v4/app/FragmentTabHost.java

/*
 * Copyright (C) 2012 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 android.support.v4.app;

import java.util.HashMap;

import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.TabHost;
import android.widget.TabWidget;

/**
 * Special TabHost that allows the use of {@link Fragment} objects for
 * its tab content.  When placing this in a view hierarchy, after inflating
 * the hierarchy you must call {@link #setup(Context, FragmentManager, int)}
 * to complete the initialization of the tab host.
 */
public class FragmentTabHost extends TabHost
        implements TabHost.OnTabChangeListener {
    private final HashMap<String, TabInfo> mTabs = new HashMap<String, TabInfo>();
    private FrameLayout mRealTabContent;
    private Context mContext;
    private FragmentManager mFragmentManager;
    private int mContainerId;
    private TabHost.OnTabChangeListener mOnTabChangeListener;
    private TabInfo mLastTab;

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

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

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

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

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

    public FragmentTabHost(Context context) {
        // Note that we call through to the version that takes an AttributeSet,
        // because the simple Context construct can result in a broken object!
        super(context, null);
        initFragmentTabHost(context, null);
    }

    public FragmentTabHost(Context context, AttributeSet attrs) {
        super(context, attrs);
        initFragmentTabHost(context, attrs);
    }

    private void initFragmentTabHost(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs,
                new int[] { android.R.attr.inflatedId }, 0, 0);
        mContainerId = a.getResourceId(0, 0);
        a.recycle();

        super.setOnTabChangedListener(this);

        // If owner hasn't made its own view hierarchy, then as a convenience
        // we will construct a standard one here.
        if (findViewById(android.R.id.tabs) == null) {
            LinearLayout ll = new LinearLayout(context);
            ll.setOrientation(LinearLayout.VERTICAL);
            addView(ll, new FrameLayout.LayoutParams(
                    ViewGroup.LayoutParams.FILL_PARENT,
                    ViewGroup.LayoutParams.FILL_PARENT));

            TabWidget tw = new TabWidget(context);
            tw.setId(android.R.id.tabs);
            tw.setOrientation(TabWidget.HORIZONTAL);
            ll.addView(tw, new LinearLayout.LayoutParams(
                    ViewGroup.LayoutParams.FILL_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT, 0));

            FrameLayout fl = new FrameLayout(context);
            fl.setId(android.R.id.tabcontent);
            ll.addView(fl, new LinearLayout.LayoutParams(0, 0, 0));

            mRealTabContent = fl = new FrameLayout(context);
            mRealTabContent.setId(mContainerId);
            ll.addView(fl, new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.FILL_PARENT, 0, 1));
        }
    }

    /**
     * @deprecated Don't call the original TabHost setup, you must instead
     * call {@link #setup(Context, FragmentManager)} or
     * {@link #setup(Context, FragmentManager, int)}.
     */
    @Override @Deprecated
    public void setup() {
        throw new IllegalStateException(
                "Must call setup() that takes a Context and FragmentManager");
    }

    public void setup(Context context, FragmentManager manager) {
        super.setup();
        mContext = context;
        mFragmentManager = manager;
        ensureContent();
    }

    public void setup(Context context, FragmentManager manager, int containerId) {
        super.setup();
        mContext = context;
        mFragmentManager = manager;
        mContainerId = containerId;
        ensureContent();
        mRealTabContent.setId(containerId);
    }

    private void ensureContent() {
        if (mRealTabContent == null) {
            mRealTabContent = (FrameLayout)findViewById(mContainerId);
            if (mRealTabContent == null) {
                throw new IllegalStateException(
                        "No tab content FrameLayout found for id " + mContainerId);
            }
        }
    }

    @Override
    public void setOnTabChangedListener(OnTabChangeListener l) {
        mOnTabChangeListener = l;
    }

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

        TabInfo info = new TabInfo(tag, clss, args);

        // Check to see if we already have a fragment for this tab, probably
        // from a previously saved state.  If so, deactivate it, because our
        // initial state is that a tab isn't shown.
        info.fragment = mFragmentManager.findFragmentByTag(tag);
        if (info.fragment != null && !info.fragment.isDetached()) {
            FragmentTransaction ft = mFragmentManager.beginTransaction();
            ft.detach(info.fragment);
            ft.commit();
        }

        mTabs.put(tag, info);
        addTab(tabSpec);
    }

    @Override
    public void onTabChanged(String tabId) {
        TabInfo newTab = mTabs.get(tabId);
        if (mLastTab != newTab) {
            FragmentTransaction ft = mFragmentManager.beginTransaction();
            if (mLastTab != null) {
                if (mLastTab.fragment != null) {
                    ft.detach(mLastTab.fragment);
                }
            }
            if (newTab != null) {
                if (newTab.fragment == null) {
                    newTab.fragment = Fragment.instantiate(mContext,
                            newTab.clss.getName(), newTab.args);
                    ft.add(mContainerId, newTab.fragment, newTab.tag);
                } else {
                    ft.attach(newTab.fragment);
                }
            }

            mLastTab = newTab;
            ft.commit();
            mFragmentManager.executePendingTransactions();
        }
        if (mOnTabChangeListener != null) {
            mOnTabChangeListener.onTabChanged(tabId);
        }
    }
}