Question

我在我的android项目中创建了一个SQLite数据库，其中包含表＆＃34; Book＆＃34;包含列id，isbn，title，resume。我想检索所有条目的isbn，title，resume并在片段的布局中显示它们。

在片段书籍中，代码行BookDAO livreBdd = new BookDAO（this）;给出错误。我需要提出一个背景，但是这个＆＃34;这个＆＃34;没有工作，＆＃34; getActivity（）。getApplicationContext（）＆＃34;都不是。

第二件事，我将在数据库中添加数据，我将使用getAllBooks（）方法检索数据库中的所有书籍，每本书都包含信息＆＃34; isbn＆＃34;，＆＃34; title＆＃34 ;和＆＃34;恢复＆＃34;我想在片段的布局中显示，我将有一个List，我怎么能使用SimpleCursorAdapter来编码？

DataBaseHandler的代码：

public class DatabaseHandler extends SQLiteOpenHelper {
public static final String BOOK_KEY = "id";
public static final String BOOK_ISBN = "isbn";
public static final String BOOK_TITLE = "title";
public static final String BOOK_RESUME = "resume";

public static final String BOOK_TABLE_NAME = "Book";
public static final String BOOK_TABLE_CREATE = "" +
        "CREATE TABLE " + BOOK_TABLE_NAME + "(" +
        BOOK_KEY + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
        BOOK_ISBN + " INTEGER, " +
        BOOK_TITLE + " TEXT NOT NULL, "+
        BOOK_RESUME + " TEXT );";

public static final String BOOK_TABLE_DROP = "DROP TABLE IF EXISTS" + BOOK_TABLE_NAME + ";";

public DatabaseHandler (Context context, String name, CursorFactory factory, int version){

    super(context, name, factory, version);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(BOOK_TABLE_CREATE);

}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL(BOOK_TABLE_DROP);
    onCreate(db);
}

}

DAOBase代码：

public abstract class DAOBase {

protected final static int VERSION = 1;
protected final static String NOM = "data.db";

protected SQLiteDatabase mdb = null;
protected  DatabaseHandler mHandler = null;

public DAOBase(){
    super();
}

public DAOBase (Context context){
    super();
    this.mHandler = new DatabaseHandler(context, NOM, null, VERSION);
}
public SQLiteDatabase open(){
    mdb = mHandler.getWritableDatabase();
    return mdb;
}
public void close(){
    mdb.close();
}
public SQLiteDatabase getMdb(){
    return mdb;
}
}

BookDAO的代码：

public class BookDAO extends DAOBase{
public static final String TABLE_NAME = "Book";
public static final String KEY = "id";
public static final String ISBN = "isbn";
public static final String TITLE = "title";
public static final String RESUME = "resume";
public static final String TABLE_CREATE =
        "CREATE TABLE " +
        TABLE_NAME + " (" + KEY + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
        ISBN + " INTEGER, " +
        TITLE + " TEXT NOT NULL," +
        RESUME + "TEXT );";
public static String TABLE_DROP = " DROP TABLE IF RXISTS" +
        TABLE_NAME + ";";

/*Add a book*/
public long insertBook(Book livre){
    ContentValues values = new ContentValues();
    values.put(ISBN, livre.getIsbn());
    values.put(TITLE, livre.getTitle());
    values.put(RESUME, livre.getResume());
    return mdb.insert(TABLE_NAME, null, values);
}

/*Update*/
public int updateBook(Book livre) {
    ContentValues values = new ContentValues();
    values.put(ISBN, livre.getIsbn());
    values.put(TITLE, livre.getTitle());
    values.put(RESUME, livre.getResume());
    return mdb.update(TABLE_NAME, values, KEY + " = ?", new String[]
            {String.valueOf(livre.getId())});
}

/*Delete a book*/
public int removeBookWithID(int id){
    return mdb.delete(TABLE_NAME, KEY + " = ?" ,  new String[]
            {String.valueOf(id)});
}

/*Get all books*/
public List<Book> getAllBooks() {
    List<Book> bookList = new ArrayList<Book>();
    String selectQuery = "SELECT  * FROM " + TABLE_NAME;
    Cursor cursor = mdb.rawQuery(selectQuery, null);
    if (cursor.moveToFirst()) {
        do {
            Book livre = new Book();
            livre.setId(Integer.parseInt(cursor.getString(0)));
            livre.setIsbn(Integer.parseInt(cursor.getString(1)));
            livre.setTitle(cursor.getString(2));
            livre.setResume(cursor.getString(3));
            bookList.add(livre);
        } while (cursor.moveToNext());
    }
    cursor.close();
    return bookList;
}

}

书的代码：

public class Book {
private int id;
private int isbn;
private String title;
private String resume;

public Book(){

}

public Book ( int isbn, String title, String resume){
    super();
    this.isbn = isbn;
    this.title = title;
    this.resume = resume;
}
public int getId(){
    return id;
}
public void setId(int id){
    this.id = id;
}
public int getIsbn(){
    return isbn;
}
public void setIsbn(int isbn){
    this.isbn = isbn;
}
public String getTitle(){
    return title;
}
public void setTitle(String title){
    this.title = title;
}
public String getResume(){
    return resume;
}
public void setResume(String resume){
    this.resume = resume;
}

}

片段代码和应该显示数据时的布局：

public class Books extends Fragment {


public Books() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View v = inflater.inflate(R.layout.fragment_books, container, false);
    return v;

    BookDAO livreBdd = new BookDAO(this);

}

}


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.nabtech.android.nabilaffoauthor.MainActivity"
tools:showIn="@layout/app_bar_main">

<TextView
    android:id="@+id/booktitle"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="50" />

<TextView
    android:id="@+id/bookisbn"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="50" />

<TextView
    android:id="@+id/bookresume"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="50" />
</LinearLayout>

Answer 1

在片段书籍中，代码行BookDAO livreBdd = new BookDAO（this）; 给出错误。我需要提出一个背景，但是这个＆＃34;这个＆＃34;没有工作

使用BookDAO livreBdd = new BookDAO(getActivity);

但是，它不能在方法的return之后，代码无法运行，可能是错误的真正原因。

但是，您可能希望在Fragment的onCreate方法中执行此操作。（见下文）

第二件事，我将在数据库中添加数据，我将使用getAllBooks（）方法检索数据库中的所有书籍，每本书都包含信息＆＃34; isbn＆＃34;，＆＃34; title＆＃34 ;和＆＃34;恢复＆＃34;我想在片段的布局中显示，我将有一个List，我怎么能使用SimpleCursorAdapter来编码？

1）在BookDAO类中创建一个方法，将提取的数据作为Cursor返回，例如

/*Get all books as Cursor*/
public Cursor getAllBooksAsCursor() {
    String selectQuery = "SELECT  * FROM " + TABLE_NAME;
    return mdb.rawQuery(selectQuery, null);
}

2）

public class Books extends Fragment {

    BooDAO livreBdd;          //<<<< Added 
    ListView youlistview;     //<<<< Added
    SimpleCursorAdapter mSCA; //<<<< Added
    Cursor booklist;          //<<<< Added


    public Books() {
        // Required empty public constructor
    }

    //<<<< onCreate Method Added
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        livreBdd = new BookDAO(getActivity); //<<<< first part of Question
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v = inflater.inflate(R.layout.fragment_books, container, false);
        //<<< All lines below added until return
        yourlistview = (ListView) view.findViewById(R.id.yourlistview);
        booklist = livereBdd.getAllBooksAsCursor();
        mSCA = new SimpleCursorAdapter(getActivity(),
            android.R.layout.simple_list_item_1, //<<<< see note1
            booklist,                            //<<<< source cursor
            new String[] {BookDAO,TITLE},        //<<<< column list see note1
            new int[]{android.R.id.text1},       //<<<< view list see note1
            0                                    //<<<< flags use 0
        );
        // Tie the adapter to the Listview
        yourlistview.setAdapter(mSCA);

        return v;

        //BookDAO livreBdd = new BookDAO(this); Can't have this after return.    
    }
}

注释

1）上面的示例使用将显示1项的内置布局。但是，您可能希望指定自己的多列布局。如果是，则使用列列表指定列名，如在游标中，作为字符串数组的附加元素。对于列列表中的每个元素，视图列表整数数组中需要有一个相应的元素，它是将接收数据的视图的id。
上述内容未经测试，因此可能包含错误，主要用作原则代码。

从SQLite数据库中检索数据并显示布局中的所有数据

1 个答案: