Question

嗨，我正在创建一个存储计数器金额的数据库。我有一个保存按钮来保存计数器中的值，还有一个视图按钮来查看这些值的表格。但是当我按下查看时屏幕是空白的

代码如下主要活动类

public class MainActivity extends Activity implements OnClickListener {

int counter;
Button add;
Button sub;
Button save;
Button view;
TextView display;
private SharedPreferences prefs;
private String prefName = "MyPref";



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

    counter = 0;
    add = (Button) findViewById(R.id.button1);
    sub = (Button) findViewById(R.id.button2);
    save = (Button) findViewById(R.id.button3);
    view = (Button) findViewById(R.id.button4);
    display = (TextView) findViewById(R.id.tvDisplay);

    save.setOnClickListener(this);
    view.setOnClickListener(this);
    add.setOnClickListener(this);
    sub.setOnClickListener(this);



}

public void onClick(View arg0){
    switch(arg0.getId()){
    case R.id.button1:
        counter++;
        display.setText("Counter " + counter );
        break;
    case R.id.button2:
        counter--;
        display.setText("Counter " + counter );
        break;
    case R.id.button3:
        boolean diditwork = true;
        try{

            StringBuilder sb = new StringBuilder();
            sb.append("");
            sb.append(counter);
            String count = sb.toString();
            counterdata entry = new counterdata(this);
            entry.open();
            entry.createEntry(count);
            entry.close();
        }catch(Exception e){
            diditwork = false;
            String error = e.toString();
            Dialog d = new Dialog(this);
            d.setTitle("Nope");
            TextView tv = new TextView(this);
            tv.setText(error);
            d.setContentView(tv);
            d.show();
        }finally {
            if(diditwork){
                Dialog d = new Dialog(this);
                d.setTitle("Hell YEa");
                TextView tv = new TextView(this);
                tv.setText("Sucess");
                d.setContentView(tv);
                d.show();
            }
        }
        break;
    case R.id.button4:
        Intent i = new Intent(MainActivity.this, SqlView.class);
        startActivity(i);
        break;
    }
}

SQL视图类

public class SqlView extends Activity {

protected void onCreate(Bundle savedInstanceState){

    super.onCreate(savedInstanceState);
    setContentView(R.layout.sqlview);
    TextView tv = (TextView) findViewById(R.id.databaseview);

    counterdata info = new counterdata(this);
    info.open();

    String data = info.getdata();
    info.close();

    tv.setText(data);

}

}

数据库表的XML

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:orientation="vertical" >

  <TableLayout
     android:layout_width="fill_parent"
     android:layout_height="fill_parent" >

     <TableRow>


    </TableRow>
   </TableLayout>

    <TextView
    android:id="@+id/databaseview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:text="get database here" />

   </LinearLayout>

处理数据库的类

    public class counterdata {

public static final String KEY_ROWID = "_id";
public static final String KEY_Amount = "_amount";

private static final String DATABASE_NAME = "CounterDb";
private static final String DATABASE_TABLE = "CounterTable";
private static final int DATABASE_VERSION = 1;

private DbHelper ourhelper;
private final Context Ourcontext;
private SQLiteDatabase ourDatabase;

private static class DbHelper extends SQLiteOpenHelper {

    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

        db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
                + "  INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_Amount
                + "  INT)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        db.execSQL("DROP TABLE IF EXITS " + DATABASE_NAME);
        onCreate(db);
    }

}

public counterdata(Context c) {
    Ourcontext = c;
}

public counterdata open() throws SQLException {
    ourhelper = new DbHelper(Ourcontext);
    ourDatabase = ourhelper.getWritableDatabase();
    return this;
}

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

public void createEntry(String count) {
    // TODO Auto-generated method stub
    ContentValues cv = new ContentValues();

    cv.put(KEY_Amount, count);
    ourDatabase.insert(DATABASE_TABLE, null, cv);

}

public String getdata() {
    // TODO Auto-generated method stub

    String[] columns = new String[]{KEY_ROWID, KEY_Amount};
    Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
    String result = " ";

    int irow = c.getColumnIndex(KEY_ROWID);
    int iamount = c.getColumnIndex(KEY_Amount);

    for(c.moveToFirst();!c.moveToLast();c.moveToNext())
    {
        result = result + c.getString(irow) + " " + c.getString(iamount) + "\n";
    }
    return result;
}
 }

任何想法？

Answer 1

我不相信你有一张表开头，因为表的语法不正确你忘了“;”在末尾。它应该如下：

db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
            + "  INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_Amount
            + "  INT);"); // here you forget the first ';'

你确定你插的是正确的吗？！

android和sqlite数据库：看不到表

1 个答案: