如何手動修改TabPageIndicator的title的解決辦法

前言

今天要講述的是關於TabPageIndicator這個控件，使用場合就是相似網易新聞的tab欄，乍一看沒什麼稀奇的，可是最近遇到的需求是在tab顯示完成後，點擊其餘按鈕要動態的去修改對應的tab的title。而後我也是陷入了一個坑，由於你們look

這是咱們TabPageIndicator的tab的title的來源，我了個去，這不是在初始化的時候完成的嗎，那咱們怎麼在不刷新總體的適配器的狀況去完成這個事情，請接着往下看，要看源碼了咯。

正文

理解初始化

首先讓咱們看看爲何getPageTitle這個方法能夠初始化TabPageIndicator的title。我先把TabPageIndicator的源碼貼出來先

/*
 * 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;
        }
    }
}

這是源碼不是很長，是爲了方便看文章的人本身能夠對照源碼去看，先看這裏

咱們是在這裏接收外部的pageTitle,而後再看addTab(i,title,iconResId)又作了什麼

在這個方法中咱們生成了TabView，並將title賦值給他，而後加入到mTabLayout容器中，那麼讓咱們大概瞭解一下TabView是什麼

嗯，咱們看到了是TextView的子類，自此咱們應該能瞭解爲何能經過重寫getPageTitle來初始化TabPageIndicator的title了。

深度分析結構

通過前面的分析咱們知道了初始化的大概，那麼若是咱們須要本身動態改變他的內部元素的屬性的時候，咱們就須要更深刻的分析，TabPageIndicator究竟是什麼，他的內部結構時怎麼構成的。

首先

public class TabPageIndicator extends HorizontalScrollView implements PageIndicator

他是個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));
    }

構造器裏面咱們能夠知道他的結構是在HorizontalScrollView裏面塞入了一個IcsLinearLayout（一種LinearLayout子類控件容器）。

而後在剛纔的addTab(i,title,iconResId)，咱們也看到了

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));
    }

他會在IcsLinearLayout裏面塞入一個個TabView控件（就是tab欄大家看到的一個個元素，?），這樣咱們就完全明白了是什麼結構了。

解決辦法

既然已經知道結構了，那咱們就開始解決如何修改屬性的問題吧，首先要找到那個最底層的那個TabView元素，並無提供直接的方法獲取，那相信你們知道android的界面結構其實就是容器包裹的方式

((TextView) ((IcsLinearLayout) tabIndicator.getChildAt(0)).getChildAt(0)).setText("0檢查項("+selectedExamineItems.size()+")");

第一個getChildAt(0)就是找到IcsLinearLayout容器，第二個getChildAt(0)就是找到IcsLinearLayout第一個TabView，我將它強制轉換爲TextView，由於原本就是TextView的子類，沒毛病。這樣一來咱們就作到手動修改title了。可是別高興太早，有瑕疵（當你修改title的內容的時候若是是增長內容字數TabView會變長，可是你再減小字數的時候，shit，它不會變短了，這太坑爹了），還有IcsLinearLayout類默認是private須要改成public否則這裏無法引用，最後請看下面的優化方案。

優化方案

想看三張圖

沒有錯我提供的思路方案就是手動修改TabView的寬度，我先將一個padding設置跟TabPageIndicator的主題設置同樣的TextView傳入咱們的內容，這樣獲得的寬度就是咱們最終須要設置的寬度了，完美！

總結

百度不是萬能的，做爲一個研發者，仍是保持閱讀源碼，提升本身分析能力纔是出路，?bye！