我想将数据从活动传输到片段，它总是打印此错误。我尝试使用不同的技术来克服这种想法，但仍然卡住了。我在活动或片段中的代码中遗漏了什么？
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.junaida.project1, PID: 14447
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.junaida.project1/com.example.junaida.project1.Year}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2957)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3018)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6724)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at com.example.junaida.project1.fragments.CardFragment.onCreateView(CardFragment.java:89)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)
at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3221)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3171)
at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:192)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:560)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:177)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1256)
at android.app.Activity.performStart(Activity.java:6959)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2920)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3018)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1653)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6724)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
此错误指向
String id = bundle.getString("id");
我将列出从
传输数据的类 public class Year extends AppCompatActivity {
ImageView back;
GridView grid;
String id;
String type;
String year;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_year);
Intent data = getIntent();
year = data.getStringExtra("year");
id = data.getStringExtra("id");
type = data.getStringExtra("type");
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
//show the original color of icons
bottomNavigationView.setItemIconTintList(null);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
Fragment selectedFragment = null;
final Bundle bundle = new Bundle() ;
Intent intent;
switch (item.getItemId()) {
case R.id.action_item1:
bundle.putString("year",year);
bundle.putString("id",id);
bundle.putString("type",type);
//selectedFragment.setArguments(bundle);
selectedFragment = new CardFragment();
selectedFragment.setArguments(bundle);
break;
case R.id.action_item2:
bundle.putString("year",year);
bundle.putString("id",id);
bundle.putString("type",type);
//selectedFragment.setArguments(bundle);
selectedFragment = new AudioFragment();
selectedFragment.setArguments(bundle);
break;
case R.id.action_item3:
bundle.putString("year",year);
bundle.putString("id",id);
bundle.putString("type",type);
//selectedFragment.setArguments(bundle);
selectedFragment = new VideoFragment();
selectedFragment.setArguments(bundle);
break;
}
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.content_frame2, selectedFragment);
transaction.commit();
return true;
}
});
//Manually displaying the first fragment - one time only
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.content_frame2, new CardFragment());
transaction.commit();
back = (ImageView)findViewById(R.id.back_year);
back.setOnClickListener(new AdapterView.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
}
});
}
}
我的片段是
public class CardFragment extends Fragment {
// String id;
// String type;
// String year;
private ListAdapter adapter;
TextView textView;
private ListView lv;
private List<ListItemsData> list = new ArrayList<ListItemsData>();
private static final String url = "http://10.94.0.204/WebApplication7/api/subjects";
public CardFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle bundle = this.getArguments();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.fragment_card, container, false);
//final ArrayList<ListItemsData> listItem = GetlistItems();
Bundle bundle = this.getArguments();
String id = bundle.getString("id");
String year = bundle.getString("year");
String type = bundle.getString("type");
final Activity mActivity = this.getActivity();
// lv.setAdapter(new ListAdapter(getActivity(), listItem));
adapter = new ListAdapter(getContext(), list);
lv.setAdapter(adapter);
try {
RequestQueue requestQueue = Volley.newRequestQueue(getContext());
String URL = "http://10.94.0.204/WebApplication7/api/subjects";
JSONObject jsonBody = new JSONObject();
// jsonBody.put("tblRegisteredUsers_nickName", username.getText().toString().trim());
jsonBody.put("id", id.toString());
jsonBody.put("Type", type.toString());
jsonBody.put("Year", year.toString());
final String requestBody = jsonBody.toString();
StringRequest stringRequest = new StringRequest(Request.Method.POST, URL, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
if (response.equals("success")) {
//login authenticated. Start the next activity of your app
Toast.makeText(getActivity(), response.toString(), Toast.LENGTH_LONG).show();
// Toast.makeText(getApplicationContext(), "registered successfully ", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(getActivity(), MainActivity.class);
// intent.putExtra("id", Id);
// intent.putExtra("year", year);
startActivity(intent);
} else {
//login failed. prompt to re-enter the credentials
Toast.makeText(mActivity.getApplicationContext(), "Failed to log In", Toast.LENGTH_SHORT).show();
Log.i("VOLLEY", response);
Toast.makeText(mActivity.getApplicationContext(), response.toString(), Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e("VOLLEY", error.toString());
}
})
{
@Override
public String getBodyContentType() {
return "application/json; charset=utf-8";
}
@Override
public byte[] getBody() throws AuthFailureError {
try {
return requestBody == null ? null : requestBody.getBytes("utf-8");
} catch (UnsupportedEncodingException uee) {
VolleyLog.wtf("Unsupported Encoding while trying to get the bytes of %s using %s", requestBody, "utf-8");
return null;
}
}
@Override
protected Response<String> parseNetworkResponse(NetworkResponse response) {
String responseString;
String json = null;
try {
json = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
responseString = String.valueOf(json).trim();
ArrayList<Response4> list_response = new ArrayList<Response4>();
Type listType = new TypeToken<List<Response4>>() {
}.getType();
list_response = new Gson().fromJson(responseString, listType);
//String check = list.get(0).getMessagesName();
for (int i = 0; i < list_response.size(); i++) {
// JSONObject obj = response.getJSONObject(i);
ListItemsData listItemData = new ListItemsData();
listItemData.setItem(list_response.get(i).getMessagesName());
listItemData.setUrl(list_response.get(i).getMessageURLNew());
//listItemData.setUrl((obj.getString("url")));
list.add(listItemData);
//Id = list.get(0).getId();
// year = list.get(0).getYear();
//Response2 yourModel = new Gson().fromJson(responseString, Response2.class);
}
// i should have this peice of code for methods that are in the background
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
adapter.notifyDataSetChanged();
}
});
// String Check = yourModel.getMessagetitle();
return Response.success(list_response.toString(), HttpHeaderParser.parseCacheHeaders(response));
}
};
requestQueue.add(stringRequest);
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return rootView;
}
答案 0 :(得分：1)
从片段中获取捆绑包时，您应该使用 getArguments（）。 得到像这样的包
public View onCreateView(LayoutInflater inflater, ViewGroup containerObject,Bundle savedInstanceState){
//here is your arguments
Bundle bundle=getArguments();
//get string like this
String year = bundle.getString("year");
}
编辑：创建一个这样的函数，并从导航菜单中添加到默认片段以及其他片段。
private Bundle getBundle(Intent data){
Bundle bundle = new Bundle();
bundle.putString("year",data.getStringExtra("year"));
bundle.putString("id",data.getStringExtra("id"));
bundle.putString("type",data.getStringExtra("type"));
}
这是最终代码
public class Year extends AppCompatActivity {
ImageView back;
GridView grid;
String id;
String type;
String year;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_year);
Intent data = getIntent();
//get a bundle set and ready to use anytime
Bundle myBundle= getBundle(data);
BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
//show the original color of icons
bottomNavigationView.setItemIconTintList(null);
bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
Fragment selectedFragment = null;
switch (item.getItemId()) {
case R.id.action_item1:
selectedFragment = new CardFragment();
selectedFragment.setArguments(myBundle);
break;
case R.id.action_item2:
selectedFragment = new AudioFragment();
selectedFragment.setArguments(myBundle);
break;
case R.id.action_item3:
selectedFragment = new VideoFragment();
selectedFragment.setArguments(myBundle);
break;
}
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.content_frame2, selectedFragment);
transaction.commit();
return true;
}
});
//Manually displaying the first fragment - one time only
CardFragment myCardFragment = new CardFragment();
myCardFragment.setArguments(myBundle);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.content_frame2, myCardFragment);
transaction.commit();
back = (ImageView)findViewById(R.id.back_year);
back.setOnClickListener(new AdapterView.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
}
});
}
private Bundle getBundle(Intent data){
Bundle bundle = new Bundle();
bundle.putString("year",data.getStringExtra("year"));
bundle.putString("id",data.getStringExtra("id"));
bundle.putString("type",data.getStringExtra("type"));
}
}