fragment（3、交互）

1、activity调用fragment，可直接通过activity内fragment的运用调用其公共方法；

2、fragment调用activity，利用getActivity（），如下：

((MainActivity) getActivity()).mainLog("hello"); //mainLog为activity中定义的方法

备注：此时要注意使用getActivity时要保证该activity与fragment关联；对动态生成的fragment，知道commit提交后，才进入fragment的oncreate.

3、回调，为满足activity与fragment的解耦，也可采用回调的方式，如下：

3.1 在fragment中定义一个回调接口，并对外暴露设置接口的方法

public class DemoFragment extends Fragment {
    private Button   mButton;
    private FragmentListner listener;
    
    public interface FragmentListner  
    {  
        void onFragmentClick();  
    }
    
    public void setFragmentListner(FragmentListner listener){
        this.listener = listener;
    }
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main, container, false);        
        mButton = (Button)view.findViewById(R.id.button1);
        mButton.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {
                if(null != listener){
                    listener.onFragmentClick();                }                
            }
        });
        
        return view;
    }
}

3.2 在activity中设置该方法（该例子中直接由fragment的按键触发fragment切换）

public class MainActivity extends FragmentActivity {

    private DemoFragment mDemo;
    private OtherFragment mDemo2;
    private Button mButton;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mButton = (Button)findViewById(R.id.button3);

        mButton.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {

                FragmentManager fm = getSupportFragmentManager();  
                FragmentTransaction transaction = fm.beginTransaction();  
                mDemo = new DemoFragment();
                mDemo.setFragmentListner(new FragmentListner(){

                    @Override
                    public void onFragmentClick() {
                        FragmentManager fm = getSupportFragmentManager();  
                        FragmentTransaction transaction = fm.beginTransaction();  
                        mDemo2 = new OtherFragment();
                        transaction.replace(R.id.fragment_content, mDemo2);
                        transaction.addToBackStack(null);
                        transaction.commit();
                    }
                    
                });
                transaction.replace(R.id.fragment_content, mDemo);
                transaction.addToBackStack(null);
                transaction.commit();
            }
        });
    }
}