android - 如何在 Android 中使用 Tab 时跨 Activity 存储信息

Question

我制作了一个使用两个选项卡的应用程序，

第一个标签，显示产品列表[菜单标签]

第二个标签，显示您添加的产品[购物车标签]

在这里，我允许用户将产品添加到购物车、更新产品数量并显示所有项目的总金额。 p>

在我的代码中，我遇到了非常小的问题，但过去两天我没有找到任何方法来解决这个问题。

问题:

每当我点击购物车选项卡查看我选择购买的产品，然后再次返回菜单选项卡选择更多要购买的产品，然后再次点击购物车选项卡查看所有产品我已经选择，在这里我可以查看所选产品但无法查看更新数量并且总金额没有任何变化[仅获取所有先前添加的项目的总计，而不是我第二次添加的项目...]

请告诉我我遗漏的地方、获取更新的数量和总价的变化、我需要添加什么代码以及我需要在我的 ViewCartActivity 类中添加的位置

ViewCartActivity.Java:

    public class ViewCartActivity extends Activity {

    TextView mTxtViewGrandTotal;
    String mGrandTotal ;


    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.viewcartactivity);

        ListView mLstView1 = (ListView) findViewById(R.id.listView1);
        mTxtViewGrandTotal = (TextView) findViewById(R.id.mTxtViewGrandTotalValue);

        ViewCartAdapter mViewCartAdpt = new ViewCartAdapter(ViewCartActivity.this);
        mLstView1.setAdapter(mViewCartAdpt);

        if (Constants.mItem_Detail.size() > 0) 
        {
            Double mGTotal = Double.parseDouble(Constants.mItem_Detail.get(0).get(SingleProductActivity.KEY_TOTAL));
            for (int i = 1; i < Constants.mItem_Detail.size(); i++) {   
                mGTotal = mGTotal + Double.parseDouble(Constants.mItem_Detail.get(i).get(SingleProductActivity.KEY_TOTAL));
            }

            mGrandTotal = String.valueOf(mGTotal);
            mTxtViewGrandTotal.setText(mGrandTotal);



            ImageButton mImgViewCart = (ImageButton) findViewById(R.id.back_btn);
            mImgViewCart.setOnClickListener(new OnClickListener() {

                public void onClick(View v) {
                    // TODO Auto-generated method stub

                        Intent mViewCartIntent = new Intent(ViewCartActivity.this, com.version.bajrang.january.menu.ArrowsActivity.class);
                        startActivity(mViewCartIntent);


                }
            });     
        }
    }   

    @Override
    protected void onResume() {
    // TODO Auto-generated method stub
    System.out.println("onResume list current size "+Constants.mItem_Detail.size());
    super.onResume();
    }
}

在 Logcat 中，我得到:

onResume list current size 3 [Number of Records]

TabActivity.Java:

    private void setTabs()
{
    addTab("Order", R.drawable.tab_order, CategoryActivity.class);
    addTab("Cart", R.drawable.tab_cart, ViewCartActivity.class);
}

@Override
    public void onBackPressed() {
    // Code to update product Quantity
    super.onBackPressed();
    Constants.mItem_Detail.clear();
}

ViewCartAdapter.Java:

 public class ViewCartAdapter extends BaseAdapter {

Activity activity;
LayoutInflater inflater;

public ViewCartAdapter(Activity a) {
    // TODO Auto-generated constructor stub
    activity = a;
    inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
    // TODO Auto-generated method stub
    return Constants.mItem_Detail.size();
}
public Object getItem(int position) {
    //return position;
    return Constants.mItem_Detail.get(position);
}
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;

}
public View getView(final int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    View vi = convertView;
    if (convertView == null)
        vi = inflater.inflate(R.layout.viewcartlist, null);
    TextView title = (TextView) vi.findViewById(R.id.title);
    TextView qty = (TextView) vi.findViewById(R.id.qty);
    TextView cost = (TextView) vi.findViewById(R.id.cost);

    HashMap<String, String> item = new HashMap<String, String>();
    item = Constants.mItem_Detail.get(position);
    // Setting all values in listview
    title.setText(item.get(SingleProductActivity.TAG_NAME));
    qty.setText(item.get(SingleProductActivity.KEY_QTY));
    cost.setText(item.get(SingleProductActivity.TAG_DURATION));
    return vi;
}   
   }

Answer 1

Rakesh 你已经在你的程序中编写了所有需要的东西，只需要在 ViewCartActivity 中从 onCreate() 方法移动到 onResume() 方法

像这样:

 public class ViewCartActivity extends Activity 
 {

TextView mTxtViewGrandTotal;
String mGrandTotal ;


@Override
protected void onCreate(Bundle savedInstanceState) 
{
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.viewcartactivity);

    ListView mLstView1 = (ListView) findViewById(R.id.listView1);
    mTxtViewGrandTotal = (TextView) findViewById(R.id.mTxtViewGrandTotalValue);

    ViewCartAdapter mViewCartAdpt = new ViewCartAdapter(ViewCartActivity.this);
    mLstView1.setAdapter(mViewCartAdpt);

        ImageButton mImgViewCart = (ImageButton) findViewById(R.id.back_btn);
        mImgViewCart.setOnClickListener(new OnClickListener() 
        {

            public void onClick(View v) {
                // TODO Auto-generated method stub

                    Intent mViewCartIntent = new Intent(ViewCartActivity.this, com.version.bajrang.january.menu.ArrowsActivity.class);
                    startActivity(mViewCartIntent);

            }
        });     
    }


@Override
protected void onResume() 
{
    super.onResume();
    System.out.println("onResume list current size " + Constants.mItem_Detail.size());

    if (Constants.mItem_Detail.size() == 0) 
    {
    return;
    }

    Double mGTotal = Double.parseDouble(Constants.mItem_Detail.get(0).get(SingleProductActivity.KEY_TOTAL));
    for (int i = 1; i < Constants.mItem_Detail.size(); i++) 
    {   
        mGTotal = mGTotal + Double.parseDouble(Constants.mItem_Detail.get(i).get(SingleProductActivity.KEY_TOTAL));
    }
    mGrandTotal = String.valueOf(mGTotal);
    mTxtViewGrandTotal.setText(mGrandTotal);
     }
   }