我正在使用使用向导创建的选项卡式布局，并且准备好了一个片段。我已将一些 EditText 添加到我的片段中，并且一切准备就绪，但是，在运行应用程序时，我在 EditText 声明中收到 NullPointerException。
片段代码：
package com.boreas.snowdaycalculatorsp2;
import android.content.Context;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class AdvancedFragment extends Fragment {
EditText inSnow, durnStorm, pSnow, pTime, fSnow, wSpeed, sGround;
public double inchSnow, durationStorm, peakSnow, peakTime, finalSnow, windSpeed, snowGround, result;
TextView results;
Button calc;
String resInt;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
inSnow = (EditText) getView().findViewById(R.id.inchesSnow);
durnStorm = (EditText)getView().findViewById(R.id.durationStorm);
pSnow = (EditText) getView().findViewById(R.id.peakRate);
pTime = (EditText)getView().findViewById(R.id.peakRateTime);
fSnow = (EditText) getView().findViewById(R.id.finalRate);
wSpeed = (EditText) getView().findViewById(R.id.windSpeed);
sGround = (EditText) getView().findViewById(R.id.snowGround);
results = (TextView) getView().findViewById(R.id.resultView);
calc = (Button) getView().findViewById(R.id.button);
return inflater.inflate(R.layout.advfrag_layout, container, false);
}
}
片段 XML：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:background="#000000"
android:layout_height="match_parent">
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/inchesSnow"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:hint="Inches of Snow"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/durationStorm"
android:layout_below="@+id/inchesSnow"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:hint="Duration of Storm"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/peakRate"
android:layout_below="@+id/durationStorm"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:hint="Peak Snow Rate"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:layout_alignParentStart="false"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/peakRateTime"
android:layout_below="@+id/peakRate"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:hint="Time of Peak Snow Rate"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberSigned"
android:ems="10"
android:id="@+id/finalRate"
android:layout_below="@+id/peakRateTime"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:hint="Final Snow Rate"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberSigned"
android:ems="10"
android:id="@+id/windSpeed"
android:layout_below="@+id/finalRate"
android:layout_alignParentLeft="true"
android:hint="Wind Speed"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:layout_alignParentRight="true"
android:singleLine="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="@+id/snowGround"
android:layout_below="@+id/windSpeed"
android:layout_alignParentLeft="true"
android:hint="Snow Already on Ground"
android:textColor="#ffffff"
android:textColorHint="#ffffff"
android:layout_alignParentRight="true"
android:singleLine="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Calculate"
android:id="@+id/button"
android:layout_below="@+id/snowGround"
android:layout_centerHorizontal="true"
android:layout_marginTop="39dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:id="@+id/resultView"
android:layout_below="@+id/button"
android:layout_alignRight="@+id/button"
android:layout_marginTop="41dp"
android:layout_alignLeft="@+id/button" />
</RelativeLayout>
主要活动：
package com.boreas.snowdaycalculatorsp2;
import java.util.Locale;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.app.FragmentPagerAdapter;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity implements ActionBar.TabListener {
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
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.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@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 PlaceholderFragment (defined as a static inner class below).
Fragment fragment;
switch (position){
case 0:
fragment = new BasicFragment();
break;
case 1:
fragment = new AdvancedFragment();
break;
default:
throw new IllegalArgumentException("Invalid Section Number");
}
return fragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return "Basic";
case 1:
return "Advanced";
}
return null;
}
}
}
关于导致 NullPointerException 的任何想法？