Android开发技巧——实现底部图标文字的导航栏

浏览数：17 / 时间：2015年06月11日

本文章的导航栏代码参考了viewpagerindicator的实现。本文叙述的是之前版本的qq或微信中，底部的图标加文字的导航栏的实现。

本例子依赖viewpagerindicator的两个接口：IconPagerAdapter及PageIndicator。这两个接口的方法如下：

package com.viewpagerindicator;

public interface IconPagerAdapter {
    int getIconResId(int index);
    int getCount();
}

package com.viewpagerindicator;

import android.support.v4.view.ViewPager;

public interface PageIndicator extends ViewPager.OnPageChangeListener {
    void setViewPager(ViewPager view);
    void setViewPager(ViewPager view, int initialPosition);
    void setCurrentItem(int item);
    void setOnPageChangeListener(ViewPager.OnPageChangeListener listener);
    void notifyDataSetChanged();
}

在本例子中，我把这两个类单独拿出来了。如果你的项目已经有依赖该库，则就不需要再去复制它们。

下面先上两张效果图。

在图中，上面的内容区域是viewpager，下面的是导航栏indicator。点击导航栏可以切换上面的页面，当然，滑动上面的页面下面的导航栏也可以切换。

接着说一下它的实现。类的代码不复杂，大部分参照了viewpagerindicator中的TabPageIndicator类来实现，不过在这里我继承的是LinearLayout，代码如下：

package com.githang.navigatordemo;

import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.viewpagerindicator.IconPagerAdapter;
import com.viewpagerindicator.PageIndicator;


import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;

/**
 * User: Geek_Soledad([email protected])
 * Date: 2014-08-27
 * Time: 09:20
 * FIXME
 */
public class IconTabPageIndicator extends LinearLayout implements PageIndicator {
    /**
     * Title text used when no title is provided by the adapter.
     */
    private static final CharSequence EMPTY_TITLE = "";

    /**
     * Interface for a callback when the selected tab has been reselected.
     */
    public interface OnTabReselectedListener {
        /**
         * Callback when the selected tab has been reselected.
         *
         * @param position Position of the current center item.
         */
        void onTabReselected(int position);
    }

    private Runnable mTabSelector;

    private final View.OnClickListener mTabClickListener = new View.OnClickListener() {
        public void onClick(View view) {
            TabView tabView = (TabView) view;
            final int oldSelected = mViewPager.getCurrentItem();
            final int newSelected = tabView.getIndex();
            mViewPager.setCurrentItem(newSelected);
            if (oldSelected == newSelected && mTabReselectedListener != null) {
                mTabReselectedListener.onTabReselected(newSelected);
            }
        }
    };

    private final LinearLayout mTabLayout;

    private ViewPager mViewPager;
    private ViewPager.OnPageChangeListener mListener;

    private int mSelectedTabIndex;

    private OnTabReselectedListener mTabReselectedListener;

    private int mTabWidth;

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

    public IconTabPageIndicator(Context context, AttributeSet attrs) {
        super(context, attrs);
        setHorizontalScrollBarEnabled(false);

        mTabLayout = new LinearLayout(context, null, R.attr.tabPageIndicator);
        addView(mTabLayout, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
    }

    public void setOnTabReselectedListener(OnTabReselectedListener listener) {
        mTabReselectedListener = listener;
    }

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int widthMode = View.MeasureSpec.getMode(widthMeasureSpec);
        final boolean lockedExpanded = widthMode == View.MeasureSpec.EXACTLY;

        final int childCount = mTabLayout.getChildCount();

        if (childCount > 1 && (widthMode == MeasureSpec.EXACTLY || widthMode == MeasureSpec.AT_MOST)) {
            mTabWidth = MeasureSpec.getSize(widthMeasureSpec) / childCount;
        } else {
            mTabWidth = -1;
        }

        final int oldWidth = getMeasuredWidth();
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int newWidth = getMeasuredWidth();

        if (lockedExpanded && oldWidth != newWidth) {
            // Recenter the tab display if we're at a new (scrollable) size.
            setCurrentItem(mSelectedTabIndex);
        }
    }

    private void animateToTab(final int position) {
        final View tabView = mTabLayout.getChildAt(position);
        if (mTabSelector != null) {
            removeCallbacks(mTabSelector);
        }
        mTabSelector = new Runnable() {
            public void run() {
                final int scrollPos = tabView.getLeft() - (getWidth() - tabView.getWidth()) / 2;
                mTabSelector = null;
            }
        };
        post(mTabSelector);
    }

    @Override
    public void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (mTabSelector != null) {
            // Re-post the selector we saved
            post(mTabSelector);
        }
    }

    @Override
    public void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mTabSelector != null) {
            removeCallbacks(mTabSelector);
        }
    }

    private void addTab(int index, CharSequence text, int iconResId) {
        final TabView tabView = new TabView(getContext());
        tabView.mIndex = index;
        tabView.setOnClickListener(mTabClickListener);
        tabView.setText(text);

        if (iconResId > 0) {
            tabView.setIcon(iconResId);
        }

        mTabLayout.addView(tabView, new LinearLayout.LayoutParams(0, MATCH_PARENT, 1));
    }

    @Override
    public void onPageScrollStateChanged(int arg0) {
        if (mListener != null) {
            mListener.onPageScrollStateChanged(arg0);
        }
    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        if (mListener != null) {
            mListener.onPageScrolled(arg0, arg1, arg2);
        }
    }

    @Override
    public void onPageSelected(int arg0) {
        setCurrentItem(arg0);
        if (mListener != null) {
            mListener.onPageSelected(arg0);
        }
    }

    @Override
    public void setViewPager(ViewPager view) {
        if (mViewPager == view) {
            return;
        }
        if (mViewPager != null) {
            mViewPager.setOnPageChangeListener(null);
        }
        final PagerAdapter adapter = view.getAdapter();
        if (adapter == null) {
            throw new IllegalStateException("ViewPager does not have adapter instance.");
        }
        mViewPager = view;
        view.setOnPageChangeListener(this);
        notifyDataSetChanged();
    }

    public void notifyDataSetChanged() {
        mTabLayout.removeAllViews();
        PagerAdapter adapter = mViewPager.getAdapter();
        IconPagerAdapter iconAdapter = null;
        if (adapter instanceof IconPagerAdapter) {
            iconAdapter = (IconPagerAdapter) adapter;
        }
        final int count = adapter.getCount();
        for (int i = 0; i < count; i++) {
            CharSequence title = adapter.getPageTitle(i);
            if (title == null) {
                title = EMPTY_TITLE;
            }
            int iconResId = 0;
            if (iconAdapter != null) {
                iconResId = iconAdapter.getIconResId(i);
            }
            addTab(i, title, iconResId);
        }
        if (mSelectedTabIndex > count) {
            mSelectedTabIndex = count - 1;
        }
        setCurrentItem(mSelectedTabIndex);
        requestLayout();
    }

    @Override
    public void setViewPager(ViewPager view, int initialPosition) {
        setViewPager(view);
        setCurrentItem(initialPosition);
    }

    @Override
    public void setCurrentItem(int item) {
        if (mViewPager == null) {
            throw new IllegalStateException("ViewPager has not been bound.");
        }
        mSelectedTabIndex = item;
        mViewPager.setCurrentItem(item);

        final int tabCount = mTabLayout.getChildCount();
        for (int i = 0; i < tabCount; i++) {
            final View child = mTabLayout.getChildAt(i);
            final boolean isSelected = (i == item);
            child.setSelected(isSelected);
            if (isSelected) {
                animateToTab(item);
            }
        }
    }

    @Override
    public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
        mListener = listener;
    }

    private class TabView extends LinearLayout {
        private int mIndex;
        private ImageView mImageView;
        private TextView mTextView;

        public TabView(Context context) {
            super(context, null, R.attr.tabView);
            View view = View.inflate(context, R.layout.tab_view, null);
            mImageView = (ImageView) view.findViewById(R.id.tab_image);
            mTextView = (TextView) view.findViewById(R.id.tab_text);
            this.addView(view);
        }

        @Override
        public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);

            // Re-measure if we went beyond our maximum size.
            if (mTabWidth > 0) {
                super.onMeasure(MeasureSpec.makeMeasureSpec(mTabWidth, MeasureSpec.EXACTLY),
                        heightMeasureSpec);
            }
        }

        public void setText(CharSequence text) {
            mTextView.setText(text);
        }

        public void setIcon(int resId) {
            if (resId > 0) {
                mImageView.setImageResource(resId);
            }
        }

        public int getIndex() {
            return mIndex;
        }
    }
}

改动的地方主要是增加一个表示导航栏按钮宽度的变量，以及导航栏的view的实现，及两个onMeasure方法。由于在这里我继承的是LinearLayout，也就是当导航栏栏目较多时，不会通过左右滑动来显示或隐藏其他按钮，而是直接平分，该部分的代码如下：

public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int widthMode = View.MeasureSpec.getMode(widthMeasureSpec);
        final boolean lockedExpanded = widthMode == View.MeasureSpec.EXACTLY;

        final int childCount = mTabLayout.getChildCount();

        if (childCount > 1 && (widthMode == MeasureSpec.EXACTLY || widthMode == MeasureSpec.AT_MOST)) {
            mTabWidth = MeasureSpec.getSize(widthMeasureSpec) / childCount;
        } else {
            mTabWidth = -1;
        }

        final int oldWidth = getMeasuredWidth();
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int newWidth = getMeasuredWidth();

        if (lockedExpanded && oldWidth != newWidth) {
            // Recenter the tab display if we're at a new (scrollable) size.
            setCurrentItem(mSelectedTabIndex);
        }
    }

当导航按钮大于1个时，直接平分。每个导航按钮的宽度即为mTabWidth。

然后重写TabView的onMeasure方法，当mTabWidth大于0时，设置它的宽度为mTabWidth，如下：

        @Override
        public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);

            // Re-measure if we went beyond our maximum size.
            if (mTabWidth > 0) {
                super.onMeasure(MeasureSpec.makeMeasureSpec(mTabWidth, MeasureSpec.EXACTLY),
                        heightMeasureSpec);
            }
        }

在这里的TabView中，我则直接使用布局文件来写，上面是一个ImageView，下面是一个TextView，代码如下（tab_view.xml）：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:background="@android:color/white"
              android:gravity="center_horizontal"
              android:addStatesFromChildren="true"
              android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/tab_image"
        android:layout_width="27dp"
        android:layout_marginTop="2dp"
        android:adjustViewBounds="true"
        android:contentDescription="@null"
        android:layout_height="27dp" />

    <TextView
        android:id="@+id/tab_text"
        android:layout_marginTop="2dp"
        android:gravity="center_horizontal|bottom"
        android:padding="2dp"
        android:layout_width="wrap_content"
        android:textColor="@color/tab_text_selector"
        android:textSize="12sp"
        android:layout_height="match_parent" />
</LinearLayout>

再看TabView内部类的构造方法代码：

 private class TabView extends LinearLayout {

        public TabView(Context context) {
            super(context, null, R.attr.tabView);
            View view = View.inflate(context, R.layout.tab_view, null);
            mImageView = (ImageView) view.findViewById(R.id.tab_image);
            mTextView = (TextView) view.findViewById(R.id.tab_text);
            this.addView(view);
        }
}

TabView是继承自LinearLayout，然后通过布局文件tab_view获取一个view，并将它加到TabView当中。但是我们并没有定义TabView本身的布局参数，所以加到它里面的view并不是居中的，而是靠左。所以我们还需要设置这个TabView的参数，通过我们定义的属性R.attr.tabView，然后调用它父类的构造方法super(context, null, R.attr.tabView)。

在IconTabPageIndicator的构造方法当中，你同样可以看到导航栏的容器——mTabLayout，同样是通过属性来创建的。如下代码：

    public IconTabPageIndicator(Context context, AttributeSet attrs) {
        super(context, attrs);
        setHorizontalScrollBarEnabled(false);

        mTabLayout = new LinearLayout(context, null, R.attr.tabPageIndicator);
        addView(mTabLayout, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
    }

定义属性的方法如下，先在res/values下新建一个attrs.xml的文件，然后加入以下内容：

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="TabView">
        <attr name="tabPageIndicator" format="reference" />
        <attr name="tabView" format="reference" />
    </declare-styleable>
</resources>

即在这里声明两个属性，一个是tabPageIndicator，另一个是tabView，它们都是引用类型的。

但仅仅这样还是不够的，因为我们只是声明了两个属性，并没有设定属性的具体内容，所以我们还需要在styles.xml文件当中设置我们的主题，代码如下(styles.xml)：

  <style name="AppTheme" parent="Theme.AppCompat.Light">
        <item name="tabView">@style/TabView</item>
        <item name="tabPageIndicator">@style/TabIndicator</item>
    </style>
    <style name="TabIndicator"/>
    <style name="TabView">
        <item name="android:addStatesFromChildren">true</item>
        <item name="android:orientation">vertical</item>
        <item name="android:gravity">bottom|center_horizontal</item>
        <item name="android:layout_width">0dp</item>
        <item name="android:background">@android:color/white</item>
        <item name="android:layout_height">match_parent</item>
    </style>

到此，我们的IconTabPageIndicator就实现好了。接下来在我们的程序中使用它：

activity的布局文件(activity_my.xml)：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MyActivity">

    <com.githang.navigatordemo.IconTabPageIndicator
        android:id="@+id/indicator"
        android:layout_alignParentBottom="true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <android.support.v4.view.ViewPager
        android:layout_above="@id/indicator"
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</RelativeLayout>

fragment的布局文件(fragment.xml)：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:gravity="center"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:background="#eee"
    tools:context=".MyActivity">

    <TextView
        android:id="@+id/text"
        android:textAppearance="@android:style/TextAppearance.Large"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</RelativeLayout>

MyActivity类的代码：

package com.githang.navigatordemo;

import android.os.Bundle;
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.view.ViewPager;

import com.viewpagerindicator.IconPagerAdapter;

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


public class MyActivity extends FragmentActivity {

    private ViewPager mViewPager;
    private IconTabPageIndicator mIndicator;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        initViews();
    }

    private void initViews() {
        mViewPager = (ViewPager) findViewById(R.id.view_pager);
        mIndicator = (IconTabPageIndicator) findViewById(R.id.indicator);
        List<BaseFragment> fragments = initFragments();
        FragmentAdapter adapter = new FragmentAdapter(fragments, getSupportFragmentManager());
        mViewPager.setAdapter(adapter);
        mIndicator.setViewPager(mViewPager);
    }

    private List<BaseFragment> initFragments() {
        List<BaseFragment> fragments = new ArrayList<BaseFragment>();

        BaseFragment userFragment = new BaseFragment();
        userFragment.setTitle("用户");
        userFragment.setIconId(R.drawable.tab_user_selector);
        fragments.add(userFragment);

        BaseFragment noteFragment = new BaseFragment();
        noteFragment.setTitle("记事本");
        noteFragment.setIconId(R.drawable.tab_record_selector);
        fragments.add(noteFragment);

        BaseFragment contactFragment = new BaseFragment();
        contactFragment.setTitle("联系人");
        contactFragment.setIconId(R.drawable.tab_user_selector);
        fragments.add(contactFragment);

        BaseFragment recordFragment = new BaseFragment();
        recordFragment.setTitle("记录");
        recordFragment.setIconId(R.drawable.tab_record_selector);
        fragments.add(recordFragment);

        return fragments;
    }

    class FragmentAdapter extends FragmentPagerAdapter implements IconPagerAdapter {
        private List<BaseFragment> mFragments;

        public FragmentAdapter(List<BaseFragment> fragments, FragmentManager fm) {
            super(fm);
            mFragments = fragments;
        }

        @Override
        public Fragment getItem(int i) {
            return mFragments.get(i);
        }

        @Override
        public int getIconResId(int index) {
            return mFragments.get(index).getIconId();
        }

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

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragments.get(position).getTitle();
        }
    }

}

BaseFragment类的代码：

package com.githang.navigatordemo;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * User: Geek_Soledad([email protected])
 * Date: 2014-08-27
 * Time: 09:01
 * FIXME
 */
public class BaseFragment extends Fragment {
    private String title;
    private int iconId;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public int getIconId() {
        return iconId;
    }

    public void setIconId(int iconId) {
        this.iconId = iconId;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment, null, false);
        TextView textView = (TextView) view.findViewById(R.id.text);
        textView.setText(getTitle());
        return view;
    }
}

项目代码下载地址：http://zdz.la/xvS4Ab

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Android开发技巧——实现底部图标文字的导航栏