Android运用onTouchEvent自定义滑动布局

/** 
 * Author：Biligle. 
 * 自定义布局 
 */ 
 
public class MyViewGroup extends ViewGroup { 
 
 private MyViewGroupListener listener;//接口，监听滑动事件 
 private int vertical = 0;//布局距离顶端距离（默认0） 
 
 public MyViewGroup(Context context) { 
 super(context); 
 } 
 
 public MyViewGroup(Context context, AttributeSet attrs) { 
 super(context, attrs); 
 } 
 
 public MyViewGroup(Context context, AttributeSet attrs, int defStyleAttr) { 
 super(context, attrs, defStyleAttr); 
 } 
 
 @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP) 
 public MyViewGroup(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { 
 super(context, attrs, defStyleAttr, defStyleRes); 
 } 
 
 
 private int downY = 0;//按下时的点 
 private int slide = 0;//最终移动距离 
 @Override 
 public boolean onTouchEvent(MotionEvent event) { 
 switch (event.getAction()){ 
  case MotionEvent.ACTION_DOWN: 
  downY = (int) event.getY(); 
  break; 
  case MotionEvent.ACTION_MOVE: 
  slide = downY - (int)event.getY(); 
  if(slide <0){//下滑 
   vertical = listener.marginTop(Math.abs(slide)); 
  }else if(slide > 0){//上滑 
   vertical = listener.marginTop(-slide); 
  } 
  break; 
  case MotionEvent.ACTION_UP: 
  if(vertical <300){ 
   //布局距离屏幕顶部小于300，就让布局充满整个屏幕 
   vertical = listener.marginTop(0); 
  } 
  break; 
 } 
 return true; 
 } 
 
 /** 
 * 测量子View 
 * @param widthMeasureSpec 
 * @param heightMeasureSpec 
 */ 
 @Override 
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
 for (int i = 0; i 

public class MainActivity extends AppCompatActivity implements MyViewGroup.MyViewGroupListener{ 
 
 /** 自定义布局（外层布局）*/ 
 private MyViewGroup myViewGroup; 
 /** 两个圆形图（在外层布局）*/ 
 private ImageView iv1,iv2/*,cloud*/; 
 /** 包裹圆形图的布局*/ 
 private RelativeLayout relativeLayout; 
 /** 外层布局参数类（这里用到了params.topMargin：上边距）*/ 
 private ViewGroup.MarginLayoutParams params; 
 /** 透明值（改变两个圆图的透明值）*/ 
 private float f; 
 /** 左右内边距（改变RelativeLayout内边距）*/ 
 private int p; 
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.activity_main); 
 myViewGroup = (MyViewGroup) findViewById(R.id.my); 
 myViewGroup.setListener(this); 
 iv1 = (ImageView) findViewById(R.id.iv1); 
 iv2 = (ImageView) findViewById(R.id.iv2); 
 relativeLayout = (RelativeLayout) findViewById(R.id.relative); 
 params = (ViewGroup.MarginLayoutParams) myViewGroup.getLayoutParams(); 
 //初始化动画（自动下滑一段儿距离），我这里写死了900 
 ObjectAnimator animator = ObjectAnimator.ofFloat(myViewGroup,"translationY", 900); 
 animator.setDuration(2000); 
 animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { 
  @Override 
  public void onAnimationUpdate(ValueAnimator animation) { 
  float y = (float)animation.getAnimatedValue(); 
  f = y/800; 
  p = (int) y/3; 
  alpha(f); 
  padding(p); 
  } 
 }); 
 animator.start(); 
// cloud = (ImageView) findViewById(R.id.cloud); 
 } 
 
 
 /** 
 * 设置上边距 
 * @param slide 滑动距离 
 * @return 返回下滑布局，距离屏幕左上角的垂直距离 
 */ 
 @Override 
 public int marginTop(int slide) { 
 params.topMargin += slide; 
 myViewGroup.setLayoutParams(params); 
 int vertical = (900 + params.topMargin); 
 if(slide == 0){ 
  //为了隐藏两张圆图，所以把Relativelayout的高度一并减除。 
  params.topMargin -= (vertical+relativeLayout.getHeight()); 
  myViewGroup.setLayoutParams(params); 
 } 
 float alpha = f + (float) params.topMargin/800;//自定义一个算法 
 alpha(alpha); 
 int padding = p + params.topMargin/3;//自定义一个算法 
 padding(padding); 
 return vertical; 
 } 
 
 /** 
 * 设置透明度 
 * @param alpha 透明值 
 */ 
 public void alpha(float alpha) { 
 iv1.setAlpha(alpha); 
 iv2.setAlpha(alpha); 
 } 
 
 /** 
 * 设置左右边距 
 * @param padding 边距值 
 */ 
 public void padding(int padding) { 
 relativeLayout.setPadding(padding, 0, padding, 0); 
 } 

<&＃63;xml version="1.0" encoding="utf-8"&＃63;>