Fragment间的交互

Fragment间的交互 

    使用回调的方式，让FragmentActivity充当中间交互的桥梁。 

public class MainActivity extends AppCompatActivity implements OnClickIndexOnclick{
    private FragmentManager fragmentManagerf;
    private  downFragment down;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fragmentManagerf = getSupportFragmentManager();
        down=(downFragment) fragmentManagerf.findFragmentByTag("down");
    }

    @Override
    public void onClick(int index) {
        down.setIndex(index);
    }
}

public interface OnClickIndexOnclick {//桥接器
    void onClick(int index);
}

public class TopFragment extends Fragment{
    private  int index=1;
    private OnClickIndexOnclick onClickIndexOnclick;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.top_layout,null);

        Button button = view.findViewById(R.id.onclick);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                index++;
                Index(index)
                ;
            }
        });
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        this.onClickIndexOnclick=(OnClickIndexOnclick) getActivity();//获取Activity的对象返回Activity

        Index(index);
    }

    private void Index(int index){
        Log.v("wang",""+index);
        onClickIndexOnclick.onClick(index);
    }
}

public class downFragment extends Fragment{
    private TextView textView;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.down_layout,null);
        textView =view.findViewById(R.id.textViewId);

        return view;
    }


    public void setIndex(int index) {
        textView.setText("当前点击了"+index+"次");
        textView.setTextSize(30);
    }
}

       MianActivity

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">
       <fragment
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:tag="top"
        android:name="project.li.com.a05_fragmenttest.TopFragment">

    </fragment>
    <fragment
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:tag="down"
        android:name="project.li.com.a05_fragmenttest.downFragment">

    </fragment>

</LinearLayout>