Android example source code file (TabWidget.java)

This example Android source code file (TabWidget.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, attributeset, content, context, drawable, drawing, graphics, imageview, layoutparams, linearlayout, onfocuschangelistener, ontabselectionchanged, override, paint, rect, resources, tabclicklistener, tabwidget, ui, view

The TabWidget.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 android.R;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnFocusChangeListener;

/**
 *
 * Displays a list of tab labels representing each page in the parent's tab
 * collection. The container object for this widget is
 * {@link android.widget.TabHost TabHost}. When the user selects a tab, this
 * object sends a message to the parent container, TabHost, to tell it to switch
 * the displayed page. You typically won't use many methods directly on this
 * object. The container TabHost is used to add labels, add the callback
 * handler, and manage callbacks. You might call this object to iterate the list
 * of tabs, or to tweak the layout of the tab list, but most methods should be
 * called on the containing TabHost object.
 * 
 * @attr ref android.R.styleable#TabWidget_divider
 * @attr ref android.R.styleable#TabWidget_tabStripEnabled
 * @attr ref android.R.styleable#TabWidget_tabStripLeft
 * @attr ref android.R.styleable#TabWidget_tabStripRight
 */
public class TabWidget extends LinearLayout implements OnFocusChangeListener {
    private OnTabSelectionChanged mSelectionChangedListener;

    private int mSelectedTab = 0;

    private Drawable mLeftStrip;
    private Drawable mRightStrip;

    private boolean mDrawBottomStrips = true;
    private boolean mStripMoved;

    private Drawable mDividerDrawable;

    private final Rect mBounds = new Rect();

    public TabWidget(Context context) {
        this(context, null);
    }

    public TabWidget(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.tabWidgetStyle);
    }

    public TabWidget(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs);

        TypedArray a =
            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.TabWidget,
                    defStyle, 0);

        mDrawBottomStrips = a.getBoolean(R.styleable.TabWidget_tabStripEnabled, true);
        mDividerDrawable = a.getDrawable(R.styleable.TabWidget_divider);
        mLeftStrip = a.getDrawable(R.styleable.TabWidget_tabStripLeft);
        mRightStrip = a.getDrawable(R.styleable.TabWidget_tabStripRight);

        a.recycle();

        initTabWidget();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        mStripMoved = true;
        super.onSizeChanged(w, h, oldw, oldh);
    }

    @Override
    protected int getChildDrawingOrder(int childCount, int i) {
        // Always draw the selected tab last, so that drop shadows are drawn
        // in the correct z-order.
        if (i == childCount - 1) {
            return mSelectedTab;
        } else if (i >= mSelectedTab) {
            return i + 1;
        } else {
            return i;
        }
    }

    private void initTabWidget() {
        setOrientation(LinearLayout.HORIZONTAL);
        mGroupFlags |= FLAG_USE_CHILD_DRAWING_ORDER;

        final Context context = mContext;
        final Resources resources = context.getResources();
        
        if (context.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.DONUT) {
            // Donut apps get old color scheme
            if (mLeftStrip == null) {
                mLeftStrip = resources.getDrawable(
                        com.android.internal.R.drawable.tab_bottom_left_v4);
            }
            if (mRightStrip == null) {
                mRightStrip = resources.getDrawable(
                        com.android.internal.R.drawable.tab_bottom_right_v4);
            }
        } else {
            // Use modern color scheme for Eclair and beyond
            if (mLeftStrip == null) {
                mLeftStrip = resources.getDrawable(
                        com.android.internal.R.drawable.tab_bottom_left);
            }
            if (mRightStrip == null) {
                mRightStrip = resources.getDrawable(
                        com.android.internal.R.drawable.tab_bottom_right);
            }
        }

        // Deal with focus, as we don't want the focus to go by default
        // to a tab other than the current tab
        setFocusable(true);
        setOnFocusChangeListener(this);
    }

    /**
     * Returns the tab indicator view at the given index.
     *
     * @param index the zero-based index of the tab indicator view to return
     * @return the tab indicator view at the given index
     */
    public View getChildTabViewAt(int index) {
        // If we are using dividers, then instead of tab views at 0, 1, 2, ...
        // we have tab views at 0, 2, 4, ...
        if (mDividerDrawable != null) {
            index *= 2;
        }
        return getChildAt(index);
    }

    /**
     * Returns the number of tab indicator views.
     * @return the number of tab indicator views.
     */
    public int getTabCount() {
        int children = getChildCount();

        // If we have dividers, then we will always have an odd number of
        // children: 1, 3, 5, ... and we want to convert that sequence to
        // this: 1, 2, 3, ...
        if (mDividerDrawable != null) {
            children = (children + 1) / 2;
        }
        return children;
    }

    /**
     * Sets the drawable to use as a divider between the tab indicators.
     * @param drawable the divider drawable
     */
    public void setDividerDrawable(Drawable drawable) {
        mDividerDrawable = drawable;
        requestLayout();
        invalidate();
    }

    /**
     * Sets the drawable to use as a divider between the tab indicators.
     * @param resId the resource identifier of the drawable to use as a
     * divider.
     */
    public void setDividerDrawable(int resId) {
        mDividerDrawable = mContext.getResources().getDrawable(resId);
        requestLayout();
        invalidate();
    }
    
    /**
     * Sets the drawable to use as the left part of the strip below the
     * tab indicators.
     * @param drawable the left strip drawable
     */
    public void setLeftStripDrawable(Drawable drawable) {
        mLeftStrip = drawable;
        requestLayout();
        invalidate();
    }

    /**
     * Sets the drawable to use as the left part of the strip below the
     * tab indicators.
     * @param resId the resource identifier of the drawable to use as the
     * left strip drawable
     */
    public void setLeftStripDrawable(int resId) {
        mLeftStrip = mContext.getResources().getDrawable(resId);
        requestLayout();
        invalidate();
    }

    /**
     * Sets the drawable to use as the right part of the strip below the
     * tab indicators.
     * @param drawable the right strip drawable
     */
    public void setRightStripDrawable(Drawable drawable) {
        mRightStrip = drawable;
        requestLayout();
        invalidate();    }

    /**
     * Sets the drawable to use as the right part of the strip below the
     * tab indicators.
     * @param resId the resource identifier of the drawable to use as the
     * right strip drawable
     */
    public void setRightStripDrawable(int resId) {
        mRightStrip = mContext.getResources().getDrawable(resId);
        requestLayout();
        invalidate();
    }
    
    /**
     * Controls whether the bottom strips on the tab indicators are drawn or
     * not.  The default is to draw them.  If the user specifies a custom
     * view for the tab indicators, then the TabHost class calls this method
     * to disable drawing of the bottom strips.
     * @param stripEnabled true if the bottom strips should be drawn.
     */
    public void setStripEnabled(boolean stripEnabled) {
        mDrawBottomStrips = stripEnabled;
        invalidate();
    }

    /**
     * Indicates whether the bottom strips on the tab indicators are drawn
     * or not.
     */
    public boolean isStripEnabled() {
        return mDrawBottomStrips;
    }

    @Override
    public void childDrawableStateChanged(View child) {
        if (getTabCount() > 0 && child == getChildTabViewAt(mSelectedTab)) {
            // To make sure that the bottom strip is redrawn
            invalidate();
        }
        super.childDrawableStateChanged(child);
    }

    @Override
    public void dispatchDraw(Canvas canvas) {
        super.dispatchDraw(canvas);

        // Do nothing if there are no tabs.
        if (getTabCount() == 0) return;

        // If the user specified a custom view for the tab indicators, then
        // do not draw the bottom strips.
        if (!mDrawBottomStrips) {
            // Skip drawing the bottom strips.
            return;
        }

        final View selectedChild = getChildTabViewAt(mSelectedTab);

        final Drawable leftStrip = mLeftStrip;
        final Drawable rightStrip = mRightStrip;

        leftStrip.setState(selectedChild.getDrawableState());
        rightStrip.setState(selectedChild.getDrawableState());

        if (mStripMoved) {
            final Rect bounds = mBounds;
            bounds.left = selectedChild.getLeft();
            bounds.right = selectedChild.getRight();
            final int myHeight = getHeight();
            leftStrip.setBounds(Math.min(0, bounds.left - leftStrip.getIntrinsicWidth()),
                    myHeight - leftStrip.getIntrinsicHeight(), bounds.left, myHeight);
            rightStrip.setBounds(bounds.right, myHeight - rightStrip.getIntrinsicHeight(),
                    Math.max(getWidth(), bounds.right + rightStrip.getIntrinsicWidth()), myHeight);
            mStripMoved = false;
        }

        leftStrip.draw(canvas);
        rightStrip.draw(canvas);
    }

    /**
     * Sets the current tab.
     * This method is used to bring a tab to the front of the Widget,
     * and is used to post to the rest of the UI that a different tab
     * has been brought to the foreground.
     *
     * Note, this is separate from the traditional "focus" that is
     * employed from the view logic.
     *
     * For instance, if we have a list in a tabbed view, a user may be
     * navigating up and down the list, moving the UI focus (orange
     * highlighting) through the list items.  The cursor movement does
     * not effect the "selected" tab though, because what is being
     * scrolled through is all on the same tab.  The selected tab only
     * changes when we navigate between tabs (moving from the list view
     * to the next tabbed view, in this example).
     *
     * To move both the focus AND the selected tab at once, please use
     * {@link #setCurrentTab}. Normally, the view logic takes care of
     * adjusting the focus, so unless you're circumventing the UI,
     * you'll probably just focus your interest here.
     *
     *  @param index The tab that you want to indicate as the selected
     *  tab (tab brought to the front of the widget)
     *
     *  @see #focusCurrentTab
     */
    public void setCurrentTab(int index) {
        if (index < 0 || index >= getTabCount()) {
            return;
        }

        getChildTabViewAt(mSelectedTab).setSelected(false);
        mSelectedTab = index;
        getChildTabViewAt(mSelectedTab).setSelected(true);
        mStripMoved = true;
    }

    /**
     * Sets the current tab and focuses the UI on it.
     * This method makes sure that the focused tab matches the selected
     * tab, normally at {@link #setCurrentTab}.  Normally this would not
     * be an issue if we go through the UI, since the UI is responsible
     * for calling TabWidget.onFocusChanged(), but in the case where we
     * are selecting the tab programmatically, we'll need to make sure
     * focus keeps up.
     *
     *  @param index The tab that you want focused (highlighted in orange)
     *  and selected (tab brought to the front of the widget)
     *
     *  @see #setCurrentTab
     */
    public void focusCurrentTab(int index) {
        final int oldTab = mSelectedTab;

        // set the tab
        setCurrentTab(index);

        // change the focus if applicable.
        if (oldTab != index) {
            getChildTabViewAt(index).requestFocus();
        }
    }

    @Override
    public void setEnabled(boolean enabled) {
        super.setEnabled(enabled);
        int count = getTabCount();

        for (int i = 0; i < count; i++) {
            View child = getChildTabViewAt(i);
            child.setEnabled(enabled);
        }
    }

    @Override
    public void addView(View child) {
        if (child.getLayoutParams() == null) {
            final LinearLayout.LayoutParams lp = new LayoutParams(
                    0,
                    ViewGroup.LayoutParams.MATCH_PARENT, 1.0f);
            lp.setMargins(0, 0, 0, 0);
            child.setLayoutParams(lp);
        }

        // Ensure you can navigate to the tab with the keyboard, and you can touch it
        child.setFocusable(true);
        child.setClickable(true);

        // If we have dividers between the tabs and we already have at least one
        // tab, then add a divider before adding the next tab.
        if (mDividerDrawable != null && getTabCount() > 0) {
            ImageView divider = new ImageView(mContext);
            final LinearLayout.LayoutParams lp = new LayoutParams(
                    mDividerDrawable.getIntrinsicWidth(),
                    LayoutParams.MATCH_PARENT);
            lp.setMargins(0, 0, 0, 0);
            divider.setLayoutParams(lp);
            divider.setBackgroundDrawable(mDividerDrawable);
            super.addView(divider);
        }
        super.addView(child);

        // TODO: detect this via geometry with a tabwidget listener rather
        // than potentially interfere with the view's listener
        child.setOnClickListener(new TabClickListener(getTabCount() - 1));
        child.setOnFocusChangeListener(this);
    }

    /**
     * Provides a way for {@link TabHost} to be notified that the user clicked on a tab indicator.
     */
    void setTabSelectionListener(OnTabSelectionChanged listener) {
        mSelectionChangedListener = listener;
    }

    public void onFocusChange(View v, boolean hasFocus) {
        if (v == this && hasFocus && getTabCount() > 0) {
            getChildTabViewAt(mSelectedTab).requestFocus();
            return;
        }

        if (hasFocus) {
            int i = 0;
            int numTabs = getTabCount();
            while (i < numTabs) {
                if (getChildTabViewAt(i) == v) {
                    setCurrentTab(i);
                    mSelectionChangedListener.onTabSelectionChanged(i, false);
                    break;
                }
                i++;
            }
        }
    }

    // registered with each tab indicator so we can notify tab host
    private class TabClickListener implements OnClickListener {

        private final int mTabIndex;

        private TabClickListener(int tabIndex) {
            mTabIndex = tabIndex;
        }

        public void onClick(View v) {
            mSelectionChangedListener.onTabSelectionChanged(mTabIndex, true);
        }
    }

    /**
     * Let {@link TabHost} know that the user clicked on a tab indicator.
     */
    static interface OnTabSelectionChanged {
        /**
         * Informs the TabHost which tab was selected. It also indicates
         * if the tab was clicked/pressed or just focused into.
         *
         * @param tabIndex index of the tab that was selected
         * @param clicked whether the selection changed due to a touch/click
         * or due to focus entering the tab through navigation. Pass true
         * if it was due to a press/click and false otherwise.
         */
        void onTabSelectionChanged(int tabIndex, boolean clicked);
    }

}