Android仿今日頭條滑動頁面導航效果

最近項目中用到了滑動頁面,也就是和目前市場上很火的"今日頭條"頁面滑動類似,在網上找了一下,大部分都是用ViewPager來實現的,剛開始我用的是ViewPager+ViewGroup,上面的標題按鈕用的是HorizontalScrollView,寫完之後感覺效果比較生硬,果斷換掉,發現了一個效果比較好的第三方,也就是今天的主題:PagerSlidingTabStrip.好了,下面來具體介紹一下PagerSlidingTabStrip,進行一下源碼解析.

一、看一下demo的樣子吧

二、把PagerSlidingTabStrip導入我們的項目中
然後在我們的布局文件中進行聲明:

<span ><?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
       xmlns:app="http://schemas.android.com/apk/res/com.hankkin.PagerSlidingTabStrip" 
       android:orientation="vertical" 
       android:layout_width="fill_parent" 
       android:layout_height="fill_parent" 
    > 
 
  <com.hankkin.PagerSlidingTabStrip.view.PagerSlidingTabStrip 
      android:id="@+id/tab" 
      app:pstsShouldExpand="false" 
      app:pstsUnderlineHeight="2dp" 
      app:pstsIndicatorHeight="2dp" 
      app:pstsIndicatorColor="@android:color/holo_blue_light" 
      app:selectedTabTextColor="@android:color/holo_blue_light" 
      app:pstsDividerColor="@android:color/transparent" 
      app:pstsTabBackground="@drawable/background" 
      android:background="@android:color/white" 
      android:layout_width="match_parent" 
      android:layout_height="55dp"/> 
 
  <android.support.v4.view.ViewPager 
      android:id="@+id/pager" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent"/> 
 
</LinearLayout></span><span > 
</span> 

上面的也就是我們的標題滑動按鈕,下面的ViewPager用來存放我們的內容
三、創建Adapter

<span >package com.hankkin.PagerSlidingTabStrip.adapter; 
 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import com.hankkin.PagerSlidingTabStrip.fragment.AndroidFragment; 
import com.hankkin.PagerSlidingTabStrip.fragment.JavaFragment; 
import com.hankkin.PagerSlidingTabStrip.fragment.ObjectCFragment; 
 
import java.util.List; 
 
public class MyAdapter extends FragmentPagerAdapter { 
  private AndroidFragment androidFragment; 
  private JavaFragment javaFragment; 
  private ObjectCFragment objectCFragment; 
  private String[] titles; 
  public MyAdapter(FragmentManager fm,String[] titles) { 
    super(fm); 
    this.titles = titles; 
  } 
 
  @Override 
  public Fragment getItem(int position) { 
    switch (position) { 
      case 0: 
        if (androidFragment == null) { 
          androidFragment = new AndroidFragment(); 
        } 
        return androidFragment; 
      case 1: 
        if (javaFragment == null) { 
          javaFragment = new JavaFragment(); 
        } 
        return javaFragment; 
      case 2: 
        if (objectCFragment == null) { 
          objectCFragment = new ObjectCFragment(); 
        } 
        return objectCFragment; 
      default: 
        return null; 
    } 
  } 
 
  @Override 
  public int getCount() { 
    return titles.length; 
  } 
 
  public String getPageTitle(int i){ 
    return titles[i]; 
  } 
 
} 
</span> 

我這裡用的是碎片Fragment,最下面的getPageTitle()是我們的PagerSlidingTabStrip中的方法,用來獲取標題
接下來我們初始化PagerSlidingTabStrip和ViewPager還有我們的碎片

<span > private void initViews(){ 
    fragments = new ArrayList<>(); 
    pagerTab = (PagerSlidingTabStrip) findViewById(R.id.tab); 
    pager = (ViewPager) findViewById(R.id.pager); 
 
    for (int i=0;i<titles.length;i++){ 
      Fragment fragment = new Fragment(); 
      fragments.add(fragment); 
    } 
 
    adapter = new MyAdapter(getSupportFragmentManager(),titles); 
    pager.setAdapter(adapter); 
    pagerTab.setViewPager(pager); 
  }</span> 

在Adapter中利用碎片管理器獲取我們的碎片和標題相對應上.這裡面需要注意提一下,如果碎片的個數比較少我們可以手動創建碎片,如果像今日頭條很多的話也沒關系,動態創建Fragment,因為我們可以看到頭條的每個碎片中的內容都是類似的,所以說動態創建也未嘗不可,只有個別特殊的我們也可以特殊處理.

就這麼簡單就可以實現類似頭條的頁面滑動效果,下面我們來看一下PagerSlidingTabStrip的源碼吧,看懂了之後也方便我們進行改進.
四、PagerSlidingTabStrip源碼解析
首先我們看幾個比較重要的屬性

private int indicatorColor = 0xFF666666;// 滑動指示器顏色 
private int underlineColor = 0x1A000000;//在視圖的底部的全寬度的線pstsunderlinecolor顏色 
private int dividerColor = 0x1A000000;//選項卡之間的分隔pstsdividercolor顏色 
 
private boolean shouldExpand = false;//pstsshouldexpand如果設置為TRUE，每個標簽都給予同樣的重量，默認為false 
private boolean textAllCaps = true;//pststextallcaps如果為真，所有選項卡標題都是大寫，默認為true 
 
private int scrollOffset = 52;//pstsscrolloffset卷軸被選擇的標簽的偏移 
private int indicatorHeight = 8;//滑動指示器pstsindicatorheight 
private int underlineHeight = 2;//在視圖的底部的全寬度的線pstsunderlineheight高度 
private int dividerPadding = 12;//pstsdividerpadding頂部和底部填充的分頻器 
private int tabPadding = 24;//pststabpaddingleftright左、右填充每個選項卡 
private int dividerWidth = 1;//選項卡分割線寬度 
 
private int tabTextSize = 12;//選項卡字體大小 
private int tabTextColor = 0xFF666666;//選項卡字體顏色 
private int selectedTabTextColor = 0xFF666666;//當前選中字體顏色 
private Typeface tabTypeface = null; 
private int tabTypefaceStyle = Typeface.NORMAL; 
 
private int lastScrollX = 0; 
 
private int tabBackgroundResId = R.drawable.background;//pststabbackground背景繪制的每個標簽，應該是一個statelistdrawable 

我們可以自己定義這些屬性的值,因為可能默認的不太好看
1.首先看一下我們的構造會初始化一些什麼屬性

<span >public PagerSlidingTabStrip(Context context, AttributeSet attrs, int defStyle) { 
    super(context, attrs, defStyle); 
 
    setFillViewport(true);//默認使子view可以拉伸來填滿整個屏幕 
    setWillNotDraw(false);//默認不執行OnDraw()方法 
    //初始化盛放按鈕標題的線性布局 
    tabsContainer = new LinearLayout(context); 
    tabsContainer.setOrientation(LinearLayout.HORIZONTAL); 
    tabsContainer.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT)); 
    addView(tabsContainer); 
 
    DisplayMetrics dm = getResources().getDisplayMetrics(); 
    //導入相應資源文件 
    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); 
 
    indicatorColor = a.getColor(R.styleable.PagerSlidingTabStrip_pstsIndicatorColor, indicatorColor); 
 
    //tab文字選中時的顏色,默認和滑動指示器的顏色一致  
    selectedTabTextColor=a.getColor(R.styleable.PagerSlidingTabStrip_selectedTabTextColor, indicatorColor); 
    //初始化屬性樣式 
    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(); 
 
    rectPaint = new Paint(); 
    rectPaint.setAntiAlias(true); 
    rectPaint.setStyle(Style.FILL); 
 
    dividerPaint = new Paint(); 
    dividerPaint.setAntiAlias(true); 
    dividerPaint.setStrokeWidth(dividerWidth); 
 
    defaultTabLayoutParams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT); 
    expandedTabLayoutParams = new LinearLayout.LayoutParams(0, LayoutParams.MATCH_PARENT, 1.0f); 
 
    if (locale == null) { 
      locale = getResources().getConfiguration().locale; 
    } 
  }</span> 

這些基本都能看懂,主要都是初始化一些屬性,代碼中也有相應的注釋,就不一一介紹了

2.定義ViewPager滑動監聽器,設置當前pager的位置

<span >private class PageListener implements OnPageChangeListener { 
 
    @Override 
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { 
      currentPosition = position; 
      currentPositionOffset = positionOffset; 
 
      scrollToChild(position, (int) (positionOffset * tabsContainer.getChildAt(position).getWidth())); 
 
      invalidate(); 
 
      if (delegatePageListener != null) { 
        delegatePageListener.onPageScrolled(position, positionOffset, positionOffsetPixels); 
      } 
    } 
 
    @Override 
    public void onPageScrollStateChanged(int state) { 
      if (state == ViewPager.SCROLL_STATE_IDLE) { 
        scrollToChild(pager.getCurrentItem(), 0); 
      } 
 
      if (delegatePageListener != null) { 
        delegatePageListener.onPageScrollStateChanged(state); 
      } 
    } 
 
    @Override 
    public void onPageSelected(int position) { 
      selectedPosition = position; 
      updateTabStyles(); 
      if (delegatePageListener != null) { 
        delegatePageListener.onPageSelected(position); 
      } 
    } 
 
  }</span> 

3.更新標題樣式,也就是滑動到當前標題下設置標題狀態

<span >private void updateTabStyles() { 
 
    for (int i = 0; i < tabCount; i++) { 
 
      View v = tabsContainer.getChildAt(i); 
 
      v.setBackgroundResource(tabBackgroundResId); 
 
      if (v instanceof TextView) { 
 
        TextView tab = (TextView) v; 
        tab.setTextSize(TypedValue.COMPLEX_UNIT_PX, tabTextSize); 
        tab.setTypeface(tabTypeface, tabTypefaceStyle); 
        tab.setTextColor(tabTextColor); 
 
        // 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)); 
          } 
        } 
        if (i == selectedPosition) { 
          tab.setTextColor(selectedTabTextColor); 
        } 
      } 
    } 
 
  }</span> 

大體就差不多這些了,好了,給大家看一下我自己完善後的樣子吧

沒有做太多調整，只是稍微的改了一下樣式，裡面還有一些比較細節的東西沒有介紹，比如標題的寬度是平均分配還是分體字體長度進行設置，我們可以修改shouldExpand屬性，大家有興趣的自己仔細研究一下吧.