Android使alertDialog.builder不会点击外面和按返回键消失的方法

public void showNoProject(){
    Builder builder = new AlertDialog.Builder(MainActivity.this)
    .setMessage("您还没有项目，请先添加项目")
    .setPositiveButton("去添加项目", new OnClickListener() {
      
      @Override
      public void onClick(DialogInterface dialog, int which) {
        dialog.dismiss();
        
      }
    })
    .setNegativeButton("关闭", new OnClickListener() {
      
      @Override
      public void onClick(DialogInterface dialog, int which) {
        dialog.dismiss();
        
      }
    });
    builder.setCancelable(false);
    builder.show();
  }

  @Override  
  public void onCreate(Bundle icicle)
  {
   super.onCreate(icicle);
   this.setCancelable(false);// 设置点击屏幕Dialog不消失
    int style = DialogFragment.STYLE_NORMAL, theme = 0;
    setStyle(style,theme);
  }

YourActivity.this.setFinishOnTouchOutside(false);