我有一个ViewPager有三个项目.我试图设置ViewPager查看最右边的页面(这将是第二个元素).这是返回IndexOutOfBounds异常,虽然我知道索引应该在边界.这是确切的堆栈：

02-22 12:22:50.256: E/AndroidRuntime(384): FATAL EXCEPTION: main

02-22 12:22:50.256: E/AndroidRuntime(384): java.lang.IndexOutOfBoundsException: index=1 count=0

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.addInArray(ViewGroup.java:2050)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.addViewInner(ViewGroup.java:1994)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.addViewInLayout(ViewGroup.java:1958)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.addViewInLayout(ViewGroup.java:1939)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.support.v4.view.ViewPager.addView(ViewPager.java:917)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.addView(ViewGroup.java:1828)

02-22 12:22:50.256: E/AndroidRuntime(384): at us.tagverse.pagertest.MasterActivity$PAdapter.instantiateItem(MasterActivity.java:518)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.support.v4.view.PagerAdapter.instantiateItem(PagerAdapter.java:110)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:649)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.support.v4.view.ViewPager.populate(ViewPager.java:783)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.View.measure(View.java:8313)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.View.measure(View.java:8313)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.View.measure(View.java:8313)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.View.measure(View.java:8313)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewRoot.performTraversals(ViewRoot.java:839)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.os.Handler.dispatchMessage(Handler.java:99)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.os.Looper.loop(Looper.java:123)

02-22 12:22:50.256: E/AndroidRuntime(384): at android.app.ActivityThread.main(ActivityThread.java:3683)

02-22 12:22:50.256: E/AndroidRuntime(384): at java.lang.reflect.Method.invokeNative(Native Method)

02-22 12:22:50.256: E/AndroidRuntime(384): at java.lang.reflect.Method.invoke(Method.java:507)

02-22 12:22:50.256: E/AndroidRuntime(384): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)

02-22 12:22:50.256: E/AndroidRuntime(384): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)

02-22 12:22:50.256: E/AndroidRuntime(384): at dalvik.system.NativeStart.main(Native Method)

注意原因是java.lang.IndexOutOfBoundsException：index = 1 count = 0.这意味着页/项的计数是0,我要求的索引是1.这两个都不是真的.这是我打电话给我的ViewPager和请求给定的页面：

ViewPager pager = (ViewPager) findViewById(R.id.ma_viewcontainer);

PAdapter adapter = new PAdapter();

pager.setAdapter(adapter);

pager.setCurrentItem(2);

请注意,此调用不会发生任何错误,并将当前项目正确设置为中间项目(索引1)：

ViewPager pager = (ViewPager) findViewById(R.id.ma_viewcontainer);

PAdapter adapter = new PAdapter();

pager.setAdapter(adapter);

pager.setCurrentItem(1);

我在视图寻呼机中有3个项目的数量.这是我的完整的PAdapter类,它扩展了PagerAdapter类：

private class PAdapter extends PagerAdapter implements TitleProvider {

private int COUNT = 3;

private static final int SETTINGS_ACTIVITY = 0;

private static final int MAIN_ACTIVITY = 1;

private static final int FRIEND_LIST_ACTIVITY = 2;

@Override

public int getCount() {

return COUNT;

}

@Override

public Object instantiateItem(View collection, int position) {

LinearLayout layout = new LinearLayout(getApplicationContext());

LayoutInflater inflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

switch(position) {

case MAIN_ACTIVITY :

layout = (LinearLayout) inflater.inflate(R.layout.main, null, false);

initMainLayout(layout);

break;

case SETTINGS_ACTIVITY :

layout = (LinearLayout) inflater.inflate(R.layout.settings, null, false);

initSettingsLayout(layout);

break;

case FRIEND_LIST_ACTIVITY :

layout = (LinearLayout) inflater.inflate(R.layout.friend_list, null, false);

initFriendListLayout(layout);

break;

}

((ViewPager)collection).addView(layout, position);

return layout;

}

@Override

public void destroyItem(View collection, int position, Object view) {

((ViewPager)collection).removeView((LinearLayout)view);

}

@Override

public boolean isViewFromObject(View v, Object o) {

return v == (LinearLayout)o;

}

@Override

public void finishUpdate(View arg0) {

//no need

}

@Override

public void restoreState(Parcelable arg0, ClassLoader arg1) {

//no need

}

@Override

public Parcelable saveState() {

return null;

}

@Override

public void startUpdate(View arg0) {

//no need

}

@Override

public String getTitle(int position) {

Resources res = getApplicationContext().getResources();

switch(position) {

case MAIN_ACTIVITY :

return res.getString(R.string.app_name);

case SETTINGS_ACTIVITY :

return res.getString(R.string.settings);

case FRIEND_LIST_ACTIVITY :

return res.getString(R.string.friend_list);

default :

return null;

}

}

}

行((ViewPager)集合).addView(layout,position);导致崩溃.

你可以看到,三个项目.使用参数为0或1的setCurrentItem()可以正常工作,但是2会导致这个奇怪的错误.我已经用尽了想法来解决它…不幸的是,ViewPager驻留在Android的一些未知的水域似乎.如果有人对如何解决这个问题有一些了解,那将是非常感激的.谢谢！

编辑：根据Shereef的建议,我尝试通过collection.getChildCount()记录子计数,得到以下结果：

02-22 15:20:42.274: E/children count(645): count: 0

02-22 15:20:42.454: E/children count(645): count: 1

02-22 15:20:42.594: E/children count(645): count: 2

这很有趣.这告诉我的是,它创建一个空的PagerAdapter,并一次添加一个.对于三个可见视图(中心,左和右),instantiateItem()被调用3次.所以我在instantiateItem()方法中添加了这个代码块：

if(((ViewPager)collection).getChildCount() == 2) {

((ViewPager)collection).setCurrentItem(2);

}

所以只有计数确定为2,它会将页面设置为2(这是一个很难解决的问题,但值得一试).我得到了一个类似的错误堆栈,首先指出：((ViewPager)集合).setCurrentItem(2);然后((ViewPager)集合).addView(layout,position);.

希望这有助于提供一些洞察力.