Question

我正在关注android SQLiteDatabase for android的教程，在这里按下计数按钮它对我来说不起作用。我添加了一些尝试方法，看看发生了什么，但它仍然无法正常工作。在这里我的代码：

public class MyDatabasaDemo extends Activity {
    private static final String DATABASE_NAME = "JADB.db";
    private static final String DATABASE_TABLE = "myTable";
    private static final String DATABASE_CREATE = "create table"+ DATABASE_TABLE;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button butCreate = (Button) findViewById(R.id.myButCreate);
        Button butAdd = (Button) findViewById(R.id.myButAdd);
        Button butCount = (Button) findViewById(R.id.myButCount);
        Button butShow = (Button) findViewById(R.id.myButShow);

        butCreate.setOnClickListener(new OnClickListener(){

            public void onClick(View arg0) {
                SQLiteDatabase myDB;
                try{
                myDB = openOrCreateDatabase(DATABASE_NAME,Context.MODE_PRIVATE,null);
                myDB.execSQL(DATABASE_CREATE);
                myDB.close();

                Toast.makeText(getApplicationContext(), "Table Creat", Toast.LENGTH_SHORT).show();

                }catch(SQLException e){
                    Toast.makeText(getApplicationContext(), "SQLException", Toast.LENGTH_SHORT);

                }
            }

        });

        butAdd.setOnClickListener(new OnClickListener(){

            public void onClick(View arg0) {
                SQLiteDatabase myDB;

                myDB = openOrCreateDatabase(DATABASE_NAME,Context.MODE_PRIVATE,null);

                ContentValues newRow = new ContentValues();
                newRow.put("col1", "ok");
                myDB.insert(DATABASE_TABLE, null, newRow);

                myDB.close();


                Toast.makeText(getApplicationContext(), "row added", Toast.LENGTH_SHORT).show();

            }

        });


        butCount.setOnClickListener(new OnClickListener(){

            public void onClick(View arg0) {
                SQLiteDatabase myDB;

                myDB = openOrCreateDatabase(DATABASE_NAME,Context.MODE_PRIVATE,null);

                String[] resultColumns = new String[]{"_id","col1"};

        Cursor allRows = myDB.query(DATABASE_TABLE, resultColumns, null, null, null, null, null, null);

                myDB.close();

                Integer c = allRows.getCount();

                Toast.makeText(getApplicationContext(), "count: "+c.toString(), Toast.LENGTH_SHORT).show();

            }

        });
    }

数据库是创建的，但是frist按钮内的toast消息不起作用，所以我想知道它是否没有关闭。

三江源

Answer 1

您正在尝试创建没有列的表，然后插入记录。您应该更改数据库创建sql：

private static final String COLUMN_ID = "_id";
private static final String COLUMN_NAME = "col1";
private static final String DATABASE_CREATE = "create table "+ DATABASE_TABLE +" ("+
    COLUMN_ID + " integer primary key autoincrement, " +
    COLUMN_NAME +" text not null"
    +");";

访问SQLite数据库时，我的代码出了什么问题？

1 个答案: