如何从自定义列表视图的文本视图中获取所有值答案

【问题标题】：How to get all values from text view of custom list view如何从自定义列表视图的文本视图中获取所有值
【发布时间】：2017-07-26 10:20:22
【问题描述】：

我想从列表视图中获取文本视图的所有值。我怎么能做到。我有一个列表视图并将数组列表放在列表视图中。我的列表视图是自定义列表视图。我想从价格文本视图中获取所有数据，然后我想显示总价格。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。我不知道我该怎么做。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。但我没有找到任何解决方案

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，它在我获得价值时显示价值，但看起来很糟糕

我调试应用程序

 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);

【问题讨论】：

我猜你的适配器中有一个列表或数组，其中包含数据。你为什么不遍历它并计算总和？可以分享一下适配器代码吗？

标签： android listview arraylist textview onitemclicklistener

【解决方案1】：

您没有在 tvprice 中设置任何价格，在 tvquantity textView 中设置数量。因此是一个空值。

【讨论】：

【解决方案2】：

由于您没有在数组列表中添加任何值，这就是您收到空指针异常的原因首先调用如下函数在您的数组列表中添加元素。然后就可以得到总价了。

    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
}

你可以使用下面的函数来得到总和

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

【讨论】：

arrayList = (ArrayList) getIntent().getSerializableExtra("selectedList");
我的数组列表有值。因为我的列表视图显示了结果。所有价格和数量均已显示，但未汇总
这些行中的哪一行在第 88 行。View view = listView.getChildAt(i); TextView tvprice = (TextView) view.findViewById(R.id.tvSetPriceOfSeletedItem); TextView tvquantity = (TextView) view.findViewById(R.id.tvQunatitySetOfSelectedItem);
TextView tvprice = (TextView) view.findViewById(R.id.tvSetPriceOfSeletedItem);
告诉我请我添加图片

【解决方案3】：

ListView 从您的ArrayList<ShowProducts> arrayList 加载数据

如果您的视图更新，请在arrayList 中更新您的模型。

然后你想得到所有产品的总价值，只要通过你的arrayList计算就可以了。不要碰View

首先，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;
}

那么如果你想计算总价 -> 只需拨打yourAdapter.getTotal()

【讨论】：

除此之外，您应该将数量保存到列表中或将其添加到您的 ShowProducts 模型中，而不是从 textview 获取文本并对其进行解析。
完全同意@TamásKozmér。
请告诉我如何通过 arrayList 计算。我不知道我是一个新开发者..
谢谢。它工作得很好。但问题就在这里。当我从加号按钮增加数量时，我如何计算？