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Android开发技巧——实现底部图标文字的导航栏
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(msdx.android@qq.com)
* 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(msdx.android@qq.com)
* 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
Android开发技巧——实现底部图标文字的导航栏
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