这是我的代码中有问题的一行：
listAdapter.setCustomButtonListener((CustomButtonListener) getActivity());**
此侦听器在AppCompatActivity内完美运行，但当我尝试在片段内使用它时会抛出ClassCastException。这是logcat：
Logcat
FATAL EXCEPTION: main Process: info.tranetech.laundry, PID: 21707
java.lang.ClassCastException: info.tranetech.laundry.pricelist.ItemListTab cannot be cast to tranetech.laundry.pricelist.CustomButtonListener
at info.tranetech.laundry.pricelist.ManItems$GetContacts.onPostExecute(ManItems.java:177)
at info.tranetech.laundry.pricelist.ManItems$GetContacts.onPostExecute(ManItems.java:98)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5748)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
这是我的界面
CustomButtonListener.java
public interface CustomButtonListener {
public void onButtonClickListener(int position, EditText editText, int value);
}
这是我的TabBar（AppCompatActivity）
ItemListTab.java
public class ItemListTab extends AppCompatActivity {
private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
private int[] tabIcons = {
R.drawable.ic_tab_favourite,
R.drawable.ic_tab_call,
R.drawable.ic_tab_contacts
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.item_list_tabs);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
setupTabIcons();
}
private void setupTabIcons() {
tabLayout.getTabAt(0).setIcon(tabIcons[0]);
tabLayout.getTabAt(1).setIcon(tabIcons[1]);
tabLayout.getTabAt(2).setIcon(tabIcons[2]);
tabLayout.getTabAt(3).setIcon(tabIcons[0]);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new ManItems(), "");
adapter.addFrag(new WomanItems(), "");
adapter.addFrag(new KidItems(), "");
adapter.addFrag(new HouseHoldItems(), "");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}
这是我的片段，我称之为
listAdapter.setCustomButtonListener（（CustomButtonListener）getActivity（））;
ManItems.java
public class ManItems extends Fragment implements CustomButtonListener{
private ListView listView;
View rootView;
Context context;
private ListAdapter listAdapter;
public static String[] ItemName, prices,ItemImage;
Button PlaceOrder;
ProgressDialog pDialog;
HashMap<String, String> itemMap;
// Hashmap for ListView
ArrayList<HashMap<String, String>> ItemList = new ArrayList<HashMap<String, String>>();
public ManItems() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
rootView = inflater.inflate(R.layout.content_main, container, false);
listView = (ListView) rootView.findViewById(R.id.customListView);
PlaceOrder = (Button) rootView.findViewById(R.id.place_order);
// Calling async task to get json
new GetContacts().execute();
PlaceOrder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (ListAdapter.map.isEmpty()) {
Toast.makeText(getActivity(), "Please select items", Toast.LENGTH_SHORT).show();
} else {
ListAdapter.map.values().removeAll(Collections.singleton("0"));
Intent intent = new Intent(getActivity(), OrderList.class);
startActivity(intent);
}
}
});
return rootView;
}
@Override
public void onButtonClickListener(int position, EditText editText, int value) {
// View view = listView.getChildAt(position);
int quantity = Integer.parseInt(editText.getText().toString());
quantity = quantity + 1 * value;
if (quantity < 0)
quantity = 0;
editText.setText(quantity + "");
}
/**
* Async task class to get json by making HTTP call
*/
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
JSONParser JP = new JSONParser();
// Making a request to url and getting response
String jsonStr = JP.makeServiceCall("http://openspace.tranetech.com/mis/Laundry/items.php", JSONParser.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
JSONArray itmeArray = jsonObj.getJSONArray("Data");
ItemName = new String[itmeArray.length()];
prices = new String[itmeArray.length()];
ItemImage = new String[itmeArray.length()];
// looping through All Contacts
for (int i = 0; i < itmeArray.length(); i++) {
JSONObject item = itmeArray.getJSONObject(i);
String price = item.getString("price").toString();
String name = item.getString("item_name").toString();
String image = item.getString("image").toString();
ItemName[i] = name;
prices[i] = price;
ItemImage[i] =image;
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing()) {
for (int z = 0; z < ItemName.length; z++) {
Log.d("Name ", "" + ItemName[z]);
Log.d("Price ", "" + prices[z]);
Log.d("Images ", "" + ItemImage[z]);
}
pDialog.dismiss();
}
// images = getResources().obtainTypedArray(R.array.ProductImages);
/**
* Updating parsed JSON data into ListView
* */
listAdapter = new ListAdapter(getActivity(), ItemName, ItemImage, prices);
listView.setAdapter(listAdapter);
listAdapter.setCustomButtonListener((CustomButtonListener) getActivity());
}
}
}
更改此 listAdapter.setCustomButtonListener（ManItems.this）;
logcat的
java.lang.NullPointerException
at info.tranetech.laundry.pricelist.ListAdapter.getView(ListAdapter.java:95)
at android.widget.AbsListView.obtainView(AbsListView.java:2768)
at android.widget.ListView.makeAndAddView(ListView.java:1817)
at android.widget.ListView.fillDown(ListView.java:703)
at android.widget.ListView.fillFromTop(ListView.java:769)
at android.widget.ListView.layoutChildren(ListView.java:1647)
at android.widget.AbsListView.onLayout(AbsListView.java:2586)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1692)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1534)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1443)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1627)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1034)
at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:744)
at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1180)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:757)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1692)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1534)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1443)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1692)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1534)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1443)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:15903)
at android.view.ViewGroup.layout(ViewGroup.java:4932)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2418)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2133)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1297)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6773)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:813)
at android.view.Choreographer.doCallbacks(Choreographer.java:613)
at android.view.Choreographer.doFrame(Choreographer.java:583)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:799)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5748)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
[1]: https://www.vlemonn.com/Blog/Android/Android-Custom-ListView-with-ImageView-EditText-and-Button/
错误位置
for (int z = 0; z < MainActivity_items.ItemImage.length; z++) {
Picasso.with(context)
.load(""+MainActivity_items.ItemImage[position])
.into(listViewHolder.ivProduct);
}
ListAdapter.java
public class ListAdapter extends BaseAdapter {
public ArrayList<Integer> quantity = new ArrayList<Integer>();
public ArrayList<Integer> price = new ArrayList<Integer>();
private String[] listViewItems, prices, static_price;
String[] images;
View row = null;
static String get_price, get_quntity;
int g_quntity, g_price, g_minus;
private Context context;
CustomButtonListener customButtonListener;
static HashMap<String, Integer> map = new HashMap<>();
public ListAdapter(Context context, String[] listViewItems, String[] images, String[] prices) {
this.context = context;
this.listViewItems = listViewItems;
this.images = images;
this.prices = prices;
for (int i = 0; i < listViewItems.length; i++) {
quantity.add(0);
}
}
public void setCustomButtonListener(CustomButtonListener customButtonListner) {
this.customButtonListener = customButtonListner;
}
@Override
public int getCount() {
return listViewItems.length;
}
@Override
public String getItem(int position) {
return listViewItems[position];
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
final ListViewHolder listViewHolder;
if (convertView == null) {
LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = layoutInflater.inflate(R.layout.activity_custom_listview, parent, false);
listViewHolder = new ListViewHolder();
listViewHolder.tvProductName = (TextView) row.findViewById(R.id.tvProductName);
listViewHolder.ivProduct = (ImageView) row.findViewById(R.id.ivproduct);
listViewHolder.tvPrices = (TextView) row.findViewById(R.id.tvProductPrice);
listViewHolder.btnPlus = (ImageButton) row.findViewById(R.id.ib_addnew);
listViewHolder.edTextQuantity = (EditText) row.findViewById(R.id.editTextQuantity);
listViewHolder.btnMinus = (ImageButton) row.findViewById(R.id.ib_remove);
static_price = context.getResources().getStringArray(R.array.Price);
row.setTag(listViewHolder);
} else {
row = convertView;
listViewHolder = (ListViewHolder) convertView.getTag();
}
//Loading image from below url into imageView
for (int z = 0; z < MainActivity_items.ItemImage.length; z++) {
Picasso.with(context)
.load(""+MainActivity_items.ItemImage[position])
.into(listViewHolder.ivProduct);
}
// listViewHolder.ivProduct.setImageResource(images.getResourceId(position, -1));
listViewHolder.edTextQuantity.setText(quantity.get(position) + "");
listViewHolder.tvProductName.setText(listViewItems[position]);
listViewHolder.tvPrices.setText(prices[position]);
listViewHolder.btnPlus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (customButtonListener != null) {
customButtonListener.onButtonClickListener(position, listViewHolder.edTextQuantity, 1);
quantity.set(position, quantity.get(position) + 1);
//price.set(position, price.get(position) + 1);
row.getTag(position);
get_price = listViewHolder.tvPrices.getText().toString();
g_price = Integer.valueOf(static_price[position]);
get_quntity = listViewHolder.edTextQuantity.getText().toString();
g_quntity = Integer.valueOf(get_quntity);
Integer.parseInt(listViewHolder.edTextQuantity.getText().toString());
map.put("" + listViewHolder.tvProductName.getText().toString(), Integer.valueOf(Integer.parseInt(listViewHolder.edTextQuantity.getText().toString())));
// Log.d("A ", "" + a);
// Toast.makeText(context, "A" + a, Toast.LENGTH_LONG).show();
// Log.d("Position ", "" + position);
// System.out.println(+position + " Values " + map.values());
listViewHolder.tvPrices.getTag();
listViewHolder.tvPrices.setText("" + g_price * g_quntity);
ShowHashMapValue();
}
}
});
listViewHolder.btnMinus.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (customButtonListener != null) {
customButtonListener.onButtonClickListener(position, listViewHolder.edTextQuantity, -1);
if (quantity.get(position) > 0)
quantity.set(position, quantity.get(position) - 1);
get_price = listViewHolder.tvPrices.getText().toString();
g_minus = Integer.valueOf(get_price);
g_price = Integer.valueOf(static_price[position]);
int minus = g_minus - g_price;
if (minus >= g_price) {
listViewHolder.tvPrices.setText("" + minus);
}
map.put("" + listViewHolder.tvProductName.getText().toString(), Integer.valueOf(Integer.parseInt(listViewHolder.edTextQuantity.getText().toString())));
ShowHashMapValue();
}
}
});
return row;
}
private void ShowHashMapValue() {
/**
* get the Set Of keys from HashMap
*/
Set setOfKeys = map.keySet();
/**
* get the Iterator instance from Set
*/
Iterator iterator = setOfKeys.iterator();
/**
* Loop the iterator until we reach the last element of the HashMap
*/
while (iterator.hasNext()) {
/**
* next() method returns the next key from Iterator instance.
* return type of next() method is Object so we need to do DownCasting to String
*/
String key = (String) iterator.next();
/**
* once we know the 'key', we can get the value from the HashMap
* by calling get() method
*/
int value = map.get(key);
System.out.println("Key: " + key + ", Value: " + value);
}
}
}
答案 0 :(得分：1)
正如错误所述，ItemListTab活动无法转换为CustomButtonListener，因为它没有实现它，当前片段。所以你需要改变
listAdapter.setCustomButtonListener((CustomButtonListener) getActivity());
到
listAdapter.setCustomButtonListener(ManItems.this);
/* Not listAdapter.setCustomButtonListener(this), otherwise
you would be referring to the AsyncTask 'GetContacts' itself */
答案 1 :(得分：0)
希望这对你有所帮助 用于在片段中使用接口侦听器 不要在片段类上实现，在Tab Activity中实现Listener 并且图片查看或片段的任何内容都应该是公共静态
答案 2 :(得分：0)
如果您使用getActivity（）
，您的活动ItemListTab必须实现CustomButtonListener传递ManItems的引用，因为ManItems实现了CustomButtonListener