java - 如何在Android中从SQLite填充ListView？

我已经实现了从SQLite填充列表视图。当我运行我的应用程序时，在创建表时出现一些错误，例如语法错误。我不知道问题出在哪里。

这是我的DataBaseHelper类：

public class DataBaseHelper extends SQLiteOpenHelper
{

    // private String TABLE_NEW_LEAD;
    public DataBaseHelper(Context context, String name,CursorFactory factory, int version)
    {
               super(context, name, factory, version);
    }
    // Called when no database exists in disk and the helper class needs
    // to create a new one.
    @Override
    public void onCreate(SQLiteDatabase _db)
    {
            _db.execSQL(DataBase_Adapter.DATABASE_CREATE_LOGIN);
            //_db.execSQL(DataBase_Adapter.CREATE_NEW_LEAD_TABLE);
            _db.execSQL(DataBase_Adapter.DATABASE_CREATE_DEFINE_PRODUCT);

    }
    // Called when there is a database version mismatch meaning that the version
    // of the database on disk needs to be upgraded to the current version.
    @Override
    public void onUpgrade(SQLiteDatabase _db, int _oldVersion, int _newVersion)
    {
            // Log the version upgrade.
            Log.w("TaskDBAdapter", "Upgrading from version " +_oldVersion + " to " +_newVersion + ", which will destroy all old data");


            _db.execSQL("DROP TABLE IF EXISTS " + "TEMPLATE");


            _db.execSQL("DROP TABLE IF EXISTS " + DataBase_Adapter.TABLE_DEFINE_PRODUCT);
            // Create a new one.
            onCreate(_db);
    }

}

这是DataBaseAdapter类

public class DataBase_Adapter
{

        //Database NAme
        static final String DATABASE_NAME = "lead_management.db";

        //Database Version
        static final int DATABASE_VERSION = 1;


        // Variable to hold the database instance
        public  SQLiteDatabase db;

        // Context of the application using the database.
        private final Context context;

        // Database open/upgrade helper
        private DataBaseHelper dbHelper;

        public  DataBase_Adapter(Context _context)
        {
            context = _context;
            dbHelper = new DataBaseHelper(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        public  DataBase_Adapter open() throws SQLException
        {
            db = dbHelper.getWritableDatabase();
            return this;
        }

        public void close()
        {
            db.close();
        }

        public  SQLiteDatabase getDatabaseInstance()
        {
            return db;
        }



 //Table Name
        static final String TABLE_DEFINE_PRODUCT="define_product";


         //Creating Define Product Table Column
         static final String KEY_DEFINE_PRODUCT_ID="id";
         static final String KEY_DEFINE_PRODUCT_NAME="name";
         static final String KEY_DEFINE_PRODUCT_DESCRIPTION="description";

        //// SQL Statement to create a Product define Database.
        static final String DATABASE_CREATE_DEFINE_PRODUCT = "CREATE TABLE"+TABLE_DEFINE_PRODUCT+"("+ KEY_DEFINE_PRODUCT_ID +" INTEGER PRIMARY KEY,"+ KEY_DEFINE_PRODUCT_NAME + "TEXT,"+ KEY_DEFINE_PRODUCT_DESCRIPTION + "TEXT,"+")";
        //Insert Products

        @SuppressWarnings("unused")
        private final ArrayList<Define_Products_BeanClass> defin_Products_list = new ArrayList<Define_Products_BeanClass>();
        public void insert_Product(Define_Products_BeanClass definProductBeanClass)
        {
             SQLiteDatabase product_db = dbHelper.getWritableDatabase();

             ContentValues contentDefinProduct_Val=new ContentValues();

             contentDefinProduct_Val.put(KEY_DEFINE_PRODUCT_NAME, definProductBeanClass.get_ProductName());
             contentDefinProduct_Val.put(KEY_DEFINE_PRODUCT_DESCRIPTION, definProductBeanClass.get_ProductDescription());
             product_db.insert(TABLE_DEFINE_PRODUCT, null, contentDefinProduct_Val);

             //Close the Database connection
             product_db.close();

        }

这是产品列表适配器类：

public class Product_List_Adapter extends BaseAdapter
{
    @SuppressWarnings("unused")
    private Context mContext;
    private ArrayList<String> Productid_ArrayList;
    private ArrayList<String> ProductName_ArrayList;
    private ArrayList<String> ProductDescription_ArrayList;


    public Product_List_Adapter(Context mContext,
            ArrayList<String> productid_ArrayList,
            ArrayList<String> productName_ArrayList,
            ArrayList<String> productDescription_ArrayList)
    {
        super();
        this.mContext = mContext;
        Productid_ArrayList = productid_ArrayList;
        ProductName_ArrayList = productName_ArrayList;
        ProductDescription_ArrayList = productDescription_ArrayList;
    }




    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return Productid_ArrayList.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int pos, View child, ViewGroup parent) {
        // TODO Auto-generated method stub
        Holder mHolder;
        LayoutInflater layoutInflater;

        if(child == null)
        {
            layoutInflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            child = layoutInflater .inflate(R.layout.define_products_listrow, null);
            mHolder = new Holder();
            mHolder.txt_product_id = (TextView)child.findViewById(R.id.txt_ProductId);
            mHolder.txt_product_name = (TextView)child.findViewById(R.id.txt_ProductName);
            mHolder.txt_product_description = (TextView)child.findViewById(R.id.txt_ProductDescr);

            child.setTag(mHolder);
        }
        else
        {
            mHolder = (Holder) child.getTag();
        }

        mHolder.txt_product_id.setText(Productid_ArrayList.get(pos));
        mHolder.txt_product_name.setText(ProductName_ArrayList.get(pos));
        mHolder.txt_product_description.setText(ProductDescription_ArrayList.get(pos));

        return child;
    }

    public class Holder {
        TextView txt_product_id;
        TextView txt_product_name;
        TextView txt_product_description;
    }
}

这是Product_Activity类：

public class DefineProducts_Activity6  extends Activity
{
    Button btnAdd_Products;
    Button btnCancel_Products;

    EditText edTxt_ProductName,edTxt_ProductDescription;
    Dialog myDialog;



    private DataBase_Adapter dbAdapter;
    private SQLiteDatabase dataBase;
    private DataBaseHelper dbHelper;

    private ArrayList<String> productId = new ArrayList<String>();
    private ArrayList<String> productName = new ArrayList<String>();
    private ArrayList<String> productDescription = new ArrayList<String>();

    private ListView productsList;
    private AlertDialog.Builder build;

    @SuppressWarnings("unused")
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.define_products_listview);

        dbAdapter=new DataBase_Adapter(this);
        dbAdapter=dbAdapter.open();

        productsList = (ListView)findViewById(R.id.products_List);

        /**__________________Button Add_______________________________________**/

        //Add Products In Listview
        btnAdd_Products=(Button)findViewById(R.id.btnAdd_DefineProduct);
        btnAdd_Products.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                myDialog=new Dialog(DefineProducts_Activity6.this);
                myDialog.setContentView(R.layout.define_product_details);
                myDialog.setTitle("Defin Product Deatail");
                myDialog.setCancelable(false);

                edTxt_ProductName=(EditText)findViewById(R.id.editText_ProductName);
                edTxt_ProductDescription=(EditText)findViewById(R.id.editText_ProductDescription);


                /**_______________________________Button Save________________________________________**/


                Button btn_DefineProduct=(Button)myDialog.findViewById(R.id.btn_Define);
                btn_DefineProduct.setOnClickListener(new OnClickListener() {



                    @Override
                    public void onClick(View v) {
                        // TODO Auto-generated method stub
                        String strProductsName = edTxt_ProductName.getText().toString().trim();
                        String strProductDescription = edTxt_ProductDescription.getText().toString().trim();

                        if(strProductsName.length()>0 && strProductDescription.length()>0)
                        {
                            dbAdapter.insert_Product(new Define_Products_BeanClass (strProductsName,strProductDescription));
                            Toast.makeText(DefineProducts_Activity6.this, "Ur Product Is Define", Toast.LENGTH_LONG).show();

                        }


                    }
                });


                /**_______________________________Button Cancel ________________________________________**/

                btnCancel_Products=(Button)myDialog.findViewById(R.id.btn_cancel_Define);
                btnCancel_Products.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        // TODO Auto-generated method stub
                        myDialog.dismiss();
                    }
                });

                myDialog.show();

            }
        });

        /**_______________________________________________________________________**/
    }


     // displays data from SQLite

    @SuppressWarnings("unused")
    private void displayData()
    {
        dataBase = dbHelper . getWritableDatabase();
        Cursor mCursor = dataBase.rawQuery("SELECT * FROM " + DataBase_Adapter.TABLE_DEFINE_PRODUCT , null);

        productId.clear();
        productName.clear();
        productDescription.clear();

        if(mCursor.moveToFirst())
        {
            do
            {
                productId.add(mCursor.getString(mCursor.getColumnIndex(DataBase_Adapter.KEY_DEFINE_PRODUCT_ID)));
                productName.add(mCursor.getString(mCursor.getColumnIndex(DataBase_Adapter.KEY_DEFINE_PRODUCT_NAME)));
                productDescription.add(mCursor.getString(mCursor.getColumnIndex(DataBase_Adapter.KEY_DEFINE_PRODUCT_DESCRIPTION)));

                }while (mCursor.moveToNext());
        }

        Product_List_Adapter productAdapter = new Product_List_Adapter(DefineProducts_Activity6.this ,productId ,productName , productDescription);

        productsList.setAdapter(productAdapter);

        mCursor.close();


    }

    @Override
    protected void onResume() {
        displayData();
        super.onResume();
    }


}

这是我的日志猫，为什么我无法恢复活动？

.11-06 12:57:32.389: W/dalvikvm(11676): threadid=1: thread exiting with uncaught exception (group=0x40015560)
11-06 12:57:32.399: E/AndroidRuntime(11676): FATAL EXCEPTION: main
11-06 12:57:32.399: E/AndroidRuntime(11676): java.lang.RuntimeException: Unable to resume activity {com.leadmgmt/com.leadmgmt.DefineProducts_Activity6}: java.lang.NullPointerException
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2135)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1668)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.os.Looper.loop(Looper.java:123)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.main(ActivityThread.java:3683)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at java.lang.reflect.Method.invokeNative(Native Method)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at java.lang.reflect.Method.invoke(Method.java:507)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at dalvik.system.NativeStart.main(Native Method)
11-06 12:57:32.399: E/AndroidRuntime(11676): Caused by: java.lang.NullPointerException
11-06 12:57:32.399: E/AndroidRuntime(11676):    at com.leadmgmt.DefineProducts_Activity6.displayData(DefineProducts_Activity6.java:80)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at com.leadmgmt.DefineProducts_Activity6.onResume(DefineProducts_Activity6.java:74)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.Activity.performResume(Activity.java:3832)
11-06 12:57:32.399: E/AndroidRuntime(11676):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)
11-06 12:57:32.399: E/AndroidRuntime(11676):    ... 12 more

最佳答案

像这样创建表。

    private static final String DATABASE_CREATE_DEFINE_PRODUCT = " CREATE TABLE "
        + TABLE_DEFINE_PRODUCT + "(" + KEY_DEFINE_PRODUCT_ID
        + " INTEGER PRIMARY KEY, " + KEY_DEFINE_PRODUCT_NAME + " TEXT, "
        + KEY_DEFINE_PRODUCT_DESCRIPTION + " TEXT " + ")";

您尚未在字段和变量名称之间留出空格。