【Android开源项目分析】TAB导航栏PagerSlidingTabStrip的使用和源码分析

转载请注明出处：http://blog.csdn.net/zhoubin1992/article/details/47382021
本文分为两部分：

• PagerSlidingTabStrip的使用

• PagerSlidingTabStrip源码分析

  PagerSlidingTabStrip项目源码下载：
  https://github.com/astuetz/PagerSlidingTabStrip
  PagerSlidingTabStrip是配合ViewPager使用的导航栏，导航栏会随着ViewPager滑动而滑动,如下图。打开源码会发现只有一个继承了HorizontalScrollView的类——PagerSlidingTabStrip.java，实现不是特别复杂。
  

PagerSlidingTabStrip的使用

我这里展示使用步骤，记录下当时遇到的问题以及解决方法。
1. 按照上面的地址下载，项目文件名PagerSlidingTabStrip-master。把library导入工程，加入library作为引用工程。
这里当时我导入后，library项目报错了。
首先是Unable to resolve target ‘android-17’错误
解决方法：http://stackoverflow.com/questions/20975056/unable-to-resolve-target-android-17
还有是项目引用了android-support-v4，然而项目并没有导入android-support-v4.jar，出现The import android.support cannot be resolved错误
解决方法：http://stackoverflow.com/questions/18299898/the-import-android-support-cannot-be-resolved
再者当导入android-support-v4.jar后，出现multiple dex files define landroid/support/annotation/AnimRes错误
解决方法：http://stackoverflow.com/questions/26342444/multiple-dex-files-define-landroid-support-annotation-animres
2. 在layout布局文件里配置PagerSlidingTabStrip控件，它通常要在ViewPager控件之上。

   <!--  通常要在ViewPager控件之上 -->    <com.astuetz.PagerSlidingTabStrip        android:id="@+id/tabs"        android:layout_width="match_parent"        android:layout_height="48dip" />      <android.support.v4.view.ViewPager        android:id="@+id/pager"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/tabs" />

3.在activity的onCreate方法或者fragment的onCreateView方法，获取PagerSlidingTabStrip控件，绑定控件到ViewPager上。
activity的onCreate方法:

        mTabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);        //初始化ViewPager并添加适配器        mPager = (ViewPager) findViewById(R.id.pager);        mAdapter = new MyPagerAdapter(getSupportFragmentManager());        mPager.setAdapter(mAdapter);        //绑定PagerSlidingTabStrip控件到ViewPager上        mTabs.setViewPager(mPager);  

我的需求是在fragment的onCreateView方法，注意代码如下：

    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.activity_recipe,                container, false);        mTabs = (PagerSlidingTabStrip) view.findViewById(R.id.tabs);        //初始化ViewPager并且添加适配器        mPager = (ViewPager) view.findViewById(R.id.pager);        mAdapter = new MyPagerAdapter(getActivity().getSupportFragmentManager());        mPager.setAdapter(mAdapter);        //绑定PagerSlidingTabStrip控件到ViewPager上        mTabs.setViewPager(mPager);          return view;    }

要注意到findViewById前需要加view,getSupportFragmentManager()前需要加getActivity()。
当时一开始没有加。出现nullpointer exception in oncreateView() of fragment错误。
解决方法：http://stackoverflow.com/questions/15644617/nullpointer-exception-in-oncreateview-of-fragment
同时注意内部类MyPagerAdapter需要自己定义，参考官方demo。这样就完成了。
总结下PagerSlidingTabStrip的使用：

• library导入工程，加入library作为引用工程；
• 布局文件配置PagerSlidingTabStrip控件；
• 在onCreate方法或onCreateView方法中获取PagerSlidingTabStrip控件，绑定到ViewPager上。

---

PagerSlidingTabStrip源码分析

首先我先总结下PagerSlidingTabStrip的主要原理，让大家有个整体把握。然后再进入源码一步步分析。

PagerSlidingTabStrip的主要原理：

1. 首先在构造方法里创建Tab的LinearLayout容器，初始化样式值，创建指示器分割线画笔等；
2. 进入setViewPager()绑定ViewPager，设置了viewpager的OnPageChangeListener为内部类PageListener，以及调用notifyDataSetChanged()；
3. 在notifyDataSetChanged()根据adapter内容创建TAB导航栏标题(icon/text)；
4. 在PageListener监听类里实现了导航栏会随着ViewPager滑动而滑动，以及调用invalidate()方法 ；
5. 触发ondraw()函数完成最终的绘制。绘制指示器,下划线和分割线。

/* * Copyright (C) 2013 Andreas Stuetz <[e-mail]> * * 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 com.astuetz;import android.annotation.SuppressLint;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Paint.Style;import android.graphics.Typeface;import android.os.Build;import android.os.Parcel;import android.os.Parcelable;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.util.TypedValue;import android.view.Gravity;import android.view.View;import android.view.ViewTreeObserver.OnGlobalLayoutListener;import android.widget.HorizontalScrollView;import android.widget.ImageButton;import android.widget.LinearLayout;import android.widget.TextView;import java.util.Locale;import com.astuetz.pagerslidingtabstrip.R;//继承HorizontalScrillView，拥有HorizontalScrillView的超出界面时可左右滑动的功能。public class PagerSlidingTabStrip extends HorizontalScrollView {    //通过 viewpager 的 adapter 可以实现接口IconTabProvider    public interface IconTabProvider {        public int getPageIconResId(int position);    }    // @formatter:off    private static final int[] ATTRS = new int[] {        android.R.attr.textSize,        android.R.attr.textColor    };    // @formatter:on    private LinearLayout.LayoutParams defaultTabLayoutParams;    private LinearLayout.LayoutParams expandedTabLayoutParams;    private final PageListener pageListener = new PageListener();    public OnPageChangeListener delegatePageListener;    private LinearLayout tabsContainer;    private ViewPager pager;    private int tabCount;    private int currentPosition = 0;    private float currentPositionOffset = 0f;    private Paint rectPaint;    private Paint dividerPaint;    private int indicatorColor = 0xFF666666;    private int underlineColor = 0x1A000000;    private int dividerColor = 0x1A000000;    private boolean shouldExpand = false;    private boolean textAllCaps = true;    private int scrollOffset = 52;    private int indicatorHeight = 8;    private int underlineHeight = 2;    private int dividerPadding = 12;    private int tabPadding = 24;    private int dividerWidth = 1;    private int tabTextSize = 12;    private int tabTextColor = 0xFF666666;    private Typeface tabTypeface = null;    private int tabTypefaceStyle = Typeface.BOLD;    private int lastScrollX = 0;    private int tabBackgroundResId = R.drawable.background_tab;    private Locale locale;    public PagerSlidingTabStrip(Context context) {        this(context, null);    }    public PagerSlidingTabStrip(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    //构造方法    public PagerSlidingTabStrip(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        setFillViewport(true);        setWillNotDraw(false);        //动态生成横向的LinearLayout，并添加        tabsContainer = new LinearLayout(context);        tabsContainer.setOrientation(LinearLayout.HORIZONTAL);        tabsContainer.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));        addView(tabsContainer);        DisplayMetrics dm = getResources().getDisplayMetrics();        //初始化样式值（指示器，下划线，分隔线和TAB文字等样式）        scrollOffset = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, scrollOffset, dm);        indicatorHeight = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, indicatorHeight, dm);        underlineHeight = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, underlineHeight, dm);        dividerPadding = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dividerPadding, dm);        tabPadding = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, tabPadding, dm);        dividerWidth = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dividerWidth, dm);        tabTextSize = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, tabTextSize, dm);        // get system attrs (android:textSize and android:textColor)        TypedArray a = context.obtainStyledAttributes(attrs, ATTRS);        tabTextSize = a.getDimensionPixelSize(0, tabTextSize);        tabTextColor = a.getColor(1, tabTextColor);        a.recycle();        // get custom attrs        a = context.obtainStyledAttributes(attrs, R.styleable.PagerSlidingTabStrip);        //获取布局文件的配置样式值        indicatorColor = a.getColor(R.styleable.PagerSlidingTabStrip_pstsIndicatorColor, indicatorColor);        underlineColor = a.getColor(R.styleable.PagerSlidingTabStrip_pstsUnderlineColor, underlineColor);        dividerColor = a.getColor(R.styleable.PagerSlidingTabStrip_pstsDividerColor, dividerColor);        indicatorHeight = a.getDimensionPixelSize(R.styleable.PagerSlidingTabStrip_pstsIndicatorHeight, indicatorHeight);        underlineHeight = a.getDimensionPixelSize(R.styleable.PagerSlidingTabStrip_pstsUnderlineHeight, underlineHeight);        dividerPadding = a.getDimensionPixelSize(R.styleable.PagerSlidingTabStrip_pstsDividerPadding, dividerPadding);        tabPadding = a.getDimensionPixelSize(R.styleable.PagerSlidingTabStrip_pstsTabPaddingLeftRight, tabPadding);        tabBackgroundResId = a.getResourceId(R.styleable.PagerSlidingTabStrip_pstsTabBackground, tabBackgroundResId);        shouldExpand = a.getBoolean(R.styleable.PagerSlidingTabStrip_pstsShouldExpand, shouldExpand);        scrollOffset = a.getDimensionPixelSize(R.styleable.PagerSlidingTabStrip_pstsScrollOffset, scrollOffset);        textAllCaps = a.getBoolean(R.styleable.PagerSlidingTabStrip_pstsTextAllCaps, textAllCaps);        a.recycle();        //指示器画笔        rectPaint = new Paint();        rectPaint.setAntiAlias(true);        rectPaint.setStyle(Style.FILL);        //分割线画笔        dividerPaint = new Paint();        dividerPaint.setAntiAlias(true);        dividerPaint.setStrokeWidth(dividerWidth);        //创建两个LinearLayout.LayoutParams，一个为适应内容长度        defaultTabLayoutParams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT);        //一个为长度比例相同        expandedTabLayoutParams = new LinearLayout.LayoutParams(0, LayoutParams.MATCH_PARENT, 1.0f);        if (locale == null) {            locale = getResources().getConfiguration().locale;        }    }    //绑定ViewPager    public void setViewPager(ViewPager pager) {        this.pager = pager;        //viewpager的adapter不能为空否则会异常，        if (pager.getAdapter() == null) {            throw new IllegalStateException("ViewPager does not have adapter instance.");        }        //设置了viewpager的OnPageChangeListener,注意是pagerSlidingTabStrip 内部类PageListener        pager.setOnPageChangeListener(pageListener);        notifyDataSetChanged();    }    public void setOnPageChangeListener(OnPageChangeListener listener) {        this.delegatePageListener = listener;    }    //创建TAB导航栏标题，初始化默认第一个标题内容    public void notifyDataSetChanged() {        //移除全部子视图，根据adapter内容addTab        tabsContainer.removeAllViews();        tabCount = pager.getAdapter().getCount();        for (int i = 0; i < tabCount; i++) {            //如果是 icon 的话，通过 viewpager 的 adapter 实现接口IconTabProvider 否则是 text             if (pager.getAdapter() instanceof IconTabProvider) {                addIconTab(i, ((IconTabProvider) pager.getAdapter()).getPageIconResId(i));            } else {                addTextTab(i, pager.getAdapter().getPageTitle(i).toString());            }        }        updateTabStyles();        getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {            @SuppressWarnings("deprecation")            @SuppressLint("NewApi")            @Override            public void onGlobalLayout() {                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {                    getViewTreeObserver().removeGlobalOnLayoutListener(this);                } else {                    getViewTreeObserver().removeOnGlobalLayoutListener(this);                }                currentPosition = pager.getCurrentItem();                scrollToChild(currentPosition, 0);            }        });    }    //添加文字TAB导航栏内容    private void addTextTab(final int position, String title) {        TextView tab = new TextView(getContext());        tab.setText(title);        tab.setGravity(Gravity.CENTER);        tab.setSingleLine();        addTab(position, tab);    }    //添加图片TAB导航栏内容    private void addIconTab(final int position, int resId) {        ImageButton tab = new ImageButton(getContext());        tab.setImageResource(resId);        addTab(position, tab);    }    private void addTab(final int position, View tab) {        tab.setFocusable(true);        tab.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                pager.setCurrentItem(position);            }        });        //设置每个tab左右的padding        tab.setPadding(tabPadding, 0, tabPadding, 0);        //往container里面动态添加tab,哪个TabLayoutParams注意看前文        tabsContainer.addView(tab, position, shouldExpand ? expandedTabLayoutParams : defaultTabLayoutParams);    }    //设置每个tab的样式    @SuppressLint("NewApi") private void updateTabStyles() {        for (int i = 0; i < tabCount; i++) {            View v = tabsContainer.getChildAt(i);            v.setBackgroundResource(tabBackgroundResId);            //背景、文字大小、颜色、字体、是否大写            if (v instanceof TextView) {                TextView tab = (TextView) v;                tab.setTextSize(TypedValue.COMPLEX_UNIT_PX, tabTextSize);                tab.setTypeface(tabTypeface, tabTypefaceStyle);                tab.setTextColor(tabTextColor);                //API控制                // setAllCaps() is only available from API 14, so the upper case is made manually if we are on a                // pre-ICS-build                if (textAllCaps) {                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {                        tab.setAllCaps(true);                    } else {                        tab.setText(tab.getText().toString().toUpperCase(locale));                    }                }            }        }    }    //滚动到特定位置,调用父类scrollTo，布局超出边界才会起作用    private void scrollToChild(int position, int offset) {        if (tabCount == 0) {            return;        }        int newScrollX = tabsContainer.getChildAt(position).getLeft() + offset;        if (position > 0 || offset > 0) {            newScrollX -= scrollOffset;        }        //滑动到的位置。        if (newScrollX != lastScrollX) {            lastScrollX = newScrollX;            scrollTo(newScrollX, 0);        }    }    //onDraw方法绘制分隔线，绘制指示器。    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        if (isInEditMode() || tabCount == 0) {            return;        }        final int height = getHeight();        // draw indicator line        //画笔颜色        rectPaint.setColor(indicatorColor);        // default: line below current tab        View currentTab = tabsContainer.getChildAt(currentPosition);        float lineLeft = currentTab.getLeft();        float lineRight = currentTab.getRight();        // if there is an offset, start interpolating left and right coordinates between current and next tab        if (currentPositionOffset > 0f && currentPosition < tabCount - 1) {            View nextTab = tabsContainer.getChildAt(currentPosition + 1);            final float nextTabLeft = nextTab.getLeft();            final float nextTabRight = nextTab.getRight();            lineLeft = (currentPositionOffset * nextTabLeft + (1f - currentPositionOffset) * lineLeft);            lineRight = (currentPositionOffset * nextTabRight + (1f - currentPositionOffset) * lineRight);        }        //根据当前tab坐标和下一个tab坐标和currentPositionOffset计算指示器坐标并绘制指示器线        canvas.drawRect(lineLeft, height - indicatorHeight, lineRight, height, rectPaint);        // draw underline        //绘制指示器矩形长条        rectPaint.setColor(underlineColor);        canvas.drawRect(0, height - underlineHeight, tabsContainer.getWidth(), height, rectPaint);        // draw divider        //绘制各个tab之间的分隔线长度为dividerPadding        dividerPaint.setColor(dividerColor);        for (int i = 0; i < tabCount - 1; i++) {            View tab = tabsContainer.getChildAt(i);            canvas.drawLine(tab.getRight(), dividerPadding, tab.getRight(), height - dividerPadding, dividerPaint);        }    }    //内部PageListener类，用于监听滑动事件得到当前滑动偏移量和当前tab    private class PageListener implements OnPageChangeListener {        //在此就实现了导航栏会随着ViewPager滑动而滑动        @Override        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {            //当前 view 的位置也即 tab 的位置            currentPosition = position;            //当前 view 滑动的距离。其中 currentPositionOffset 为 float，介于 0~1 代表相对于 tab 宽偏移的比例            currentPositionOffset = positionOffset;            //根据上面得到的 view 的位置和偏移位置，来同步 tab 的位置和偏移距离。            scrollToChild(position, (int) (positionOffset * tabsContainer.getChildAt(position).getWidth()));             //重绘 view，实现 tab 滑动的效果。            invalidate();            //给pagerslidingtab加滑动监听delegatePageListener            //下面的 delegatePageListener 就是我们设置的 viewpager.setOnPageChangeListener.而现在把它封装在整个 pagerSlidingTabStrip 中，实现 viewpager 滑动的效果。            if (delegatePageListener != null) {                delegatePageListener.onPageScrolled(position, positionOffset, positionOffsetPixels);            }        }        //重写onPageScrollStateChanged        @Override        public void onPageScrollStateChanged(int state) {            //滑动结束。positionOffset 归零            if (state == ViewPager.SCROLL_STATE_IDLE) {                scrollToChild(pager.getCurrentItem(), 0);            }            //调用 viewpager.setOnPageChangeListener            if (delegatePageListener != null) {                delegatePageListener.onPageScrollStateChanged(state);            }        }        //重写onPageSelected        @Override        public void onPageSelected(int position) {            //调用 viewpager.setOnPageChangeListener            if (delegatePageListener != null) {                delegatePageListener.onPageSelected(position);            }        }    }    public void setIndicatorColor(int indicatorColor) {        this.indicatorColor = indicatorColor;        invalidate();    }    public void setIndicatorColorResource(int resId) {        this.indicatorColor = getResources().getColor(resId);        invalidate();    }    public int getIndicatorColor() {        return this.indicatorColor;    }    public void setIndicatorHeight(int indicatorLineHeightPx) {        this.indicatorHeight = indicatorLineHeightPx;        invalidate();    }    public int getIndicatorHeight() {        return indicatorHeight;    }    public void setUnderlineColor(int underlineColor) {        this.underlineColor = underlineColor;        invalidate();    }    public void setUnderlineColorResource(int resId) {        this.underlineColor = getResources().getColor(resId);        invalidate();    }    public int getUnderlineColor() {        return underlineColor;    }    public void setDividerColor(int dividerColor) {        this.dividerColor = dividerColor;        invalidate();    }    public void setDividerColorResource(int resId) {        this.dividerColor = getResources().getColor(resId);        invalidate();    }    public int getDividerColor() {        return dividerColor;    }    public void setUnderlineHeight(int underlineHeightPx) {        this.underlineHeight = underlineHeightPx;        invalidate();    }    public int getUnderlineHeight() {        return underlineHeight;    }    public void setDividerPadding(int dividerPaddingPx) {        this.dividerPadding = dividerPaddingPx;        invalidate();    }    public int getDividerPadding() {        return dividerPadding;    }    public void setScrollOffset(int scrollOffsetPx) {        this.scrollOffset = scrollOffsetPx;        invalidate();    }    public int getScrollOffset() {        return scrollOffset;    }    public void setShouldExpand(boolean shouldExpand) {        this.shouldExpand = shouldExpand;        requestLayout();    }    public boolean getShouldExpand() {        return shouldExpand;    }    public boolean isTextAllCaps() {        return textAllCaps;    }    public void setAllCaps(boolean textAllCaps) {        this.textAllCaps = textAllCaps;    }    public void setTextSize(int textSizePx) {        this.tabTextSize = textSizePx;        updateTabStyles();    }    public int getTextSize() {        return tabTextSize;    }    public void setTextColor(int textColor) {        this.tabTextColor = textColor;        updateTabStyles();    }    public void setTextColorResource(int resId) {        this.tabTextColor = getResources().getColor(resId);        updateTabStyles();    }    public int getTextColor() {        return tabTextColor;    }    public void setTypeface(Typeface typeface, int style) {        this.tabTypeface = typeface;        this.tabTypefaceStyle = style;        updateTabStyles();    }    public void setTabBackground(int resId) {        this.tabBackgroundResId = resId;    }    public int getTabBackground() {        return tabBackgroundResId;    }    public void setTabPaddingLeftRight(int paddingPx) {        this.tabPadding = paddingPx;        updateTabStyles();    }    public int getTabPaddingLeftRight() {        return tabPadding;    }    //activity销毁时在onSaveInstanceState记录当前页数，    //当onRestoreInstanceState获得当前页数并重新    //requestLayout进行测量、布局和绘制    @Override    public void onRestoreInstanceState(Parcelable state) {        SavedState savedState = (SavedState) state;        super.onRestoreInstanceState(savedState.getSuperState());        currentPosition = savedState.currentPosition;        requestLayout();    }    @Override    public Parcelable onSaveInstanceState() {        Parcelable superState = super.onSaveInstanceState();        SavedState savedState = new SavedState(superState);        savedState.currentPosition = currentPosition;        return savedState;    }    static class SavedState extends BaseSavedState {        int currentPosition;        public SavedState(Parcelable superState) {            super(superState);        }        private SavedState(Parcel in) {            super(in);            currentPosition = in.readInt();        }        @Override        public void writeToParcel(Parcel dest, int flags) {            super.writeToParcel(dest, flags);            dest.writeInt(currentPosition);        }        public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {            @Override            public SavedState createFromParcel(Parcel in) {                return new SavedState(in);            }            @Override            public SavedState[] newArray(int size) {                return new SavedState[size];            }        };    }}

总结

• LinearLayout创建Tab容器；
• 在PageListener监听类里获取当前偏移量并随着ViewPager滑动而滑动；
• 在onDraw方法绘制指示器、下划线和分割线。

参考文献：

公共技术点之 View 绘制流程
PagerSlidingTabStrip 源码解析