因此,当我启动应用程序时,我得到致命的异常主要说没有空的构造函数。 然后,当我添加空构造函数时,它给出了“构造函数SQLiteOpenHelper()未定义”错误。
这是我的第一个应用程序,所以我不知道该怎么做。
以下是代码:
package com.example.lightalarmclock;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
public class writeAlarm extends Activity {
public static final String PREFS = "positions";
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private DbHelper ourHelper;
private static String pos1 = "0";
private static String pos2 = "0";
private static String pos3 = "0";
private static String pos4 = "0";
private static String timeSet;
private static int rep1 = 0;
private static int rep2 = 0;
private static int rep3 = 0;
private static int rep4 = 0;
private static int rep5 = 0;
private static int rep6 = 0;
private static int rep7 = 0;
private static int repB;
private static int repSet;
private static final String DATABASE_NAME = "alarmDB";
private static final String DATABASE_TABLE = "alarmStack";
private static final int DATABASE_VERSION = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public void updateVars() {
SharedPreferences positions = getSharedPreferences(PREFS, 0);
//TODO import from sharedPreferences to local vars
}
private static class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public DbHelper() {
super();
}
@Override
public void onCreate(SQLiteDatabase db) {
//writing to database
if (rep1 >= 0 || rep2 >= 0 || rep3 >= 0 || rep4 >= 0 || rep5 >= 0 || rep6 >= 0 || rep7 >= 0) {
repB = 1;
}
else {
repB = 0;
}
//setting time
timeSet= pos4+pos3+":"+pos2+pos1;
//Writing
db.execSQL
("INSERT INTO TABLE alarmDB.alarmStack(alarm_time, alarm_repeat, rep1, rep2, rep3, rep4, rep5, rep6, rep7) " +
"VALUES (" + timeSet + ", " + repB + ", "+ rep1 +", "+ rep2 +", "+ rep3 +", "+ rep4 +", "+ rep5 +", "+ rep6 +", "+ rep7 +")");
//launch backToMain
backToMain(null);
}
public static void backToMain(Context ctx) {
// do some stuff here
ctx.startActivity(new Intent(ctx, MainActivity.class));
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public void backToMain() {
Intent j = new Intent(writeAlarm.this, MainActivity.class);
startActivity(j);
}
public writeAlarm (Context c) {
ourContext = c;
}
public writeAlarm open() {
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
ourHelper.close();
}
}
答案 0 :(得分:3)
对于班级DbHelper extends SQLiteOpenHelper
,你这样做:
public DbHelper() {
super();
}
如果查看Android docs for SQLiteOpenHelper,则没有SQLiteOpenHelper()
构造函数,因此抱怨。
答案 1 :(得分:1)
http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html
看看他是公共的指导者并传递正确的参与者
SQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version)
创建一个帮助对象来创建,打开和/或管理数据库。
SQLiteOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler)
创建一个帮助对象来创建,打开和/或管理数据库。
您需要使用以上两个构造函数之一。但你有
public DbHelper() { // remove this
super();
}
你已经拥有
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
编辑:
您正在创建Activity
类的构造函数,这是错误的
public class writeAlarm extends Activity {
你有
public writeAlarm (Context c) {
ourContext = c;
}
我建议你移动这个
private static class DbHelper extends SQLiteOpenHelper {
分隔.java文件
答案 2 :(得分:0)
太多东西!!
删除它:
public DbHelper() {
super();
}
而且:
public writeAlarm (Context c){
ourContext = c;
}
在onCreate上放了这个:
ourContext = this;
在
@Override
public void onCreate(SQLiteDatabase db) {
您必须创建数据库。
答案 3 :(得分:0)
我为SqlLiteHelper显示了一个例子
1)为sqlitehelper创建类
public class SQLHelper扩展了SQLiteOpenHelper {
public static final String DB_NAME = "myDatabase";
public static final String TBL_NAME = "myTable";
public static final String COL1 = "ID";
public static final String COL2 = "Name";
public static final String COL3 = "Mobile";
public SQLHelper(Context context) {
super(context, DB_NAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(createTable Query);
Log.d("tag", "Succesffull");
}
public void InsertData(String val1,String val2) {
SQLiteDatabase db = getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COL2, val1);
cv.put(COL3, val2);
db.insert(TBL_NAME, COL1, cv);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}}
在打电话后创建你的课程 //初始化SQLHelper类
SQLHelper帮助程序;
//简单地传递您当前的活动
helper = new SQLHelper(MainActivity.this);