Android 自定义对话框

package com.example.popup_vs_dialog;

import android.app.Activity;
import android.app.Dialog;
import android.graphics.Rect;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.PopupWindow;

public class MainActivity extends Activity {

    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        final ImageView img1 = (ImageView)this.findViewById(R.id.img1);
        img1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                usePopup(img1);
            }
        });
        
        final ImageView img2 = (ImageView)this.findViewById(R.id.img2);
        img2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                useDialog(img2);
            }
        });
    }
    
    private void usePopup(final ImageView anchor){
        LayoutInflater mInflater = LayoutInflater.from(this);
         ViewGroup rootView = (ViewGroup)mInflater.inflate(R.layout.menu, null);
         rootView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        final PopupWindow popup = new PopupWindow(this);
        //setContentView之前一定要设置宽高，否则不显示
        popup.setWidth(WindowManager.LayoutParams.WRAP_CONTENT);
        popup.setHeight(WindowManager.LayoutParams.WRAP_CONTENT);
        //去掉默认的背景 
        popup.setBackgroundDrawable(new ColorDrawable(android.R.color.transparent));
        popup.setContentView(rootView);
        //点击空白处的时候PopupWindow会消失
        popup.setTouchable(true); 
        popup.setOutsideTouchable(true);
        //如果focusable为false，在一个Activity弹出一个PopupWindow，按返回键，由于PopupWindow没有焦点，会直接退出Activity。如果focusable为true，PopupWindow弹出后，所有的触屏和物理按键都有PopupWindows处理。
        popup.setFocusable(true);
        //计算弹框位置
        int[] xy = calcPopupXY(rootView,anchor);
        //不用任何gravity，使用绝对的(x,y)坐标
        popup.showAtLocation((View)anchor.getParent(),Gravity.NO_GRAVITY, xy[0], xy[1]);
    }
    
    private void useDialog(final ImageView anchor){
        LayoutInflater mInflater = LayoutInflater.from(this);
         ViewGroup rootView = (ViewGroup)mInflater.inflate(R.layout.menu, null);
         rootView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
        Dialog dialog = new Dialog(this);
        WindowManager.LayoutParams params = dialog.getWindow().getAttributes();
        params.width = WindowManager.LayoutParams.WRAP_CONTENT;
        params.height = WindowManager.LayoutParams.WRAP_CONTENT;
        //去掉默认的背景,下面两个都可以
        dialog.getWindow().setBackgroundDrawable(new ColorDrawable(android.R.color.transparent));
        //dialog.getWindow().setBackgroundDrawableResource(android.R.color.transparent);
        //http://stackoverflow.com/questions/12348405/dialog-is-bigger-than-expected-when-using-relativelayout
        //dialog默认都是有title的
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);//去掉标题，否则会影响高度计算，一定要在setContentView之前调用，终于明白有一个设置theme的构造函数的目的了
        dialog.setContentView(rootView);
    
        //计算弹框位置
        int[] xy = calcPopupXY(rootView,anchor);
        //gravity的默认值为Gravity.CENTER,即Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL.
        //参考: http://www.cnblogs.com/angeldevil/archive/2012/03/31/2426242.html
        dialog.getWindow().setGravity(Gravity.LEFT | Gravity.TOP);
        params.x = xy[0];
        params.y = xy[1];
        
        dialog.show();
    }
    
    private int[] calcPopupXY(View rootView, View anchor){
        int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);  
        int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED); 
        rootView.measure(w, h);  
        int popupWidth = rootView.getMeasuredWidth();
        int popupHeight = rootView.getMeasuredHeight();
        Rect anchorRect = getViewAbsoluteLocation(anchor);
        int x = anchorRect.left + (anchorRect.right - anchorRect.left)/2 - popupWidth / 2;
        int y = anchorRect.top - popupHeight;
        return new int[]{x,y};
    }
    
    public static Rect getViewAbsoluteLocation(View view){
        if(view == null){
            return new Rect();
        }
        // 获取View相对于屏幕的坐标
        int[] location = new int[2] ;
        view.getLocationOnScreen(location);//这是获取相对于屏幕的绝对坐标，而view.getLocationInWindow(location); 是获取window上的相对坐标，本例中只有一个window，二者等价
        // 获取View的宽高
        int width = view.getMeasuredWidth();
        int height = view.getMeasuredHeight();
        // 获取View的Rect
        Rect rect = new Rect();
        rect.left = location[0];
        rect.top = location[1];
        rect.right = rect.left + width;
        rect.bottom = rect.top + height;
        return rect;
    }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/img1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:src="@drawable/img" />
    
    <ImageView
        android:id="@+id/img2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/img1"
        android:layout_marginLeft="50dp"
        android:layout_alignTop="@id/img1"
        android:src="@drawable/img" />

</RelativeLayout>