Android NestedScrollView/ScrollView包裹ViewPager自适应高度

当Android的NestedScrollView/ScrollView这类滚动View包裹ViewPager时候，ViewPager中的Fragment包含的又是一系列高度值不固定的View如RecyclerView等等，就会造成ViewPager高度无法自适应子Fragment里面的View的高度，解决方法其中之一就是重新改造ViewPager，让其能自动适应子Fragment里面的View高度，改造后的AutofitHeightViewPager：

import android.content.Context; import android.support.v4.view.ViewPager; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import java.util.HashMap; import java.util.LinkedHashMap; public class AutofitHeightViewPager extends ViewPager { public static final String POSITION = "position"; private int mCurPosition; private int mHeight = 0; private HashMap<Integer, View> mChildrenViews = new LinkedHashMap<Integer, View>(); private boolean scrollble = true; public AutofitHeightViewPager(Context context) { super(context); } public AutofitHeightViewPager(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { if (mChildrenViews.size() > mCurPosition) { View child = mChildrenViews.get(mCurPosition); if (child != null) { child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)); mHeight = child.getMeasuredHeight(); } } if (mHeight != 0) { heightMeasureSpec = MeasureSpec.makeMeasureSpec(mHeight, MeasureSpec.EXACTLY); } super.onMeasure(widthMeasureSpec, heightMeasureSpec); } public void updateHeight(int current) { this.mCurPosition = current; if (mChildrenViews.size() > current) { ViewGroup.LayoutParams layoutParams = getLayoutParams(); if (layoutParams == null) { layoutParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, mHeight); } else { layoutParams.height = mHeight; } setLayoutParams(layoutParams); } } public void setViewPosition(View view, int position) { mChildrenViews.put(position, view); } @Override public boolean onTouchEvent(MotionEvent ev) { if (!scrollble) { return true; } return super.onTouchEvent(ev); } public boolean isScrollble() { return scrollble; } public void setScrollble(boolean scrollble) { this.scrollble = scrollble; } }

自适应高度的ViewPager思路是每一次切换时候，重新设置ViewPager的高度值。
使用方法有四点必须实现：
1，先把AutofitHeightViewPager像Android原生的ViewPager一样写进xml布局。
2，在上层Java代码的mViewPager添加的切换事件addOnPageChangeListener里面每次updateHeight，例如:

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { mViewPager.updateHeight(position); } @Override public void onPageScrollStateChanged(int state) { } });

3，构建mViewPager肯定要设置FragmentPagerAdapter，在把创建Fragment喂给FragmentPagerAdapter时候，给Fragment把当前Fragment位置position设置进去，例如：

 Fragment xxxFragment = new XXXFragment(); Bundle xxxBunle = new Bundle(); xxxBunle.putInt(AutofitHeightViewPager.POSITION, 1); //1为当前位置，这里的位置索引即为要传递的值，不同的Fragment按照先后添加顺序添加和传递索引 xxxFragment.setArguments(xxxBunle); mPagerAdapter.addFragment(xxxFragment)

4，然后转入到具体的XXXFragment里面，把当前XXXFragment创建的View高度传回给AutofitHeightViewPager,一般是在onCreateView：

 int pos = getArguments().getInt(AutofitHeightViewPager.POSITION); (强制转换为ViewPager所在的Activity) getActivity()).mViewPager.setViewPosition(view, pos);