詳解Android PopupWindow怎么合理控制彈出位置（showAtLocation）

// 一個(gè)自定義的布局，作為顯示的內(nèi)容
Context context = null;　　// 真實(shí)環(huán)境中要賦值
int layoutId = 0;　　　　　　// 布局ID
View contentView = LayoutInflater.from(context).inflate(layoutId, null);
   
final PopupWindow popupWindow = new PopupWindow(contentView,
        LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, true);

popupWindow.setTouchable(true);
// 如果不設(shè)置PopupWindow的背景，有些版本就會(huì)出現(xiàn)一個(gè)問(wèn)題：無(wú)論是點(diǎn)擊外部區(qū)域還是Back鍵都無(wú)法dismiss彈框
// 這里單獨(dú)寫一篇文章來(lái)分析
popupWindow.setBackgroundDrawable(new ColorDrawable());
// 設(shè)置好參數(shù)之后再show
popupWindow.showAsDropDown(contentView);

  /**
   * 計(jì)算出來(lái)的位置，y方向就在anchorView的上面和下面對(duì)齊顯示，x方向就是與屏幕右邊對(duì)齊顯示
   * 如果anchorView的位置有變化，就可以適當(dāng)自己額外加入偏移來(lái)修正
   * @param anchorView 呼出window的view
   * @param contentView  window的內(nèi)容布局
   * @return window顯示的左上角的xOff,yOff坐標(biāo)
   */
  private static int[] calculatePopWindowPos(final View anchorView, final View contentView) {
    final int windowPos[] = new int[2];
    final int anchorLoc[] = new int[2];
　　　　 // 獲取錨點(diǎn)View在屏幕上的左上角坐標(biāo)位置
    anchorView.getLocationOnScreen(anchorLoc);
    final int anchorHeight = anchorView.getHeight();
    // 獲取屏幕的高寬
    final int screenHeight = ScreenUtils.getScreenHeight(anchorView.getContext());
    final int screenWidth = ScreenUtils.getScreenWidth(anchorView.getContext());
    contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
    // 計(jì)算contentView的高寬
    final int windowHeight = contentView.getMeasuredHeight();
    final int windowWidth = contentView.getMeasuredWidth();
    // 判斷需要向上彈出還是向下彈出顯示
    final boolean isNeedShowUp = (screenHeight - anchorLoc[1] - anchorHeight < windowHeight);
    if (isNeedShowUp) {
      windowPos[0] = screenWidth - windowWidth;
      windowPos[1] = anchorLoc[1] - windowHeight;
    } else {
      windowPos[0] = screenWidth - windowWidth;
      windowPos[1] = anchorLoc[1] + anchorHeight;
    }
    return windowPos;
  }

View windowContentViewRoot = 我們要設(shè)置給PopupWindow進(jìn)行顯示的View
int windowPos[] = calculatePopWindowPos(view, windowContentViewRoot);
int xOff = 20；// 可以自己調(diào)整偏移
windowPos[0] -= xOff;
popupwindow.showAtLocation(view, Gravity.TOP | Gravity.START, windowPos[0], windowPos[1]);
// windowContentViewRoot是根布局View

  /**
   * 獲取屏幕高度(px)
   */
  public static int getScreenHeight(Context context) {
    return context.getResources().getDisplayMetrics().heightPixels;
  }
  /**
   * 獲取屏幕寬度(px)
   */
  public static int getScreenWidth(Context context) {
    return context.getResources().getDisplayMetrics().widthPixels;
  }