我有一个问题，我一直试图解决很长一段时间。我通过了许多问题，包括强制关闭和感谢上帝我成功地解决了它。然而，现在，我已经达到了一个步骤，在logcat中没有显示任何问题，但是我没有达到预期的结果。
这是我的数据库：
package SQL;
import java.util.LinkedList;
import java.util.List;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class Database extends SQLiteOpenHelper{
public static final String id_sub = "id_sub";
public final String table_sub= "subjects";
public static final String table_hw = "homeworks";
public static final String table_marks = "marks";
public static final String table_q = "quizzes";
public static final String id_mark = "id_m";
public static final String id_hw= "id_hw";
public static final String id_q = "id_q";
public static final String SSubject ="subject";
public static final String Mark= "mark";
public static final String Homework = "homework";
public static final String Quiz = "quiz";
public static final String name = "iSchool";
public static final int version = 1;
public Database(Context context) {
super(context, name, null, version);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE "+ table_sub +" ( "+id_sub +" INTEGER PRIMARY KEY
AUTOINCREMENT , "+ SSubject +" TEXT NOT NULL );");
db.execSQL("CREATE TABLE "+ table_marks+" ( "+ id_mark +" INTEGER PRIMARY KEY
AUTOINCREMENT , "+ Mark
+" TEXT NOT NULL, "+SSubject+" TEXT NOT NULL);" );
db.execSQL("CREATE TABLE "+ table_hw +" ( "+ id_hw +" INTEGER PRIMARY KEY
AUTOINCREMENT , "+SSubject
+" TEXT NOT NULL, "+Homework+" TEXT NOT NULL ) ;");
db.execSQL("CREATE TABLE "+ table_q +" ( "+ id_q +" INTEGER PRIMARY KEY
AUTOINCREMENT, " +SSubject
+" TEXT NOT NULL, "+Quiz+" TEXT NOT NULL ) ;");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS "+table_sub );
db.execSQL("DROP TABLE IF EXISTS " +table_hw);
db.execSQL("DROP TABLE IF EXISTS "+ table_q);
db.execSQL("DROP TABLE IF EXISTS "+ table_marks);
onCreate(db);
}
//-------------------------------------------Todo Table
CRUD------------------------------------\\
public Subject getSubject(long subs_id){
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.query(table_sub, new String[]{id_sub,SSubject}," id
=? ",new String[]{String.valueOf(id_sub)},null,null,null,null);
if(c != null){
c.moveToFirst();
}
Subject sub = new Subject();
sub.setId(Integer.parseInt(c.getString(0)));
sub.setSubjectstr(c.getString(1));
return sub;
}
public void addSubject(Subject subject){
SQLiteDatabase db = this.getWritableDatabase();
String sq = "SELECT*FROM "+ table_sub;
Cursor c = db.rawQuery(sq,null);
ContentValues contentValues = new ContentValues();
contentValues.put(SSubject, subject.getSubjectstr());
db.insert(table_sub, null , contentValues);
db.close();
}
public List<Subject> getSubjects(){
SQLiteDatabase db = this.getReadableDatabase();
String sss = "SELECT*FROM "+ table_sub;
Cursor c = db.rawQuery(sss, null);
List<Subject> list = new LinkedList<Subject>();
if(c.moveToFirst()){
do{Subject sub = new Subject();
sub.setId(Integer.parseInt(c.getString(0)));
sub.setSubjectstr(c.getString(1));
list.add(sub);
}while(c.moveToNext());
}
return list;
}
public int updateSub(Subject sub){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put("id_sub", sub.getId());
cv.put("SSubject", sub.getSubjectstr());
int i = db.update(table_sub,cv , id_sub+ " =? ",new String[]
{String.valueOf(sub.getId())});
return i;
}
public void deleteSub(Subject sub){
SQLiteDatabase db = this.getWritableDatabase();
db.delete(table_sub, id_sub+ " =? ",new String[]{String.valueOf
(sub.getId())});
db.close();
}
}
这是我使用数据库的Activity
package com.Turki.ischool;
import java.util.ArrayList;
import java.util.List;
import SQL.Database;
import SQL.Subject;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
public class FirstRun extends Activity {
String subido;
Database helper;
Cursor c;
EditText et;
ListView lv;
String subs;
List<Subject> ss;
SQLiteDatabase db;
String[] fromColumns = {helper.SSubject};
int[] toViews = {R.id.subber};
AlertDialog.Builder ad;
AlertDialog alert;
EditText addBar;
public void ADialog(){
LayoutInflater inflater = LayoutInflater.from(this);
View prompt = inflater.inflate(R.layout.dialog,null);
AlertDialog.Builder adb = new AlertDialog.Builder(this);
adb.setView(prompt);
addBar = (EditText)prompt.findViewById(R.id.addBar);
adb
.setCancelable(true)
.setNeutralButton("Next", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
}
})
.setPositiveButton("Add",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
subido = addBar.getText().toString();
adder();
}
})
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
dialog.cancel();
}
})
.setTitle("Add Subject");
alert = adb.create();
alert.show();
}
public void adder() {
//Initialization
helper = new Database(this);
db = helper.getWritableDatabase();
//Adding a Subject
helper.addSubject(new Subject(subido));
db.close();
helper.close();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.first);
//Initialization
helper = new Database(this);
lv = (ListView)findViewById(R.id.listView1);
List<Subject> list = helper.getSubjects();
ArrayList<Subject> list2 = new ArrayList<Subject>();
for(Subject list3 : list){
list2.add(list3);
}
ArrayAdapter<Subject> aa = new ArrayAdapter<Subject>(this,
android.R.layout.simple_list_item_1, list2);
lv.setAdapter(aa);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
getMenuInflater().inflate(R.menu.first_run, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
switch(item.getItemId()){
case R.id.actionAdd :
ADialog();
}
return super.onOptionsItemSelected(item);
}
}
knowing that the logcat doesn't display any problem
提醒：问题是listView中没有显示任何内容，或者没有正确地向数据库添加项目。
更新：我的应用程序似乎实际上在列表视图中显示了一个结果。但它会在很多时间后显示它，并显示如下内容：SQL.Subject@42103b88
答案 0 :(得分：0)
matiash？如果你逃避并解析你的东西，rawQuery很好。如果您计划使用连接或复杂的查询，则需要使用rawQuery。
答案 1 :(得分：0)
谢谢大家但是我通过在oncrreate方法和adder方法上放置了read方法来解决我的问题。我也将getSubjects（）的类型更改为List，并将列表设置为取得sub.getSubjectstr的值（）并且工作正常。