com.github.mobile.ui.fragments.TabsAdapter.java Source code

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Here is the source code for com.github.mobile.ui.fragments.TabsAdapter.java

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/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.github.mobile.ui.fragments;

import java.util.ArrayList;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TabHost;
import android.widget.TabWidget;

/**
 * This is a helper class that implements the management of tabs and all
 * details of connecting a ViewPager with associated TabHost. It relies on a
 * trick. Normally a tab host has a simple API for supplying a View or
 * Intent that each tab will show. This is not sufficient for switching
 * between pages. So instead we make the content part of the tab host
 * 0dp high (it is not shown) and the TabsAdapter supplies its own dummy
 * view to show as the tab content. It listens to changes in tabs, and takes
 * care of switch to the correct paged in the ViewPager whenever the selected
 * tab changes.
 */
public class TabsAdapter extends FragmentPagerAdapter
        implements TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener {
    private final Context mContext;
    private final TabHost mTabHost;
    private final ViewPager mViewPager;
    private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();

    static final class TabInfo {
        private final String tag;
        private final Class<?> clss;
        private final Bundle args;

        TabInfo(final String _tag, final Class<?> _class, final Bundle _args) {
            tag = _tag;
            clss = _class;
            args = _args;
        }
    }

    static class DummyTabFactory implements TabHost.TabContentFactory {
        private final Context mContext;

        public DummyTabFactory(final Context context) {
            mContext = context;
        }

        @Override
        public View createTabContent(final String tag) {
            final View v = new View(mContext);
            v.setMinimumWidth(0);
            v.setMinimumHeight(0);
            return v;
        }
    }

    public TabsAdapter(final FragmentActivity activity, final TabHost tabHost, final ViewPager pager) {
        super(activity.getSupportFragmentManager());
        mContext = activity;
        mTabHost = tabHost;
        mViewPager = pager;
        mTabHost.setOnTabChangedListener(this);
        mViewPager.setAdapter(this);
        mViewPager.setOnPageChangeListener(this);
    }

    public void addTab(final TabHost.TabSpec tabSpec, final Class<?> clss, final Bundle args) {
        tabSpec.setContent(new DummyTabFactory(mContext));
        final String tag = tabSpec.getTag();

        final TabInfo info = new TabInfo(tag, clss, args);
        mTabs.add(info);
        mTabHost.addTab(tabSpec);
        notifyDataSetChanged();
    }

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

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

    @Override
    public void onPageScrollStateChanged(final int state) {
    }

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

    @Override
    public void onPageSelected(final int position) {
        // unfortunately when TabHost changes the current tab, it kindly
        // also takes care of putting focus on it when not in touch mode.
        // The jerk.
        // This hack tries to prevent this from pulling focus out of our
        // ViewPager.
        final TabWidget widget = mTabHost.getTabWidget();
        final int oldFocusability = widget.getDescendantFocusability();
        widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);
        mTabHost.setCurrentTab(position);
        widget.setDescendantFocusability(oldFocusability);
    }

    @Override
    public void onTabChanged(final String tabId) {
        final int position = mTabHost.getCurrentTab();
        mViewPager.setCurrentItem(position);
    }
}