ScrollView滚动到底部和顶部的检测

本文链接 http://write.blog.csdn.net/postedit/9831793

1. 源起

很多分页加载的组件都是继承自ScrollView，分页要检查是否滚动到底部，下拉刷新需要检测是否滚动到顶部。

2. 代码

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >

<ScrollView
android:id="@+id/scroll_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" >

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/darker_gray"
android:orientation="vertical" >

<TextView
android:layout_width="wrap_content"
android:layout_height="2000dip"
android:text="text" />
</LinearLayout>
</ScrollView>

</RelativeLayout>

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ScrollView view = (ScrollView) findViewById(R.id.scroll_view);
view.setOnTouchListener(new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
if (v.getScrollY() <= 0) {
Log.d("scroll view", "top");
} else if (view.getChildAt(0).getMeasuredHeight() <= v.getHeight() + v.getScrollY()) {
Log.d("scroll view", "bottom");
Log.d("scroll view", "view.getMeasuredHeight() = " + view.getMeasuredHeight()
+ ", v.getHeight() = " + v.getHeight()
+ ", v.getScrollY() = " + v.getScrollY()
+ ", view.getChildAt(0).getMeasuredHeight() = " + view.getChildAt(0).getMeasuredHeight());
}
break;
default:
break;
}
return false;
} });
}
}

3. 说明

检测滚动的时机

上面是在ScrollView的onTouchListener里面检测，如果是继承ScrollView，也可以在onTouchEvent或者onInterceptTouchEvent中判断。

检测中的取值

v.getScrollY()表示scrollview的上面滚出去的长度。

v.getHeight()表示scrollview本身看上去的高度。

view.getChildAt(0).getMeasuredHeight()是内容的高度。这里不能用view.getMeasureHeight()。

view.getMeasuredHeight() = 1038

v.getHeight() = 1038

v.getScrollY() = 2962

view.getChildAt(0).getMeasuredHeight() = 4000