PagerAdapter中的InstantiateItem(ViewGroup，int)和ViewPager中的AddView混淆 [英] instantiateItem(ViewGroup, int) in PagerAdapter and AddView in ViewPager confusion

问题描述

到目前为止，我一直在整理示例，以整体了解Android SDK的API.但是，我陷入了僵局.

So far I've been hacking together examples to get a feel for the APIs the Android SDK as a whole. However, I've hit an impasse.

我正在尝试使用XML文件中的2个TextViews膨胀LinearLayout.这些将是分页的视图.我根本无法使它正常工作，并意识到我完全不了解代码在做什么.

I'm trying to Inflate a LinearLayout with 2 TextViews from an XML file. These will be then Views that are paged. I simply can't get this to work and realize that I totally don't understand what's going on with the code.

查看源代码，我可以看到ViewPager.addNewItem方法从提供的适配器中调用InstantiateItem.在populate()中调用addNewItem.在其他许多地方调用populate().

Looking at the source I can see that the method ViewPager.addNewItem calls the InstantiateItem from the supplied adapter. And addNewItem is called in populate(). populate() is called in a number of other places.

无论如何，在该示例中，我已经体验到，对于PagerAdapter重写该方法时，必须在对addView()的调用中包含对addView()的调用，该调用是从ViewPager作为参数传递的.

Anyway, in the example, I've experienced that when the method is overridden for PagerAdapter one must include a call to addView() on the ViewPager collection that is passed from the ViewPager as an argument.

如果我想添加多个视图，我认为这是多次调用addView()的情况，但是由于InstantiateItem()将一个Object返回给ViewPager(在示例中，我让它返回了它添加的视图)我不知道返回什么.我试图返回膨胀的视图和其他一些东西.

If I wish to add multiple views I thought this would be a case of calling addView() more than once but as instantiateItem() returns an Object to ViewPager (in the example I had it returns the view that it added) I don't know what to return. I've tried returning the inflated view and a number of other things.

请，有人可以解释一下这里发生了什么事吗?

Please, can someone explain what is happening here?

非常感谢.

@Override
public Object instantiateItem(View collection, int position) {

    layout = inflater.inflate(R.layout.animallayout, null);
    TextView tv = (TextView) layout.findViewById(R.id.textView1);
    tv.setText("1________________>" + position);

    TextView tv2 = (TextView) layout.findViewById(R.id.textView2);
    tv.setText("2________________>" + position);

    ((ViewPager) collection).addView(layout);
    return layout;
}

推荐答案

我最近实现了此方法，这是我的instantiateItem方法(使其可读性最小化.

I've recently implemented this and this is my instantiateItem method (made it a bit minimal for readability.

@Override
public Object instantiateItem(View collection, int position) {
    Evaluation evaluation = evaluations.get(position);

    View layout = inflater.inflate(R.layout.layout_evaluation, null);

    TextView evaluationSummary = (TextView) layout.findViewById(R.id.evaluation_summary);
    evaluationSummary.setText(evaluation.getEvaluationSummary());

    ((ViewPager) collection).addView(layout);

    return layout;
}

@Override
public void destroyItem(View collection, int position, Object view) {
     ((ViewPager) collection).removeView((View) view);
}

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

因此对于显示的页面，我使用位置作为索引从evaluations列表中获取数据. 然后给具有视图的Layout充气，我也将添加数据. 然后，我得到TextView来设置评估摘要文本. 然后将整个Layout添加到ViewPager. 最后，还会返回Layout.

So for the page that is displayed, I get the data from my evaluations list using the position as the index. Then inflate the Layout which has the views I will add my data too. Then I get the TextView to set the evaluation summary text on. Then the whole Layout is added to the ViewPager. And finally the Layout is also returned.

如果仍然无法发布代码，则将其删除.

If you still can't get it post your code.

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