Question

在Android应用程序中我希望通过三个EditText视图从用户获取输入然后按ta按钮我想将它们保存到我的数据库中，但是当我按下按钮时出现意外错误使我的应用程序关闭我应该怎样管理这个？

这是我的按钮：

//---btnInsert
        Button btnInsert=(Button)findViewById(R.id.btnInsert);

        btnInsert.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                DBAdapter    db = new DBAdapter(DatabaseAndroid10.this); 
                 long id;
                 String ISBN;
                 String Title;
                 String Publisher;

                 EditText txtISBN=(EditText)findViewById(R.id.txtISBN);
                 EditText txtTitle=(EditText)findViewById(R.id.txtTitle);
                 EditText txtPublisher=(EditText)findViewById(R.id.txtPublisher);

                  ISBN = txtISBN.getText().toString();
                  Title=txtTitle.getText().toString();
                  Publisher=txtPublisher.getText().toString();

                  id = db.insertTitle(
                            ISBN,Title,Publisher);    

                    db.close();
            }   
        });

这是我的DBAdapter：

package com.example.databaseandroid10;

import android.content.ContentValues;

public class DBAdapter 
{
    public static final String KEY_ROWID = "_id";
    public static final String KEY_ISBN = "isbn";
    public static final String KEY_TITLE = "title";
    public static final String KEY_PUBLISHER = "publisher";    
    private static final String TAG = "DBAdapter";

    private static final String DATABASE_NAME = "books";
    private static final String DATABASE_TABLE = "titles";
    private static final int DATABASE_VERSION = 1;

    private static final String DATABASE_CREATE =
        "create table titles (_id integer primary key autoincrement, "
        + "isbn text not null, title text not null, " 
        + "publisher text not null);";

    private final Context context; 

    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public DBAdapter(Context ctx) 
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }

    private static class DatabaseHelper extends SQLiteOpenHelper 
    {
        DatabaseHelper(Context context) 
        {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

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

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, 
        int newVersion) 
        {
            Log.w(TAG, "Upgrading database from version " + oldVersion 
                    + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS titles");
            onCreate(db);
        }
    }    

    //---opens the database---
    public DBAdapter open() throws SQLException 
    {
        db = DBHelper.getWritableDatabase();
        return this;
    }

    //---closes the database---    
    public void close() 
    {
        DBHelper.close();
    }

    //---insert a title into the database---
    public long insertTitle(String isbn, String title, String publisher) 
    {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_ISBN, isbn);
        initialValues.put(KEY_TITLE, title);
        initialValues.put(KEY_PUBLISHER, publisher);
        return db.insert(DATABASE_TABLE, null, initialValues);
    }

    //---deletes a particular title---
    public boolean deleteTitle(long rowId) 
    {
        return db.delete(DATABASE_TABLE, KEY_ROWID + 
                "=" + rowId, null) > 0;
    }

    //---retrieves all the titles---
    public Cursor getAllTitles() 
    {
        return db.query(DATABASE_TABLE, new String[] {
                KEY_ROWID, 
                KEY_ISBN,
                KEY_TITLE,
                KEY_PUBLISHER}, 
                null, 
                null, 
                null, 
                null, 
                null);
    }

    //---retrieves a particular title---
    public Cursor getTitle(long rowId) throws SQLException 
    {
        Cursor mCursor =
                db.query(true, DATABASE_TABLE, new String[] {
                        KEY_ROWID,
                        KEY_ISBN, 
                        KEY_TITLE,
                        KEY_PUBLISHER
                        }, 
                        KEY_ROWID + "=" + rowId, 
                        null,
                        null, 
                        null, 
                        null, 
                        null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    //---updates a title---
    public boolean updateTitle(long rowId, String isbn, 
    String title, String publisher) 
    {
        ContentValues args = new ContentValues();
        args.put(KEY_ISBN, isbn);
        args.put(KEY_TITLE, title);
        args.put(KEY_PUBLISHER, publisher);
        return db.update(DATABASE_TABLE, args, 
                         KEY_ROWID + "=" + rowId, null) > 0;
    }
}

提前致谢

Answer 1

在将值插入数据库之前，您不是打开数据库，因此会出现此错误，所以

写下面的代码行

db.open();  // For Open Database

前

id = db.insertTitle(ISBN,Title,Publisher);  // For Insert value into Database

它将解决您的问题。

Answer 2

问题::

在向数据库添加新值

之前，Yor没有打开数据库

解决方案::

首先更改操作数据库的代码：

db.open(); // open database here  before inserting 

id = db.insertTitle(ISBN,Title,Publisher);    

db.close(); //close database here  after inserting

通过EditText字符串将数据插入数据库

2 个答案: