Android仿QQ消息提示点拖拽功能

很久以前，发现qq有一个很有趣的功能，就是未读消息的红点是可以拖拽的，而且在任何地方都可以随意拖拽，并且有一个弹性的动画，非常有趣，而且也是一个非常方便的功能，于是总想仿制一个，虽说仿制，但也只是他的拖拽功能，弹性效果还是能力有限。

不多说 先上效果

一个自定义的view 使用方式也很简单

<com.weizhenbin.show.widget.vanishview
  android:layout_width="30dp"
  android:layout_height="30dp"
  android:text="5"
  android:layout_alignparentbottom="true"
  android:gravity="center"
  android:textcolor="#fff"
  android:id="@+id/vv"
  android:layout_marginbottom="35dp"
  android:layout_marginleft="80dp"
  android:background="@drawable/shape_red_bg"/>

然后先看下源码

**
 * created by weizhenbin on 16/6/1.
 * <p/>
 * 一个可以随意拖动的view
 */
public class vanishview extends textview {
 private context context;
 /**窗口管理器*/
 private windowmanager windowmanager;

 /**用来存储镜像的imageview*/
 private imageview iv;

 /** 状态栏高度*/
 private int statusheight = 0;

 /**按下的坐标x 相对于view自身*/
 private int dx = 0;

 /**按下的坐标y 相对于view自身*/
 private int dy = 0;

 /**镜像bitmap*/
 private bitmap tmp;

 /**按下的坐标x 相对于屏幕*/
 private float downx = 0;

 /**按下的坐标y 相对于屏幕*/
 private float downy = 0;

 /**属性动画 用于回弹效果*/
 private valueanimator animator;

 /**窗口参数*/
 private windowmanager.layoutparams mwindowlayoutparams;

 /**接口对象*/
 private onlistener listener;
 public vanishview(context context) {
  super(context);
  init(context);
 }

 public vanishview(context context, attributeset attrs) {
  super(context, attrs);
  init(context);
 }

 public vanishview(context context, attributeset attrs, int defstyleattr) {
  super(context, attrs, defstyleattr);
  init(context);
 }

 private void init(context context) {
  this.context = context;
  windowmanager = ((activity) context).getwindowmanager();
  statusheight = getstatusheight(context);
 }

 @override
 public boolean ontouchevent(motionevent event) {
  switch (event.getaction()) {
   case motionevent.action_down:
    dx = (int) event.getx();
    dy = (int) event.gety();
    downx = event.getrawx();
    downy = event.getrawy();
    addwindow(context, event.getrawx(), event.getrawy());
    setvisibility(invisible);
    break;
   case motionevent.action_move:
    mwindowlayoutparams.x = (int) (event.getrawx() - dx);
    mwindowlayoutparams.y = (int) (event.getrawy() - statusheight - dy);
    windowmanager.updateviewlayout(iv, mwindowlayoutparams);
    break;
   case motionevent.action_up:
    int distance=distance(new mypoint(event.getrawx(), event.getrawy()), new mypoint(downx, downy));
    if(distance<400) {
     scroll(new mypoint(event.getrawx(), event.getrawy()), new mypoint(downx, downy));
    }else {
     if(listener!=null){
      listener.ondismiss();
     }
     windowmanager.removeview(iv);
    }
    break;
  }
  return true;
 }

 /**
  * 构建一个窗口 用于存放和移动镜像
  * */
 private void addwindow(context context, float downx, float dowmy) {
  mwindowlayoutparams = new windowmanager.layoutparams();
  mwindowlayoutparams.width = windowmanager.layoutparams.wrap_content;
  mwindowlayoutparams.height = windowmanager.layoutparams.wrap_content;
  iv = new imageview(context);
  mwindowlayoutparams.format = pixelformat.rgba_8888;
  mwindowlayoutparams.gravity = gravity.top | gravity.left;
  mwindowlayoutparams.x = (int) (downx - dx);
  mwindowlayoutparams.y = (int) (dowmy - statusheight - dy);
  //获取view的镜像bitmap
  this.setdrawingcacheenabled(true);
  tmp = bitmap.createbitmap(this.getdrawingcache());
  //释放缓存
  this.destroydrawingcache();
  iv.setimagebitmap(tmp);
  windowmanager.addview(iv, mwindowlayoutparams);
 }


 /**
  * 使用属性动画 实现缓慢回弹效果
  * */
 private void scroll(mypoint start, mypoint end) {
  animator = valueanimator.ofobject(new mytypeevaluator(), start, end);
  animator.setduration(200);
  animator.addupdatelistener(new valueanimator.animatorupdatelistener() {
   @override
   public void onanimationupdate(valueanimator animation) {
    mypoint point = (mypoint) animation.getanimatedvalue();
    mwindowlayoutparams.x = (int) (point.x - dx);
    mwindowlayoutparams.y = (int) (point.y - statusheight - dy);
    windowmanager.updateviewlayout(iv, mwindowlayoutparams);
   }
  });
  animator.addlistener(new animatorlisteneradapter() {
   @override
   public void onanimationend(animator animation) {
    super.onanimationend(animation);
    windowmanager.removeview(iv);
    setvisibility(visible);
   }

  });
  animator.start();
 }

 /**
  * 计算两点的距离
  */
 private int distance(mypoint point1, mypoint point2) {
  int distance = 0;
  if (point1 != null && point2 != null) {
   float dx = point1.x - point2.x;
   float dy = point1.y - point2.y;
   distance = (int) math.sqrt(dx * dx + dy * dy);
  }
  return distance;

 }

 /**
  * 获取状态栏的高度
  */
 private static int getstatusheight(context context) {
  int statusheight = 0;
  rect localrect = new rect();
  ((activity) context).getwindow().getdecorview().getwindowvisibledisplayframe(localrect);
  statusheight = localrect.top;
  if (0 == statusheight) {
   class<?> localclass;
   try {
    localclass = class.forname("com.android.internal.r$dimen");
    object localobject = localclass.newinstance();
    int i5 = integer.parseint(localclass.getfield("status_bar_height").get(localobject).tostring());
    statusheight = context.getresources().getdimensionpixelsize(i5);
   } catch (exception e) {
    e.printstacktrace();
   }
  }
  return statusheight;
 }

 class mypoint {
  float x;
  float y;

  public mypoint(float x, float y) {
   this.x = x;
   this.y = y;
  }

  @override
  public string tostring() {
   return "mypoint{" +
     "x=" + x +
     ", y=" + y +
     '}';
  }
 }

 class mytypeevaluator implements typeevaluator<mypoint> {

  @override
  public mypoint evaluate(float fraction, mypoint startvalue, mypoint endvalue) {
   mypoint point = startvalue;
   point.x = startvalue.x + fraction * (endvalue.x - startvalue.x);
   point.y = startvalue.y + fraction * (endvalue.y - startvalue.y);
   return point;
  }
 }

 /**事件回调借口*/
 public interface onlistener{
  void ondismiss();
 }

 public void setlistener(onlistener listener) {
  this.listener = listener;
 }

实现这一功能其实也不难，这个功能涉及到以下几个知识点

使用windowmanager添加一个view
使用valueanimator属性动画实现回弹效果
getx和getrawx,gety和getrawy的区别

1.使用windowmanager添加一个view

 /**
  * 构建一个窗口 用于存放和移动镜像
  * */
 private void addwindow(context context, float downx, float dowmy) {
  mwindowlayoutparams = new windowmanager.layoutparams();
  mwindowlayoutparams.width = windowmanager.layoutparams.wrap_content;
  mwindowlayoutparams.height = windowmanager.layoutparams.wrap_content;
  iv = new imageview(context);
  mwindowlayoutparams.format = pixelformat.rgba_8888;
  mwindowlayoutparams.gravity = gravity.top | gravity.left;
  mwindowlayoutparams.x = (int) (downx - dx);
  mwindowlayoutparams.y = (int) (dowmy - statusheight - dy);
  //获取view的镜像bitmap
  this.setdrawingcacheenabled(true);
  tmp = bitmap.createbitmap(this.getdrawingcache());
  //释放缓存
  this.destroydrawingcache();
  iv.setimagebitmap(tmp);
  windowmanager.addview(iv, mwindowlayoutparams);
 }

这一步是为了投影一个镜像来达到拖动view的一个假像效果，使用imageview来显示。这里为了使投影没用偏移需要了解getx getrawx gety getrawy的区别

getx和gety 是相对于view自身的，getrawx和getrawy是像对屏幕的，这里还要扣除掉状态栏的高度。

2.移动

 windowmanager.updateviewlayout(iv, mwindowlayoutparams);

3.使用valueanimator属性动画实现回弹效果

这里自定义了typeevaluator实现点的位移动画

class mytypeevaluator implements typeevaluator<mypoint> {

  @override
  public mypoint evaluate(float fraction, mypoint startvalue, mypoint endvalue) {
   mypoint point = startvalue;
   point.x = startvalue.x + fraction * (endvalue.x - startvalue.x);
   point.y = startvalue.y + fraction * (endvalue.y - startvalue.y);
   return point;
  }
 }


 /**
  * 使用属性动画 实现缓慢回弹效果
  * */
 private void scroll(mypoint start, mypoint end) {
  animator = valueanimator.ofobject(new mytypeevaluator(), start, end);
  animator.setduration(200);
  animator.addupdatelistener(new valueanimator.animatorupdatelistener() {
   @override
   public void onanimationupdate(valueanimator animation) {
    mypoint point = (mypoint) animation.getanimatedvalue();
    mwindowlayoutparams.x = (int) (point.x - dx);
    mwindowlayoutparams.y = (int) (point.y - statusheight - dy);
    windowmanager.updateviewlayout(iv, mwindowlayoutparams);
   }
  });
  animator.addlistener(new animatorlisteneradapter() {
   @override
   public void onanimationend(animator animation) {
    super.onanimationend(animation);
    windowmanager.removeview(iv);
    setvisibility(visible);
   }

  });
  animator.start();
 }

通过属性动画实现一个回弹效果

4.触发消失的时机

 /**
  * 计算两点的距离
  */
 private int distance(mypoint point1, mypoint point2) {
  int distance = 0;
  if (point1 != null && point2 != null) {
   float dx = point1.x - point2.x;
   float dy = point1.y - point2.y;
   distance = (int) math.sqrt(dx * dx + dy * dy);
  }
  return distance;
 }

计算两点之间的距离来触发一个回调事件。

int distance=distance(new mypoint(event.getrawx(), event.getrawy()), new mypoint(downx, downy));
    if(distance<400) {
     scroll(new mypoint(event.getrawx(), event.getrawy()), new mypoint(downx, downy));
    }else {
     if(listener!=null){
      listener.ondismiss();
     }
     windowmanager.removeview(iv);
    }

代码分析就到这里，实现这个功能的核心代码都在这里。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。