我正在尝试为ViewPageAdapter创建片段，以便为beetwin 6个不同的图像进行浏览 这是我的代码：
package com.example.newyorkfinal;
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.FragmentStatePagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.widget.ImageView;
import android.widget.Toast;
public class CatalogActivity extends FragmentActivity {
/**
* The number of pages (wizard steps) to show in this demo.
*/
private static final int NUM_PAGES = 6;
/**
* The pager widget, which handles animation and allows swiping horizontally to access previous
* and next wizard steps.
*/
private ViewPager mPager;
/**
* The pager adapter, which provides the pages to the view pager widget.
*/
private PagerAdapter mPagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.catalog_pager);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
}
@Override
public void onBackPressed() {
if (mPager.getCurrentItem() == 0) {
// If the user is currently looking at the first step, allow the system to handle the
// Back button. This calls finish() on this activity and pops the back stack.
super.onBackPressed();
} else {
// Otherwise, select the previous step.
mPager.setCurrentItem(mPager.getCurrentItem() - 1);
}
}
/**
* A simple pager adapter that represents 5 ScreenSlidePageFragment objects, in
* sequence.
*/
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
ImageView catalogImage;
catalogImage = (ImageView) findViewById(R.id.catalogImageSlide);
switch (position){
case 0:
{
Toast.makeText(getBaseContext(), String.valueOf(position), 200).show();
catalogImage.setImageResource(R.drawable.page_1_12_tel);
break;
}
case 1:
{
Toast.makeText(getBaseContext(), String.valueOf(position++), 200).show();
catalogImage.setImageResource(R.drawable.page_2_11);
break;
}
case 2:
{
Toast.makeText(getBaseContext(), String.valueOf(position++), 200).show();
catalogImage.setImageResource(R.drawable.page_3_10);
break;
}
case 3:
{
Toast.makeText(getBaseContext(), String.valueOf(position++), 200).show();
catalogImage.setImageResource(R.drawable.page_4_9);
break;
}
case 4:
{
Toast.makeText(getBaseContext(), String.valueOf(position++), 200).show();
catalogImage.setImageResource(R.drawable.page_5_8);
break;
}
case 5:
{
Toast.makeText(getBaseContext(), String.valueOf(position++), 200).show();
catalogImage.setImageResource(R.drawable.page_6_7);
break;
}}
return new CatalogFragment() ;
}
@Override
public int getCount() {
return NUM_PAGES;
}
}
}
我的交换机案例中有一个空指针错误，我想我在我的代码中错误的prace中定义了catalogImage，但我找不到答案
09-13 17:31:30.170: E/AndroidRuntime(17862): FATAL EXCEPTION: main
09-13 17:31:30.170: E/AndroidRuntime(17862): java.lang.NullPointerException
09-13 17:31:30.170: E/AndroidRuntime(17862): at com.example.newyorkfinal.CatalogActivity$ScreenSlidePagerAdapter.getItem(CatalogActivity.java:81)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:105)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:829)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.support.v4.view.ViewPager.populate(ViewPager.java:979)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.support.v4.view.ViewPager.populate(ViewPager.java:911)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1432)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.View.measure(View.java:15855)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.View.measure(View.java:15855)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.View.measure(View.java:15855)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
09-13 17:31:30.170: E/AndroidRuntime(17862): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:302)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.View.measure(View.java:15855)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
09-13 17:31:30.170: E/AndroidRuntime(17862): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2472)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.View.measure(View.java:15855)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1905)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1284)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.Choreographer.doFrame(Choreographer.java:532)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.os.Handler.handleCallback(Handler.java:730)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.os.Handler.dispatchMessage(Handler.java:92)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.os.Looper.loop(Looper.java:137)
09-13 17:31:30.170: E/AndroidRuntime(17862): at android.app.ActivityThread.main(ActivityThread.java:5287)
09-13 17:31:30.170: E/AndroidRuntime(17862): at java.lang.reflect.Method.invokeNative(Native Method)
09-13 17:31:30.170: E/AndroidRuntime(17862): at java.lang.reflect.Method.invoke(Method.java:525)
09-13 17:31:30.170: E/AndroidRuntime(17862): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
09-13 17:31:30.170: E/AndroidRuntime(17862): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
09-13 17:31:30.170: E/AndroidRuntime(17862): at dalvik.system.NativeStart.main(Native Method)
catalog_slide.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@color/BurlyWood" >
<ScrollView
android:id="@+id/contentCatalog"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/catalogImageSlide"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:lineSpacingMultiplier="1.2"
android:padding="16dp"
android:src="@drawable/page_1_12_tel" />
</ScrollView>
</LinearLayout>
catalog_pager.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
CatalogFragment.java
package com.example.newyorkfinal;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
public class CatalogFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(
R.layout.catalog_slide, container, false);
return rootView;
}
}
答案 0 :(得分：2)
您应该向CatalogFragment添加一个参数，该参数接收需要加载的图像资源。并在CatalogFragment中加载imageview。
目前，您正在更改一些随机的imageview，然后加载CatalogFragment，它不知道ImageView，也不知道它要加载的资源。