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

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。

 

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

 

 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。

 

 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();

 

//----------------------------------------------------------------------------------------------

类似于ProgressDialog、AlertDialog都继承自Dialog。

而Dialog定义里面

public class Dialog implements DialogInterface, Window.Callback,
        KeyEvent.Callback, OnCreateContextMenuListener {
    private static final String TAG = "Dialog";
    private Activity mOwnerActivity;
    
    final Context mContext;
    final WindowManager mWindowManager;
    Window mWindow;
    // ......
}

而View和普通的View（Button，TextView等等）里面没有Window的。