一、基本用法

一般做法，新建类继承popupwindow。例

/** * popupwindow基本用法 * Created by Administrator on 2015/11/25. */public class DemoBasePop extends PopupWindow {  private LinearLayout linear_layout;  private TextView dbp_text;  private Context context;  public DemoBasePop(final Activity context) {    super(context);    this.context = context;    View view = LayoutInflater.from(context).inflate(R.layout.demo_base_pop,null);    setContentView(view);    setWidth(ViewGroup.LayoutParams.MATCH_PARENT);    setHeight(200);//    setHeight(ViewGroup.LayoutParams.MATCH_PARENT);    setFocusable(true);    setBackgroundDrawable(new BitmapDrawable());    setTouchable(true);    setOutsideTouchable(true);    setAnimationStyle(R.style.popwin_anim_style);//    setAnimationStyle(0);   0是没有animation    initView(view);  }  private void initView(View view) {    dbp_text = (TextView) view.findViewById(R.id.dbp_text);  }}

研究下popupwindow源码，以showAsDropDown来讲

public void showAsDropDown(View anchor, int xoff, int yoff) {    if (isShowing() || mContentView == null) {      return;    }    registerForScrollChanged(anchor, xoff, yoff);    mIsShowing = true;    mIsDropdown = true;    WindowManager.LayoutParams p = createPopupLayout(anchor.getWindowToken());    preparePopup(p);    updateAboveAnchor(findDropDownPosition(anchor, p, xoff, yoff));    if (mHeightMode < 0) p.height = mLastHeight = mHeightMode;    if (mWidthMode < 0) p.width = mLastWidth = mWidthMode;    p.windowAnimations = computeAnimationResource();    invokePopup(p);  }

第11行创建WindowManager.LayoutParams。第12行preparePopup（）中：

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.setBackgroundDrawable(mBackground);      popupViewContainer.addView(mContentView, listParams);      mPopupView = popupViewContainer;    } else {      mPopupView = mContentView;    }

如果做了setBackgroundDrawable(new BitmapDrawable());那么mBackground则不为空，则会用PopupViewContainer作为mPopupView（即内容view）。而PopupViewContainer的dispatchKeyEvent对返回键做了处理，按返回键后其中调用dismiss（）方法。其onTouchEvent对触摸事件做了处理，其源码：

public boolean onTouchEvent(MotionEvent event) {      final int x = (int) event.getX();      final int y = (int) event.getY();      //点击外部隐藏      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);      }    }

系统做了这些处理，随之而来一个问题，如果我们要监听物理返回键该怎么办。看了上面的过程，我们可以想到将

setBackgroundDrawable(null);然后通过设置view的key监听，监听到后做相应的处理。view.setOnKeyListener(new View.OnKeyListener() {      @Override      public boolean onKey(View v, int keyCode, KeyEvent event) {        if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {          if (event.getAction() == KeyEvent.ACTION_DOWN              && event.getRepeatCount() == 0) {            outAnimator.start();            return true;          }        }        return false;      }    });