在 android studio 的列表视图上编写按钮单击事件时应用程序崩溃
Application crashing when writing button click event on listview in android studio
我已经尝试了几乎所有提供的所有技巧 sites.When 我将 onClickListener 添加到按钮或适配器的 getview 中的任何其他控件，应用程序崩溃。当我删除点击代码时，应用程序不会崩溃。但我需要在列表视图中的按钮上编写点击事件。任何类型的建议将不胜感激！
这是我的 ListView 适配器代码。
public class CustomListAdapter extends BaseAdapter{
private Activity activity;
private LayoutInflater inflater;
private List<ProductDetails> productDetailsList;
// Context context;
int prodId;
String prodName, prodPrice, prodImgUrl, prodDescription;
ImageLoader imageLoader = VolleySingleton.getInstance().getImageLoader();
public CustomListAdapter(Activity activity, List<ProductDetails> productDetailsList){
this.activity = activity;
this.productDetailsList = productDetailsList;
}
@Override
public int getCount() {
return productDetailsList.size();
}
@Override
public Object getItem(int position) {
return productDetailsList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
final PlaceHolder holder = new PlaceHolder();
if (inflater == null)
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
Log.d("Inflater", "checked inflater null");
if (convertView == null){
Log.d("convertView ", "checked convertView null");
convertView = inflater.inflate(R.layout.single_product_list,null);
Log.d("convertView assigned ", "placed the inflater to convertView ");
}
if (imageLoader == null)
imageLoader = VolleySingleton.getInstance().getImageLoader();
Log.d("Image Loader", "checked Image loader null");
holder.imgProduct = (NetworkImageView) convertView.findViewById(R.id.network_prod_img);
Log.d("Image View", "checked referred image view");
holder.nameProduct = (TextView) convertView.findViewById(R.id.prod_name);
Log.d("nameProduct text View", "checked referred nameProduct view");
holder.priceProduct = (TextView) convertView.findViewById(R.id.prod_price);
Log.d("priceProduct text View", "checked referred priceProduct view");
holder.addToCart = (Button)convertView.findViewById(R.id.add_cart_btn);
Log.d("priceProduct Button", "checked referred Add to cart button");
//get the product data for the row
ProductDetails pd = productDetailsList.get(position);
Log.d("PRODUCT DATA", "got product data for the row");
//set the product image to the layout
holder.imgProduct.setImageUrl(pd.getProductImgUrl(), imageLoader);
Log.d("SET IMAGE", "set the product image to the layout");
//set the product name to the layout
holder.nameProduct.setText(pd.getProductName());
Log.d("SET NAME", "set the product name to the layout");
//set the product price to the layout
holder.priceProduct.setText(String.valueOf(pd.getProductPrice()));
Log.d("SET PRICE", "set the product price to the layout");
//when clicking on the product name and image
holder.nameProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("","");
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
holder.imgProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
holder.addToCart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
return convertView;
}
public void gotoProdDetails(int position){
prodId = productDetailsList.get(position).getProductId();
prodName = productDetailsList.get(position).getProductName();
prodPrice = productDetailsList.get(position).getProductPrice();
prodDescription = productDetailsList.get(position).getProductDesc();
prodImgUrl = productDetailsList.get(position).getProductImgUrl();
Intent intent1 = new Intent(activity, ProductDescription.class);
intent1.putExtra("prodId", prodId);
intent1.putExtra("prodName",prodName);
intent1.putExtra("prodPrice",prodPrice);
intent1.putExtra("prodDescription",prodDescription);
intent1.putExtra("prodImgUrl", prodImgUrl);
activity.startActivity(intent1);
}
class PlaceHolder{
NetworkImageView imgProduct;
TextView nameProduct;
TextView priceProduct;
Button addToCart;
}
LogCat如下
11-04 04:25:39.105 1210-1261/system_process W/AudioService: onLoadSoundEffects(), Error -1 while loading samples
11-04 04:25:39.115 897-897/com.example.android.shoppingcart D/onItemClick id: 7
11-04 04:25:39.325 897-897/com.example.android.shoppingcart W/EGL_emulation: eglSurfaceAttrib not implemented
11-04 04:25:39.355 897-897/com.example.android.shoppingcart W/EGL_emulation: eglSurfaceAttrib not implemented
11-04 04:25:39.415 897-897/com.example.android.shoppingcart D/ProductList: [{"id":"7","id_prod":"5","description_prod":"chip","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/5.jpg","price_prod":"2.98","name_prod":"Ele1"},{"id":"7","id_prod":"6","description_prod":"Laptops","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/6.jpg","price_prod":"24259","name_prod":"Ele2"},{"id":"7","id_prod":"7","description_prod":"Chip Board","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/7.jpg","price_prod":"122.98","name_prod":"Ele3"}]
11-04 04:25:39.415 897-897/com.example.android.shoppingcart D/convertView: checked convertView null
11-04 04:25:39.415 897-897/com.example.android.shoppingcart I/dalvikvm-heap: Grow heap (frag case) to 4.118MB for 360012-byte allocation
11-04 04:25:39.435 897-897/com.example.android.shoppingcart I/dalvikvm-heap: Grow heap (frag case) to 4.888MB for 810012-byte allocation
11-04 04:25:39.445 897-897/com.example.android.shoppingcart D/convertView assigned: placed the inflater to convertView
11-04 04:25:39.445 897-897/com.example.android.shoppingcart D/priceProduct Button: checked referred Add to cart button
11-04 04:25:39.445 897-897/com.example.android.shoppingcart W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xb37f0678)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: FATAL EXCEPTION: main
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: java.lang.NullPointerException
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.ListView.onMeasure(ListView.java:1159)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:393)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189)
11-04 04:25:40.155 1374-1374/com.android.launcher W/EGL_emulation: eglSurfaceAttrib not implemented
activity_products_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.android.shoppingcart.ProductList">
<ListView
android:id="@+id/prod_list"
android:layout_width="match_parent"
android:background="@android:color/transparent"
android:cacheColorHint="@android:color/transparent"
android:layout_height="wrap_content">
</ListView>
</LinearLayout>
single_product_list.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/single_product_row"
android:padding="15dp">
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/network_prod_img"
android:layout_width="140dp"
android:layout_height="140dp"
android:src="@drawable/small_default"
android:scaleType="centerCrop"
android:layout_marginRight="20dp"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true" />
<TextView
android:id="@+id/prod_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/def_prod_name"
android:textSize="17sp"
android:padding="5dp"
android:layout_alignTop="@+id/network_prod_img"
android:layout_toEndOf="@+id/network_prod_img"
android:layout_alignParentEnd="true" />
<TextView
android:id="@+id/prod_price"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/price_val"
android:layout_below="@+id/prod_name"
android:padding="5dp"
android:textSize="15sp"
android:layout_toEndOf="@+id/network_prod_img"
/>
<Button
android:id="@+id/btn_add_cart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/add"
android:padding="12dp"
android:layout_below="@id/prod_price"
android:layout_toEndOf="@id/network_prod_img"
android:background="#E57373"
/>
</RelativeLayout>
似乎有两种方法可以使按钮起作用：（我更喜欢第二种，文字较少）
1) Java: OnClickHandlers:
Button button = (Button)findViewById(R.id.corky);
button.setOnClickListener(this);
2) XML 按钮减量：android:onClick="your_method_that_does_something"
我没看到你在做什么，是创建按钮。然后将按钮连接到 UI 中的一个东西。然后附加一个监听器。
*编辑；你能附上 XML 文件吗？我认为你的问题（也）在那里。
*编辑2；以这种方式更改按钮（向您展示它是如何工作的，并不能解决您所有的问题）：
<Button
android:id="@+id/btn_add_cart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/add"
android:padding="12dp"
android:layout_below="@id/prod_price"
android:layout_toEndOf="@id/network_prod_img"
android:background="#E57373"
android:onClick="toastMe"
/>
并将此方法添加到您的 java 代码中，在主 class.
public void toastMe() {
Toast.makeText(activity, "Button works", Toast.LENGTH_SHORT).show();
}
java.lang.NullPointerException。
意味着您的声明中有些地方是错误的，这就是为什么它们显示 NULL。
Button btn_Call ; // declare at the top of the class before oncreate.
btn_Call = (Button) findViewById(R.id.btn_Call);
btn_Call.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// code here
}
});
感谢您的所有回答...他们帮助我进行更多研究！终于找到解决方法了
为了使按钮可点击以及列表视图可点击，我编写了 2 个不同的点击事件，如下所示：
在 MainActivity.java 外 onCreate():
public void addToCart(View view) {
Button bt = (Button) view;
/*To get the position of the corresponding row clicked*/
View parentRow = (View) view.getParent();
ListView listView = (ListView) parentRow.getParent();
final int position = listView.getPositionForView(parentRow);
Toast.makeText(this, productDetailsList.get(position).getProductName() + " added to cart", Toast.LENGTH_LONG).show();
}
在 OnCreate() 内部：
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(context, "An item of the ListView is clicked.", Toast.LENGTH_LONG).show();
prodId = productDetailsList.get(position).getProductId();
prodName = productDetailsList.get(position).getProductName();
prodPrice = productDetailsList.get(position).getProductPrice();
prodDescription = productDetailsList.get(position).getProductDesc();
prodImgUrl = productDetailsList.get(position).getProductImgUrl();
Intent intent1 = new Intent(getApplicationContext(), ProductDescription.class);
intent1.putExtra("prodId", prodId);
intent1.putExtra("prodName", prodName);
intent1.putExtra("prodPrice", prodPrice);
intent1.putExtra("prodDescription", prodDescription);
intent1.putExtra("prodImgUrl", prodImgUrl);
startActivity(intent1);
}
});
我已经尝试了几乎所有提供的所有技巧 sites.When 我将 onClickListener 添加到按钮或适配器的 getview 中的任何其他控件，应用程序崩溃。当我删除点击代码时，应用程序不会崩溃。但我需要在列表视图中的按钮上编写点击事件。任何类型的建议将不胜感激！
这是我的 ListView 适配器代码。
public class CustomListAdapter extends BaseAdapter{
private Activity activity;
private LayoutInflater inflater;
private List<ProductDetails> productDetailsList;
// Context context;
int prodId;
String prodName, prodPrice, prodImgUrl, prodDescription;
ImageLoader imageLoader = VolleySingleton.getInstance().getImageLoader();
public CustomListAdapter(Activity activity, List<ProductDetails> productDetailsList){
this.activity = activity;
this.productDetailsList = productDetailsList;
}
@Override
public int getCount() {
return productDetailsList.size();
}
@Override
public Object getItem(int position) {
return productDetailsList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
final PlaceHolder holder = new PlaceHolder();
if (inflater == null)
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
Log.d("Inflater", "checked inflater null");
if (convertView == null){
Log.d("convertView ", "checked convertView null");
convertView = inflater.inflate(R.layout.single_product_list,null);
Log.d("convertView assigned ", "placed the inflater to convertView ");
}
if (imageLoader == null)
imageLoader = VolleySingleton.getInstance().getImageLoader();
Log.d("Image Loader", "checked Image loader null");
holder.imgProduct = (NetworkImageView) convertView.findViewById(R.id.network_prod_img);
Log.d("Image View", "checked referred image view");
holder.nameProduct = (TextView) convertView.findViewById(R.id.prod_name);
Log.d("nameProduct text View", "checked referred nameProduct view");
holder.priceProduct = (TextView) convertView.findViewById(R.id.prod_price);
Log.d("priceProduct text View", "checked referred priceProduct view");
holder.addToCart = (Button)convertView.findViewById(R.id.add_cart_btn);
Log.d("priceProduct Button", "checked referred Add to cart button");
//get the product data for the row
ProductDetails pd = productDetailsList.get(position);
Log.d("PRODUCT DATA", "got product data for the row");
//set the product image to the layout
holder.imgProduct.setImageUrl(pd.getProductImgUrl(), imageLoader);
Log.d("SET IMAGE", "set the product image to the layout");
//set the product name to the layout
holder.nameProduct.setText(pd.getProductName());
Log.d("SET NAME", "set the product name to the layout");
//set the product price to the layout
holder.priceProduct.setText(String.valueOf(pd.getProductPrice()));
Log.d("SET PRICE", "set the product price to the layout");
//when clicking on the product name and image
holder.nameProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("","");
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
holder.imgProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
holder.addToCart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(activity, "clicked on add to cart button", Toast.LENGTH_LONG).show();
}
});
return convertView;
}
public void gotoProdDetails(int position){
prodId = productDetailsList.get(position).getProductId();
prodName = productDetailsList.get(position).getProductName();
prodPrice = productDetailsList.get(position).getProductPrice();
prodDescription = productDetailsList.get(position).getProductDesc();
prodImgUrl = productDetailsList.get(position).getProductImgUrl();
Intent intent1 = new Intent(activity, ProductDescription.class);
intent1.putExtra("prodId", prodId);
intent1.putExtra("prodName",prodName);
intent1.putExtra("prodPrice",prodPrice);
intent1.putExtra("prodDescription",prodDescription);
intent1.putExtra("prodImgUrl", prodImgUrl);
activity.startActivity(intent1);
}
class PlaceHolder{
NetworkImageView imgProduct;
TextView nameProduct;
TextView priceProduct;
Button addToCart;
}
LogCat如下
11-04 04:25:39.105 1210-1261/system_process W/AudioService: onLoadSoundEffects(), Error -1 while loading samples
11-04 04:25:39.115 897-897/com.example.android.shoppingcart D/onItemClick id: 7
11-04 04:25:39.325 897-897/com.example.android.shoppingcart W/EGL_emulation: eglSurfaceAttrib not implemented
11-04 04:25:39.355 897-897/com.example.android.shoppingcart W/EGL_emulation: eglSurfaceAttrib not implemented
11-04 04:25:39.415 897-897/com.example.android.shoppingcart D/ProductList: [{"id":"7","id_prod":"5","description_prod":"chip","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/5.jpg","price_prod":"2.98","name_prod":"Ele1"},{"id":"7","id_prod":"6","description_prod":"Laptops","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/6.jpg","price_prod":"24259","name_prod":"Ele2"},{"id":"7","id_prod":"7","description_prod":"Chip Board","image_url":"http:\/\/192.168.1.8\/shopping_cart\/images\/products\/7.jpg","price_prod":"122.98","name_prod":"Ele3"}]
11-04 04:25:39.415 897-897/com.example.android.shoppingcart D/convertView: checked convertView null
11-04 04:25:39.415 897-897/com.example.android.shoppingcart I/dalvikvm-heap: Grow heap (frag case) to 4.118MB for 360012-byte allocation
11-04 04:25:39.435 897-897/com.example.android.shoppingcart I/dalvikvm-heap: Grow heap (frag case) to 4.888MB for 810012-byte allocation
11-04 04:25:39.445 897-897/com.example.android.shoppingcart D/convertView assigned: placed the inflater to convertView
11-04 04:25:39.445 897-897/com.example.android.shoppingcart D/priceProduct Button: checked referred Add to cart button
11-04 04:25:39.445 897-897/com.example.android.shoppingcart W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xb37f0678)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: FATAL EXCEPTION: main
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: java.lang.NullPointerException
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.ListView.onMeasure(ListView.java:1159)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:393)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-04 04:25:39.445 897-897/com.example.android.shoppingcart E/AndroidRuntime: at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189)
11-04 04:25:40.155 1374-1374/com.android.launcher W/EGL_emulation: eglSurfaceAttrib not implemented
activity_products_list.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.android.shoppingcart.ProductList">
<ListView
android:id="@+id/prod_list"
android:layout_width="match_parent"
android:background="@android:color/transparent"
android:cacheColorHint="@android:color/transparent"
android:layout_height="wrap_content">
</ListView>
</LinearLayout>
single_product_list.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/single_product_row"
android:padding="15dp">
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/network_prod_img"
android:layout_width="140dp"
android:layout_height="140dp"
android:src="@drawable/small_default"
android:scaleType="centerCrop"
android:layout_marginRight="20dp"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true" />
<TextView
android:id="@+id/prod_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/def_prod_name"
android:textSize="17sp"
android:padding="5dp"
android:layout_alignTop="@+id/network_prod_img"
android:layout_toEndOf="@+id/network_prod_img"
android:layout_alignParentEnd="true" />
<TextView
android:id="@+id/prod_price"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/price_val"
android:layout_below="@+id/prod_name"
android:padding="5dp"
android:textSize="15sp"
android:layout_toEndOf="@+id/network_prod_img"
/>
<Button
android:id="@+id/btn_add_cart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/add"
android:padding="12dp"
android:layout_below="@id/prod_price"
android:layout_toEndOf="@id/network_prod_img"
android:background="#E57373"
/>
</RelativeLayout>
似乎有两种方法可以使按钮起作用：（我更喜欢第二种，文字较少）
1) Java: OnClickHandlers:
Button button = (Button)findViewById(R.id.corky);
button.setOnClickListener(this);
2) XML 按钮减量：android:onClick="your_method_that_does_something"
我没看到你在做什么，是创建按钮。然后将按钮连接到 UI 中的一个东西。然后附加一个监听器。
*编辑；你能附上 XML 文件吗？我认为你的问题（也）在那里。
*编辑2；以这种方式更改按钮（向您展示它是如何工作的，并不能解决您所有的问题）：
<Button
android:id="@+id/btn_add_cart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/add"
android:padding="12dp"
android:layout_below="@id/prod_price"
android:layout_toEndOf="@id/network_prod_img"
android:background="#E57373"
android:onClick="toastMe"
/>
并将此方法添加到您的 java 代码中，在主 class.
public void toastMe() {
Toast.makeText(activity, "Button works", Toast.LENGTH_SHORT).show();
}
java.lang.NullPointerException。 意味着您的声明中有些地方是错误的，这就是为什么它们显示 NULL。
Button btn_Call ; // declare at the top of the class before oncreate.
btn_Call = (Button) findViewById(R.id.btn_Call);
btn_Call.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// code here
}
});
感谢您的所有回答...他们帮助我进行更多研究！终于找到解决方法了
为了使按钮可点击以及列表视图可点击，我编写了 2 个不同的点击事件，如下所示：
在 MainActivity.java 外 onCreate():
public void addToCart(View view) {
Button bt = (Button) view;
/*To get the position of the corresponding row clicked*/
View parentRow = (View) view.getParent();
ListView listView = (ListView) parentRow.getParent();
final int position = listView.getPositionForView(parentRow);
Toast.makeText(this, productDetailsList.get(position).getProductName() + " added to cart", Toast.LENGTH_LONG).show();
}
在 OnCreate() 内部：
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(context, "An item of the ListView is clicked.", Toast.LENGTH_LONG).show();
prodId = productDetailsList.get(position).getProductId();
prodName = productDetailsList.get(position).getProductName();
prodPrice = productDetailsList.get(position).getProductPrice();
prodDescription = productDetailsList.get(position).getProductDesc();
prodImgUrl = productDetailsList.get(position).getProductImgUrl();
Intent intent1 = new Intent(getApplicationContext(), ProductDescription.class);
intent1.putExtra("prodId", prodId);
intent1.putExtra("prodName", prodName);
intent1.putExtra("prodPrice", prodPrice);
intent1.putExtra("prodDescription", prodDescription);
intent1.putExtra("prodImgUrl", prodImgUrl);
startActivity(intent1);
}
});