應用程序在從表中讀取行時崩潰

Question

從表中讀取一行時出現錯誤。我的應用程序是這樣的：

在您選擇要顯示
• 然後另一活動將開始出現在數據庫

• 每一個進入該表的主要活動

• ，當你點擊項目在列表視圖中，另一個活動將開始在編輯文本中加載選定的行列 - 這是發生錯誤的地方。

  public class DVD_activity extends AppCompatActivity { 
  String a; 
  String b; 
  DB_Worker dw; 
  int x; 
  
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      setContentView(R.layout.activity_dvd_activity); 
      NapojAdapter(); 
      pridajListener(); 
  } 
  
  private void NapojAdapter() { 
      dw = new DB_Worker(this); 
      SimpleCursorAdapter myAdapter = new SimpleCursorAdapter(this,R.layout.dvd_list_layout,dw.VratKurzorD(),new String[] { DVD.KEY_ID, 
        DVD.KEY_title,DVD.KEY_autor},new int[] {R.id.id2, R.id.nazov, R.id.autor},0); 
  
      ListView lv = (ListView)findViewById(R.id.listView2); 
      lv.setAdapter(myAdapter); 
  } 
  
  @Override 
  public boolean onCreateOptionsMenu(Menu menu) { 
      getMenuInflater().inflate(R.menu.menu_dvd_activity, menu); 
      return true; 
  } 
  
  @Override 
  public boolean onOptionsItemSelected(MenuItem item) { 
      int id = item.getItemId(); 
  
      if (id == R.id.action_settings) { 
       return true; 
      } 
  
      return super.onOptionsItemSelected(item); 
  } 
  
  public void button4click(View view) { 
      Intent intent = new Intent (this, Pridaj_DVD.class); 
      String verzia = "1"; 
      intent.putExtra("verzia",verzia); 
      startActivityForResult(intent, 1); 
  } 
  
  private void pridajListener() { 
      AdapterView.OnItemClickListener mMessageClickedHandler = new AdapterView.OnItemClickListener() {public void onItemClick(AdapterView parent, View v, int position, long id) { 
  
       TextView lv = (TextView)v.findViewById(R.id.id2); 
       x = Integer.parseInt(lv.getText().toString()); 
       DVD s = dw.getDVD(x); 
       a =s.title; 
       b = s.autor; 
       String verzia = "2"; 
       Intent intent = new Intent(DVD_activity.this,Pridaj_DVD.class); 
       intent.putExtra("verzia", verzia); 
       intent.putExtra("a",a); 
       intent.putExtra("b",b); 
       startActivityForResult(intent, 1); 
  
      }}; 
      ListView myList= (ListView) findViewById(R.id.listView2); 
      myList.setOnItemClickListener(mMessageClickedHandler); 
  
  } 
  
  protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
      if (requestCode == 1) { 
       if (resultCode == 0) { 
        DVD s = new DVD(); 
        s.title = data.getStringExtra("a"); 
        s.autor = data.getStringExtra("b"); 
        dw.addDVD(s); 
        NapojAdapter(); 
        } 
       if (resultCode == 1) { 
        dw.deleteDVD(x); 
        NapojAdapter(); 
       } 
       if (resultCode == 2) { 
        a = data.getStringExtra("a"); 
        b = data.getStringExtra("b"); 
        dw.updateDVD(Integer.toString(x),a,b); 
        NapojAdapter(); 
       } 
  
      } 
  } 
  } 
  

這裏是DB_WORKER類：

public class DB_Worker { 
public SQLiteDatabase db; 
private DB_Helper dbHelper; 

public DB_Worker(Context context) { 
    dbHelper = new DB_Helper(context); 
    db = dbHelper.getWritableDatabase(); 
} 

public void addDVD(DVD s) { 

    ContentValues values = new ContentValues(); 
    values.put(DVD.KEY_title, s.title); 
    values.put(DVD.KEY_autor, s.autor); 

    long newRowId = db.insert(DVD.TABLE,null,values); 
} 

public DVD getDVD(long ID) { 
    DVD s = new DVD(); 

    VratKurzorD(); 
    String[] projection = {DVD.KEY_title, DVD.KEY_autor}; 
    String selection = DVD.KEY_ID; 
    String[] selectionArgs = {""+ID}; 
    Cursor c = db.query(DVD.TABLE,projection,selection,selectionArgs,null,null,null); 

    s.DVD_ID = ID; 
    s.title = c.getString(c.getColumnIndex(DVD.KEY_title)); 
    s.autor = c.getString(c.getColumnIndex(DVD.KEY_autor)); 

    c.close(); 
    return s; 
} 

public void updateDVD(String ID, String title, String autor) 
{ 
    ContentValues cv = new ContentValues(); 
    cv.put(DVD.KEY_title,title); 
    cv.put(DVD.KEY_autor, autor); 
    db.update(DVD.TABLE, cv, DVD.KEY_ID + "= ?", new String[]{ID}); 
} 

public void deleteDVD(int ID) { 
    db.delete(DVD.TABLE, DVD.KEY_ID + "= ?", new String[]{"" + ID}); 
} 

public Cursor VratKurzorD() { 
    Cursor c = db.rawQuery("select * from "+DVD.TABLE, null); 
    c.moveToFirst(); 
    return c; 
} 

} 

，這裏是錯誤：

從日誌

12-03 23:11:42.240 2067-2067/com.example.lowrider.pozicovna E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.lowrider.pozicovna, PID: 2067 java.lang.IllegalArgumentException: Cannot bind argument at index 1 because the index is out of range. The statement has 0 parameters. 
     at android.database.sqlite.SQLiteProgram.bind(SQLiteProgram.java:212) 
     at android.database.sqlite.SQLiteProgram.bindString(SQLiteProgram.java:166) 
     at android.database.sqlite.SQLiteProgram.bindAllArgsAsStrings(SQLiteProgram.java:200) 
     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:47) 
     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316) 
     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1163) 
     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1034) 
     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1202) 
     at com.example.lowrider.pozicovna.DB_Worker.getDVD(DB_Worker.java:78) 
     at com.example.lowrider.pozicovna.DVD_activity$1.onItemClick(DVD_activity.java:66) 
     at android.widget.AdapterView.performItemClick(AdapterView.java:310) 
     at android.widget.AbsListView.performItemClick(AbsListView.java:1145) 
     at android.widget.AbsListView$PerformClick.run(AbsListView.java:3042) 
     at android.widget.AbsListView$3.run(AbsListView.java:3879) 
     at android.os.Handler.handleCallback(Handler.java:739) 
     at android.os.Handler.dispatchMessage(Handler.java:95) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5417) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Answer 1

信息：Cannot bind argument at index 1 because the index is out of range. The statement has 0 parameters.表明，在某些地方，你已經寫像這樣的查詢： Select * from table這不需要任何參數，但你論據交付。 因此，您應該在您的代碼中搜索沒有任何?的查詢，但您將參數傳遞給該函數。

Answer 2

在方法getDVD(long ID)改變

String selection = DVD.KEY_ID; 

到

String selection = DVD.KEY_ID + "=?"; 

更新1：

此外，添加一個呼叫到moveToFirst()定位光標到第一行：

Cursor c = db.query(DVD.TABLE,projection,selection,selectionArgs,null,null,null); 
c.moveToFirst(); 

如果遊標至少包含一行，這將起作用。如果光標可能爲空，則需要檢查返回的布爾狀態。