如何访问片段变量到主活动类

Question

我有1个主活动类和1个片段类:

我想访问片段类的变量到我的主活动类:

Myfragment类:

public class DemoFragment extends Fragment {
Public String mydata="hello";
.. //other code
}

Mainactivity类:

public class MainActivity extends ActionBarActivity {
   ..//other code
   DemoFragment df;
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        df = new DemoFragment();
        String newdata = df.mydata; //access from fragment but it shows null
    }
}

那么我怎么能访问片段类变量值到主活动?

Answer 1

在你的片段中创建

(a)两个字段:

listener mCallback;
Activity mActivity;

(b)接口:

interface mydataBack(){
   public void bringBackString(String stringSentBack);
}

(c)方法

@Override
        public void onAttach(Activity activity) {
            mActivity=activity;
            super.onAttach(activity);
        mCallback = (listener) mActivity;
        }`

然后在Fragment中调用方法bringBackString(String)当你希望返回字符串。

在你的mainactivity中:

(a)添加"implements.. ..."

类声明

public class MainActivity extends ActionBarActivity implements DemoFragment.listener {  etc   and

(b)实现接口方法:

public void bringBackString(String stringBroughtBack){
....  do something with the string
}

Answer 2

你必须使用
公共静态字符串mydata = "hello "然后在活动中使用df。mydata