Android模仿To圈儿个人资料界面层叠淡入淡出显示效果

android:background="@drawable/top"

package com.whale.nangua.toquan; 
import android.animation.ObjectAnimator; 
import android.app.Activity; 
import android.content.Context; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageView; 
import android.widget.LinearLayout; 
import android.widget.RelativeLayout; 
import android.widget.ScrollView; 
import android.widget.Toast; 
public class MainActivity extends Activity { 
LinearLayout myscrollLinearlayout; 
LinearLayout mainheadview; //顶部个人资料视图 
RelativeLayout mainactionbar; //顶部菜单栏 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.userinfo_layout); 
initView(); 
} 
int Y; 
int position = 0; //拖动Linearlayout的距离Y轴的距离 
int scrollviewdistancetotop = 0; //headView的高 
int menubarHeight = 0; 
int chufaHeight = 0; //需要触发动画的高 
float scale; //像素密度 
int headViewPosition = 0; 
ImageView userinfo_topbar; 
static boolean flag = true; 
static boolean topmenuflag = true; 
private void initView() { 
userinfo_topbar = (ImageView) findViewById(R.id.userinfo_topbar); 
//获得像素密度 
scale = this.getResources().getDisplayMetrics().density; 
mainheadview = (LinearLayout) findViewById(R.id.mainheadview); 
mainactiOnbar= (RelativeLayout) findViewById(R.id.mainactionbar); 
menubarHeight = (int) (55 * scale); 
chufaHeight = (int) (110 * scale); 
scrollviewdistancetotop = (int) ((260 )*scale); 
position = scrollviewdistancetotop; 
myscrollLinearlayout = (LinearLayout) findViewById(R.id.myscrollLinearlayout); 
myscrollLinearlayout.setY( scrollviewdistancetotop); //要减去Absolote布局距离顶部的高度 
myscrollLinearlayout.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
} 
}); 
myscrollLinearlayout.setOnTouchListener(new View.OnTouchListener() { 
@Override 
public boolean onTouch(View v, MotionEvent event) { 
switch (event.getAction()) { 
case MotionEvent.ACTION_DOWN: 
//按下的Y的位置 
Y = (int) event.getRawY(); 
break; 
case MotionEvent.ACTION_MOVE: 
int nowY = (int) myscrollLinearlayout.getY(); //拖动界面的Y轴位置 
int tempY = (int) (event.getRawY() - Y); //手移动的偏移量 
Y = (int) event.getRawY(); 
if ((nowY + tempY >= 0) && (nowY + tempY <= scrollviewdistancetotop)) { 
if ((nowY + tempY <= menubarHeight)&& (topmenuflag == true) ){ 
userinfo_topbar.setVisibility(View.VISIBLE); 
topmenuflag = false; 
} else if ((nowY + tempY > menubarHeight) && (topmenuflag == flag)) { 
userinfo_topbar.setVisibility(View.INVISIBLE); 
topmenuflag = true; 
} 
int temp = position += tempY; 
myscrollLinearlayout.setY(temp); 
int headviewtemp = headViewPosition += (tempY/5); 
mainheadview.setY(headviewtemp); 
} 
//顶部的动画效果 
if ((myscrollLinearlayout.getY() <= chufaHeight) && (flag == true)) { 
ObjectAnimator anim = ObjectAnimator.ofFloat(mainheadview, "alpha", 1, 0.0f); 
anim.setDuration(500); 
anim.start(); 
flag = false; 
} else if ((myscrollLinearlayout.getY() > chufaHeight + 40) && (flag == false)) { 
ObjectAnimator anim = ObjectAnimator.ofFloat(mainheadview, "alpha", 0.0f, 1f); 
anim.setDuration(500); 
anim.start(); 
flag = true; 
} 
break; 
} 
return false; 
} 
}); 
} 
}