AlertDialog的点击事件报错！！！求大神

final ListView lv=(ListView)findViewById(R.id.listView1);

		final ArrayList<HashMap<String, Object>> listItem = new ArrayList<HashMap<String,Object>>();

		HashMap<String, Object> map = new HashMap<String, Object>();

		final SimpleAdapter mSimpleAdapter=new SimpleAdapter(this,listItem,R.layout.item,new String[]{"1","2"},new int[]{R.id.itemtext1,R.id.itemtext2});

		lv.setAdapter(mSimpleAdapter);

                Button btn=(Button)findViewById(R.id.add);

		btn.setOnClickListener(new View.OnClickListener() {

			

			@Override

			public void onClick(View v) {

				// TODO 自动生成的方法存根

				Builder builder=new AlertDialog.Builder(MainActivity.this);

				builder.setTitle("添加任务：");

				LayoutInflater inflater=getLayoutInflater();

				View view=inflater.inflate(R.layout.addactivity, null);

				builder.setView(view);

				builder.setPositiveButton("添加", new DialogInterface.OnClickListener() {

					

					@Override

					public void onClick(DialogInterface dialog, int which) {

						// TODO 自动生成的方法存根

						EditText editname=(EditText)findViewById(R.id.editName);

						String name=editname.getText().toString();

						EditText edittime=(EditText)findViewById(R.id.editTime);

						String time=edittime.getText().toString();

						HashMap<String, Object> map = new HashMap<String, Object>();

						map.put("1", name);

						map.put("2", time);

						

						listItem.add(map);

						

						mSimpleAdapter.notifyDataSetChanged();

					}

				});

				builder.setNegativeButton("取消", null);

				builder.create().show();

				}

		});

这是代码，简单说一下，在主界面放一个button和一个listview，点击button弹出AlertDialog，AlertDialog是通过addactivity.xml来布局的，在AlertDialog里面有两个EditText(editName,editTime)，我希望通过setPosttiveButton获取这两个EditText的值，放到主界面的ListView里面，可是这样报错，大神帮忙看一下哪里错了，谢谢