Android------------fragment数据传递

一、activity向fragment的数值之间的传递

　　之间传递的关键函数fragemnt(自己创建的fragment去调用).setArgument(bundle) 和getArgument()

　　以下有许多注意事项：

　　MainActivity.java

public class MainActivity extends AppCompatActivity {

    private FragmentManager manager;
    private FragmentTransaction transition;
    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        editText = findViewById(R.id.edit_content);
        manager = getSupportFragmentManager();
        transition = manager.beginTransaction();
        transition.add(R.id.line_content, new ResultFragment());
        transition.commit();
    }

    public void SendMessage(View view){
        String info = editText.getText().toString().trim();
        ResultFragment result = new ResultFragment();
        Bundle bundle = new Bundle();
        bundle.putString("info",info);
        result.setArguments(bundle);
        
　　     //即使是全局对象也要重新得到transition的对象，否则会抛出异常，单步调试F7或者F8就可以知道了
        manager = getSupportFragmentManager();
        transition = manager.beginTransaction();
        transition.replace(R.id.line_content,result);
        transition.commit();

    }
}


ResultFlagment.java

public class ResultFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.countfragment,null);
        TextView textView = view.findViewById(R.id.textView);
        Bundle bundle = getArguments();

　　　　　//一定要对Bundle就行判断，否则会抛出bundle.getString()得不到字符串的异常
        if(bundle != null)
        {
            String info = bundle.getString("info");
            textView.setText(info);
        }
        return view;
    }
}


二、fragmeng向activity传数值
　　
　　注意事项：得到MyListner的对象一般在onCreate或者在onAttach()方法里面进行初始化

　　ResourceFragment.java  

public class ResoureFragment extends Fragment {
    private EditText editText;
    private Button button;
    private MyListner myListner;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myListner = (MyListner) getActivity();
        Log.i("info111", "onCreate-------->myListner=="+myListner);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.resource,null);
        button = view.findViewById(R.id.button);
        editText = view.findViewById(R.id.edit_content);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String s = editText.getText().toString().trim();
                myListner.SendMessage(s);
            }
        });

        return view;
    }
    public interface MyListner{
        void SendMessage(String s);
    }
}

　　MainActivity.java的讲解

public class MainActivity extends AppCompatActivity implements ResoureFragment.MyListner {
    private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = findViewById(R.id.getText);
    }

    @Override
    public void SendMessage(String s) {
            textView.setText(s);
    }
}

activity_main.xml文件
注意事项：
引用其他的fragment的时候一定加上它的属性ID，否则会报错

<fragment
    android:id="@+id/line_exercise"
    android:name="com.example.zhang.fragment_activity.ResoureFragment"
    android:layout_width="match_parent"
    android:layout_height="300dp"
    android:layout_marginTop="10dp" />

知识点的讲解：java的多态性

1.MainActivity extends AppCompatActivity implements ResoureFragment.MyListner
　　MainActivity是AppCompatActivity的子类，同时也是MyListner的子类

2.myListner = (MyListner) getActivity();
　　这一步的得到是fragment的当前的类的Activity的窗口，他又MyListner的子类，所以就出现回调函数这样的方法
　　举例说明：
　　A extent B
　　B b = new A();
　　其实b这个时候获得是A的对象，和myListner = (MyListner) getActivity()方法相近

     

三、fragment和fragment的之间的数值传递