viewpager的高度自适应fragment的高度

如果不处理的话，viewpager是统一的高度，fragment的底部会空白一段距离，处理之后，viewpager的高度跟随fragment保持一致。

首先是viewpager

/**
 * 自适应高度的 viewpager
 */
public class WrapContentHeightViewPager extends ViewPager {
    private int current;
    private int height = 0;


    private boolean scrollble = true;
    /**
     * 保存position与对于的View
     */
    private HashMap<Integer, View> mChildrenViews = new LinkedHashMap<Integer, View>();

    public WrapContentHeightViewPager(Context context) {
        super(context);
    }

    public WrapContentHeightViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//        int height = 0;
//        for (int i = 0; i < getChildCount(); i++) {
//            View child = getChildAt(i);
//            child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
//            int h = child.getMeasuredHeight();
//            if (h > height) height = h;
//        }
//        heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

//        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mChildrenViews.size() > current) {
            View child = mChildrenViews.get(current);
            child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
            height = child.getMeasuredHeight();
        }
        if (mChildrenViews.size() != 0) {
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
        }
        LogUtil.d("height","onMeasure="+height);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    }

    public void resetHeight(int current) {
        this.current = current;
        if (mChildrenViews.size() > current) {

            ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) getLayoutParams();
            if (layoutParams == null) {
                layoutParams = new ConstraintLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, height);
            } else {
                layoutParams.height = height;
            }
            setLayoutParams(layoutParams);
            LogUtil.d("height","height="+height);
        }
    }

    /**
     * 保存position与对于的View
     */
    public void setObjectForPosition(View view, int position) {
        mChildrenViews.put(position, view);
    }

    @Override

    public void setCurrentItem(int item) {
        //去除页面切换时的滑动翻页效果
        super.setCurrentItem(item, false);

    }

}

第一步;在activity中，布局中使用自定义的viewpager，

第二步，在activity中把viewpager传递到fragment中去，并且在fragment中存储 下标和view。

activity中：把viewpager传递给fragment

fragment0.setPager(viewpager);
fragment1.setPager(viewpager);
fragment2.setPager(viewpager);

fragment中：

WrapContentHeightViewPager pager;

public void setPager(WrapContentHeightViewPager pager) {
    this.pager = pager;
}

fragment的初始化中：传入view和下标

pager.setObjectForPosition(getView(),pagerIndex);

第三步:在切换tab的时候，重新测量viewpager的高度

/**
 * tab切换时候的监听
 */
class TabSelectListener implements TabLayout.OnTabSelectedListener {
    @Override
    public void onTabSelected(TabLayout.Tab tab) {
        /**在这里记录TabLayout选中后内容更新已读标记**/
        if (!ConstellationActivity.this.isFinishing()) {
            int position = tab.getPosition();
            viewpager.resetHeight(position);
            if (null != tab.getCustomView()) {
                View line = tab.getCustomView().findViewById(R.id.view_line);
                line.setVisibility(View.VISIBLE);
            }
        }
    }

}

这样，fragment的高度和viewpager的高度保持一致。