Android Criminal实例--（7）SQLite数据库

建立数据库需要的属性名称和数据库名
使用内部类存储属性名称及数据库名

public class CrimeDbSchema {

    public static final class CrimeTable{
        public static final String NAME="crimes";

        public static final class cols{

            public static final String UUID="uuid";
            public static final String TITLE="title";
            public static final String DATE="date";
            public static final String SOLVED="solved";

        }
    }

}

建立数据库

public class CrimeBaseHelper extends SQLiteOpenHelper {

    private static final int VERSION=1;
    private static final String DATABASE_NAME="crimeBase.db";

    public CrimeBaseHelper(Context context) {
        super(context, DATABASE_NAME, null, VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table "+ CrimeTable.NAME+"("+
        "_id integer primary key autoincrement,"+
        CrimeTable.cols.UUID+","+
        CrimeTable.cols.TITLE+","+
        CrimeTable.cols.DATE+","+
        CrimeTable.cols.SOLVED+")");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

获取数据库中元素值，将cursor封装，方便直接调用

public class CrimeCursorWrapper extends CursorWrapper {
    /**
     * Creates a cursor wrapper.
     *
     * @param cursor The underlying cursor to wrap.
     */
    public CrimeCursorWrapper(Cursor cursor) {
        super(cursor);
    }

    public Crime getCrime(){
        String uuidString=getString(getColumnIndex(CrimeTable.cols.UUID));
        String title=getString(getColumnIndex(CrimeTable.cols.TITLE));
        long date=getLong(getColumnIndex(CrimeTable.cols.DATE));
        int isSolved=getInt(getColumnIndex(CrimeTable.cols.SOLVED));

        Crime crime=new Crime(UUID.fromString(uuidString));
        crime.setTitle(title);
        crime.setDate(new Date(date));
        crime.setChecked(isSolved!=0);

        return crime;
    }
}

修改CrimeLab，用数据库存储数据

public class CrimeLab {

    private Context mContext;
    private SQLiteDatabase mDatabase;

    //创建静态单例
    private static CrimeLab sCrimeLab;

    public static CrimeLab getCrimeLab(Context context){
        if(sCrimeLab==null){
            sCrimeLab=new CrimeLab(context);
        }
        return sCrimeLab;
    }

    //向数组列表中添加对象
    public CrimeLab(Context context){
        mContext=context.getApplicationContext();
        mDatabase=new CrimeBaseHelper(mContext).getWritableDatabase();
     //   mCrimes=new ArrayList<>();
//        for(int i=0;i<100;i++){
//            Crime crime=new Crime();
//            crime.setTitle("Crime "+i);
//            crime.setChecked(i%2==0);
//            mCrimes.add(crime);
//        }


    }

   // private List<Crime> mCrimes;

    //获取列表数组
    public List<Crime> getCrimes() {
        //return mCrimes;
        List<Crime> crimes=new ArrayList<>();

        CrimeCursorWrapper cursor=queryCrime(null,null);

        try{
            cursor.moveToFirst();
            while(!cursor.isAfterLast()){
                crimes.add(cursor.getCrime());
                cursor.moveToNext();
            }
        }finally {
            cursor.close();
        }

        return crimes;
    }

    //返回列表数组中指定对象
    public Crime getCrime(UUID id){
//        for(Crime crime:mCrimes){
//            if(crime.getId().equals(id)){
//                return crime;
//            }
//        }
       // return null;

        CrimeCursorWrapper cursor=queryCrime(CrimeTable.cols.UUID+"=?",new String[]{id.toString()});

        try{
            if(cursor.getCount()==0){
                return null;
            }
            cursor.moveToFirst();
            return  cursor.getCrime();
        }finally {
            cursor.close();
        }



    }

    public void addCrime(Crime c){
       // mCrimes.add(c);

        ContentValues values=getContentValues(c);
        mDatabase.insert(CrimeTable.NAME,null,values);
    }


    private static ContentValues getContentValues(Crime crime){
        ContentValues values=new ContentValues();
        values.put(CrimeTable.cols.UUID,crime.getId().toString());
        values.put(CrimeTable.cols.TITLE,crime.getTitle());
        values.put(CrimeTable.cols.DATE,crime.getDate().getTime());
        values.put(CrimeTable.cols.SOLVED,crime.isChecked() ? 1:0);

        return values;

    }

    public void updateCrime(Crime crime){
        String uuidString=crime.getId().toString();
        ContentValues values=getContentValues(crime);
        mDatabase.update(CrimeTable.NAME,values,CrimeTable.cols.UUID+ "=?",new String[]{uuidString});
    }

    private CrimeCursorWrapper queryCrime(String whereClause, String[] whereArgs){
        Cursor cursor=mDatabase.query(CrimeTable.NAME,null,whereClause,whereArgs,null,null,null);
        return new CrimeCursorWrapper(cursor);
    }
}