android PopupWindow点击外部和返回键消失的解决方法

刚接手popupwindow的时候，我们都可能觉得很简单，因为它确实很简单，不过运气不好的可能就会踩到一个坑：

点击popupwindow最外层布局以及点击返回键popupwindow不会消失

新手在遇到这个问题的时候可能会折腾半天，最后通过强大的网络找到一个解决方案，那就是跟popupwindow设置一个背景

popupwindow.setbackgrounddrawable(drawable),这个drawable随便一个什么类型的都可以，只要不为空。

 demo地址：smartpopupwindow_jb51.rar

 下面从源码（我看的是android-22）上看看到底发生了什么事情导致返回键不能消失弹出框：

先看看弹出框显示的时候代码showasdropdown，里面有个preparepopup方法。

 public void showasdropdown(view anchor, int xoff, int yoff, int gravity) {
    if (isshowing() || mcontentview == null) {
      return;
    }

    registerforscrollchanged(anchor, xoff, yoff, gravity);

    misshowing = true;
    misdropdown = true;

    windowmanager.layoutparams p = createpopuplayout(anchor.getwindowtoken());
    preparepopup(p);

    updateaboveanchor(finddropdownposition(anchor, p, xoff, yoff, gravity));

    if (mheightmode < 0) p.height = mlastheight = mheightmode;
    if (mwidthmode < 0) p.width = mlastwidth = mwidthmode;

    p.windowanimations = computeanimationresource();

    invokepopup(p);
 }

再看preparepopup方法

  /**
   * <p>prepare the popup by embedding in into a new viewgroup if the
   * background drawable is not null. if embedding is required, the layout
   * parameters' height is modified to take into account the background's
   * padding.</p>
   *
   * @param p the layout parameters of the popup's content view
   */
  private void preparepopup(windowmanager.layoutparams p) {
    if (mcontentview == null || mcontext == null || mwindowmanager == null) {
      throw new illegalstateexception("you must specify a valid content view by "
          + "calling setcontentview() before attempting to show the popup.");
    }

    if (mbackground != null) {
      final viewgroup.layoutparams layoutparams = mcontentview.getlayoutparams();
      int height = viewgroup.layoutparams.match_parent;
      if (layoutparams != null &&
          layoutparams.height == viewgroup.layoutparams.wrap_content) {
        height = viewgroup.layoutparams.wrap_content;
      }

      // when a background is available, we embed the content view
      // within another view that owns the background drawable
      popupviewcontainer popupviewcontainer = new popupviewcontainer(mcontext);
      popupviewcontainer.layoutparams listparams = new popupviewcontainer.layoutparams(
          viewgroup.layoutparams.match_parent, height
      );
      popupviewcontainer.setbackground(mbackground);
      popupviewcontainer.addview(mcontentview, listparams);

      mpopupview = popupviewcontainer;
    } else {
      mpopupview = mcontentview;
    }

    mpopupview.setelevation(melevation);
    mpopupviewinitiallayoutdirectioninherited =
        (mpopupview.getrawlayoutdirection() == view.layout_direction_inherit);
    mpopupwidth = p.width;
    mpopupheight = p.height;
  }

上面可以看到mbackground不为空的时候，会popupviewcontainer作为mcontentview的parent，下面看看popupviewcontainer到底干了什么

  private class popupviewcontainer extends framelayout {
    private static final string tag = "popupwindow.popupviewcontainer";

    public popupviewcontainer(context context) {
      super(context);
    }

    @override
    protected int[] oncreatedrawablestate(int extraspace) {
      if (maboveanchor) {
        // 1 more needed for the above anchor state
        final int[] drawablestate = super.oncreatedrawablestate(extraspace + 1);
        view.mergedrawablestates(drawablestate, above_anchor_state_set);
        return drawablestate;
      } else {
        return super.oncreatedrawablestate(extraspace);
      }
    }

    @override
    public boolean dispatchkeyevent(keyevent event) {　　// 这个方法里面实现了返回键处理逻辑，会调用dismiss
      if (event.getkeycode() == keyevent.keycode_back) {
        if (getkeydispatcherstate() == null) {
          return super.dispatchkeyevent(event);
        }

        if (event.getaction() == keyevent.action_down
            && event.getrepeatcount() == 0) {
          keyevent.dispatcherstate state = getkeydispatcherstate();
          if (state != null) {
            state.starttracking(event, this);
          }
          return true;
        } else if (event.getaction() == keyevent.action_up) {
          keyevent.dispatcherstate state = getkeydispatcherstate();
          if (state != null && state.istracking(event) && !event.iscanceled()) {
            dismiss();
            return true;
          }
        }
        return super.dispatchkeyevent(event);
      } else {
        return super.dispatchkeyevent(event);
      }
    }

    @override
    public boolean dispatchtouchevent(motionevent ev) {
      if (mtouchinterceptor != null && mtouchinterceptor.ontouch(this, ev)) {
        return true;
      }
      return super.dispatchtouchevent(ev);
    }

    @override
    public boolean ontouchevent(motionevent event) { // 这个方法里面实现点击消失逻辑
      final int x = (int) event.getx();
      final int y = (int) event.gety();
      
      if ((event.getaction() == motionevent.action_down)
          && ((x < 0) || (x >= getwidth()) || (y < 0) || (y >= getheight()))) {
        dismiss();
        return true;
      } else if (event.getaction() == motionevent.action_outside) {
        dismiss();
        return true;
      } else {
        return super.ontouchevent(event);
      }
    }

    @override
    public void sendaccessibilityevent(int eventtype) {
      // clinets are interested in the content not the container, make it event source
      if (mcontentview != null) {
        mcontentview.sendaccessibilityevent(eventtype);
      } else {
        super.sendaccessibilityevent(eventtype);
      }
    }
  }

看到上面红色部分的标注可以看出，这个内部类里面封装了处理返回键退出和点击外部退出的逻辑，但是这个类对象的构造过程中（preparepopup方法中）却有个mbackground != null的条件才会创建

而mbackground对象在setbackgrounddrawable方法中被赋值，看到这里应该就明白一切了。

  /**
   * specifies the background drawable for this popup window. the background
   * can be set to {@code null}.
   *
   * @param background the popup's background
   * @see #getbackground()
   * @attr ref android.r.styleable#popupwindow_popupbackground
   */
  public void setbackgrounddrawable(drawable background) {
    mbackground = background;
    // 省略其他的
  }

setbackgrounddrawable方法除了被外部调用，构造方法中也会调用，默认是从系统资源中取的

  /**
   * <p>create a new, empty, non focusable popup window of dimension (0,0).</p>
   * 
   * <p>the popup does not provide a background.</p>
   */
  public popupwindow(context context, attributeset attrs, int defstyleattr, int defstyleres) {
    mcontext = context;
    mwindowmanager = (windowmanager)context.getsystemservice(context.window_service);

    final typedarray a = context.obtainstyledattributes(
        attrs, r.styleable.popupwindow, defstyleattr, defstyleres);
    final drawable bg = a.getdrawable(r.styleable.popupwindow_popupbackground);
    melevation = a.getdimension(r.styleable.popupwindow_popupelevation, 0);
    moverlapanchor = a.getboolean(r.styleable.popupwindow_overlapanchor, false);

    final int animstyle = a.getresourceid(r.styleable.popupwindow_popupanimationstyle, -1);
    manimationstyle = animstyle == r.style.animation_popupwindow ? -1 : animstyle;

    a.recycle();

    setbackgrounddrawable(bg);
  }

有些版本没有，android6.0版本preparepopup如下： 

  /**
   * prepare the popup by embedding it into a new viewgroup if the background
   * drawable is not null. if embedding is required, the layout parameters'
   * height is modified to take into account the background's padding.
   *
   * @param p the layout parameters of the popup's content view
   */
  private void preparepopup(windowmanager.layoutparams p) {
    if (mcontentview == null || mcontext == null || mwindowmanager == null) {
      throw new illegalstateexception("you must specify a valid content view by "
          + "calling setcontentview() before attempting to show the popup.");
    }

    // the old decor view may be transitioning out. make sure it finishes
    // and cleans up before we try to create another one.
    if (mdecorview != null) {
      mdecorview.canceltransitions();
    }

    // when a background is available, we embed the content view within
    // another view that owns the background drawable.
    if (mbackground != null) {
      mbackgroundview = createbackgroundview(mcontentview);
      mbackgroundview.setbackground(mbackground);
    } else {
      mbackgroundview = mcontentview;
    }

    mdecorview = createdecorview(mbackgroundview);

    // the background owner should be elevated so that it casts a shadow.
    mbackgroundview.setelevation(melevation);

    // we may wrap that in another view, so we'll need to manually specify
    // the surface insets.
    final int surfaceinset = (int) math.ceil(mbackgroundview.getz() * 2);
    p.surfaceinsets.set(surfaceinset, surfaceinset, surfaceinset, surfaceinset);
    p.hasmanualsurfaceinsets = true;

    mpopupviewinitiallayoutdirectioninherited =
        (mcontentview.getrawlayoutdirection() == view.layout_direction_inherit);
    mpopupwidth = p.width;
    mpopupheight = p.height;
  }

这里实现返回键监听的代码是mdecorview = createdecorview(mbackgroundview)，这个并没有受到那个mbackground变量的控制，所以这个版本应该没有我们所描述的问题，感兴趣的可以自己去尝试一下

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