Android_Fragment和Activity之间的通信

Fragment 的生命周期是随着activity变化而变化的。

如果activity要给在运行的时候给fragment传人数据则需要fragment实现一个自定义的接口，并且实现接口里面的方法，在activity里面保存这个接口并且在需要传人数据的时候调用这个方法即可。

如果fragment运行的时候需要给activity传数据了？activity先实现这个接口，然后在fragment里面重写onAttach(Activity act)这个方法，并在这个方法里面讲activity强制转换为接口类，然后在fragment使用的时候调用这个接口类的方法。

请看下面的例子：

activity给fragment里面传人数据：

public class MainActivity extends Activity{
    private TestFragment fragment;//fragment
    private UpdateFragment updateFragment;//fragment实现的接口
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        initView();

    }
    private void initView() {
        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragment = new TestFragment();
        updateFragment = fragment;
        fragmentTransaction.add(R.id.main, fragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commitAllowingStateLoss();
    }
    @Override
    protected void onResume() {
        //改变fragment里面textView的值
        updateFragment.setData("王五");
        super.onResume();
    }

}

接口类

public interface UpdateFragment {
    void setData(String str);
}

Fragment类：

public class TestFragment extends Fragment implements UpdateFragment{

    private View view;
    private TextView txt;
    public TestFragment() {
        super();
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        if (null == view){
            view = inflater.inflate(R.layout.activity_main, container, false);
            txt = (TextView)view.findViewById(R.id.tv);
        }
        return view;
    }
    @Override
    public void setData(String str) {
        if (null != txt) {
            txt.setText(str);
        }
    }

}

Fragment给activity传入数据demo：

Activity类：

public class MainActivity extends Activity implements UpdateFragment{
    private static final String TAG = MainActivity.class.getSimpleName();
    private TestFragment fragment;//fragment
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);
        initView();

    }
    private void initView() {
        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragment = new TestFragment();
        fragmentTransaction.add(R.id.main, fragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commitAllowingStateLoss();
    }
    @Override
    protected void onResume() {
        super.onResume();
    }
    @Override
    public void setData(String str) {
        if (null != str ){
            Log.d(TAG, "setData:"+str);
        }
    }

接口类和上面的是一样的就不写了

Fragment类：

public class TestFragment extends Fragment{

    private View view;
    private TextView txt;
    private Button btn;
    private UpdateFragment updateFragment;
    public TestFragment() {
        super();
    }

    @Override
    public void onAttach(Activity activity) {
        try {
            updateFragment = (UpdateFragment)activity;
        } catch (Exception e) {
            e.printStackTrace();
        }
        super.onAttach(activity);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        if (null == view){
            view = inflater.inflate(R.layout.activity_main, container, false);
            txt = (TextView)view.findViewById(R.id.tv);
            btn = (Button)view.findViewById(R.id.btn);
            btn.setOnClickListener(clickListener);
        }
        return view;
    }
    private OnClickListener clickListener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            if (null != txt) {
                updateFragment.setData(txt.getText().toString());
            }

        }
    };

}