使用FragmentPagerAdapter向左侧添加选项卡

Question

这将是关于标签的最后一个问题,我保证:)(也许)所以从以前的问题和尝试和错误我有FragmentPagerAdapter调用PagerAdapter创建一些选项卡,并使我能够动态创建新选项卡.问题是新选项卡将始终插入到现有选项卡的右侧:

(图片:

我尝试了以下方法:

1. 添加一个静态条目"null",在创建初始选项卡集时会跳过该条目.然后在创建"Temp Tab"时,我可以将该条目覆盖到我想要的任何片段.给了我一些奇怪的IllegalSTateException ...

2. 我认为这将是最好的,实际上真的很想工作:而不是添加片段:

   private final List<Fragment> mFragments = new ArrayList<Fragment>();
   
   public void addFragment(Fragment fragment) {
       mFragments.add(fragment);
       notifyDataSetChanged();
   }
   

使用

mFragments.add(0, fragment);

但它给出了一条带有消息的IllegalStateException:

Can't change tag of fragment ChatFragment

当我尝试添加临时片段时.现在,有两个问题:

1. 有没有办法绕过该片段选项卡,我可以暂时取走所有片段标签并重建它们全部或其他东西吗？要么

2. 有没有更好,更优雅的方式来做到这一点？或者我应该重新设计我的UI,以便可以使用右侧的选项卡？:P

编辑:这里有一些代码:(我从不想把死亡之墙发给人们,因为它可能吓跑他们:o)

FragmentPagerAdapter:

public class PagerAdapter extends FragmentPagerAdapter {

  private Context mContext;

  public PagerAdapter(FragmentManager fm, Context context) {
    super(fm);
    mContext = context;
  }

  private final List<Fragment> mFragments = new ArrayList<Fragment>();
  public void addFragment(Fragment fragment) {
    mFragments.add(fragment);
    notifyDataSetChanged();
  }

  @Override
  public Fragment getItem(int position) {
    return mFragments.get(position);
  }

  @Override
  public int getCount() {
    return mFragments.size();
  }

  @Override
  public String getPageTitle(int position) {

    switch (position) {
    case 0:
      return mContext.getString(R.string.tab_title_chats);
    case 1:
      return mContext.getString(R.string.tab_title_contacts);
    case 2:
      return mContext.getString(R.string.tab_title_create);
    }
    return "WOOPS";

  }

}

MainActivty:

public class LaunchActivity extends FragmentActivity implements ActionBar.TabListener {

  private PagerAdapter mAdapter;
  private FragmentManager man;
  private ViewPager mViewPager;
  private ActionBar actionBar;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_container);

    // Set up the action bar.
    actionBar = getActionBar();
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // Layout stuff
    mViewPager = (ViewPager) findViewById(R.id.masterViewPager);

    // Creating the mAdapter and initializing the mViewPager
    man = getSupportFragmentManager();
    mAdapter = new PagerAdapter(man, getApplicationContext());
    mViewPager.setAdapter(mAdapter);

    for (int i = 0; i < 2; i++) {
      makeFragments(i);
      System.out.println("Baking tasty fragment instances...nom nom nom");
    }

    // Called when tab changes
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
      @Override
      public void onPageSelected(int position) {
        actionBar.setSelectedNavigationItem(position);
      }
    });

    for (int i = 0; i < mAdapter.getCount(); i++) {
      System.out.println("Working...");

      actionBar.addTab(actionBar.newTab().setText(mAdapter.getPageTitle(i)).setTabListener(this));
    }

  }

  // Add fragment instances to ArrayList depending on their future position on the ActionBar
  private void makeFragments(int i) {

    if (i == 0) {
      mAdapter.addFragment(ChatFragment.getInstance());

    }
    else if (i == 1) {
      mAdapter.addFragment(ContactFragment.getInstance());
    }
  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.layout_container, menu);
    return true;

  }

  @Override
  public void onTabSelected(Tab tab, FragmentTransaction ft) {
    mViewPager.setCurrentItem(tab.getPosition());

  }

  public void addTab(int i) {
    mAdapter.addFragment(ComposeFragment.getInstance());
    System.out.println("Created new Fragment, now adding it as a tab");
    actionBar.addTab(actionBar.newTab().setText(mAdapter.getPageTitle(i)).setTabListener(this));
    System.out.println("Added it as a tab. Hurray");

  }

  /** IGNORE BELOW **/

  @Override
  public void onTabUnselected(Tab tab, FragmentTransaction ft) {
  }

  @Override
  public void onTabReselected(Tab tab, FragmentTransaction ft) {
  }



}

堆栈跟踪:

    03-18 18:32:29.274: E/AndroidRuntime(26435): FATAL EXCEPTION: main
    03-18 18:32:29.274: E/AndroidRuntime(26435): java.lang.IllegalStateException: Can't change tag of fragment ChatFragment{41492428 #1 id=0x7f070004 android:switcher:2131165188:1}: was android:switcher:2131165188:1 now android:switcher:2131165188:2
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:398)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:389)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:801)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager.populate(ViewPager.java:992)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:523)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:495)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager.dataSetChanged(ViewPager.java:875)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.ViewPager$PagerObserver.onChanged(ViewPager.java:2690)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:37)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.support.v4.view.PagerAdapter.notifyDataSetChanged(PagerAdapter.java:276)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at com.package.subpackage.components.PagerAdapter.addFragment(PagerAdapter.java:25)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at com.package.subpackage.someapp.core.LaunchActivity.addTab(LaunchActivity.java:116)
    03-18 18:32:29.274: E/AndroidRuntime(26435):    at com.

com.package.subpackage.fragments.full.ChatFragment$1.onClick(ChatFragment.java:51)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.view.View.performClick(View.java:4204)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.view.View$PerformClick.run(View.java:17355)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.os.Handler.handleCallback(Handler.java:725)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.os.Looper.loop(Looper.java:137)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at android.app.ActivityThread.main(ActivityThread.java:5041)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at java.lang.reflect.Method.invokeNative(Native Method)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at java.lang.reflect.Method.invoke(Method.java:511)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-18 18:32:29.274: E/AndroidRuntime(26435):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

我可以通过重写 OnPageChangeListener 的 onPageSelected 方法来实现这一点。假设您有三个页面，顺序为 A<->B<->C。目标是如果我们从 A 向右滚动则到达 C，类似地如果我们从 C 向左滚动则到达 A。

为此，请将您的页面定义为 5 个页面 (3+2)，并按如下方式组织页面：

C<->A<->B<->C<->A

现在在 onPageSelected 方法中，检查如果位置为 0，则将其更改为 3 (getCount()-2)，如果位置为 4 (getCount()-1)，则将其更改为 1。确保这样可以帮助您。

谢谢