fragment監聽返回鍵。有時候在activity中點選了物理返回鍵，不只是返回上一層。所以這時候需要在fragment中處理物理返回鍵的事件。

首先建立一個介面

public interface FragmentBackListener {
 
	void  onbackForward(); 
}

宿主在宿主activity中：

public class MainActivity extends Activity {

	private FragmentBackListener backListener;
	private boolean isInterception = false;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
	}

	public FragmentBackListener getBackListener() {
		return backListener;
	}

	public void setBackListener(FragmentBackListener backListener) {
		this.backListener = backListener;
	}

	public boolean isInterception() {
		return isInterception;
	}

	public void setInterception(boolean isInterception) {
		this.isInterception = isInterception;
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {

			if (isInterception()) {
				if (backListener != null) {
					backListener.onbackForward();
					return false;
				}
			}

		}
		return super.onKeyDown(keyCode, event);
	}

}
 

public class MFragment extends Fragment implements FragmentBackListener{


	@Override
	public void onAttach(Activity activity) {
		// TODO Auto-generated method stub
		super.onAttach(activity);
		if(activity instanceof MainActivity){
			((MainActivity)activity).setBackListener(this);
			((MainActivity)activity).setInterception(true);
		}
	}
	
	@Override
	public void onDetach() {
		super.onDetach();
		if(getActivity() instanceof MainActivity){
			((MainActivity)getActivity()).setBackListener(null);
			((MainActivity)getActivity()).setInterception(false);
		}
	}

	@Override
	public void onbackForward() {
		// 處理fragment的返回事件
		
	}
	
}