某些设备上定制ViewPager渲染问题

Question

我开发了一种应用程序中选择员工的滚动机制。这是一个自定义视图页，可以在屏幕上同时显示多个项目（在我的情况下为3个），并且两侧都被阴影包围。

以下是它在像 Nexus 5、Nexus 4、Galaxy S3 这样的设备上的外观和工作方式:

但是在一些设备上，比如(Sony Xperia和不同种类的Motorola)，渲染效果看起来很差，以下是结果:

关于我提到的代码，我参考了这篇博客文章，作者是@Commonsware：

http://commonsware.com/blog/2012/08/20/multiple-view-viewpager-options.html

第三个选项是代码，你可以在这里找到。

这是我的相关代码：

PagerContainer：

    public class PagerContainer extends FrameLayout implements ViewPager.OnPageChangeListener {

    private ViewPager mPager;
    boolean mNeedsRedraw = false;

    public PagerContainer(Context context) {
        super(context);
        init();
    }

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

    public PagerContainer(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        //Disable clipping of children so non-selected pages are visible
        setClipChildren(false);

        //Child clipping doesn't work with hardware acceleration in Android 3.x/4.x
        //You need to set this value here if using hardware acceleration in an
        // application targeted at these releases.
        if (Build.VERSION.SDK_INT >= 11 && Build.VERSION.SDK_INT < 19)
        {
            setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        }
    }

    @Override
    protected void onFinishInflate() {
        try {
            mPager = (ViewPager) getChildAt(0);
            mPager.setOnPageChangeListener(this);
        } catch (Exception e) {
            throw new IllegalStateException("The root child of PagerContainer must be a ViewPager");
        }
    }

    public ViewPager getViewPager() {
        return mPager;
    }

    private Point mCenter = new Point();
    private Point mInitialTouch = new Point();

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        mCenter.x = w / 2;
        mCenter.y = h / 2;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        //We capture any touches not already handled by the ViewPager
        // to implement scrolling from a touch outside the pager bounds.
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mInitialTouch.x = (int)ev.getX();
                mInitialTouch.y = (int)ev.getY();
            default:
                ev.offsetLocation(mCenter.x - mInitialTouch.x, mCenter.y - mInitialTouch.y);
                break;
        }

        return mPager.dispatchTouchEvent(ev);
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        //Force the container to redraw on scrolling.
        //Without this the outer pages render initially and then stay static
        if (mNeedsRedraw) invalidate();
    }

    @Override
    public void onPageSelected(int position) { 
        invalidate();
    }

    @Override
    public void onPageScrollStateChanged(int state) {
        mNeedsRedraw = (state != ViewPager.SCROLL_STATE_IDLE);
    }
}

初始化部分：

  //Size View Pager:
    //========================================
    pagerSize = mContainerSize.getViewPager();
    adapter = new MySizePagerAdapter();
    pagerSize.setAdapter(adapter);
    //Necessary or the pager will only have one extra page to show  make this at least however many pages you can see
    pagerSize.setOffscreenPageLimit(adapter.getCount());
    //A little space between pages
    pagerSize.setPageMargin(15);
    //If hardware acceleration is enabled, you should also remove  clipping on the pager for its children.
    pagerSize.setClipChildren(false);

更多的研究让我了解到，这个问题与某些设备中的硬件加速有关。但是，通过代码禁用它也没有帮助我解决问题。

- Emil Adz

Answer 1

我建议将ViewPager及其子项的layerType设置为软件渲染，而不是父帧布局。您也可以参考这篇博客文章：http://udinic.wordpress.com/2013/09/16/viewpager-and-hardware-acceleration/

- dandc87

---

谢谢你的回答，现在我对为什么会发生这种情况有了更清晰的想法，但是你提供的解决方案和博客文章中的解决方案仍然没有帮助到我。不过还是要给你加一分努力。 - Emil Adz

Answer 2

我最终使用了另一个实现ViewPager的方法，它给了我相同的结果，但渲染问题在那里并没有出现，这是代码：

  private class MyTypePagerAdapter extends PagerAdapter {

    @Override
    public Object instantiateItem(ViewGroup container, int position) {

        TextView view = new TextView(getActivity());
        view.setText(mTempBeverageList.get(position).getName().toUpperCase());
        if (!wasTypeChanged && (!isLocaleHebrew  && position == 1))
        {
            view.setTypeface(null, Typeface.BOLD);
            view.setTextSize(19);
        }
        else
        {
            view.setTextSize(16);
        }
        view.setSingleLine();
        view.setGravity(Gravity.CENTER);
        view.setTextColor(getResources().getColor(R.color.cups_black));
        view.setBackgroundColor(getResources().getColor(R.color.cups_cyan));
        container.addView(view);
        return view;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
      container.removeView((View)object);
    }

    @Override
    public int getCount() {
      return mTempBeverageList.size();
    }

    @Override
    public float getPageWidth(int position) {
      return (0.33333f);
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
      return (view == object);
    }
} 

而初始化部分：

pagerType= (ViewPager) view.findViewById(R.id.pagerType);   
pagerType.setAdapter(new MyTypePagerAdapter());
pagerType.setOffscreenPageLimit(6);

- Emil Adz