前言
今天要讲述的是关于TabPageIndicator这个控件，使用场合就是类似网易新闻的tab栏，乍一看没什么稀奇的，但是最近遇到的需求是在tab显示完成后，点击其他按钮要动态的去修改对应的tab的title。然后我也是陷入了一个坑，因为大家look
这是我们TabPageIndicator的tab的title的来源，我了个去，这不是在初始化的时候完成的吗，那我们怎么在不刷新整体的适配器的情况去完成这个事情，请接着往下看，要看源码了咯。
正文
理解初始化
首先让我们看看为什么getPageTitle这个方法可以初始化TabPageIndicator的title。我先把TabPageIndicator的源码贴出来先
/*
* Copyright (C) 2011 The Android Open Source Project
* Copyright (C) 2011 Jake Wharton
*
* 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.viewpagerindicator;
import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.HorizontalScrollView;
import android.widget.LinearLayout;
import android.widget.TextView;
import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
import static android.view.ViewGroup.LayoutParams.WRAP_CONTENT;
/**
* This widget implements the dynamic action bar tab behavior that can change
* across different configurations or circumstances.
*/
public class TabPageIndicator extends HorizontalScrollView 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 OnClickListener mTabClickListener = new 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 IcsLinearLayout mTabLayout;
private ViewPager mViewPager;
private OnPageChangeListener mListener;
private int mMaxTabWidth;
private int mSelectedTabIndex;
private OnTabReselectedListener mTabReselectedListener;
public TabPageIndicator(Context context) {
this(context, null);
}
public TabPageIndicator(Context context, AttributeSet attrs) {
super(context, attrs);
setHorizontalScrollBarEnabled(false);
mTabLayout = new IcsLinearLayout(context, R.attr.vpiTabPageIndicatorStyle);
addView(mTabLayout, new ViewGroup.LayoutParams(WRAP_CONTENT, MATCH_PARENT));
}
public void setOnTabReselectedListener(OnTabReselectedListener listener) {
mTabReselectedListener = listener;
}
@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
final boolean lockedExpanded = widthMode == MeasureSpec.EXACTLY;
setFillViewport(lockedExpanded);
final int childCount = mTabLayout.getChildCount();
if (childCount > 1 && (widthMode == MeasureSpec.EXACTLY || widthMode == MeasureSpec.AT_MOST)) {
if (childCount > 2) {
mMaxTabWidth = (int)(MeasureSpec.getSize(widthMeasureSpec) * 0.8f);
} else {
mMaxTabWidth = MeasureSpec.getSize(widthMeasureSpec) / 2;
}
} else {
mMaxTabWidth = -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;
smoothScrollTo(scrollPos, 0);
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.setFocusable(true);
tabView.setOnClickListener(mTabClickListener);
tabView.setText(text);
if (iconResId != 0) {
tabView.setCompoundDrawablesWithIntrinsicBounds(iconResId, 0, 0, 0);
}
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(OnPageChangeListener listener) {
mListener = listener;
}
public OnPageChangeListener getOnPageChangeListener() {
return mListener;
}
private class TabView extends TextView {
private int mIndex;
public TabView(Context context) {
super(context, null, R.attr.vpiTabPageIndicatorStyle);
}
@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// Re-measure if we went beyond our maximum size.
if (mMaxTabWidth > 0 && getMeasuredWidth() > mMaxTabWidth) {
super.onMeasure(MeasureSpec.makeMeasureSpec(mMaxTabWidth, MeasureSpec.EXACTLY),
heightMeasureSpec);
}
}
public int getIndex() {
return mIndex;
}
}
}这是源码不是很长，是为了方便看文章的人自己可以对照源码去看，先看这里
我们是在这里接收外部的pageTitle,然后再看addTab(i,title,iconResId)又做了什么
在这个方法中我们生成了TabView，并将title赋值给他，然后加入到mTabLayout容器中，那么让我们大概了解一下TabView是什么
嗯，我们看到了是TextView的子类，自此我们应该能了解为什么能通过重写getPageTitle来初始化TabPageIndicator的title了。
深度分析结构
经过前面的分析我们知道了初始化的大概，那么如果我们需要自己动态改变他的内部元素的属性的时候，我们就需要更深入的分析，TabPageIndicator到底是什么，他的内部结构时怎么构成的。
首先
public class TabPageIndicator extends HorizontalScrollView implements PageIndicator 他是个HorizontalScrollView
public TabPageIndicator(Context context, AttributeSet attrs) {
super(context, attrs);
setHorizontalScrollBarEnabled(false);
mTabLayout = new IcsLinearLayout(context, R.attr.vpiTabPageIndicatorStyle);
addView(mTabLayout, new ViewGroup.LayoutParams(WRAP_CONTENT, MATCH_PARENT));
}构造器里面我们可以知道他的结构是在HorizontalScrollView里面塞入了一个IcsLinearLayout（一种LinearLayout子类控件容器）。
然后在刚才的addTab(i,title,iconResId)，我们也看到了
private void addTab(int index, CharSequence text, int iconResId) {
final TabView tabView = new TabView(getContext());
tabView.mIndex = index;
tabView.setFocusable(true);
tabView.setOnClickListener(mTabClickListener);
tabView.setText(text);
if (iconResId != 0) {
tabView.setCompoundDrawablesWithIntrinsicBounds(iconResId, 0, 0, 0);
}
mTabLayout.addView(tabView, new LinearLayout.LayoutParams(0, MATCH_PARENT, 1));
}他会在IcsLinearLayout里面塞入一个个TabView控件（就是tab栏你们看到的一个个元素，?），这样我们就彻底明白了是什么结构了。
解决办法
既然已经知道结构了，那我们就开始解决如何修改属性的问题吧，首先要找到那个最底层的那个TabView元素，并没有提供直接的方法获取，那相信大家知道android的界面结构其实就是容器包裹的方式
((TextView) ((IcsLinearLayout) tabIndicator.getChildAt(0)).getChildAt(0)).setText("0检查项("+selectedExamineItems.size()+")");第一个getChildAt(0)就是找到IcsLinearLayout容器，第二个getChildAt(0)就是找到IcsLinearLayout第一个TabView，我将它强制转换为TextView，因为本来就是TextView的子类，没毛病。这样一来我们就做到手动修改title了。但是别高兴太早，有瑕疵（当你修改title的内容的时候如果是增加内容字数TabView会变长，但是你再减少字数的时候，shit，它不会变短了，这太坑爹了），还有IcsLinearLayout类默认是private需要改为public不然这里没法引用，最后请看下面的优化方案。
优化方案
想看三张图
没有错我提供的思路方案就是手动修改TabView的宽度，我先将一个padding设置跟TabPageIndicator的主题设置一样的TextView传入我们的内容，这样得到的宽度就是我们最终需要设置的宽度了，完美！
总结
百度不是万能的，作为一个研发者，还是保持阅读源码，提高自己分析能力才是出路，?bye！
android
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