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Android example source code file (TabHost.java)

This example Android source code file (TabHost.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, app, content, contentstrategy, factorycontentstrategy, framelayout, indicatorstrategy, layoutinflater, os, override, string, tabhost, tabspec, tabwidget, textview, ui, util, view, viewidcontentstrategy, viewindicatorstrategy

The TabHost.java Android example source code

/*
 * Copyright (C) 2006 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.widget;

import com.android.internal.R;

import android.app.LocalActivityManager;
import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.SoundEffectConstants;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.view.Window;

import java.util.ArrayList;
import java.util.List;

/**
 * Container for a tabbed window view. This object holds two children: a set of tab labels that the
 * user clicks to select a specific tab, and a FrameLayout object that displays the contents of that
 * page. The individual elements are typically controlled using this container object, rather than
 * setting values on the child elements themselves.
 */
public class TabHost extends FrameLayout implements ViewTreeObserver.OnTouchModeChangeListener {

    private TabWidget mTabWidget;
    private FrameLayout mTabContent;
    private List<TabSpec> mTabSpecs = new ArrayList(2);
    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected int mCurrentTab = -1;
    private View mCurrentView = null;
    /**
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected LocalActivityManager mLocalActivityManager = null;
    private OnTabChangeListener mOnTabChangeListener;
    private OnKeyListener mTabKeyListener;

    public TabHost(Context context) {
        super(context);
        initTabHost();
    }

    public TabHost(Context context, AttributeSet attrs) {
        super(context, attrs);
        initTabHost();
    }

    private void initTabHost() {
        setFocusableInTouchMode(true);
        setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);

        mCurrentTab = -1;
        mCurrentView = null;
    }

    /**
     * Get a new {@link TabSpec} associated with this tab host.
     * @param tag required tag of tab.
     */
    public TabSpec newTabSpec(String tag) {
        return new TabSpec(tag);
    }



    /**
      * <p>Call setup() before adding tabs if loading TabHost using findViewById().
      * <i>However: You do not need to call setup() after getTabHost()
      * in {@link android.app.TabActivity TabActivity}.
      * Example:</p>
<pre>mTabHost = (TabHost)findViewById(R.id.tabhost);
mTabHost.setup();
mTabHost.addTab(TAB_TAG_1, "Hello, world!", "Tab 1");
      */
    public void setup() {
        mTabWidget = (TabWidget) findViewById(com.android.internal.R.id.tabs);
        if (mTabWidget == null) {
            throw new RuntimeException(
                    "Your TabHost must have a TabWidget whose id attribute is 'android.R.id.tabs'");
        }

        // KeyListener to attach to all tabs. Detects non-navigation keys
        // and relays them to the tab content.
        mTabKeyListener = new OnKeyListener() {
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                switch (keyCode) {
                    case KeyEvent.KEYCODE_DPAD_CENTER:
                    case KeyEvent.KEYCODE_DPAD_LEFT:
                    case KeyEvent.KEYCODE_DPAD_RIGHT:
                    case KeyEvent.KEYCODE_DPAD_UP:
                    case KeyEvent.KEYCODE_DPAD_DOWN:
                    case KeyEvent.KEYCODE_ENTER:
                        return false;

                }
                mTabContent.requestFocus(View.FOCUS_FORWARD);
                return mTabContent.dispatchKeyEvent(event);
            }

        };

        mTabWidget.setTabSelectionListener(new TabWidget.OnTabSelectionChanged() {
            public void onTabSelectionChanged(int tabIndex, boolean clicked) {
                setCurrentTab(tabIndex);
                if (clicked) {
                    mTabContent.requestFocus(View.FOCUS_FORWARD);
                }
            }
        });

        mTabContent = (FrameLayout) findViewById(com.android.internal.R.id.tabcontent);
        if (mTabContent == null) {
            throw new RuntimeException(
                    "Your TabHost must have a FrameLayout whose id attribute is "
                            + "'android.R.id.tabcontent'");
        }
    }

    /**
     * If you are using {@link TabSpec#setContent(android.content.Intent)}, this
     * must be called since the activityGroup is needed to launch the local activity.
     *
     * This is done for you if you extend {@link android.app.TabActivity}.
     * @param activityGroup Used to launch activities for tab content.
     */
    public void setup(LocalActivityManager activityGroup) {
        setup();
        mLocalActivityManager = activityGroup;
    }


    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        final ViewTreeObserver treeObserver = getViewTreeObserver();
        if (treeObserver != null) {
            treeObserver.addOnTouchModeChangeListener(this);
        }
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        final ViewTreeObserver treeObserver = getViewTreeObserver();
        if (treeObserver != null) {
            treeObserver.removeOnTouchModeChangeListener(this);
        }
    }

    /**
     * {@inheritDoc}
     */
    public void onTouchModeChanged(boolean isInTouchMode) {
        if (!isInTouchMode) {
            // leaving touch mode.. if nothing has focus, let's give it to
            // the indicator of the current tab
            if (mCurrentView != null && (!mCurrentView.hasFocus() || mCurrentView.isFocused())) {
                mTabWidget.getChildTabViewAt(mCurrentTab).requestFocus();
            }
        }
    }

    /**
     * Add a tab.
     * @param tabSpec Specifies how to create the indicator and content.
     */
    public void addTab(TabSpec tabSpec) {

        if (tabSpec.mIndicatorStrategy == null) {
            throw new IllegalArgumentException("you must specify a way to create the tab indicator.");
        }

        if (tabSpec.mContentStrategy == null) {
            throw new IllegalArgumentException("you must specify a way to create the tab content");
        }
        View tabIndicator = tabSpec.mIndicatorStrategy.createIndicatorView();
        tabIndicator.setOnKeyListener(mTabKeyListener);

        // If this is a custom view, then do not draw the bottom strips for
        // the tab indicators.
        if (tabSpec.mIndicatorStrategy instanceof ViewIndicatorStrategy) {
            mTabWidget.setStripEnabled(false);
        }
        mTabWidget.addView(tabIndicator);
        mTabSpecs.add(tabSpec);

        if (mCurrentTab == -1) {
            setCurrentTab(0);
        }
    }


    /**
     * Removes all tabs from the tab widget associated with this tab host.
     */
    public void clearAllTabs() {
        mTabWidget.removeAllViews();
        initTabHost();
        mTabContent.removeAllViews();
        mTabSpecs.clear();
        requestLayout();
        invalidate();
    }

    public TabWidget getTabWidget() {
        return mTabWidget;
    }

    public int getCurrentTab() {
        return mCurrentTab;
    }

    public String getCurrentTabTag() {
        if (mCurrentTab >= 0 && mCurrentTab < mTabSpecs.size()) {
            return mTabSpecs.get(mCurrentTab).getTag();
        }
        return null;
    }

    public View getCurrentTabView() {
        if (mCurrentTab >= 0 && mCurrentTab < mTabSpecs.size()) {
            return mTabWidget.getChildTabViewAt(mCurrentTab);
        }
        return null;
    }

    public View getCurrentView() {
        return mCurrentView;
    }

    public void setCurrentTabByTag(String tag) {
        int i;
        for (i = 0; i < mTabSpecs.size(); i++) {
            if (mTabSpecs.get(i).getTag().equals(tag)) {
                setCurrentTab(i);
                break;
            }
        }
    }

    /**
     * Get the FrameLayout which holds tab content
     */
    public FrameLayout getTabContentView() {
        return mTabContent;
    }

    @Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        final boolean handled = super.dispatchKeyEvent(event);

        // unhandled key ups change focus to tab indicator for embedded activities
        // when there is nothing that will take focus from default focus searching
        if (!handled
                && (event.getAction() == KeyEvent.ACTION_DOWN)
                && (event.getKeyCode() == KeyEvent.KEYCODE_DPAD_UP)
                && (mCurrentView != null)
                && (mCurrentView.isRootNamespace())
                && (mCurrentView.hasFocus())
                && (mCurrentView.findFocus().focusSearch(View.FOCUS_UP) == null)) {
            mTabWidget.getChildTabViewAt(mCurrentTab).requestFocus();
            playSoundEffect(SoundEffectConstants.NAVIGATION_UP);
            return true;
        }
        return handled;
    }


    @Override
    public void dispatchWindowFocusChanged(boolean hasFocus) {
        if (mCurrentView != null){
            mCurrentView.dispatchWindowFocusChanged(hasFocus);
        }
    }

    public void setCurrentTab(int index) {
        if (index < 0 || index >= mTabSpecs.size()) {
            return;
        }

        if (index == mCurrentTab) {
            return;
        }

        // notify old tab content
        if (mCurrentTab != -1) {
            mTabSpecs.get(mCurrentTab).mContentStrategy.tabClosed();
        }

        mCurrentTab = index;
        final TabHost.TabSpec spec = mTabSpecs.get(index);

        // Call the tab widget's focusCurrentTab(), instead of just
        // selecting the tab.
        mTabWidget.focusCurrentTab(mCurrentTab);

        // tab content
        mCurrentView = spec.mContentStrategy.getContentView();

        if (mCurrentView.getParent() == null) {
            mTabContent
                    .addView(
                            mCurrentView,
                            new ViewGroup.LayoutParams(
                                    ViewGroup.LayoutParams.MATCH_PARENT,
                                    ViewGroup.LayoutParams.MATCH_PARENT));
        }

        if (!mTabWidget.hasFocus()) {
            // if the tab widget didn't take focus (likely because we're in touch mode)
            // give the current tab content view a shot
            mCurrentView.requestFocus();
        }

        //mTabContent.requestFocus(View.FOCUS_FORWARD);
        invokeOnTabChangeListener();
    }

    /**
     * Register a callback to be invoked when the selected state of any of the items
     * in this list changes
     * @param l
     * The callback that will run
     */
    public void setOnTabChangedListener(OnTabChangeListener l) {
        mOnTabChangeListener = l;
    }

    private void invokeOnTabChangeListener() {
        if (mOnTabChangeListener != null) {
            mOnTabChangeListener.onTabChanged(getCurrentTabTag());
        }
    }

    /**
     * Interface definition for a callback to be invoked when tab changed
     */
    public interface OnTabChangeListener {
        void onTabChanged(String tabId);
    }


    /**
     * Makes the content of a tab when it is selected. Use this if your tab
     * content needs to be created on demand, i.e. you are not showing an
     * existing view or starting an activity.
     */
    public interface TabContentFactory {
        /**
         * Callback to make the tab contents
         *
         * @param tag
         *            Which tab was selected.
         * @return The view to display the contents of the selected tab.
         */
        View createTabContent(String tag);
    }


    /**
     * A tab has a tab indicator, content, and a tag that is used to keep
     * track of it.  This builder helps choose among these options.
     *
     * For the tab indicator, your choices are:
     * 1) set a label
     * 2) set a label and an icon
     *
     * For the tab content, your choices are:
     * 1) the id of a {@link View}
     * 2) a {@link TabContentFactory} that creates the {@link View} content.
     * 3) an {@link Intent} that launches an {@link android.app.Activity}.
     */
    public class TabSpec {

        private String mTag;

        private IndicatorStrategy mIndicatorStrategy;
        private ContentStrategy mContentStrategy;

        private TabSpec(String tag) {
            mTag = tag;
        }

        /**
         * Specify a label as the tab indicator.
         */
        public TabSpec setIndicator(CharSequence label) {
            mIndicatorStrategy = new LabelIndicatorStrategy(label);
            return this;
        }

        /**
         * Specify a label and icon as the tab indicator.
         */
        public TabSpec setIndicator(CharSequence label, Drawable icon) {
            mIndicatorStrategy = new LabelAndIconIndicatorStrategy(label, icon);
            return this;
        }

        /**
         * Specify a view as the tab indicator.
         */
        public TabSpec setIndicator(View view) {
            mIndicatorStrategy = new ViewIndicatorStrategy(view);
            return this;
        }

        /**
         * Specify the id of the view that should be used as the content
         * of the tab.
         */
        public TabSpec setContent(int viewId) {
            mContentStrategy = new ViewIdContentStrategy(viewId);
            return this;
        }

        /**
         * Specify a {@link android.widget.TabHost.TabContentFactory} to use to
         * create the content of the tab.
         */
        public TabSpec setContent(TabContentFactory contentFactory) {
            mContentStrategy = new FactoryContentStrategy(mTag, contentFactory);
            return this;
        }

        /**
         * Specify an intent to use to launch an activity as the tab content.
         */
        public TabSpec setContent(Intent intent) {
            mContentStrategy = new IntentContentStrategy(mTag, intent);
            return this;
        }


        public String getTag() {
            return mTag;
        }
    }

    /**
     * Specifies what you do to create a tab indicator.
     */
    private static interface IndicatorStrategy {

        /**
         * Return the view for the indicator.
         */
        View createIndicatorView();
    }

    /**
     * Specifies what you do to manage the tab content.
     */
    private static interface ContentStrategy {

        /**
         * Return the content view.  The view should may be cached locally.
         */
        View getContentView();

        /**
         * Perhaps do something when the tab associated with this content has
         * been closed (i.e make it invisible, or remove it).
         */
        void tabClosed();
    }

    /**
     * How to create a tab indicator that just has a label.
     */
    private class LabelIndicatorStrategy implements IndicatorStrategy {

        private final CharSequence mLabel;

        private LabelIndicatorStrategy(CharSequence label) {
            mLabel = label;
        }

        public View createIndicatorView() {
            final Context context = getContext();
            LayoutInflater inflater =
                    (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View tabIndicator = inflater.inflate(R.layout.tab_indicator,
                    mTabWidget, // tab widget is the parent
                    false); // no inflate params

            final TextView tv = (TextView) tabIndicator.findViewById(R.id.title);
            tv.setText(mLabel);

            if (context.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.DONUT) {
                // Donut apps get old color scheme
                tabIndicator.setBackgroundResource(R.drawable.tab_indicator_v4);
                tv.setTextColor(context.getResources().getColorStateList(R.color.tab_indicator_text_v4));
            }
            
            return tabIndicator;
        }
    }

    /**
     * How we create a tab indicator that has a label and an icon
     */
    private class LabelAndIconIndicatorStrategy implements IndicatorStrategy {

        private final CharSequence mLabel;
        private final Drawable mIcon;

        private LabelAndIconIndicatorStrategy(CharSequence label, Drawable icon) {
            mLabel = label;
            mIcon = icon;
        }

        public View createIndicatorView() {
            final Context context = getContext();
            LayoutInflater inflater =
                    (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View tabIndicator = inflater.inflate(R.layout.tab_indicator,
                    mTabWidget, // tab widget is the parent
                    false); // no inflate params

            final TextView tv = (TextView) tabIndicator.findViewById(R.id.title);
            tv.setText(mLabel);

            final ImageView iconView = (ImageView) tabIndicator.findViewById(R.id.icon);
            iconView.setImageDrawable(mIcon);

            if (context.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.DONUT) {
                // Donut apps get old color scheme
                tabIndicator.setBackgroundResource(R.drawable.tab_indicator_v4);
                tv.setTextColor(context.getResources().getColorStateList(R.color.tab_indicator_text_v4));
            }
            
            return tabIndicator;
        }
    }

    /**
     * How to create a tab indicator by specifying a view.
     */
    private class ViewIndicatorStrategy implements IndicatorStrategy {

        private final View mView;

        private ViewIndicatorStrategy(View view) {
            mView = view;
        }

        public View createIndicatorView() {
            return mView;
        }
    }

    /**
     * How to create the tab content via a view id.
     */
    private class ViewIdContentStrategy implements ContentStrategy {

        private final View mView;

        private ViewIdContentStrategy(int viewId) {
            mView = mTabContent.findViewById(viewId);
            if (mView != null) {
                mView.setVisibility(View.GONE);
            } else {
                throw new RuntimeException("Could not create tab content because " +
                        "could not find view with id " + viewId);
            }
        }

        public View getContentView() {
            mView.setVisibility(View.VISIBLE);
            return mView;
        }

        public void tabClosed() {
            mView.setVisibility(View.GONE);
        }
    }

    /**
     * How tab content is managed using {@link TabContentFactory}.
     */
    private class FactoryContentStrategy implements ContentStrategy {
        private View mTabContent;
        private final CharSequence mTag;
        private TabContentFactory mFactory;

        public FactoryContentStrategy(CharSequence tag, TabContentFactory factory) {
            mTag = tag;
            mFactory = factory;
        }

        public View getContentView() {
            if (mTabContent == null) {
                mTabContent = mFactory.createTabContent(mTag.toString());
            }
            mTabContent.setVisibility(View.VISIBLE);
            return mTabContent;
        }

        public void tabClosed() {
            mTabContent.setVisibility(View.GONE);
        }
    }

    /**
     * How tab content is managed via an {@link Intent}: the content view is the
     * decorview of the launched activity.
     */
    private class IntentContentStrategy implements ContentStrategy {

        private final String mTag;
        private final Intent mIntent;

        private View mLaunchedView;

        private IntentContentStrategy(String tag, Intent intent) {
            mTag = tag;
            mIntent = intent;
        }

        public View getContentView() {
            if (mLocalActivityManager == null) {
                throw new IllegalStateException("Did you forget to call 'public void setup(LocalActivityManager activityGroup)'?");
            }
            final Window w = mLocalActivityManager.startActivity(
                    mTag, mIntent);
            final View wd = w != null ? w.getDecorView() : null;
            if (mLaunchedView != wd && mLaunchedView != null) {
                if (mLaunchedView.getParent() != null) {
                    mTabContent.removeView(mLaunchedView);
                }
            }
            mLaunchedView = wd;

            // XXX Set FOCUS_AFTER_DESCENDANTS on embedded activities for now so they can get
            // focus if none of their children have it. They need focus to be able to
            // display menu items.
            //
            // Replace this with something better when Bug 628886 is fixed...
            //
            if (mLaunchedView != null) {
                mLaunchedView.setVisibility(View.VISIBLE);
                mLaunchedView.setFocusableInTouchMode(true);
                ((ViewGroup) mLaunchedView).setDescendantFocusability(
                        FOCUS_AFTER_DESCENDANTS);
            }
            return mLaunchedView;
        }

        public void tabClosed() {
            if (mLaunchedView != null) {
                mLaunchedView.setVisibility(View.GONE);
            }
        }
    }

}

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