效果图：

代码：

public class ViewActivity extends Activity implements View.OnClickListener {

    PopupWindow popWindow;

    LinearLayout rootView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        requestWindowFeature(Window.FEATURE_NO_TITLE);

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_view);

        rootView = (LinearLayout) findViewById(R.id.ll_rootview);

        initPopWindow(this);

    }

    @Override

    public void onClick(View v) {

        popWindow.showAtLocation(rootView, Gravity.CENTER, 0, 0);

    }

    public void initPopWindow(Context context) {

        View view = LayoutInflater.from(context).inflate(R.layout.view_share, null);

        popWindow = new PopupWindow(view, RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT, true);

        ImageView iv_cancel = (ImageView) view.findViewById(R.id.iv_cancel);

        iv_cancel.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                popWindow.dismiss();

            }

        });

        //给popupwindow设置返回键监听

        popWindow.getContentView().setFocusableInTouchMode(true);

        popWindow.getContentView().setFocusable(true);

        popWindow.getContentView().setOnKeyListener(new View.OnKeyListener() {

            @Override

            public boolean onKey(View v, int keyCode, KeyEvent event) {

                if (event.getAction() == KeyEvent.ACTION_DOWN && keyCode == KeyEvent.KEYCODE_BACK) {

                    if (popWindow != null && popWindow.isShowing()) {

                        popWindow.dismiss();

                    }

                    return true;

                }

                return false;

            }

        });

    }

}

背景是否为灰色：

//直接在view_share的根布局设置背景颜色就能够

  android:background="#aa666666"