转到另一个选项卡时，选项卡式 android 应用程序崩溃（android -> java -> android 工作室）
Tabbed android application crashes when going to another tab (android -> java -> android studio)
我说的是 android 开发中的预览应用程序，但是当转到另一个选项卡时，该应用程序在模拟器中崩溃了。
这是日志输出：
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation D/AndroidRuntime﹕ Shutting down VM
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb0ccfb20)
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.android.effectivenavigation, PID: 2495
java.lang.NullPointerException
at com.example.android.effectivenavigation.MainActivity$AppSectionsPagerAdapter$DummySectionFragment.onCreateView(MainActivity.java:194)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:555)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:495)
at com.example.android.effectivenavigation.MainActivity.onTabSelected(MainActivity.java:100)
at com.android.internal.app.ActionBarImpl.selectTab(ActionBarImpl.java:577)
at com.android.internal.app.ActionBarImpl$TabImpl.select(ActionBarImpl.java:1105)
at com.android.internal.widget.ScrollingTabContainerView$TabClickListener.onClick(ScrollingTabContainerView.java:547)
at android.view.View.performClick(View.java:4438)
at android.view.View$PerformClick.run(View.java:18422)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
这是应用程序的主要activity
/*
* Copyright 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.effectivenavigation;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
* three primary sections of the app. We use a {@link android.support.v4.app.FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
/**
* The {@link ViewPager} that will display the three primary sections of the app, one at a
* time.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home/Up button should not be enabled, since there is no hierarchical
// parent.
actionBar.setHomeButtonEnabled(false);
// Specify that we will be displaying tabs in the action bar.
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// When swiping between different app sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mAppSectionsPagerAdapter.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
// listener for when this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mAppSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@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 onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new slaapkamer();
case 1:
return new woonkamer();
default:
// The other sections of the app are dummy placeholders.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
fragment.setArguments(args);
return fragment;
}
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
if (position == 0) {
return "slaapkamer";
} else if (position == 1) {
return "woonkamer";
} else {
return "geavanceerd";
}
}
/**
* A fragment that launches other parts of the demo application.
*/
public static class slaapkamer extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
//place the shit that should happen
return rootView;
}
}
public static class woonkamer extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad2, container, false);
//place the shit that should happen
return rootView;
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
}
我找不到问题所在。
也许是旁注，我是 java.
的新手
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
if (args != null) {
((TextView) rootView.findViewById(R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
}
return rootView;
}
}
您必须在使用前检查 args != null 是否为 null 并将 android.R.id.text1 替换为 R.id.text1
我说的是 android 开发中的预览应用程序，但是当转到另一个选项卡时，该应用程序在模拟器中崩溃了。 这是日志输出：
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation D/AndroidRuntime﹕ Shutting down VM
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb0ccfb20)
01-04 11:02:19.103 2495-2495/com.example.android.effectivenavigation E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.android.effectivenavigation, PID: 2495
java.lang.NullPointerException
at com.example.android.effectivenavigation.MainActivity$AppSectionsPagerAdapter$DummySectionFragment.onCreateView(MainActivity.java:194)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:555)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:495)
at com.example.android.effectivenavigation.MainActivity.onTabSelected(MainActivity.java:100)
at com.android.internal.app.ActionBarImpl.selectTab(ActionBarImpl.java:577)
at com.android.internal.app.ActionBarImpl$TabImpl.select(ActionBarImpl.java:1105)
at com.android.internal.widget.ScrollingTabContainerView$TabClickListener.onClick(ScrollingTabContainerView.java:547)
at android.view.View.performClick(View.java:4438)
at android.view.View$PerformClick.run(View.java:18422)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
这是应用程序的主要activity
/*
* Copyright 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.effectivenavigation;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
* three primary sections of the app. We use a {@link android.support.v4.app.FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
/**
* The {@link ViewPager} that will display the three primary sections of the app, one at a
* time.
*/
ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
// Specify that the Home/Up button should not be enabled, since there is no hierarchical
// parent.
actionBar.setHomeButtonEnabled(false);
// Specify that we will be displaying tabs in the action bar.
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager, attaching the adapter and setting up a listener for when the
// user swipes between sections.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// When swiping between different app sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mAppSectionsPagerAdapter.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
// listener for when this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mAppSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
@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 onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
* sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new slaapkamer();
case 1:
return new woonkamer();
default:
// The other sections of the app are dummy placeholders.
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
fragment.setArguments(args);
return fragment;
}
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
if (position == 0) {
return "slaapkamer";
} else if (position == 1) {
return "woonkamer";
} else {
return "geavanceerd";
}
}
/**
* A fragment that launches other parts of the demo application.
*/
public static class slaapkamer extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
//place the shit that should happen
return rootView;
}
}
public static class woonkamer extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_launchpad2, container, false);
//place the shit that should happen
return rootView;
}
}
/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
((TextView) rootView.findViewById(android.R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
}
我找不到问题所在。 也许是旁注，我是 java.
的新手/**
* A dummy fragment representing a section of the app, but that simply displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
Bundle args = getArguments();
if (args != null) {
((TextView) rootView.findViewById(R.id.text1)).setText(
getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
}
return rootView;
}
}
您必须在使用前检查 args != null 是否为 null 并将 android.R.id.text1 替换为 R.id.text1