Unable to add window -- token null is not for an appli,无法在window中弹出对话框

原博客地址：http://aijiawang-126-com.javaeye.com/blog/662336

在Activity中newSpinner是我把mContext传入，但是出了android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application这个错误，参考了达人的文章终于搞定。



view plaincopy to clipboardprint?

private Context mcontext;
@Override
protected void onCreate(Bundle savedInstanceState) {mcontext = getApplicationContext();
System.out.println("mcontext=" + mcontext);
}

view plaincopy to clipboardprint?

new AlertDialog.Builder(mcontext)  
            .setIcon(android.R.drawable.ic_dialog_alert)  
            .setTitle("Warnning")  
            .setMessage(  
                    "You forget to write the message. Do you want to fill out it ??")  
            .setPositiveButton("Yes", positiveListener).setNegativeButton(  
                    "No", negativeListener).create().show();  

	new AlertDialog.Builder(mcontext)
				.setIcon(android.R.drawable.ic_dialog_alert)
				.setTitle("Warnning")
				.setMessage(
						"You forget to write the message. Do you want to fill out it ??")
				.setPositiveButton("Yes", positiveListener).setNegativeButton(
						"No", negativeListener).create().show();

导致报这个错是在于new AlertDialog.Builder(mcontext)，虽然这里的参数是AlertDialog.Builder(Context context)但我们不能使用getApplicationContext()获得的Context,而必须使用Activity,因为只有一个Activity才能添加一个窗体。



解决方法：将new AlertDialog.Builder(Context context)中的参数用Activity.this（Activity是你的Activity的名称）来填充就可以正确的创建一个Dialog了。



view plaincopy to clipboardprint?

new AlertDialog.Builder(MyActivity.this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Warnning")
.setMessage(
"You forget to write the message. Do you want to fill out it ??")
.setPositiveButton("Yes", positiveListener).setNegativeButton(
"No", negativeListener).create().show();