FragmentPagerAdapter troubles and woes: Constructo

Edit: I have reworked some of my code to try and get past the error (but now the app crashes on launch). First, my class now extends FragmentActivity so that I can access the method, getSupportFragmentManager();. Then, within on create, I changed my constructor:

mTabsAdapter = new TabsAdapter(this.getSupportFragmentManager(), this, mViewPager);

From there, in my subclass, I changed the code to reflect this:

public TabsAdapter(FragmentManager fm, Activity activity, ViewPager pager) {
    super(fm);
    mContext = activity;
    mActionBar = activity.getActionBar();
    mViewPager = pager;
    mViewPager.setAdapter(this);
    mViewPager.setOnPageChangeListener(this);
}

As I said, it still crashes, any ideas at this point?

Begin original question: I have the following error: “The constructor FragmentPagerAdapter(FragmentManager) is undefined”*

When I try to execute the following line:

super(activity.getFragmentManager()); this line follows my public TabsAdapter(Activity activity, ViewPager pager) { which is extending FragmentPagerAdapter.

Basically, I am trying to get my 8+ fragment app (8 fragment, one activity which hosts a set of ActionBar tabs linked to each fragment [only one is seen here for brevity's sake "loginTab"]).

Here’s my whole code:

Edit: Pages that I have used for reference: http://developer.android.com/reference/android/support/v4/view/ViewPager.html

http://thepseudocoder.wordpress.com/2011/10/05/android-page-swiping-using-viewpager/

package com.davekelley.polling;

import java.util.ArrayList;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.widget.Button;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;

public class Polling extends Activity {

    private ViewPager mViewPager;
    private TabsAdapter mTabsAdapter;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mViewPager = new ViewPager(this);
        mViewPager.setId(R.id.pager);
        setContentView(mViewPager);
        final ActionBar bar = getActionBar();
        bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        bar.setDisplayShowTitleEnabled(false);
        bar.setDisplayShowHomeEnabled(false);
        mTabsAdapter = new TabsAdapter(this, mViewPager);
        mTabsAdapter.addTab(bar.newTab().setText(“Simple”),
        LoginFragment.class, null);
        mTabsAdapter.addTab(bar.newTab().setText(“Simple”),
        EconFragment.class, null);
        mTabsAdapter.addTab(bar.newTab().setText(“Simple”),
        PoliticsFragment.class, null);

        if (savedInstanceState != null) {
            bar.setSelectedNavigationItem(savedInstanceState.getInt(“tab”, 0));
        }
    }
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt(“tab”, getActionBar().getSelectedNavigationIndex());
    }

    public static class TabsAdapter extends FragmentPagerAdapter
    implements ActionBar.TabListener, ViewPager.OnPageChangeListener {
        private final Context mContext;
        private final ActionBar mActionBar;
        private final ViewPager mViewPager;
        private final ArrayList mTabs = new ArrayList();

        static final class TabInfo {
            private final Class clss;
            private final Bundle args;

            TabInfo(Class _class, Bundle _args) {
                clss = _class;
                args = _args;
            }
        }

        public TabsAdapter(Activity activity, ViewPager pager) {
            super(activity.getFragmentManager());
            mContext = activity;
            mActionBar = activity.getActionBar();
            mViewPager = pager;
            mViewPager.setAdapter(this);
            mViewPager.setOnPageChangeListener(this);
        }

        public void addTab(ActionBar.Tab tab, Class clss, Bundle args) {
            TabInfo info = new TabInfo(clss, args);
            tab.setTag(info);
            tab.setTabListener(this);
            mTabs.add(info);
            mActionBar.addTab(tab);
            notifyDataSetChanged();
        }

        public int getCount() {
            return mTabs.size();
        }

        public Fragment getItem(int position) {
            TabInfo info = mTabs.get(position);
            return Fragment.instantiate(mContext, info.clss.getName(), info.args);
        }

        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        }

        public void onPageSelected(int position) {
            mActionBar.setSelectedNavigationItem(position);
        }

        public void onPageScrollStateChanged(int state) {
        }

        public void onTabSelected(Tab tab, FragmentTransaction ft) {
            Object tag = tab.getTag();
            for (int i=0; i<mTabs.size(); i++) {
                if (mTabs.get(i) == tag) {
                    mViewPager.setCurrentItem(i);
                }
            }
        }

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

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

        public void onTabReselected(Tab tab, android.app.FragmentTransaction ft) {
        }

        public void onTabSelected(Tab tab, android.app.FragmentTransaction ft) {
        }

        public void onTabUnselected(Tab tab, android.app.FragmentTransaction ft) {
        }
    }
}

Any idea what's going on here and what I can do to fix it? My Fragment classes are very simple at the moment, but will eventually load data from an SQL server (at the meantime, they just return a simple inflated layout).

回答1:

I have solved the problem. It was a myriad of solutions that was required.

First, I had to extend FragmentActivity.

public class Polling extends FragmentActivity {

Then, when creating my TabsAdapter, I had to send a call to this (the FragmentActivity itself):

mTabsAdapter = new TabsAdapter(this, mViewPager);

Then, when making the constructor in the TabsAdapter subclass, I had to change the parameter to FragmentActivity rather than Activity:

public TabsAdapter(FragmentActivity activity, ViewPager pager) {
    super(activity.getSupportFragmentManager());

Finally, I had to change my import statement in my Fragment classes to reflect the use of the compatibility library rather than the regular fragment package:

import android.support.v4.app.Fragment;

So, now my ViewPager functions. Of course, clicking on each individual tab icon to switch between tabs no longer works (so I am working on that solution as soon as I send this message). Regardless, now that the ViewPager functions, I can move on to more pressing issues in my app. Thanks to LouisLouis for starting me down the correct path. I eventually used CountingFragment.java to help me see where my errors were, as well as FragmentTabsPager.java from ActionBarSherlock's code to determine the need to specify FragmentActivity.

回答2:

You need to change the lines

public TabsAdapter(Activity activity, ViewPager pager) {
    super(activity.getFragmentManager());

public TabsAdapter(Activity activity, ViewPager pager) {
    super(activity.getSupportFragmentManager());

This will supply the android.support.v4.app.FragmentManager which is needed by the constructor for android.support.v4.app.FragmentPagerAdapter. You are currently supplying android.app.FragmentManager, which is what is returned from activity.getFragmentManager(). That is causing a type mismatch which is the root cause of your error.