android dialog的圆角不显示问题

//第一套代码
//控制代码
package com.myapp.mydialog;

import com.myapp.myapptest.R;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.Window;

public class MyDialog extends Dialog{

public MyDialog(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);//需要在设置内容之前定义
setContentView(R.layout.dialog_one);
}

}

//视图代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/dialog_bg"
android:orientation="vertical" >

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:src="@drawable/power_red" />

</LinearLayout>

//资源代码

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<corners android:radius="50dp">
</corners>
</shape>

显示结果



------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

第二套代码

package com.myapp.mydialog;

import com.myapp.myapptest.R;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.Window;

public class MyDialog extends Dialog{

public MyDialog(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
//requestWindowFeature(Window.FEATURE_NO_TITLE);//需要在设置内容之前定义--------------------->改变处
setContentView(R.layout.dialog_one);
}

}

其他不变



对比两幅图，结果显而易见

解决方法：加上语句getWindow().setBackgroundDrawableResource(android.R.color.transparent); 

解决后：

<pre name="code" class="java">package com.myapp.mydialog;

import com.myapp.myapptest.R;

import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;

public class MyDialog extends Dialog{

public MyDialog(Context context) {
super(context);
// TODO Auto-generated constructor stub
}

@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);//需要在设置内容之前定义
getWindow().setBackgroundDrawableResource(android.R.color.transparent);
setContentView(R.layout.dialog_one);
}

}