Question

我想从列表视图中获取文本视图的所有值。我怎么做。我有一个列表视图，并在列表视图中放置一个数组列表。我的列表视图是一个自定义列表视图。我想从价格文本视图中获取所有数据，然后我想显示价格的总和。我做了一些代码，但给出了一些错误这是我的代码。

public class SelectedProductFromShopingCartShow extends AppCompatActivity {

    ArrayList<ShowProducts> arrayList = new ArrayList<>();
    String condition = "SelectedItemsFromShoppingCart";
    CustomAdapter customAdapter;
    ListView listView;
    TextView tvTotal;
    int total;
    private static final String TAG = "SelectedProductFromShop";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_selected_product_from_shoping_cart_show);
        listView = (ListView) findViewById(R.id.listViewSelectedItemsOfShopingCart);
        tvTotal = (TextView) findViewById(R.id.tvTotal);

        arrayList = (ArrayList<ShowProducts>) getIntent().getSerializableExtra("selectedList");

        customAdapter = new CustomAdapter(SelectedProductFromShopingCartShow.this, R.layout.show_selected_item_of_shopingcart, condition, arrayList);
        listView.setAdapter(customAdapter);
        total = getTotal(listView);
        tvTotal.setText(String.valueOf(total).toString());
    }

    public int getTotal(ListView listView) {
        int sum = 0;
        for (int i = 0; i < listView.getCount(); i++) {
            Log.d(TAG, "getTotal: "+listView.getCount());
            Log.d(TAG, "getTotal: "+arrayList.size());
            View view = listView.getChildAt(i);
            TextView tvprice = (TextView) view.findViewById(R.id.tvSetPriceOfSeletedItem);
            TextView tvquantity = (TextView) view.findViewById(R.id.tvQunatitySetOfSelectedItem);

            int price = Integer.parseInt(tvprice.getText().toString());
            int quantity = Integer.parseInt(tvquantity.getText().toString());
            sum = sum + price * quantity;
        }
        return sum;

    }
}

这是我的错误。我不知道怎么做。请帮帮我。

07-26 18:03:49.404 21155-21155/com.sizdom.sizdomstockmanager E/AndroidRuntime: FATAL EXCEPTION: main
                                                                               java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sizdom.sizdomstockmanager/com.sizdom.sizdomstockmanager.SelectedProductFromShopingCartShow}: java.lang.NullPointerException
                                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2204)
                                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2254)
                                                                                   at android.app.ActivityThread.access$600(ActivityThread.java:141)
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                   at android.os.Looper.loop(Looper.java:137)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5069)
                                                                                   at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                   at java.lang.reflect.Method.invoke(Method.java:511)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                                                   at dalvik.system.NativeStart.main(Native Method)
                                                                                Caused by: java.lang.NullPointerException
                                                                                   at com.sizdom.sizdomstockmanager.SelectedProductFromShopingCartShow.getTotal(SelectedProductFromShopingCartShow.java:88)
                                                                                   at com.sizdom.sizdomstockmanager.SelectedProductFromShopingCartShow.onCreate(SelectedProductFromShopingCartShow.java:38)
                                                                                   at android.app.Activity.performCreate(Activity.java:5104)
                                                                                   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1092)
                                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
                                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2254) 
                                                                                   at android.app.ActivityThread.access$600(ActivityThread.java:141) 
                                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                                                   at android.os.Looper.loop(Looper.java:137) 
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:5069) 
                                                                                   at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                                   at java.lang.reflect.Method.invoke(Method.java:511) 
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
                                                                                   at dalvik.system.NativeStart.main(Native Method)

我查看了多个网站的解决方案。但我找不到任何解决方案

自定义适配器

public class CustomAdapter extends ArrayAdapter {
    private List<Integer> list;
    private List<ShowProducts> listShowProducts;
    private Context context;
    private int resource;
    private String condition;
    String uri;
    private static final String TAG = "CustomAdapter";
    int i = 0;

    public CustomAdapter(@NonNull Context context, @LayoutRes int resource, List<ShowProducts> objects) {
        super(context, resource, objects);
        this.context = context;
        this.resource = resource;
        this.listShowProducts = objects;
    }

    @Override
    public int getCount() {
        return super.getCount();
    }

    @Nullable
    @Override
    public Object getItem(int position) {
        return super.getItem(position);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {

        View view = LayoutInflater.from(context).inflate(resource, parent, false);   
            final ShowProducts showProducts = listShowProducts.get(position);

            ImageView imageView = (ImageView) view.findViewById(R.id.imageViewOfSelecteditem);
            ImageView plus = (ImageView) view.findViewById(R.id.imageviewPlus);
            ImageView minus = (ImageView) view.findViewById(R.id.imageviewminus);
            TextView tvSetNameOfSeletedItem = (TextView) view.findViewById(R.id.tvSetNameOfSeletedItem);
            TextView tvSetSizeOfSeletedItem = (TextView) view.findViewById(R.id.tvSetSizeOfSeletedItem);
            TextView tvSetPriceOfSeletedItem = (TextView) view.findViewById(R.id.tvSetPriceOfSeletedItem);
            final TextView tvQunatitySetOfSelectedItem = (TextView) view.findViewById(R.id.tvQunatitySetOfSelectedItem);
           tvSetNameOfSeletedItem.setText(showProducts.getProduct_name().toString());
            tvSetSizeOfSeletedItem.setText(showProducts.getSize_name());
            tvSetPriceOfSeletedItem.setText(String.valueOf(showProducts.getSize_price()).toString());
            uri = showProducts.getProduct_photo().toString();

            Picasso.with(context).load(uri).into(imageView);

            plus.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int a=Integer.parseInt(tvQunatitySetOfSelectedItem.getText().toString());
                    a++;
                    if (a<=showProducts.getSize_quantity())
                    tvQunatitySetOfSelectedItem.setText(String.valueOf(a).toString());
                }
            });

            minus.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    int a=Integer.parseInt(tvQunatitySetOfSelectedItem.getText().toString());
                    a--;
                    if (a>0)
                    tvQunatitySetOfSelectedItem.setText(String.valueOf(a).toString());
                }
            });
        }
        return view;
    }
}

这是我的列表视图，它显示了我获得价值但看起来很恐怖的价值

我调试了应用

 public int getTotal(ListView listView) {
        int sum = 0;
        for (int i = 0; i < listView.getCount(); i++) { // i=0;
            Log.d(TAG, "getTotal: "+listView.getCount()); 
            Log.d(TAG, "getTotal: "+arrayList.size()); // arraylist=4;
            View view = listView.getChildAt(i); //view=null;
            TextView tvprice = (TextView) view.findViewById(R.id.tvSetPriceOfSeletedItem);
            Log.d(TAG, "getTotal: "+tvprice.getText());
            TextView tvquantity = (TextView) view.findViewById(R.id.tvQunatitySetOfSelectedItem);

Answer 1

您没有在tvquantity textView中设置tvprice和数量的任何价格。因此为空值。

Answer 2

ListView加载ArrayList<ShowProducts> arrayList

中的数据

如果您的观看次数有所更新，请在arrayList内更新您的模型。

然后，您希望获得所有产品的总价值，只需通过arrayList计算即可完成。请勿触摸View

首先，请确保您的模型包含2个字段：quantity和price。其次，在Adapter

中定义2个方法

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {

    View view = LayoutInflater.from(context).inflate(resource, parent, false);
    ShowProducts showProducts = listShowProducts.get(position);
    // Handle your views...

    plus.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int quantity = Integer.valueOf(tvQunatitySetOfSelectedItem.getText().toString());
            quantity++;
            if (quantity <= showProducts.getSize_quantity()) {
                tvQunatitySetOfSelectedItem.setText(String.valueOf(quantity));
                showProducts.setQuantity(quantity); // If your model doesn't have this field, create it
            }
        }
    });

    minus.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int quantity = Integer.valueOf(tvQunatitySetOfSelectedItem.getText().toString());
            quantity--;
            if (quantity > 0) {
                tvQunatitySetOfSelectedItem.setText(String.valueOf(quantity));
                showProducts.setQuantity(quantity); // If your model doesn't have this field, create it
            }
        }
    });

    return view;
}

public float getTotal() { // You can use int, long or double ... It's up to you
    float result = 0;
    for (ShowProducts showProducts : listShowProducts) {
        result += showProducts.getPrice() * showProducts.getQuantity();
    }
    return result;
}

然后，如果你想计算总价 - ＆gt;只需致电yourAdapter.getTotal()

即可

Answer 3

因为你没有在你的arraylist中添加任何值，这就是你获得nullpointer异常的原因首先调用下面的函数来添加arraylist中的元素。然后你就能得到总价。

    private void addProducts() {
        ShowProducts products = new ShowProducts();
        products.price = 100;
        products.quantity = 10;
        arrayList.add(products);
        }

@Override
    protected void onCreate(Bundle savedInstanceState) {
// your code
addProducts();
//yourcode
}

您可以使用以下函数获取总和

private int total() {
int sum = 0;
for(ShowProducts product: arraylist) {
sum += product.price;
}

如何从自定义列表视图的文本视图中获取所有值

3 个答案: