Android中Activity与Fragment之间的传值问题

Activity与Fragment之间的传值问题

Activity传值给Fragment

添加Fragment的Activity：

 Fragment01 fragment = new Fragment01();
        Bundle bundle = new Bundle();
        bundle.putString("str","这是Activity传来的值");
        fragment.setArguments(bundle);

        fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fm01id,fragment01);
        fragmentTransaction.commit();
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Fragment中接受Activity传过来的值：

String str = (String)getArguments().get(“str”);
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Fragment传值给Activity：

实现思路：
1.在Fragment中写一个回调接口
2.在activity中实现这个回调接口
3.在Fragment中onAttach 方法中得到activity中实现好的 实例化接口对象
4.用接口的对象 进行传值

Activity：

public class MainActivity extends Activity implements CallBackValue{  

    private TextView tv1;  
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  

        tv1 = (TextView) findViewById(R.id.tv1);  

        FragmentManager manager = getFragmentManager();  
        FragmentTransaction transaction =   manager.beginTransaction();  
        transaction.add(R.id.contents, new Fragmen1());  
        transaction.commit();  

    }  
    //要获取的值  就是这个参数的值  
    @Override  
    public void SendMessageValue(String strValue) {  
        // TODO Auto-generated method stub  
        tv1.setText(strValue);  
    }  
} 
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Fragment：

public class Fragmen1 extends Fragment{  
    private Button btn1;  
    private EditText et1;  
    CallBackValue callBackValue;  

    /** 
     * fragment与activity产生关联是  回调这个方法  
     */  
    @Override  
    public void onAttach(Activity activity) {  
        // TODO Auto-generated method stub  
        super.onAttach(activity);  
        //当前fragment从activity重写了回调接口  得到接口的实例化对象  
        callBackValue =(CallBackValue) getActivity();  
    }  


    @Override  
    public View onCreateView(LayoutInflater inflater, ViewGroup container,  
            Bundle savedInstanceState) {  
        // TODO Auto-generated method stub  
        View view = inflater.inflate(R.layout.fragment_layout1, container, false);  
         btn1 = (Button) view.findViewById(R.id.btn1);  
         et1 = (EditText) view.findViewById(R.id.et1);  
         btn1.setOnClickListener(new OnClickListener() {  

            @Override  
            public void onClick(View v) {  
                // TODO Auto-generated method stub  
                String strValue = et1.getText().toString().trim();  
                callBackValue.SendMessageValue(strValue);  

            }  
        });  

        return view;  
    }  
    //定义一个回调接口  
    public interface CallBackValue{  
        public void SendMessageValue(String strValue);  
    }  
}  
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onAttach的解决方案 ：

今天在写一个Fragment的Demo中，在onAttach中进行赋值工作，结果显示并没有赋值，意味着onAttach并没有调用，最终在stackFlow找到了答案：

It’s not called because this method has been added in API 23. If you run your application on a device with API 23 (marshmallow) then onAttach(Context) will be called. On all previous Android Versions onAttach(Activity) will be called.

我是看  onAttach(Activity) 方法被deprecation了，所以用最新的 onAttach(Context) 方法，哪想到在API低于 23 的版本中不会去调用后者，只会去调用onAttach(Activity)。下面是看到的一个比较好的解决方案：

 /*
 * onAttach(Context) is not called on pre API 23 versions of Android and onAttach(Activity) is deprecated
 * Use onAttachToContext instead
 */
    @TargetApi(23)
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        onAttachToContext(context);
    }
 
    /*
     * Deprecated on API 23
     * Use onAttachToContext instead
     */
    @SuppressWarnings(“deprecation”)
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            onAttachToContext(activity);
        }
    }
 
    /*
     * Called when the fragment attaches to the context
     */
    protected void onAttachToContext(Context context) {
       //do something
    }

在用Fragment时，这样复写onAttach方法就可以减少API的影响了。ps：也真是出鬼了，昨天手机才升级的6.0，结果今天搞的手机测试正常，平板（api:4.4）测试不正常，愁死我了。这个问题告诉我，google不断发布兼容库意义重大啊！！！