我遇到了一些问题。似乎我随机从 findViewById() 返回 null。有时它返回 TextView 和 LinearLayout ..有时它只是给出 null 异常。
- 这是如果它正确返回的话。
- 如果我重新调试它。最终结果会是这样...
而在调试期间的其他时间它将返回 null。
有什么方法可以达到稳定的结果吗？
记录 Java 案例。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_log_acase);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.new_case, menu);
return true;
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
if (position == 0)
{
Fragment fragment = new PatientInfoFragment();
Bundle args = new Bundle();
fragment.setArguments(args);
return fragment;
}
else if (position == 1)
{
Fragment fragment2 = new EncounterFragment();
Bundle args = new Bundle();
fragment2.setArguments(args);
return fragment2;
}
else if (position == 2)
{
Fragment fragment3 = new ProcedureFragment();
Bundle args = new Bundle();
fragment3.setArguments(args);
return fragment3;
}
return null;
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return "Patient Info";
case 1:
return "Encounter";
case 2:
return "Procedure";
}
return null;
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
case R.id.ProgressBtn:
openProgress();
break;
case R.id.SavedCasesBtn:
openSaveCases();
break;
case R.id.action_newcase_save:
openSave();
return true;
case R.id.action_newcase_send:
openSend();
return true;
case R.id.action_settings:
Intent intent = new Intent(LogACase.this, PrefsActivity.class);
startActivity(intent);
break;
}
return super.onOptionsItemSelected(item);
}
public void openSave()
{
}
public void openSend()
{
String encounterValue, procedureValue;
encounterValue = retrieveEncounterValue();
procedureValue = retrieveProcedureValue();
}
public String retrieveEncounterValue()
{
String encounterValue = null;
//Encounter
LinearLayout ListV =(LinearLayout) findViewById(R.id.encounterslist);
//Get the number of rows - Correct number of row.
for(int i = 0 ; i<ListV.getChildCount();i++)
{
//get that row 's listV
LinearLayout listParent = (LinearLayout) ListV.getChildAt(i);
//Nested LL is 2nd item of listParent.
LinearLayout nestedLL = (LinearLayout)listParent.getChildAt(1);
//Get the checkbox in that nested.
CheckBox cb = (CheckBox) nestedLL.getChildAt(0);
//If it's checked
if(cb.isChecked())
{
//take the ID value of the checked and add it to encouterSelected array.
TextView idTV = (TextView) listParent.getChildAt(0);
encounterSelected.add(idTV.getText());
}
}
//Sort the array on order before sending it back to NewCases
Collections.sort(encounterSelected);
StringBuilder full = new StringBuilder();
int B = encounterSelected.size();
if (B != 0)
{
encounterValue = full.append(encounterSelected).toString();
encounterValue = encounterValue.replaceAll("\\s","");
}
else
{
encounterValue = "No Encounter Selected";
}
//Patient Info
history = (CheckBox) findViewById(R.id.checkbox_history);
physical = (CheckBox) findViewById(R.id.checkbox_physical);
patientInitial = (EditText) findViewById(R.id.InitialTextEdit);
locSpinner = (Spinner) findViewById(R.id.locationSpinner);
dateOfDiagnosis = (EditText) findViewById(R.id.showMyDate);
siteLocation = locSpinner.getSelectedItem().toString();
wardClinic = (EditText) findViewById(R.id.WardClinicTextEdit);
// Declaration into String
String patientInitialText = patientInitial.getText().toString();
String dateOfDiagnosisText = dateOfDiagnosis.getText().toString();
String siteLocationText = locSpinner.getSelectedItem().toString();
String wardClinicText = wardClinic.getText().toString();
String historyText = "N";
String physicalText = "N";
if (history.isChecked()) {
historyText = "Y";
}
if (physical.isChecked()) {
physicalText = "Y";
}
if (patientInitialText.trim().equals("")) {
Toast.makeText(this, "Initial cannot be empty ", Toast.LENGTH_SHORT)
.show();
} else if (wardClinicText.trim().equals("")) {
Toast.makeText(this, "Ward/Clinic Cannot be empty",
Toast.LENGTH_SHORT).show();
}
return encounterValue;
}
public String retrieveProcedureValue()
{
String procedureValue = null;
LinearLayout ListProcedure =(LinearLayout) findViewById(R.id.procedureslistParent);
//Get the number of rows - Correct number of row.
for(int i = 0 ; i<ListProcedure.getChildCount();i++)
{
//get that row 's listV
LinearLayout listParent = (LinearLayout) ListProcedure.getChildAt(i);
//Nested LL is 2nd item of listParent.
LinearLayout nestedLL = (LinearLayout)listParent.getChildAt(1);
//Get the checkbox in that nested.
CheckBox cb = (CheckBox) nestedLL.getChildAt(0);
//If it's checked
if(cb.isChecked())
{
//take the ID value of the checked and add it to encouterSelected array.
TextView idTV = (TextView) listParent.getChildAt(0);
procedureSelected.add(idTV.getText());
}
}
//Sort the array on order before sending it back to NewCases
Collections.sort(procedureSelected);
int B = procedureSelected.size();
if (B != 0)
{
StringBuilder full = new StringBuilder();
procedureValue = full.append(procedureSelected).toString();
procedureValue = procedureValue.replaceAll("\\s","");
}
else
{
procedureValue = "No Procedure Selected";
}
return procedureValue;
}
public void openProgress()
{
Intent progressIntent = new Intent(this, ScanSelected.class);
progressIntent.putExtra(EXTRA_MESSAGE, "MyProgress");
startActivity(progressIntent);
}
public void openSaveCases()
{
Intent savedCaseIntent = new Intent(this, SavedCases.class);
startActivity(savedCaseIntent);
}
}
患者信息 fragment
public class PatientInfoFragment extends Fragment{
public static final String ARG_SECTION_NUMBER = "section_number";
// DATABASE ADAPTOR
patientDbAdapter patientDB;
Context myContext;
String ID = "0";
// SPINNER AND SEARCH VIEW
private SearchView mSearchView;
private TextView mStatusView;
private Spinner locationSpinner;
// DATE SPINNER
private int mYear;
private int mMonth;
private int mDay;
private TextView mDateDisplay;
static final int DIALOG_ALERT = 1;
// declaration
private EditText patientInitial, dateOfDiagnosis, wardClinic;
private Spinner locSpinner;
private CheckBox history, physical;
private String siteLocation;
String patientKey = "com.example.app.datetime";
// Verification
Boolean fromBase = false;
//Data From PatientDetails
String strValue1 ;
String strValue2 ;
String strValue3 ;
String strValue4 ;
String strValue5 ;
String strValue6 ;
private String patientID;
static final int DATE_DIALOG_ID = 0;
View rootView;
public PatientInfoFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.activity_patient_info,
container, false);
history = (CheckBox) rootView.findViewById(R.id.checkbox_history);
physical = (CheckBox) rootView.findViewById(R.id.checkbox_physical);
patientInitial = (EditText) rootView.findViewById(R.id.InitialTextEdit);
locSpinner = (Spinner) rootView.findViewById(R.id.locationSpinner);
dateOfDiagnosis = (EditText) rootView.findViewById(R.id.showMyDate);
siteLocation = locSpinner.getSelectedItem().toString();
wardClinic = (EditText) rootView.findViewById(R.id.WardClinicTextEdit);
// listener for the Ward/ClinicSpinner
addListenerOnSpinnerItemSelection();
//mDateDisplay.setOnClickListener(new View.OnClickListener() {
// public void onClick(View v) {
// showDatePicker();
// }
// });
return rootView;
}
private void RetrieveDataFromDatabaseBasedOnID(String paramString) {
myContext = getActivity();
// Opening of database
patientDB = new patientDbAdapter(myContext);
patientDB.open();
ID = paramString;
Cursor mCursor = this.patientDB
.retrievePatientEntriesBasedOnID(paramString);
if ((mCursor != null) && (mCursor.getCount() > 0)) {
mCursor.moveToFirst();
mCursor.getString(0); // ID
this.strValue1 = mCursor.getString(1); // Initial
this.strValue2 = mCursor.getString(2);// Date
this.strValue3 = mCursor.getString(3);// SiteLocation
this.strValue4 = mCursor.getString(4);// WardClinic
this.strValue5 = mCursor.getString(5);// CheckBoxHistory
this.strValue6 = mCursor.getString(6);// CheckBoxPhysical
patientInitial = (EditText) rootView.findViewById(R.id.InitialTextEdit);
locSpinner = (Spinner) rootView.findViewById(R.id.locationSpinner);
dateOfDiagnosis = (EditText) rootView.findViewById(R.id.showMyDate);
siteLocation = locSpinner.getSelectedItem().toString();
wardClinic = (EditText) rootView.findViewById(R.id.WardClinicTextEdit);
history = (CheckBox) rootView.findViewById(R.id.checkbox_history);
physical = (CheckBox) rootView.findViewById(R.id.checkbox_physical);
patientInitial.setText(strValue1);
dateOfDiagnosis.setText(strValue2);
// ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
// R.array.location_arrays, android.R.layout.simple_spinner_item);
// int S = adapter.getPosition(strValue3);
// locSpinner.setSelection(S);
wardClinic.setText(strValue4);
if (strValue5.equals("Y")) {
history.setChecked(true);
}
if (strValue6.equals("Y")) {
physical.setChecked(true);
}
fromBase = true;
} else {
fromBase = false;
}
}
// Listen to the spinner Item Selection - Completed
public void addListenerOnSpinnerItemSelection() {
locationSpinner = (Spinner) rootView.findViewById(R.id.locationSpinner);
// locationSpinner.setOnItemSelectedListener(new
// CustomOnItemSelectedListener());
}
// Listen to the spinner
public void addListenerOnButton() {
// retrieveValue
locationSpinner = (Spinner) rootView.findViewById(R.id.locationSpinner);
}
public void openPatientSearch() {
Intent patientDetailsIntent = new Intent(myContext, PatientDetails.class);
//StartActivityForResult doesn't work for fragment
// PatientInfo.this.startActivityForResult(patientDetailsIntent, 1);
}
患者信息 XML。
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/patientTableLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingTop="@dimen/activity_vertical_margin"
android:background="@drawable/bg"
android:shrinkColumns="1" >
<!-- 2 columns Row 2 -->
<!-- Patient Initials Row -->
<TableRow
android:id="@+id/tableRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dip" >
<TextView
android:id="@+id/InitialsTextView"
android:text="Patient Initials:"
android:textStyle="bold"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall" />
<EditText
android:id="@+id/InitialTextEdit"
android:layout_span="2"
android:singleLine="true"
android:layout_height="wrap_content"
android:layout_weight="0.6"
android:inputType="textVisiblePassword"
android:imeOptions="actionNext"
android:hint="@string/patient_input" />
</TableRow>
<!-- End Of row 1 -->
<!-- Row 2 -->
<!-- Date Of Diagnosis Row -->
<TableRow
android:id="@+id/tableRow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dip" >
<TextView
android:id="@+id/DiagnosisTextView"
android:textStyle="bold"
android:text="Date of Diagnosis:"
android:textAppearance="?android:attr/textAppearanceSmall" />
<EditText
android:id="@+id/showMyDate"
android:hint="Enter Date here"
android:editable="false"
android:focusableInTouchMode="false"
android:layout_height="wrap_content"
android:layout_weight="0.6"/>
</TableRow>
<!-- End of row 2 -->
<!-- Row 3 -->
<!-- Date Of Diagnosis Row -->
<TableRow
android:id="@+id/tableRow3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dip" >
<TextView
android:id="@+id/LocationTextView"
android:textStyle="bold"
android:text="Site/Location:"
android:textAppearance="?android:attr/textAppearanceSmall" />
<Spinner
android:id="@+id/locationSpinner"
android:layout_height="wrap_content"
android:layout_weight="0.6"
android:entries="@array/location_arrays"
android:prompt="@string/DateSpinnerText" />
</TableRow>
<!-- End of row 3 -->
<!-- Row 4 -->
<!-- ward/clinic Row -->
<TableRow
android:id="@+id/tableRow4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dip" >
<TextView
android:id="@+id/WardClinicTextView"
android:textStyle="bold"
android:text="Ward/Clinic:"
android:textAppearance="?android:attr/textAppearanceSmall" />
<EditText
android:id="@+id/WardClinicTextEdit"
android:layout_height="wrap_content"
android:layout_weight="0.6"
android:singleLine="true"
android:hint="Good to include bed no." />
</TableRow>
<!-- End of row 4 -->
<!-- edittext span 2 column -->
<TableRow
android:id="@+id/tableRow3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="5dip" >
</TableRow>
<!-- just draw a red line -->
<View
android:layout_height="2dip"
android:background="#0000FF" />
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<CheckBox android:id="@+id/checkbox_history"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:text="Performed History"
/>
<CheckBox android:id="@+id/checkbox_physical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textStyle="bold"
android:text="Performed Physical"
/>
</LinearLayout>
</TableLayout>
最佳答案
由于您似乎“随机”获得有效 View 或 NPE(引号)，因此我发现了 ViewPager/Adapter 缓存/回收问题。在寻呼机中设置 setOffscreenPageLimit 以包含所有 3 个 fragment (默认情况下，它默认为任一侧 1 Fragment，IIRC)应该可以解决此问题.
作为建议，我建议将菜单选项放在相关的 fragment 中，而不是放在您的 Activity 中，因为逻辑取决于与特定 fragment 内的 View 相关的数据，这可能或可能当您选择菜单选项时，不会缓存在 ViewPager 中。
我应该注意到，提供仅 fragment 的菜单项是完全可以的，并期望它们与寻呼机透明地工作(即，它们随着 fragment 的出现和消失而出现和消失)。
关于java - FindViewByID fragment 为空，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21057799/