嗯，我有recyclerView和一个片段作为Master Detail Flow的示例 现在我从json获取数据，并在recyclerView中完美解析 问题是每当我单击它时，都会得到null异常。
public class ItemDetailFragment extends Fragment {
/**
* The fragment argument representing the item ID that this fragment
* represents.
*/
public static final String ARG_ITEM_ID = "item_id";
/**
* The dummy content this fragment is presenting.
*/
private DummyContent.DummyItem mItem;
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public ItemDetailFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments().containsKey(ARG_ITEM_ID)) {
// Load the dummy content specified by the fragment
// arguments. In a real-world scenario, use a Loader
// to load content from a content provider.
mItem = DummyContent.ITEM_MAP.get(getArguments().getString(ARG_ITEM_ID));
Activity activity = this.getActivity();
CollapsingToolbarLayout appBarLayout = (CollapsingToolbarLayout) activity.findViewById(R.id.toolbar_layout);
if (appBarLayout != null) {
appBarLayout.setTitle(mItem.id);
}
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.item_detail, container, false);
// Show the dummy content as text in a TextView.
if (mItem != null) {
((TextView) rootView.findViewById(R.id.item_detail)).setText("hello");
}
return rootView;
}
这是活动
public class ItemDetailActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_item_detail);
Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own detail action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
// Show the Up button in the action bar.
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.setDisplayHomeAsUpEnabled(true);
}
// savedInstanceState is non-null when there is fragment state
// saved from previous configurations of this activity
// (e.g. when rotating the screen from portrait to landscape).
// In this case, the fragment will automatically be re-added
// to its container so we don't need to manually add it.
// For more information, see the Fragments API guide at:
//
// http://developer.android.com/guide/components/fragments.html
//
if (savedInstanceState == null) {
// Create the detail fragment and add it to the activity
// using a fragment transaction.
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID,
getIntent().getStringExtra(ItemDetailFragment.ARG_ITEM_ID));
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.add(R.id.item_detail_container, fragment)
.commit();
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == android.R.id.home) {
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
navigateUpTo(new Intent(this, ItemListActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
}
这是我获取json和ItemlistActivity的地方
public class ItemListActivity extends AppCompatActivity {
View recyclerView;
/**
* Whether or not the activity is in two-pane mode, i.e. running on a tablet
* device.
*/
private boolean mTwoPane;
RequestQueue queue;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_item_list);
queue = Volley.newRequestQueue(this);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
toolbar.setTitle(getTitle());
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
recyclerView = findViewById(R.id.item_list);
assert recyclerView != null;
if (findViewById(R.id.item_detail_container) != null) {
// The detail container view will be present only in the
// large-screen layouts (res/values-w900dp).
// If this view is present, then the
// activity should be in two-pane mode.
mTwoPane = true;
}
connection();
}
private void setupRecyclerView(@NonNull RecyclerView recyclerView) {
recyclerView.setAdapter(new SimpleItemRecyclerViewAdapter(DummyContent.ITEMS));
}
public class SimpleItemRecyclerViewAdapter
extends RecyclerView.Adapter<ViewHolder> {
private final List<DummyContent.DummyItem> mValues;
public SimpleItemRecyclerViewAdapter(List<DummyContent.DummyItem> items) {
mValues = items;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.item_list_content, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
String profilePicUrl = mValues.get(position).profile_pic;
String full_name = mValues.get(position).full_name;
String state = mValues.get(position).state;
String city = mValues.get(position).city;
String phoneNo = mValues.get(position).phone_no;
holder.full_name.setText("Name : " +full_name);
holder.state.setText("State : " +state);
holder.city.setText("City : " +city);
holder.phone_number.setText("Phone Number : " +phoneNo);
Glide.with(getApplicationContext())
.load(profilePicUrl)
.fitCenter()
.override(500,500)
.into(holder.profile_pic);
holder.mView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.item_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, ItemDetailActivity.class);
Log.e("hello",holder.mItem.full_name);
intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
context.startActivity(intent);
}
}
});
}
@Override
public int getItemCount() {
return mValues.size();
}
}
public void connection(){
final String url = "aaaaa";
// prepare the Request
JsonObjectRequest getRequest = new JsonObjectRequest(Request.Method.GET, url, null,
new Response.Listener<JSONObject>()
{
@Override
public void onResponse(JSONObject response) {
// display response
try {
JSONArray jsonArray = response.getJSONArray("results");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject test = jsonArray.getJSONObject(i);
String gender = test.getString("gender");
String full_name = test.getJSONObject("name").getString("title") + " " +
test.getJSONObject("name").getString("first") + " " +
test.getJSONObject("name").getString("last");
String state = test.getJSONObject("location").getString("state");
String city = test.getJSONObject("location").getString("city");
String phone_no = test.getString("phone");
String profile_pic = test.getJSONObject("picture").getString("large");
String id = test.getJSONObject("id").getString("name");
Log.d("test2222", gender + " \n " + full_name + " \n " + state + " \n " + city + " \n " + phone_no + "\n" + profile_pic
+ "\n" + id);
addItem(new DummyContent.DummyItem(gender,profile_pic, full_name, state, city, phone_no,"hello"));
}
setupRecyclerView((RecyclerView) recyclerView);
} catch (JSONException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener()
{
@Override
public void onErrorResponse(VolleyError error) {
Log.d("Error.Response", error.toString());
Toast.makeText(getApplicationContext(),"check internet connection",Toast.LENGTH_SHORT).show();
}
}
);
// add it to the RequestQueue
queue.add(getRequest);
}
最后是虚拟内容
public class DummyContent {
/**
* An array of sample (dummy) items.
*/
public static final List<DummyItem> ITEMS = new ArrayList<DummyItem>();
/**
* A map of sample (dummy) items, by ID.
*/
public static final Map<String, DummyItem> ITEM_MAP = new HashMap<String, DummyItem>();
private static final int COUNT = 25;
static {
// Add some sample items.
}
public static void addItem(DummyItem item) {
ITEMS.add(item);
ITEM_MAP.put(item.full_name, item);
}
/**
* A dummy item representing a piece of content.
*/
public static class DummyItem {
public final String id;
public final String profile_pic;
public final String full_name;
public final String state;
public final String city;
public final String phone_no;
public final String data;
public DummyItem(String id ,String profile_pic, String full_name, String state ,String city,String phone_no,String data) {
this.id = id;
this.profile_pic = profile_pic;
this.full_name = full_name;
this.state = state;
this.city = city;
this.phone_no = phone_no;
this.data = data;
}
@Override
public String toString() {
return full_name;
}
}
}
现在的问题是我想获取与片段相同的数据（文本或图像） 我的问题是我什至无法显示带有自定义“ hello world”文本视图的片段，每当我单击recyclerview时都会出现异常，因此请向我解释代码中的错误在哪里
这是ViewHolder
public class ViewHolder extends RecyclerView.ViewHolder {
public final View mView;
public final ImageView profile_pic;
public final TextView full_name;
public final TextView state;
public final TextView city;
public final TextView phone_number;
public DummyContent.DummyItem mItem;
public ViewHolder(View view) {
super(view);
mView = view;
profile_pic = (ImageView) view.findViewById(R.id.profile_pic);
full_name = (TextView) view.findViewById(R.id.full_name_txt);
state = (TextView) view.findViewById(R.id.state_txt);
city = (TextView) view.findViewById(R.id.city_txt);
phone_number = (TextView) view.findViewById(R.id.phone_no_txt);
}
@Override
public String toString() {
return super.toString() + " '" + full_name.getText() + "'";
}
}
答案 0 :(得分：0)
您将获得空值，因为您正在使用ViewHolder类中的mItem而不进行初始化，该值为null。
尝试一下：
DummyContent.DummyItem mItem = mValues.get(position); //initialize here, not in ViewHolder class
holder.mView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID, mItem.id); //use without holder
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.item_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, ItemDetailActivity.class);
Log.e("hello",holder.mItem.full_name);
intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, mItem.id); //same here
context.startActivity(intent);
}
}
});