Android中的PopupWindow中getWidth、getHeight为0或者-2

浏览数：34 / 时间：2015年06月11日

　　在Android开发中，需要用到PopupWindow这个类。在初始化完成，显示之前，都需要获得这个对象的width，height去计算popupWindow弹出的位置。

这个时候会发现取得的width和height都是-2；使用popupWindow.getContentView().getMeasuredWidth()和popupWindow.getContentView().getMeasuredHeight()取得的值都是0。如下面的代码：

activity_main.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3               android:orientation="vertical"
 4               android:layout_width="fill_parent"
 5               android:layout_height="fill_parent"
 6         >
 7 
 8     <Button
 9             android:layout_width="wrap_content"
10             android:layout_height="wrap_content"
11             android:text="New Button"
12             android:id="@+id/button"
13             android:layout_gravity="center_horizontal"/>
14 </LinearLayout>

popwin_layout.xml

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3               android:orientation="vertical"
 4               android:layout_width="match_parent"
 5               android:layout_height="match_parent">
 6     <ImageView
 7             android:layout_width="wrap_content"
 8             android:layout_height="wrap_content"
 9             android:src="@drawable/ic_launcher"/>
10 </LinearLayout>

MyActivity.class

 1 package com.example.popwinsize;
 2 
 3 import android.app.Activity;
 4 import android.graphics.drawable.BitmapDrawable;
 5 import android.os.Bundle;
 6 import android.text.Layout;
 7 import android.util.Log;
 8 import android.view.LayoutInflater;
 9 import android.view.View;
10 import android.view.ViewGroup;
11 import android.widget.Button;
12 import android.widget.PopupWindow;
13 
14 public class MyActivity extends Activity {
15 
16     private PopupWindow mPopWin;
17 
18     private Button mButton;
19 
20     /**
21      * Called when the activity is first created.
22      */
23     @Override
24     public void onCreate(Bundle savedInstanceState) {
25         super.onCreate(savedInstanceState);
26         setContentView(R.layout.activity_main);
27         mButton = (Button) findViewById(R.id.button);
28         mButton.setOnClickListener(new ButtonClickListener());
29 
30         initPopupWindow();
31     }
32 
33     /**
34      * 初始化PopupWindow
35      */
36     private void initPopupWindow() {
37         View contentView = LayoutInflater.from(this).inflate(R.layout.popwin_layout, null);
38         mPopWin = new PopupWindow(contentView,
39                 ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
40         mPopWin.setBackgroundDrawable(new BitmapDrawable());    //设置背景，否则setOutsideTouchable无效
41         mPopWin.setOutsideTouchable(true);                      //设置点击PopupWindow以外的地方关闭PopupWindow
42         mPopWin.setFocusable(true);                             //获取焦点
43     }
44 
45     class ButtonClickListener implements View.OnClickListener {
46 
47         @Override
48         public void onClick(View v) {
49             //点击在按钮的中下方弹出mPopWin
50 
51             int btnWidth = v.getMeasuredWidth();
52             int btnHeight = v.getMeasuredHeight();
53 
54             int popWidth = mPopWin.getContentView().getMeasuredWidth();
55             int popHeight = mPopWin.getContentView().getMeasuredHeight();
56             Log.i("Button.size", "width=" + btnWidth + "; height=" + btnHeight);
57             Log.i("PopupWindow.size", "width=" + popWidth + "; height=" + popHeight);
58             //mPopWin.showAsDropDown(v);    //这个是在按钮的下方出现，x值与按钮的x值相等
59 
60             int xoff = (int)((float)(btnWidth - popWidth)/2);    //PopupWindow的x偏移值
61             int yoff = 0;                                        //因为相对于按钮的下方，所以该值为0
62 
63             mPopWin.showAsDropDown(v, xoff, yoff);
64         }
65     }
66 }

这个时候你会发现，出现的效果并不是您想要的效果，是在按钮是右下方出现

LogCat捕获的结果是：

　　 I/Button.size﹕ width=176; height=72
　　 I/PopupWindow.size﹕ width=0; height=0

出现这个的原因就是因为PopupWindow的尺寸拿不到，因为内容的View的width和height都是wrap_content，所以在PopupWindow里面的contentView还没被绘制出来的时候，这两个值都还是0。

如果直接调用PopupWindow的getWidth()和getHeight()，会发现拿到的都是ViewGroup.LayoutParams.WRAP_CONTENT的值 -2;

解决的方法就是在初始化contentView的时候，强制绘制contentView，并且马上初始化contentView的尺寸。这里只需要一句代码即可

看下面的MyActivity.class的第38行代码：

 1 package com.example.popwinsize;
 2 
 3 import android.app.Activity;
 4 import android.graphics.drawable.BitmapDrawable;
 5 import android.os.Bundle;
 6 import android.text.Layout;
 7 import android.util.Log;
 8 import android.view.LayoutInflater;
 9 import android.view.View;
10 import android.view.ViewGroup;
11 import android.widget.Button;
12 import android.widget.PopupWindow;
13 
14 public class MyActivity extends Activity {
15 
16     private PopupWindow mPopWin;
17 
18     private Button mButton;
19 
20     /**
21      * Called when the activity is first created.
22      */
23     @Override
24     public void onCreate(Bundle savedInstanceState) {
25         super.onCreate(savedInstanceState);
26         setContentView(R.layout.activity_main);
27         mButton = (Button) findViewById(R.id.button);
28         mButton.setOnClickListener(new ButtonClickListener());
29 
30         initPopupWindow();
31     }
32 
33     /**
34      * 初始化PopupWindow
35      */
36     private void initPopupWindow() {
37         View contentView = LayoutInflater.from(this).inflate(R.layout.popwin_layout, null);
38         contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
39         mPopWin = new PopupWindow(contentView,
40                 ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
41         mPopWin.setBackgroundDrawable(new BitmapDrawable());    //设置背景，否则setOutsideTouchable无效
42         mPopWin.setOutsideTouchable(true);                        //设置点击PopupWindow以外的地方关闭PopupWindow
43         mPopWin.setFocusable(true);                                //获取焦点
44     }
45 
46     class ButtonClickListener implements View.OnClickListener {
47 
48         @Override
49         public void onClick(View v) {
50             //点击在按钮的中下方弹出mPopWin
51 
52             int btnWidth = v.getMeasuredWidth();
53             int btnHeight = v.getMeasuredHeight();
54 
55             int popWidth = mPopWin.getContentView().getMeasuredWidth();
56             int popHeight = mPopWin.getContentView().getMeasuredHeight();
57             Log.i("Button.size", "width=" + btnWidth + "; height=" + btnHeight);
58             Log.i("PopupWindow.size", "width=" + popWidth + "; height=" + popHeight);
59             //mPopWin.showAsDropDown(v);    //在按钮的下方出现，x值与按钮的x值相等
60 
61             int xoff = (int)((float)(btnWidth - popWidth)/2);    //PopupWindow的x偏移值
62             int yoff = 0;                                        //因为相对于按钮的下方，所以该值为0
63 
64             mPopWin.showAsDropDown(v, xoff, yoff);
65         }
66     }
67 }