滚动型检测结束 [英] Detect end of ScrollView

问题描述

我有一个应用程序，具有使用滚动型的活动。我需要当用户获取到滚动型的底部，以检测。我做了一些googleing，我发现的此页面在这里解释。但是，在这个例子中，该人延伸滚动型。正如我所说的，我向活动和必须扩展活动。

I have an app, that has an Activity that uses a ScrollView. I need to detect when user gets to the bottom of the ScrollView. I did some googleing and i found this page where is explained. but, in the example, that guys extends ScrollView. As i said, i extend Activity and MUST extend Activity.

于是，我说：好吧，让我们尝试做延伸滚动型的自定义类，覆盖onScrollChanged（）方法，检测滚动的结束，并采取相应的行动。

So, i said "ok, let's try to make a custom class extending ScrollView, override the onScrollChanged() method, detect the end of the scroll, and act accordingly".

我做到了，但在这行：

scroll=(ScrollViewExt) findViewById(R.id.scrollView1);

它抛出java.lang.ClassCastException。我改变了标签我的XML，但是，很明显，这是行不通的。我的问题是：为什么，如果ScrollViewExt延伸滚动型，投我的脸一个ClassCastException？有没有什么办法来检测滚动的结束不会弄乱太多了？

it throws a java.lang.ClassCastException. I changed the tags in my XML but, obviously, it doesn't work. My questions are: Why, if ScrollViewExt extends ScrollView, throws to my face a ClassCastException? is there any way to detect end of scrolling without messing too much?

感谢你的人。

编辑： 如所承诺的，这里是一片我的XML的事项：

As promised, here is the piece of my XML that matters:

<ScrollView
        android:id="@+id/scrollView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >


        <WebView
            android:id="@+id/textterms"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center_horizontal"
            android:textColor="@android:color/black" />

    </ScrollView>

我改变了它的TextView到的WebView要能证明里面的文字。我想实现的是接受按钮不激活，直到合同条款充分阅读的事情。我的扩展类被称为ScrollViewExt。如果我更改了标签滚动型为ScrollViewExt它抛出一个android.view.InflateException：二进制XML文件中的行＃44：错误充气类ScrollViewExt，因为它不理解的标签ScrollViewText。我不认为它有一个解决方案...

I changed it from TextView to WebView to be able of justifying the text inside. What i want to achieve is the "Accept button doesn't activate until the terms of the contract are fully read" thing. My extended class is called ScrollViewExt. If i change the tag "ScrollView" for "ScrollViewExt" it throws an "android.view.InflateException: Binary XML file line #44: Error inflating class ScrollViewExt", because it doesn't understands the tag ScrollViewText. I don't think it has a solution...

谢谢您的回答！

推荐答案

做到了！

除了修复亚历山大好心给我的，我不得不创建一个接口：

Aside of the fix Alexandre kindly provide me, I had to create an Interface:

public interface ScrollViewListener {
    void onScrollChanged(ScrollViewExt scrollView, 
                         int x, int y, int oldx, int oldy);
}

于是，我不得不覆盖从滚动型的OnScrollChanged方法在我ScrollViewExt：

Then, i had to override the OnScrollChanged method from ScrollView in my ScrollViewExt:

public class ScrollViewExt extends ScrollView {
    private ScrollViewListener scrollViewListener = null;
    public ScrollViewExt(Context context) {
        super(context);
    }

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

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

    public void setScrollViewListener(ScrollViewListener scrollViewListener) {
        this.scrollViewListener = scrollViewListener;
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (scrollViewListener != null) {
            scrollViewListener.onScrollChanged(this, l, t, oldl, oldt);
        }
    }
}

现在，作为亚历山大说，把包名的XML标记（我的错），使我的Activity类实现之前创建的接口，然后，把它放在一起：

Now, as Alexandre said, put the package name in the XML tag (my fault), make my Activity class implement the interface created before, and then, put it all together:

scroll = (ScrollViewExt) findViewById(R.id.scrollView1);
scroll.setScrollViewListener(this);

和在该方法中OnScrollChanged，从接口...

And in the method OnScrollChanged, from the interface...

@Override
public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {
    // We take the last son in the scrollview
    View view = (View) scrollView.getChildAt(scrollView.getChildCount() - 1);
    int diff = (view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY()));

    // if diff is zero, then the bottom has been reached
    if (diff == 0) {
        // do stuff
    }
}

和它的工作！

非常感谢你的帮助，亚历山大！

Thank you very much for your help, Alexandre!

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