我试图使用片段与一个ViewPager使用FragmentPagerAdapter。
我想要实现的是替换一个片段,位于ViewPager的第一页,与另一个。
寻呼机由两个页面组成。第一个是FirstPagerFragment,第二个是SecondPagerFragment。点击第一页的一个按钮。我想用NextFragment替换FirstPagerFragment。
下面是我的代码。
public class FragmentPagerActivity extends FragmentActivity {
static final int NUM_ITEMS = 2;
MyAdapter mAdapter;
ViewPager mPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_pager);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
}
/**
* Pager Adapter
*/
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public int getCount() {
return NUM_ITEMS;
}
@Override
public Fragment getItem(int position) {
if(position == 0) {
return FirstPageFragment.newInstance();
} else {
return SecondPageFragment.newInstance();
}
}
}
/**
* Second Page FRAGMENT
*/
public static class SecondPageFragment extends Fragment {
public static SecondPageFragment newInstance() {
SecondPageFragment f = new SecondPageFragment();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//Log.d("DEBUG", "onCreateView");
return inflater.inflate(R.layout.second, container, false);
}
}
/**
* FIRST PAGE FRAGMENT
*/
public static class FirstPageFragment extends Fragment {
Button button;
public static FirstPageFragment newInstance() {
FirstPageFragment f = new FirstPageFragment();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//Log.d("DEBUG", "onCreateView");
View root = inflater.inflate(R.layout.first, container, false);
button = (Button) root.findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
FragmentTransaction trans = getFragmentManager().beginTransaction();
trans.replace(R.id.first_fragment_root_id, NextFragment.newInstance());
trans.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
trans.addToBackStack(null);
trans.commit();
}
});
return root;
}
/**
* Next Page FRAGMENT in the First Page
*/
public static class NextFragment extends Fragment {
public static NextFragment newInstance() {
NextFragment f = new NextFragment();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//Log.d("DEBUG", "onCreateView");
return inflater.inflate(R.layout.next, container, false);
}
}
}
...这里是XML文件
fragment_pager.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:padding="4dip"
android:gravity="center_horizontal"
android:layout_width="match_parent" android:layout_height="match_parent">
<android.support.v4.view.ViewPager
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1">
</android.support.v4.view.ViewPager>
</LinearLayout>
first.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/first_fragment_root_id"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button android:id="@+id/button"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="to next"/>
</LinearLayout>
现在的问题是……我应该使用哪个ID
trans.replace(R.id.first_fragment_root_id, NextFragment.newInstance());
?
如果我用r。id。first_fragment_root_id,替换工作,但Hierarchy Viewer显示一个奇怪的行为,如下所示。
一开始的情况是
更换后的情况是
正如你所看到的,有一些错误,我希望在替换片段后找到与第一张图片中相同的状态。
我已经实现了一个解决方案:
标签内的动态片段替换
维护每个选项卡的历史记录
处理方向变化
实现这一目标的技巧如下:
使用notifyDataSetChanged()方法来应用片段替换
片段管理器只用于后台,而不用于片段替换
使用纪念品模式(堆栈)维护历史记录
适配器代码如下:
public class TabsAdapter extends FragmentStatePagerAdapter implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
/** The sherlock fragment activity. */
private final SherlockFragmentActivity mActivity;
/** The action bar. */
private final ActionBar mActionBar;
/** The pager. */
private final ViewPager mPager;
/** The tabs. */
private List<TabInfo> mTabs = new LinkedList<TabInfo>();
/** The total number of tabs. */
private int TOTAL_TABS;
private Map<Integer, Stack<TabInfo>> history = new HashMap<Integer, Stack<TabInfo>>();
/**
* Creates a new instance.
*
* @param activity the activity
* @param pager the pager
*/
public TabsAdapter(SherlockFragmentActivity activity, ViewPager pager) {
super(activity.getSupportFragmentManager());
activity.getSupportFragmentManager();
this.mActivity = activity;
this.mActionBar = activity.getSupportActionBar();
this.mPager = pager;
mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
}
/**
* Adds the tab.
*
* @param image the image
* @param fragmentClass the class
* @param args the arguments
*/
public void addTab(final Drawable image, final Class fragmentClass, final Bundle args) {
final TabInfo tabInfo = new TabInfo(fragmentClass, args);
final ActionBar.Tab tab = mActionBar.newTab();
tab.setTabListener(this);
tab.setTag(tabInfo);
tab.setIcon(image);
mTabs.add(tabInfo);
mActionBar.addTab(tab);
notifyDataSetChanged();
}
@Override
public Fragment getItem(final int position) {
final TabInfo tabInfo = mTabs.get(position);
return Fragment.instantiate(mActivity, tabInfo.fragmentClass.getName(), tabInfo.args);
}
@Override
public int getItemPosition(final Object object) {
/* Get the current position. */
int position = mActionBar.getSelectedTab().getPosition();
/* The default value. */
int pos = POSITION_NONE;
if (history.get(position).isEmpty()) {
return POSITION_NONE;
}
/* Checks if the object exists in current history. */
for (Stack<TabInfo> stack : history.values()) {
TabInfo c = stack.peek();
if (c.fragmentClass.getName().equals(object.getClass().getName())) {
pos = POSITION_UNCHANGED;
break;
}
}
return pos;
}
@Override
public int getCount() {
return mTabs.size();
}
@Override
public void onPageScrollStateChanged(int arg0) {
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
@Override
public void onPageSelected(int position) {
mActionBar.setSelectedNavigationItem(position);
}
@Override
public void onTabSelected(final ActionBar.Tab tab, final FragmentTransaction ft) {
TabInfo tabInfo = (TabInfo) tab.getTag();
for (int i = 0; i < mTabs.size(); i++) {
if (mTabs.get(i).equals(tabInfo)) {
mPager.setCurrentItem(i);
}
}
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
public void replace(final int position, final Class fragmentClass, final Bundle args) {
/* Save the fragment to the history. */
mActivity.getSupportFragmentManager().beginTransaction().addToBackStack(null).commit();
/* Update the tabs. */
updateTabs(new TabInfo(fragmentClass, args), position);
/* Updates the history. */
history.get(position).push(new TabInfo(mTabs.get(position).fragmentClass, mTabs.get(position).args));
notifyDataSetChanged();
}
/**
* Updates the tabs.
*
* @param tabInfo
* the new tab info
* @param position
* the position
*/
private void updateTabs(final TabInfo tabInfo, final int position) {
mTabs.remove(position);
mTabs.add(position, tabInfo);
mActionBar.getTabAt(position).setTag(tabInfo);
}
/**
* Creates the history using the current state.
*/
public void createHistory() {
int position = 0;
TOTAL_TABS = mTabs.size();
for (TabInfo mTab : mTabs) {
if (history.get(position) == null) {
history.put(position, new Stack<TabInfo>());
}
history.get(position).push(new TabInfo(mTab.fragmentClass, mTab.args));
position++;
}
}
/**
* Called on back
*/
public void back() {
int position = mActionBar.getSelectedTab().getPosition();
if (!historyIsEmpty(position)) {
/* In case there is not any other item in the history, then finalize the activity. */
if (isLastItemInHistory(position)) {
mActivity.finish();
}
final TabInfo currentTabInfo = getPrevious(position);
mTabs.clear();
for (int i = 0; i < TOTAL_TABS; i++) {
if (i == position) {
mTabs.add(new TabInfo(currentTabInfo.fragmentClass, currentTabInfo.args));
} else {
TabInfo otherTabInfo = history.get(i).peek();
mTabs.add(new TabInfo(otherTabInfo.fragmentClass, otherTabInfo.args));
}
}
}
mActionBar.selectTab(mActionBar.getTabAt(position));
notifyDataSetChanged();
}
/**
* Returns if the history is empty.
*
* @param position
* the position
* @return the flag if empty
*/
private boolean historyIsEmpty(final int position) {
return history == null || history.isEmpty() || history.get(position).isEmpty();
}
private boolean isLastItemInHistory(final int position) {
return history.get(position).size() == 1;
}
/**
* Returns the previous state by the position provided.
*
* @param position
* the position
* @return the tab info
*/
private TabInfo getPrevious(final int position) {
TabInfo currentTabInfo = history.get(position).pop();
if (!history.get(position).isEmpty()) {
currentTabInfo = history.get(position).peek();
}
return currentTabInfo;
}
/** The tab info class */
private static class TabInfo {
/** The fragment class. */
public Class fragmentClass;
/** The args.*/
public Bundle args;
/**
* Creates a new instance.
*
* @param fragmentClass
* the fragment class
* @param args
* the args
*/
public TabInfo(Class fragmentClass, Bundle args) {
this.fragmentClass = fragmentClass;
this.args = args;
}
@Override
public boolean equals(final Object o) {
return this.fragmentClass.getName().equals(o.getClass().getName());
}
@Override
public int hashCode() {
return fragmentClass.getName() != null ? fragmentClass.getName().hashCode() : 0;
}
@Override
public String toString() {
return "TabInfo{" +
"fragmentClass=" + fragmentClass +
'}';
}
}
第一次添加所有选项卡时,我们需要调用createHistory()方法来创建初始历史记录
public void createHistory() {
int position = 0;
TOTAL_TABS = mTabs.size();
for (TabInfo mTab : mTabs) {
if (history.get(position) == null) {
history.put(position, new Stack<TabInfo>());
}
history.get(position).push(new TabInfo(mTab.fragmentClass, mTab.args));
position++;
}
}
每次你想要替换一个片段到一个特定的标签,你调用:
replace(final int position, final Class fragmentClass, final Bundle args)
/* Save the fragment to the history. */
mActivity.getSupportFragmentManager().beginTransaction().addToBackStack(null).commit();
/* Update the tabs. */
updateTabs(new TabInfo(fragmentClass, args), position);
/* Updates the history. */
history.get(position).push(new TabInfo(mTabs.get(position).fragmentClass, mTabs.get(position).args));
notifyDataSetChanged();
在back被按下时,你需要调用back()方法:
public void back() {
int position = mActionBar.getSelectedTab().getPosition();
if (!historyIsEmpty(position)) {
/* In case there is not any other item in the history, then finalize the activity. */
if (isLastItemInHistory(position)) {
mActivity.finish();
}
final TabInfo currentTabInfo = getPrevious(position);
mTabs.clear();
for (int i = 0; i < TOTAL_TABS; i++) {
if (i == position) {
mTabs.add(new TabInfo(currentTabInfo.fragmentClass, currentTabInfo.args));
} else {
TabInfo otherTabInfo = history.get(i).peek();
mTabs.add(new TabInfo(otherTabInfo.fragmentClass, otherTabInfo.args));
}
}
}
mActionBar.selectTab(mActionBar.getTabAt(position));
notifyDataSetChanged();
}
解决方案与夏洛克动作栏和滑动手势。
我找到了一个简单的解决方案,即使你想在中间添加新的片段或替换当前片段,它也能很好地工作。在我的解决方案中,您应该重写getItemId(),它应该为每个片段返回唯一的id。不是默认的位置。
就是这样:
public class DynamicPagerAdapter extends FragmentPagerAdapter {
private ArrayList<Page> mPages = new ArrayList<Page>();
private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
public DynamicPagerAdapter(FragmentManager fm) {
super(fm);
}
public void replacePage(int position, Page page) {
mPages.set(position, page);
notifyDataSetChanged();
}
public void setPages(ArrayList<Page> pages) {
mPages = pages;
notifyDataSetChanged();
}
@Override
public Fragment getItem(int position) {
if (mPages.get(position).mPageType == PageType.FIRST) {
return FirstFragment.newInstance(mPages.get(position));
} else {
return SecondFragment.newInstance(mPages.get(position));
}
}
@Override
public int getCount() {
return mPages.size();
}
@Override
public long getItemId(int position) {
// return unique id
return mPages.get(position).getId();
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
Fragment fragment = (Fragment) super.instantiateItem(container, position);
while (mFragments.size() <= position) {
mFragments.add(null);
}
mFragments.set(position, fragment);
return fragment;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
mFragments.set(position, null);
}
@Override
public int getItemPosition(Object object) {
PagerFragment pagerFragment = (PagerFragment) object;
Page page = pagerFragment.getPage();
int position = mFragments.indexOf(pagerFragment);
if (page.equals(mPages.get(position))) {
return POSITION_UNCHANGED;
} else {
return POSITION_NONE;
}
}
}
注意:在这个例子中,FirstFragment和SecondFragment扩展了抽象类PageFragment,它有方法getPage()。
这就是我实现目标的方法。
首先,在viewPager标签中添加Root_fragment,你想在其中实现按钮点击片段事件。例子;
@Override
public Fragment getItem(int position) {
if(position==0)
return RootTabFragment.newInstance();
else
return SecondPagerFragment.newInstance();
}
首先,RootTabFragment应该包含FragmentLayout来改变片段。
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/root_frame"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
然后,在RootTabFragment onCreateView内部,实现FirstPagerFragment的fragmentChange
getChildFragmentManager().beginTransaction().replace(R.id.root_frame, FirstPagerFragment.newInstance()).commit();
在那之后,实现onClick事件为您的按钮在FirstPagerFragment和使片段改变像那样再次。
getChildFragmentManager().beginTransaction().replace(R.id.root_frame, NextFragment.newInstance()).commit();
希望这对你们有帮助。