android-PagerAdapter

public abstract class

PagerAdapter

extends Object

java.lang.Object   ↳android.support.v4.view.PagerAdapter已知直接子类

FragmentPagerAdapter, FragmentStatePagerAdapter

类概述

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Base class providing the adapter to populate pages inside of a ViewPager. You will most likely want to use a more specific implementation of this, such asFragmentPagerAdapter or FragmentStatePagerAdapter.

When you implement a PagerAdapter, you must override the following methods at minimum:

• instantiateItem(ViewGroup, int)
• destroyItem(ViewGroup, int, Object)
• getCount()
• isViewFromObject(View, Object)

PagerAdapter is more general than the adapters used for AdapterViews. Instead of providing a View recycling mechanism directly ViewPager uses callbacks to indicate the steps taken during an update. A PagerAdapter may implement a form of View recycling if desired or use a more sophisticated method of managing page Views such as Fragment transactions where each page is represented by its own Fragment.

ViewPager associates each page with a key Object instead of working with Views directly. This key is used to track and uniquely identify a given page independent of its position in the adapter. A call to the PagerAdapter method startUpdate(ViewGroup) indicates that the contents of the ViewPager are about to change. One or more calls to instantiateItem(ViewGroup, int) and/or destroyItem(ViewGroup, int, Object) will follow, and the end of an update will be signaled by a call tofinishUpdate(ViewGroup). By the time finishUpdate returns the views associated with the key objects returned by instantiateItem should be added to the parent ViewGroup passed to these methods and the views associated with the keys passed to destroyItem should be removed. The method isViewFromObject(View, Object)identifies whether a page View is associated with a given key object.

A very simple PagerAdapter may choose to use the page Views themselves as key objects, returning them from instantiateItem(ViewGroup, int) after creation and adding them to the parent ViewGroup. A matching destroyItem(ViewGroup, int, Object) implementation would remove the View from the parent ViewGroup andisViewFromObject(View, Object) could be implemented as return view == object;.

PagerAdapter supports data set changes. Data set changes must occur on the main thread and must end with a call to notifyDataSetChanged() similar to AdapterView adapters derived from BaseAdapter. A data set change may involve pages being added, removed, or changing position. The ViewPager will keep the current page active provided the adapter implements the method getItemPosition(Object).

概述

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常量intPOSITION_NONE intPOSITION_UNCHANGED 公有构造函数PagerAdapter()公有方法voiddestroyItem(ViewGroup container, int position, Object object)

Remove a page for the given position.

voiddestroyItem(View container, int position, Object object)

该 method 从 API 级别 开始已经废弃。 Use destroyItem(ViewGroup, int, Object)

voidfinishUpdate(View container)

该 method 从 API 级别 开始已经废弃。 Use finishUpdate(ViewGroup)

voidfinishUpdate(ViewGroup container)

Called when the a change in the shown pages has been completed.

abstract intgetCount()

Return the number of views available.

intgetItemPosition(Object object)

Called when the host view is attempting to determine if an item's position has changed.

CharSequencegetPageTitle(int position)

This method may be called by the ViewPager to obtain a title string to describe the specified page.

floatgetPageWidth(int position)

Returns the proportional width of a given page as a percentage of the ViewPager's measured width from (0.f-1.f]

ObjectinstantiateItem(ViewGroup container, int position)

Create the page for the given position.

ObjectinstantiateItem(View container, int position)

该 method 从 API 级别 开始已经废弃。 Use instantiateItem(ViewGroup, int)

abstract booleanisViewFromObject(View view, Object object)

Determines whether a page View is associated with a specific key object as returned by instantiateItem(ViewGroup, int).

voidnotifyDataSetChanged()

This method should be called by the application if the data backing this adapter has changed and associated views should update.

voidregisterDataSetObserver(DataSetObserver observer)

Register an observer to receive callbacks related to the adapter's data changing.

voidrestoreState(Parcelable state, ClassLoader loader)

Restore any instance state associated with this adapter and its pages that was previously saved by saveState().

ParcelablesaveState()

Save any instance state associated with this adapter and its pages that should be restored if the current UI state needs to be reconstructed.

voidsetPrimaryItem(View container, int position, Object object)

该 method 从 API 级别 开始已经废弃。 Use setPrimaryItem(ViewGroup, int, Object)

voidsetPrimaryItem(ViewGroup container, int position, Object object)

Called to inform the adapter of which item is currently considered to be the "primary", that is the one show to the user as the current page.

voidstartUpdate(View container)

该 method 从 API 级别 开始已经废弃。 Use startUpdate(ViewGroup)

voidstartUpdate(ViewGroup container)

Called when a change in the shown pages is going to start being made.

voidunregisterDataSetObserver(DataSetObserver observer)

Unregister an observer from callbacks related to the adapter's data changing.

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继承方法

 From class java.lang.Object

常量

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public static final int POSITION_NONE

常量值： -2 (0xfffffffe)

public static final int POSITION_UNCHANGED

常量值： -1 (0xffffffff)