Android的对话框有两种：PopupWindow和AlertDialog。它们的不同点在于：
AlertDialog的位置固定，而PopupWindow的位置可以随意AlertDialog是非阻塞线程的，而PopupWindow是阻塞线程的PopupWindow的位置按照有无偏移分，可以分为偏移和无偏移两种；按照参照物的不同，可以分为相对于某个控件（Anchor锚）和相对于父控件。具体如下showAsDropDown(View anchor)：相对某个控件的位置（正左下方），无偏移showAsDropDown(View anchor, int xoff, int yoff)：相对某个控件的位置，有偏移showAtLocation(View parent, int gravity, int x, int y)：相对于父控件的位置（例如正中央Gravity.CENTER，下方Gravity.BOTTOM等），可以设置偏移或无偏移下面通过一个Demo讲解（解释看注释）：main.xml[html] <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <Button android:id="@+id/button01" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="以自己为Anchor，不偏移" /> <Button android:id="@+id/button02" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="以自己为Anchor，有偏移" /> <Button android:id="@+id/button03" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="以屏幕中心为参照，不偏移（正中间）" /> <Button android:id="@+id/button04" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="以屏幕下方为参照，下方中间" /> </LinearLayout>popup_window.xml
[html]<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="" android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="#00FF00" android:orientation="vertical" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="选择状态：" android:textColor="@android:color/white" android:textSize="20px" /> <RadioGroup android:id="@+id/radioGroup" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="vertical" > <RadioButton android:text="在线" /> <RadioButton android:text="离线" /> <RadioButton android:text="隐身" /> </RadioGroup> </LinearLayout>PopupWindowDemoActivity.java
[java]package com.tianjf; import android.app.Activity; import android.os.Bundle; import android.view.Gravity; import android.view.LayoutInflater; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.PopupWindow; import android.widget.RadioGroup; import android.widget.RadioGroup.OnCheckedChangeListener; public class PopupWindowDemoActivity extends Activity implements OnClickListener, OnCheckedChangeListener { private Button mbutton01; private Button mbutton02; private Button mbutton03; private Button mbutton04; private PopupWindow mPopupWindow; // 屏幕的width private int mScreenWidth; // 屏幕的height private int mScreenHeight; // PopupWindow的width private int mPopupWindowWidth; // PopupWindow的height private int mPopupWindowHeight; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mbutton01 = (Button) findViewById(R.id.button01); mbutton02 = (Button) findViewById(R.id.button02); mbutton03 = (Button) findViewById(R.id.button03); mbutton04 = (Button) findViewById(R.id.button04); mbutton01.setOnClickListener(this); mbutton02.setOnClickListener(this); mbutton03.setOnClickListener(this); mbutton04.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { // 相对某个控件的位置（正左下方），无偏移 case R.id.button01: getPopupWindowInstance(); mPopupWindow.showAsDropDown(v); break; // 相对某个控件的位置（正左下方），有偏移 case R.id.button02: getPopupWindowInstance(); mPopupWindow.showAsDropDown(v, 50, 50);// X、Y方向各偏移50 break; // 相对于父控件的位置，无偏移 case R.id.button03: getPopupWindowInstance(); mPopupWindow.showAtLocation(v, Gravity.CENTER, 0, 0); break; // 相对于父控件的位置，有偏移 case R.id.button04: getPopupWindowInstance(); mPopupWindow.showAtLocation(v, Gravity.BOTTOM, 0, 50); break; default: break; } } @Override public void onCheckedChanged(RadioGroup group, int checkedId) { mPopupWindow.dismiss(); } /* * 获取PopupWindow实例 */ private void getPopupWindowInstance() { if (null != mPopupWindow) { mPopupWindow.dismiss(); return; } else { initPopuptWindow(); } } /* * 创建PopupWindow */ private void initPopuptWindow() { LayoutInflater layoutInflater = LayoutInflater.from(this); View popupWindow = layoutInflater.inflate(R.layout.popup_window, null); RadioGroup radioGroup = (RadioGroup) popupWindow.findViewById(R.id.radioGroup); radioGroup.setOnCheckedChangeListener(this); // 创建一个PopupWindow // 参数1：contentView 指定PopupWindow的内容 // 参数2：width 指定PopupWindow的width // 参数3：height 指定PopupWindow的height mPopupWindow = new PopupWindow(popupWindow, 100, 130); // 获取屏幕和PopupWindow的width和height mScreenWidth = getWindowManager().getDefaultDisplay().getWidth(); mScreenWidth = getWindowManager().getDefaultDisplay().getHeight(); mPopupWindowWidth = mPopupWindow.getWidth(); mPopupWindowHeight = mPopupWindow.getHeight(); } }