2:
ans = rbOption2.getText().toString();
break;
case R.id.rbOption3:
ans = rbOption3.getText().toString();
break;
case R.id.rbOption4:
ans = rbOption4.getText().toString();
break;
//default:
//break;
}
if(ans.equals(answer)){
score++;
}
Toast.makeText(NewActivity.this, ans,
Toast.LENGTH_SHORT).show();
//Toast.makeText(NewActivity.this, answer,
Toast.LENGTH_SHORT).show();
}
}
});
bPreQue.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if(!cur.isBeforeFirst()){
tvNextQue.setText("Q. " +
cur.getString(cur.getColumnIndex("question")));
rbOption1.setText("" +
cur.getString(cur.getColumnIndex("option1")));
rbOption2.setText("" +
cur.getString(cur.getColumnIndex("option2")));
rbOption3.setText("" +
cur.getString(cur.getColumnIndex("option3")));
rbOption4.setText("" +
cur.getString(cur.getColumnIndex("option4")));
id = cur.getInt(cur.getColumnIndex("id"));
answer = cur.getString(cur.getColumnIndex("answer"));
cur.moveToPrevious();
}
}
});
}
}
我认为某种程度上没有在设备中创建数据库。（只是一种意见）
答案 0 :(得分：0)
如果您更改了表的架构，则必须从设备/仿真器中卸载应用程序并重新运行，以便重新创建数据库。
然后将执行数据库类的onCreate()并创建表。
因此，您必须在数据库帮助程序类的onCreate()中包括所有必要的语句。