我想开发一个应用程序,我需要在Android中使用SQLite数据库。下面是显示的代码,它实现了数据库及其应用程序随机数据所需的所有操作(只是为了首先成功实现逻辑)。
此代码是用DBHelperDisplay.java编写的,它是由MainActivity.java通过intent调用的。
我的DBHelperDisplay.java:
package course.examples.jumboquest;
import java.util.Random;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
//import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
//import android.content.Intent;
import android.os.CountDownTimer;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;
public class DBHelperDisplay extends ActionBarActivity {
TextView tv;
DBHelper myDB;
RadioGroup radioChoices;
RadioButton rbtChoice;
Button btSubmit;
String choice1;
String choice2;
String choice3;
String choice4;
String strAns;
CustomTimer cdt;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.dbhelper_display);
cdt = new CustomTimer(20000, 1000);
cdt.start();
myDB = new DBHelper(this);
myDB.insertQuestion(1, "who is the team member whose name starts with s?", "Vinita", "Akanksha", "Swati", "Megha", "Swati");
myDB.insertQuestion(2, "who is the team member whose name starts with m?", "Vinita", "Akanksha", "Swati", "Megha", "Megha");
myDB.insertQuestion(3, "who is the team member whose name starts with a?", "Vinita", "Akanksha", "Swati", "Megha", "Akanksha");
myDB.insertQuestion(4, "who is the team member whose name starts with v?", "Vinita", "Akanksha", "Swati", "Megha", "Vinita");
myDB.insertQuestion(5, "who is the team member whose name ends with i?", "Vinita", "Akanksha", "Swati", "Megha", "Swati");
Cursor rs = myDB.getData();
String Question = rs.getString(rs.getColumnIndex(DBHelper.Col_Ques));
choice1 = rs.getString(rs.getColumnIndex(DBHelper.Col_Choice1));
choice2 = rs.getString(rs.getColumnIndex(DBHelper.Col_Choice2));
choice3 = rs.getString(rs.getColumnIndex(DBHelper.Col_Choice3));
choice4 = rs.getString(rs.getColumnIndex(DBHelper.Col_Choice4));
strAns = rs.getString(rs.getColumnIndex(DBHelper.Col_Ans));
tv = (TextView) findViewById(R.id.timertxt);
final TextView quest = (TextView) findViewById(R.id.quest);
quest.setText(Question);
//final TextView ans = (TextView) findViewById(R.id.ans);
Button btClear = (Button)findViewById(R.id.btClear);
btClear.setText("CLEAR");
addListenerRadioChoices() ;
btClear.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
//ans.setText("");
}
});
}
public void addListenerRadioChoices(){
radioChoices = (RadioGroup) findViewById(R.id.radioChoices);
((RadioButton) radioChoices.getChildAt(0)).setText(choice1);
((RadioButton) radioChoices.getChildAt(1)).setText(choice2);
((RadioButton) radioChoices.getChildAt(2)).setText(choice3);
((RadioButton) radioChoices.getChildAt(3)).setText(choice4);
btSubmit = (Button)findViewById(R.id.btSubmit);
btSubmit.setText("SUBMIT");
btSubmit.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
int selected = radioChoices.getCheckedRadioButtonId();
rbtChoice = (RadioButton) findViewById(selected);
String Ans = rbtChoice.getText().toString();
if(Ans.equalsIgnoreCase(strAns)){
cdt.cancel();
//ans.setText(" ANSWER");
}
/* else{
// ans.setText("WRONG ANSWER");
}*/
}
});
}
public class CustomTimer extends CountDownTimer{
//TextView ed;
public CustomTimer(long millisInFuture, long countDownInterval){
super(millisInFuture, countDownInterval);
}
@Override
public void onTick(long millisUntilFinished){
//current = millisUntilFinished/1000;
tv.setText("Time Left:" + millisUntilFinished/1000);
}
@Override
public void onFinish() {
tv.setText("Time Up - lost the game!");
}
}
public class DBHelper extends SQLiteOpenHelper {
public static final String Database_Name = "Questions.db";
public static final String Table_Name = "Comics";
public static final String Col_ID = "id";
public static final String Col_Ques = "question";
public static final String Col_Choice1 = "choice1";
public static final String Col_Choice2 = "choice2";
public static final String Col_Choice3 = "choice3";
public static final String Col_Choice4 = "choice4";
public static final String Col_Ans = "answer";
public DBHelper(Context context){
super(context, Database_Name, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db){
// TODO Auto-generated method stub
db.execSQL(
"CREATE TABLE Comics" +
"(id integer primary key, question text, choice1 text, choice2 text, choice3 text, choice4 text, answer text)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS Comics");
onCreate(db);
}
public boolean insertQuestion(int id, String question, String choice1, String choice2, String choice3, String choice4, String answer){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("id",id);
contentValues.put("question",question);
contentValues.put("choice1",choice1);
contentValues.put("choice2",choice2);
contentValues.put("choice3",choice3);
contentValues.put("choice4",choice4);
contentValues.put("answer",answer);
db.insert("Comics", null, contentValues);
db.close();
return true;
}
public Cursor getData(){
SQLiteDatabase db = this.getReadableDatabase();
int numRows = (int)DatabaseUtils.queryNumEntries(db,Table_Name);
int min = 1;
int max = numRows;
Random r = new Random();
int id = r.nextInt(max - min + 1) + min;
Cursor res= db.rawQuery("Select * from Comics where id = " + id + "", null);
return res;
}
}
}
我的AndroidManifest.xml文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="course.examples.jumboquest"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".DBHelperDisplay"></activity>
</application>
</manifest>
执行上面的代码时,我收到以下错误:
我搜索了很多,发现很多堆栈溢出链接有同样的问题,但仍然没有解决。我是这个话题的新手。请帮帮我。
答案 0 :(得分:3)
我有两个适配器:
public class DBController_for_drivinglicense扩展了SQLiteOpenHelper {
public DBController_for_drivinglicense(Context applicationcontext) {
super(applicationcontext,"nozadb", null, 1);
}
//Creates Table
@Override
public void onCreate(SQLiteDatabase database) {
String query;
query = "CREATE TABLE if not exists drivinglicense ( id INTEGER PRIMARY KEY, comment TEXT,rates float,names TEXT,date DEFAULT CURRENT_TIMESTAMP, udpateStatus TEXT)";
database.execSQL(query);
}
第一个适配器是:
public DBController_for_landregistration(Context applicationcontext) {
super(applicationcontext,"nozadb", null, 1);
}
@Override
public void onCreate(SQLiteDatabase database) {
String query;
query = "CREATE TABLE if not exists landregistration ( id INTEGER PRIMARY KEY, comment TEXT,rates float,names TEXT,date DEFAULT CURRENT_TIMESTAMP, udpateStatus TEXT)";
database.execSQL(query);
}
当我把第二个改为:
public class DBController_for_drivinglicense扩展了SQLiteOpenHelper {
public DBController_for_drivinglicense(Context applicationcontext) {
super(applicationcontext,"nozadb", null, 2);
}
//Creates Table
@Override
public void onCreate(SQLiteDatabase database) {
String query;
query = "CREATE TABLE if not exists drivinglicense ( id INTEGER PRIMARY KEY, comment TEXT,rates float,names TEXT,date DEFAULT CURRENT_TIMESTAMP, udpateStatus TEXT)";
database.execSQL(query);
}