android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application

这个错误是我在看Android SDK文档时，在一个Button的监听器里写了一个自定义的处理条，

代码如下:

//自定义处理条
dialog6.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
AlertDialog.Builder builder;
AlertDialog alertDialog;
Context mContext = getApplicationContext();

LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.custom_dialog, (ViewGroup)findViewById(R.id.layout_root));

TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("Hello, this is a custom dialog!");
ImageView image = (ImageView) layout.findViewById(R.id.image);
image.setImageResource(R.drawable.icon);
builder = new AlertDialog.Builder(mContext);
builder.setView(layout);
alertDialog = builder.create();
alertDialog.show();
}
});

问题出在这句Context mContext = getApplicationContext();

应该写成Activity.this. Activity所在的Activity.

这是解释http://tech.shantanugoel.com/2010/07/08/badtokenexception-android-dialog-getapplicationcontext.html。