[Android] ScrollView滚动到底部和顶部的检测
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
<SPAN style="FONT-FAMILY: Microsoft YaHei; FONT-SIZE: 18px"><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></SPAN> <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>[java] view plaincopyprint? <SPAN style="FONT-FAMILY: Microsoft YaHei; FONT-SIZE: 18px">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; } }); } }</SPAN> 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
检测滚动的时机有很多,这里是在ScrollView外面检测,使用onTouch的MotionEvent.ACTION_MOVE。如果是继承ScrollView,可以在其他回调的时候检测。
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
补充:移动开发 , Android ,