Pop up a top alert Dialog like TYPE_SYSTEM_ALERT

package com.android.autologin;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnDismissListener;
import android.os.Bundle;
import android.widget.EditText;

/**
 *     This is the dialog Activity used as an AlertDialog for the user to interact.
 * Requires android:launchMode="singleInstance" in your AndroidManifest to work
 * properly.
 * <p/>
 *     当Dialog有编辑框时如果选择会弹菜单窗口就不要用 AlertDialog(Application)
 * 再添加WindowManager.LayoutParams. TYPE_SYSTEM_ALERT，
 * <pre>
 *         Context applicationContext = mainActivity.getApplicationContext();
 *        AlertDialog.Builder dlgBuilder = new AlertDialog.Builder(applicationContext);
 *        EditText et = new EditText(mainActivity);
 *        dlgBuilder.setTitle(mainActivity.getTitle());
 *        dlgBuilder.setPositiveButton(android.R.string.ok, null);
 *        dlgBuilder.setNegativeButton(android.R.string.cancel, null);
 *        dlgBuilder.setIcon(android.R.drawable.ic_dialog_alert);
 *        dlgBuilder.setView(et);
 *        AlertDialog dialog = dlgBuilder.create();
 *        dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
 *        dialog.show();
 * </pre>
 * 防止报错
 * attrs.token = null,
 * BadTokenException("Unable to add window -- token " + attrs.token + " is not for an application")
 * 
 * @usage
 * 
 * <i>.java</i>
 *        
 * <code><pre>
 *         Intent dialogIntent = new Intent(mContext, AlertActivity.class);
 *         dialogIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 *         mContext.startActivity(dialogIntent);
 * </pre></code> 
 * 
 * <i>AndroidManifest.xml</i>
 * 
 * <pre>
 *         < activity
 *             android:name=".AlertActivity"
 *             android:excludeFromRecents="true"
 *             android:finishOnTaskLaunch="true"
 *             android:launchMode="singleInstance"
 *             android:theme="@android:style/Theme.Dialog" >
 *         < /activity>
 * </pre>
 * 
 * @author Sansan
 **/
public class AlertActivity extends Activity implements DialogInterface.OnClickListener, OnDismissListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // setContentView(R.layout.alertactivity);
        
        
        // Get root view from current activity
        // @see http://stackoverflow.com/questions/4486034/get-root-view-from-current-activity
        
        // //rootview
        //// check layouts in hierarchyviewer.
        
        // findViewById(android.R.id.content) is giving me the root view
        // findViewById(android.R.id.content).getRootView()
        //getWindow().getDecorView().findViewById(android.R.id.content)
        
        // //-------------------------------------------------------------------------------------------
        // //This is what I use to get the root view as found in the XML file assigned with setContentView
        // //This answer gave the view without the status bar - which is what I wanted. I was looking for 
        // //the pixel width + height of the visible part of the activity. This one works, thanks!
        //
        //This excludes ActionBar!
        //final ViewGroup viewGroup = (ViewGroup) ((ViewGroup) this.findViewById(android.R.id.content)).getChildAt(0);
        // //-------------------------------------------------------------------------------------------
        
        
        // //-------------------------------------------------------------------------------------------
        // //I tested this in android 4.0.3, only:
        //
        // getWindow().getDecorView().getRootView();
        //
        // //give the same view what we get from
        //
        // anyview.getRootView();  == com.android.internal.policy.impl.PhoneWindow$DecorView@#########
        //
        // //and
        //
        // getWindow().getDecorView().findViewById(android.R.id.content)
        
        // //giving child of its == android.widget.FrameLayout@#######
        // //Please confirm.
        // //-------------------------------------------------------------------------------------------
        
        
        //getWindow().getDecorView().setVisibility(View.GONE);
        
        //requestWindowFeature(Window.FEATURE_NO_TITLE);//去掉标题栏
        
        // //Error, if select any text to pop up a system menu view, such as
        // paste in
        // // the Dialog.
        // //@see android/view/ViewRootImpl.java
        // //case WindowManagerGlobal.ADD_NOT_APP_TOKEN: throw new
        // //WindowManager.BadTokenException("Unable to add window -- token " +
        // //attrs.token + " is not for an application");
        // Context applicationContext = this.getApplicationContext();
        // AlertDialog.Builder dlgBuilder = new
        // AlertDialog.Builder(applicationContext);

        AlertDialog.Builder dlgBuilder = new AlertDialog.Builder(this);
        EditText et = new EditText(this);

        dlgBuilder.setTitle(this.getTitle());
        dlgBuilder.setPositiveButton(android.R.string.ok, AlertActivity.this);
        dlgBuilder.setNegativeButton(android.R.string.cancel, AlertActivity.this);
        dlgBuilder.setIcon(android.R.drawable.ic_dialog_alert);
        dlgBuilder.setView(et);
        AlertDialog dialog = dlgBuilder.create();
        // dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
        dialog.setCanceledOnTouchOutside(false);
        dialog.setOnDismissListener(this);
        dialog.show();
    }

    /**
     * meanwhile, finish the AlertActivity.
     */
    @Override
    public void onDismiss(DialogInterface dialog) {
        finish();
    }

    @Override
    public void onClick(DialogInterface dialog, int which) {

    }
}