我在片段中使用了一个viewpager。但是当我尝试运行代码时，我得到NullPointerException.Below是代码
ImageAdapter.java：
package com.example.sabudaniel61.ktdc;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
/**
* Created by Sabudaniel61 on 2015-10-29.
*/
public class ImageAdapter extends PagerAdapter {
private int images[]=new int[]{R.drawable.slide2,R.drawable.room1,R.drawable.room2};
private Context context;
ImageAdapter(Context context){
this.context=context;
}
@Override
public int getCount() {
return images.length;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
LayoutInflater inflater=(LayoutInflater) new MascotFragment().getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v=inflater.inflate(R.layout.mascotimages,container,false);
ImageView imageView=(ImageView) v.findViewById(R.id.imageView1);
imageView.setImageResource(images[position]);
((ViewPager) container).addView(v);
return v;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
((ViewPager) container).removeView((LinearLayout) object);
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view==(LinearLayout) object;
}
}
mascotlayout.xml
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:scrollbars="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</android.support.v4.view.ViewPager>.
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/text"
android:textColor="#424242"
android:text="Address"
android:textSize="30sp"
android:layout_below="@+id/viewpager"
android:layout_centerHorizontal="true"
/>
<View
android:layout_width="wrap_content"
android:layout_height="1dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_below="@+id/text"
android:background="#9FA8DA"></View>
<android.support.v7.widget.CardView
android:layout_height="150dp"
android:layout_width="match_parent"
android:layout_below="@+id/text"
android:layout_margin="8dp"
android:layout_marginLeft="20dp"
android:layout_marginRight="20dp"
android:id="@+id/cardView"
><RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#80000000"
android:inputType="textMultiLine"
android:textSize="25sp"
android:id="@+id/text1"
android:gravity="center"
android:layout_marginTop="30dp"
android:text="Aranya Nivas\nThekkady\nIdukki 685536"
/></RelativeLayout></android.support.v7.widget.CardView>
<ImageButton
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_alignParentLeft="true"
android:id="@+id/imageButton"
android:background="@drawable/calls"
android:clickable="true"
android:layout_marginLeft="30dp"
android:layout_below="@+id/cardView"
/>
<ImageButton
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_centerHorizontal="true"
android:layout_centerInParent="true"
android:id="@+id/imageButton1"
android:background="@drawable/mails"
android:layout_below="@+id/cardView"
/>
<ImageButton
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_below="@+id/cardView"
android:layout_marginRight="30dp"
android:layout_alignParentRight="true"
android:background="@drawable/location"
android:id="@+id/imageButton2"
></ImageButton>
<Button
android:layout_width="wrap_content"
android:layout_height="30dp"
android:id="@+id/text3"
android:elevation="3dp"
android:textColor="#f9fff6"
android:background="@drawable/shape"
android:layout_marginRight="10dp"
android:layout_alignParentRight="true"
android:layout_marginTop="890dp"
android:text=" Conducted Tours >> "
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/text2"
android:text="Facilities"
android:layout_marginLeft="20dp"
android:textSize="25sp"
android:layout_marginTop="200dp"
android:layout_below="@+id/text3"
android:textColor="#000000" />
<ImageView
android:layout_width="10dp"
android:layout_height="10dp"
android:layout_below="@+id/text2"
android:background="#40000000"
android:layout_marginTop="13dp"
android:id="@+id/image24"
android:layout_marginLeft="20dp"/>
<TextView
android:layout_width="170dp"
android:layout_height="20dp"
android:textColor="#80000000"
android:text="Ayurveda therapies"
android:layout_marginLeft="10dp"
android:layout_below="@+id/text2"
android:layout_marginTop="10dp"
android:layout_toRightOf="@+id/image24"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/text19"
android:layout_below="@+id/text2"
android:text="Attractions"
android:textSize="25sp"
android:textColor="#000000"
android:layout_marginLeft="20dp"
android:layout_marginTop="30dp"/>
<ImageView
android:layout_width="15dp"
android:layout_height="15dp"
android:src="@android:drawable/alert_dark_frame"
android:id="@+id/image16"
android:layout_toLeftOf="@+id/text20"
android:layout_marginTop="390dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Kerala Legislature Complex"
android:id="@+id/text20"
android:textColor="#80000000"
android:layout_below="@+id/text19"
android:layout_marginLeft="40dp"
/>
<ImageView
android:layout_width="10dp"
android:layout_height="10dp"
android:background="#40000000"
android:id="@+id/image17"
android:layout_marginLeft="20dp"
android:layout_below="@+id/text19"
android:layout_marginTop="3dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Science and Technology Museum Complex"
android:id="@+id/text21"
android:textColor="#80000000"
android:layout_below="@+id/text20"
android:layout_marginLeft="40dp"
/>
<ImageView
android:layout_width="10dp"
android:layout_height="10dp"
android:layout_below="@+id/image17"
android:id="@+id/image18"
android:layout_marginTop="7dp"
android:layout_marginLeft="20dp"
android:background="#40000000"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text21"
android:id="@+id/text22"
android:text="Priyadarshini Planetarium"
android:layout_marginLeft="40dp"/>
<ImageView
android:layout_width="10dp"
android:layout_height="10dp"
android:layout_marginLeft="20dp"
android:background= "#40000000"
android:id="@+id/image19"
android:layout_marginTop="7dp"
android:layout_below="@+id/image18"
/>
<ImageView
android:layout_width="10dp"
android:layout_height="10dp"
android:layout_marginLeft="20dp"
android:background= "#40000000"
android:id="@+id/image28"
android:layout_marginTop="7dp"
android:layout_below="@+id/image19"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="40dp"
android:id="@+id/text23"
android:text="The Napier Museum"
android:layout_below="@+id/text22"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:layout_below="@+id/text23"
android:layout_alignParentLeft="true"
android:id="@+id/text24"
android:textSize="25sp"
android:textColor="#000000"
android:layout_marginLeft="20dp"
android:text="Activities"/>
<ImageView
android:layout_width="15dp"
android:layout_height="15dp"
android:src="@android:drawable/alert_dark_frame"
android:layout_below="@+id/text24"
android:id="@+id/image20"
android:layout_marginTop="2dp"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text24"
android:text="Morning and evening walks inside the property or in the adjaecent museum compound and kanakakkunu Palace Compound"
android:layout_marginLeft="20dp"
android:id="@+id/text25"
/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image21"
android:layout_below="@+id/text25"
android:src="@android:drawable/alert_dark_frame"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text25"
android:id="@+id/text26"
android:text="Visit museum ,zoo, art gallery and other places of historical importance"
android:layout_marginLeft="20dp"/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image22"
android:layout_below="@+id/image21"
android:src="@android:drawable/alert_dark_frame"
android:layout_marginTop="19dp"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text26"
android:id="@+id/text27"
android:text="Visit beaches(Kovalam and Shanghumugham)"
android:layout_marginLeft="20dp"/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image23"
android:layout_below="@+id/image22"
android:src="@android:drawable/alert_dark_frame"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text27"
android:id="@+id/text28"
android:text="Visit backwaters(Veli and Akkulam)"
android:layout_marginLeft="20dp"/>
<Button
android:layout_width="15dp"
android:layout_height="30dp"
android:background="@drawable/shape"
android:layout_alignParentRight="true"
android:text="Know more >>>"
android:id="@+id/button3"
android:textColor="#f9fff6"
android:layout_below="@+id/text28"
android:layout_toEndOf="@+id/imageButton1" />
<View
android:layout_width="match_parent"
android:layout_height="2dp"
android:background="#a8a8bd"
android:layout_below="@+id/text28"
android:layout_marginTop="50dp"
android:id="@+id/view5"></View>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Gallery"
android:id="@+id/gallery"
android:textSize="35sp"
android:textColor="#52ff61"
android:layout_below="@+id/button3"
android:layout_marginTop="20dp"/>
<View
android:layout_width="match_parent"
android:layout_height="2dp"
android:layout_below="@+id/gallery"
android:id="@+id/view6"
android:layout_marginTop="20dp"
android:background="#a8a8bd"
></View>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Accesibility"
android:textSize="35sp"
android:id="@+id/access"
android:layout_marginTop="20dp"
android:layout_below="@+id/view6"
android:textColor="#52ff61"
/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image25"
android:layout_marginTop="2dp"
android:layout_below="@+id/access"
android:src="@android:drawable/alert_dark_frame"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/access"
android:id="@+id/text29"
android:text="Nearest Bus Terminal:Thiruvananthapuram, about 4 km"
android:layout_marginLeft="20dp"/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image26"
android:layout_below="@+id/image25"
android:src="@android:drawable/alert_dark_frame"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text29"
android:id="@+id/text30"
android:text="Nearest railway Terminal:Thiruvananthapuram, about 4 km"
android:layout_marginLeft="20dp"/>
<ImageView android:layout_width="15dp"
android:layout_height="15dp"
android:id="@+id/image27"
android:layout_below="@+id/image26"
android:layout_marginTop="2dp"
android:src="@android:drawable/alert_dark_frame"
>
</ImageView>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/text30"
android:id="@+id/text31"
android:text="Nearest airport:Thiruvananthapuram International Airport, about 7 km"
android:layout_marginLeft="20dp"/>
</RelativeLayout>
</ScrollView>
MainActivity.java：
我只发布两个代码，因为它包含很多其他代码
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
ImageAdapter imageadapter = new ImageAdapter(this);
viewPager.setAdapter(imageadapter);
mascotimages.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content" android:id="@+id/imageView1"
android:src="@drawable/slide2" android:adjustViewBounds="true"
android:scaleType="fitXY"
android:contentDescription="slide2"/>
</LinearLayout>
错误：
> Caused by: java.lang.NullPointerException: Attempt to invoke virtual
> method 'void
> android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)'
> on a null object reference
> at com.example.sabudaniel61.ktdc.MainActivity.onCreate(MainActivity.java:34)
> at android.app.Activity.performCreate(Activity.java:5933)
> at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
> at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
> at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
> at android.app.ActivityThread.access$800(ActivityThread.java:144)
> at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
> at android.os.Handler.dispatchMessage(Handler.java:102)
> at android.os.Looper.loop(Looper.java:135)
> at android.app.ActivityThread.main(ActivityThread.java:5221)
> at java.lang.reflect.Method.invoke(Native Method)
> at java.lang.reflect.Method.invoke(Method.java:372)
> at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
> at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 10-29
> 03:35:27.166 2500-2500/com.example.sabudaniel61.ktdc I/Process﹕
> Sending signal. PID: 2500 SIG: 9