Android中使用ScrollView实现滑动到底部显示加载更多

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 android:layout_width="fill_parent" 
 android:layout_height="fill_parent"> 
 <ScrollView 
 android:id="@+id/scrollview" 
 android:layout_width="fill_parent" 
 android:layout_height="wrap_content" 
 android:scrollbars="none" > 
 <TextView 
 android:id="@+id/text" 
 android:layout_width="fill_parent" 
 android:layout_height="wrap_content" /> 
 </ScrollView> 
 <Button 
 android:id="@+id/next" 
android:layout_gravity="bottom|center_horizontal" 
 android:layout_width="wrap_content" 
 android:layout_height="wrap_content" 
 android:visibility="invisible" 
 android:text="点击加载更多" /> 
</FrameLayout> 

package com.example.scrollview; 
import android.opengl.Visibility; 
import android.os.Bundle; 
import android.app.Activity; 
import android.support.v4.app.NotificationCompat.Action; 
import android.util.Log; 
import android.view.Menu; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.View.OnTouchListener; 
import android.view.Window; 
import android.widget.Button; 
import android.widget.ScrollView; 
import android.widget.TextView; 
import android.widget.Toast; 
public class MainActivity extends Activity { 
 private ScrollView scroll; 
 private TextView text; 
 private Button button; 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 requestWindowFeature(Window.FEATURE_NO_TITLE); 
 setContentView(R.layout.activity_main); 
 scroll=(ScrollView) findViewById(R.id.scrollview); 
 text=(TextView) findViewById(R.id.text); 
 button=(Button) findViewById(R.id.next); 
 text.setText(getResources().getString(R.string.lyric)); 
 button.setOnClickListener(new OnClickListener() { 
 @Override 
 public void onClick(View v) { 
 // TODO Auto-generated method stub 
 text.append(getResources().getString(R.string.lyric)); 
 button.setVisibility(View.INVISIBLE); 
 } 
 }); 
 scroll.setOnTouchListener(new OnTouchListener() { 
 @Override 
 public boolean onTouch(View v, MotionEvent event) { 
 // TODO Auto-generated method stub 
 switch(event.getAction()){ 
  case MotionEvent.ACTION_MOVE:{ 
  break; 
  } 
  case MotionEvent.ACTION_DOWN:{ 
  break; 
  } 
  case MotionEvent.ACTION_UP:{ 
  //当文本的measureheight 等于scroll滚动的长度+scroll的height 
  if(scroll.getChildAt(0).getMeasuredHeight()<=scroll.getScrollY()+scroll.getHeight()){ 
  button.setVisibility(View.VISIBLE); 
  }else{ 
  } 
  break; 
  } 
 } 
 return false; 
 } 
 }); 
 } 
}