MainActivity setOnClickListener中的java.lang.NullPointerException
当我运行我的应用程序时,我在第56行不断得到一个NullPointerException,如下面的调试日志所示。我对android应用程序的编程比较陌生,所以我不知道这里发生了什么。有人能帮我解决这个问题吗? My MainActivity.java:MainActivity setOnClickListener中的java.lang.NullPointerException,java,android,nullpointerexception,Java,Android,Nullpointerexception,当我运行我的应用程序时,我在第56行不断得到一个NullPointerException,如下面的调试日志所示。我对android应用程序的编程比较陌生,所以我不知道这里发生了什么。有人能帮我解决这个问题吗? My MainActivity.java: package com.termite.pockettube; import java.util.Locale; import android.content.Intent; import android.os.Bundle; import
package com.termite.pockettube;
import java.util.Locale;
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.app.NavUtils;
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.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends FragmentActivity implements View.OnClickListener{
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. 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}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
Button button;
@Override
protected 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.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
button = (Button) findViewById(R.id.button);
button.setOnClickListener(this); //this is line 56
}
public void countryOnClick() {
startActivity(new Intent("com.termite.pockettube.COUNTRY"));
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.button:
countryOnClick();
break;
}
}
@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;
}
/**
* 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.
switch (position) {
case 0:
Fragment1 fragment1 = new Fragment1();
return fragment1;
case 1:
Fragment2 fragment2 = new Fragment2();
return fragment2;
case 2:
Fragment3 fragment3 = new Fragment3();
return fragment3;
case 3:
Fragment4 fragment4 = new Fragment4();
return fragment4;
case 4:
Fragment5 fragment5 = new Fragment5();
return fragment5;
}
return null;
}
@Override
public int getCount() {
// Show 5 total pages.
return 5;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
case 3:
return getString(R.string.title_section4).toUpperCase(l);
case 4:
return getString(R.string.title_section5).toUpperCase(l);
}
return null;
}
}
}
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
这是我尝试运行应用程序时的调试日志:
12-20 01:13:26.898: D/AndroidRuntime(6539): Shutting down VM
12-20 01:13:26.906: W/dalvikvm(6539): threadid=1: thread exiting with uncaught exception (group=0x40af21f8)
12-20 01:13:26.906: E/AndroidRuntime(6539): FATAL EXCEPTION: main
12-20 01:13:26.906: E/AndroidRuntime(6539): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.termite.pockettube/com.termite.pockettube.MainActivity}: java.lang.NullPointerException
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2035)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2060)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.access$600(ActivityThread.java:127)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1181)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.os.Handler.dispatchMessage(Handler.java:99)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.os.Looper.loop(Looper.java:137)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.main(ActivityThread.java:4558)
12-20 01:13:26.906: E/AndroidRuntime(6539): at java.lang.reflect.Method.invokeNative(Native Method)
12-20 01:13:26.906: E/AndroidRuntime(6539): at java.lang.reflect.Method.invoke(Method.java:511)
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-20 01:13:26.906: E/AndroidRuntime(6539): at dalvik.system.NativeStart.main(Native Method)
12-20 01:13:26.906: E/AndroidRuntime(6539): Caused by: java.lang.NullPointerException
12-20 01:13:26.906: E/AndroidRuntime(6539): at com.termite.pockettube.MainActivity.onCreate(MainActivity.java:56)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.Activity.performCreate(Activity.java:4635)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
12-20 01:13:26.906: E/AndroidRuntime(6539): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1999)
12-20 01:13:26.906: E/AndroidRuntime(6539): ... 11 more
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
清单xml代码:
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
activity_main.xml:
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<android.support.v4.view.PagerTabStrip
android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_gravity="top"
android:background="#33b5e5"
android:paddingBottom="4dp"
android:paddingTop="4dp"
android:textColor="#fff"
>
</android.support.v4.view.PagerTabStrip>
</android.support.v4.view.ViewPager>
fragment1.xml:
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity$DummySectionFragment" >
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_alignParentTop="true"
android:text="@string/button" />
</RelativeLayout>
检查
R.id.button
,按钮是否在R.layout.activity\u main
布局中
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
发布您的活动\u main.xml
布局
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
做下面的事
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
在activity\u main.xml
中添加按钮或更改代码
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
button = (Button) mViewPager.findViewById(R.id.button);
button.setOnClickListener(this);
按钮为空。初始化失败
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
activity\u main.xml
中需要按钮,id也应该是按钮
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
findViewById
在当前展开的布局中查找id为的视图。所以,如果您在activity\u main.xml
中有按钮,那么您的初始化工作正常,否则您将获得NPE`
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
activity\u main.xml
中没有按钮。S0button=(button)findViewById(R.id.button)代码>失败
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
按钮处于碎片1中。因此,您需要膨胀布局fragment1.xml
,然后在onCreateView
中初始化按钮,而不是在Activity中初始化按钮。您需要在Activity\u main.xml
中按下按钮,因为您在fragment\u 1.xml
中添加了该按钮,这就是NPE的原因
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
在activity\u main.xml中添加按钮将解决您的问题
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
**activity_main.xml
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="@dimen/padding_Small"
android:shrinkColumns="*"
android:stretchColumns="*" >
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<android.support.v4.view.PagerTabStrip
android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_gravity="top"
android:background="#33b5e5"
android:paddingBottom="4dp"
android:paddingTop="4dp"
android:textColor="#fff" />
</android.support.v4.view.ViewPager>
<Button
android:id="@+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:text="ButtonText" />
</RelativeLayout>
试试看
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
立即创建
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
然后试试看
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
private OnClickListener buttonListener = new OnClickListener() {
public void onClick(View v) {
//Do Work Here
}
};
您的错误在getItem(Position)方法中。即使您的适配器大小是5,它也会为您提供比5更大的位置。在这样的时刻,从那里返回null
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
您可以通过添加一条Log语句来检查这一点,在getItem方法的开头打印位置值谢谢大家的输入,所有这些都可以结束NPE,但它没有执行我希望它完成的任务。我将按钮添加到y Fragment1.java文件中,然后它就工作了
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.termite.pockettube.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.termite.pockettube.CountryActivity"
android:label="@string/title_activity_country" >
<intent-filter>
<action android:name="com.termite.pockettube.COUNTRY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
package com.termite.pockettube;
import com.termite.pockettube.MainActivity.SectionsPagerAdapter;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
public class Fragment1 extends Fragment implements View.OnClickListener {
Button button;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Get the view from fragmenttab1.xml
View view = inflater.inflate(R.layout.fragment1, container, false);
button = (Button)view.findViewById(R.id.button);
button.setOnClickListener(this);
return view;
}
/* @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}*/
public void countryOnClick() {
startActivity(new Intent("com.termite.pockettube.COUNTRY"));
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.button:
countryOnClick();
break;
}
}
}
什么是第56行MainActivity.java?我认为按钮在片段中,所以在适配器中设置click listener。你不能在这里找到它,可能是按钮有问题显示你的xml代码,这将很容易找到错误。检查xml文件中的按钮id。它与“按钮”相同吗?这是否给出了NullPointerException
?这是一个NPE。因此他的一个视图可能是空的。不是因为intnet。你能解释一下你的解决方案吗!?nullpointerexception当对象为Null时发生,我认为您必须首先定义AOObject,然后使用其方法,您可以通过这种方式进行测试,我希望这种方式可以帮助您。欢迎@saeid,这个答案与您之前的其他答案一样。你的答案有什么不同?