Question

我试图从我的数据库中获取数据，并且我已检查表中是否有数据。

我收到此错误：

 Process: com.example.olev.shoppinglist, PID: 4636
    java.lang.OutOfMemoryError: Failed to allocate a 13571692 byte allocation with 3197016 free bytes and 3MB until OOM
            at java.util.ArrayList.add(ArrayList.java:118)
            at com.example.olev.shoppinglist.DBHandler.getProductsFromDb(DBHandler.java:63)
            at com.example.olev.shoppinglist.MainActivity.getProductsFromDb(MainActivity.java:66)
            at com.example.olev.shoppinglist.MainActivity.onCreate(MainActivity.java:39)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

MY DBHandler：

public void onCreate(SQLiteDatabase db) {
        String query= "CREATE TABLE " + TABLE_PRODUCTS + " ("+
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                COLUMN_PRODUCTNAME + " TEXT," +
                COLUMN_ISCHECKED + " BOOLEAN" +
                ");";
        db.execSQL(query);
    }
public ArrayList<Product> getProductsFromDb(){
        ArrayList<Product> products= new ArrayList<>();
        SQLiteDatabase db=getWritableDatabase();
        String query= "SELECT * FROM "+ TABLE_PRODUCTS +";";

        Cursor c= db.rawQuery(query,null);
        c.moveToFirst();
        while (!c.isAfterLast()){
            if(c.getString(c.getColumnIndex("productname"))!=null){
                Product product=new Product(Integer.parseInt(c.getString(c.getColumnIndex(COLUMN_ID))),COLUMN_PRODUCTNAME,Boolean.valueOf(c.getString(c.getColumnIndex(COLUMN_ISCHECKED))));
                products.add(product);
            }
        }
        db.close();
        return products;
    }

最后我的主要：

ArrayAdapter<Product> adapter;
    ArrayList<Product> productnames=new ArrayList<>();
    DBHandler dbhandler;





    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ListView productList=(ListView)findViewById(android.R.id.list);

        dbhandler=new DBHandler(this,null,null,1);
        getProductsFromDb();
        adapter= new CustomAdapter(this,productnames);
        productList.setAdapter(adapter);

    }



 public void getProductsFromDb() {
            ArrayList<Product> products=dbhandler.getProductsFromDb();
            productnames.addAll(products);
            adapter.notifyDataSetChanged();
    }

总而言之，getProductsFromDb（）以某种方式产生了这个错误。

Answer 1

你忘记了c.moveToNext();。这意味着您将一次又一次地从数据库中读取第一行，并且您将一次又一次地创建相同的Product，并一次又一次地将它添加到您的列表中，并且您将获得Out Of Memory错误。这样做：

[...]

while (!c.isAfterLast()){
   if(c.getString(c.getColumnIndex("productname"))!=null) {
      Product product=new Product(Integer.parseInt(c.getString(c.getColumnIndex(COLUMN_ID))),COLUMN_PRODUCTNAME,Boolean.valueOf(c.getString(c.getColumnIndex(COLUMN_ISCHECKED))));
      products.add(product);
   }
   c.moveToNext();
}

从SQlite数据库获取对象？

1 个答案: