Android源码解析-仿今日头条PagerSlidingTabStrip滑动页面导航效果

版权声明:本文为博主原创文章,转载请标明出处。 https://blog.csdn.net/lyhhj/article/details/48687389

最近项目中用到了滑动页面,也就是和目前市场上很火的"今日头条"页面滑动类似,在网上找了一下,大部分都是用ViewPager来实现的,刚开始我用的是ViewPager+ViewGroup,上面的标题按钮用的是HorizontalScrollView,写完之后感觉效果比较生硬,果断换掉,发现了一个效果比较好的第三方,也就是今天的主题:PagerSlidingTabStrip.好了,下面来具体介绍一下PagerSlidingTabStrip,进行一下源码解析.

一: 到GitHub上去下载源码和Demo

GitHub地址:

https://github.com/astuetz/PagerSlidingTabStrip

先看一下demo的样子吧

Android源码解析-仿今日头条PagerSlidingTabStrip滑动页面导航效果Android源码解析-仿今日头条PagerSlidingTabStrip滑动页面导航效果


二:把PagerSlidingTabStrip导入我们的项目中

然后在我们的布局文件中进行声明:
<span style="font-size:14px;"><?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 style="font-size:18px;">
</span>
上面的也就是我们的标题滑动按钮,下面的ViewPager用来存放我们的内容

三:创建Adapter

<span style="font-size:14px;">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;

/**
 * Created by Hankkin on 15/9/20.
 */
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>

我这里用的是碎片Fragment,最下面的getPageTitle()是我们的PagerSlidingTabStrip中的方法,用来获取标题
接下来我们初始化PagerSlidingTabStrip和ViewPager还有我们的碎片
<span style="font-size:14px;">  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中利用碎片管理器获取我们的碎片和标题相对应上.这里面需要注意提一下,如果碎片的个数比较少我们可以手动创建碎片,如果像今日头条很多的话也没关系,动态创建Fragment,因为我们可以看到头条的每个碎片中的内容都是类似的,所以说动态创建也未尝不可,只有个别特殊的我们也可以特殊处理.

就这么简单就可以实现类似头条的页面滑动效果,下面我们来看一下PagerSlidingTabStrip的源码吧,看懂了之后也方便我们进行改进.

四:PagerSlidingTabStrip源码解析

首先我们看几个比较重要的属性
	private int indicatorColor = 0xFF666666;//	滑动指示器颜色
	private int underlineColor = 0x1A000000;//在视图的底部的全宽度的线pstsunderlinecolor颜色
	private int dividerColor = 0x1A000000;//选项卡之间的分隔pstsdividercolor颜色

	private boolean shouldExpand = false;//pstsshouldexpand如果设置为TRUE,每个标签都给予同样的重量,默认为false
	private boolean textAllCaps = true;//pststextallcaps如果为真,所有选项卡标题都是大写,默认为true

	private int scrollOffset = 52;//pstsscrolloffset卷轴被选择的标签的偏移
	private int indicatorHeight = 8;//滑动指示器pstsindicatorheight
	private int underlineHeight = 2;//在视图的底部的全宽度的线pstsunderlineheight高度
	private int dividerPadding = 12;//pstsdividerpadding顶部和底部填充的分频器
	private int tabPadding = 24;//pststabpaddingleftright左、右填充每个选项卡
	private int dividerWidth = 1;//选项卡分割线宽度

	private int tabTextSize = 12;//选项卡字体大小
	private int tabTextColor = 0xFF666666;//选项卡字体颜色
	private int selectedTabTextColor = 0xFF666666;//当前选中字体颜色
	private Typeface tabTypeface = null;
	private int tabTypefaceStyle = Typeface.NORMAL;

	private int lastScrollX = 0;

	private int tabBackgroundResId = R.drawable.background;//pststabbackground背景绘制的每个标签,应该是一个statelistdrawable
我们可以自己定义这些属性的值,因为可能默认的不太好看
1.首先看一下我们的构造会初始化一些什么属性
<span style="font-size:14px;">public PagerSlidingTabStrip(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);

		setFillViewport(true);//默认使子view可以拉伸来填满整个屏幕
		setWillNotDraw(false);//默认不执行OnDraw()方法
		//初始化盛放按钮标题的线性布局
		tabsContainer = new LinearLayout(context);
		tabsContainer.setOrientation(LinearLayout.HORIZONTAL);
		tabsContainer.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
		addView(tabsContainer);

		DisplayMetrics dm = getResources().getDisplayMetrics();
		//导入相应资源文件
		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文字选中时的颜色,默认和滑动指示器的颜色一致 
		selectedTabTextColor=a.getColor(R.styleable.PagerSlidingTabStrip_selectedTabTextColor, indicatorColor);
		//初始化属性样式
		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>
这些基本都能看懂,主要都是初始化一些属性,代码中也有相应的注释,就不一一介绍了

2.定义ViewPager滑动监听器,设置当前pager的位置
<span style="font-size:14px;">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.更新标题样式,也就是滑动到当前标题下设置标题状态
<span style="font-size:14px;">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>
大体就差不多这些了,好了,给大家看一下我自己完善后的样子吧
Android源码解析-仿今日头条PagerSlidingTabStrip滑动页面导航效果
没有做太多调整,只是稍微的改了一下样式,里面还有一些比较细节的东西没有介绍,比如标题的宽度是平均分配还是分体字体长度进行设置,我们可以修改shouldExpand属性
大家有兴趣的自己仔细研究一下吧.





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