Activity与Fragment通信 多接口实现优化

1.问题

我们都知道Activity与Fragment通信的几种方式，推崇的应该是谷歌给出的接口方案。

地址：https://developer.android.com/training/basics/fragments/communicating.html#DefineInterface

当一个Activity与多个Fragment通信时，可能要定义多个接口，下面这种思想是减少接口的定义，可以编写出一套统一的代码。

2.思想

对方法对象的封装，key作为方法名字，value作为方法对象

使用效果和接口差不多

3.主要代码

方法的封装类

/** * key为Fragment的标示 * value为回调函数 */public class Functions{    private HashMap<String,FunctionWithParamAndResult> mFunctionWithParamAndResults ;    public static class Function{        String functionName;        public Function(String functionName){            this.functionName = functionName;        }    }    /**带有参数和返回值的抽象方法的类*/    public static abstract class FunctionWithParamAndResult<Param,Result> extends Function{        public FunctionWithParamAndResult(String functionName) {            super(functionName);        }        public abstract Result function(Param param);    }    /**添加带参数的函数*/    public Functions addFunction(FunctionWithParamAndResult function){        if(function == null){            return this;        }        if(mFunctionWithParamAndResults == null){            mFunctionWithParamAndResults = new HashMap<>();        }        mFunctionWithParamAndResults.put(function.functionName,function);        return this;    }    /** 调用具有参数的函数*/    public <Param, Result> Result invokeFunction(String funcName, Class<Result> classofR,                                                 Param param)throws NoFunctionException {        FunctionWithParamAndResult func = null;        if(mFunctionWithParamAndResults != null){            func = mFunctionWithParamAndResults.get(funcName);            if(func != null){                if(classofR != null){                    return classofR.cast(func.function(param));//安全的                }                return (Result)func.function(param);            } else {                throw new NoFunctionException("has no Function：" + funcName                        + "found in FunctionWithParamAndResult");            }        }        return null;    }}

BaseFragment 和 MainFragment

MainFragment中定义static FUNC_WPAR可以对应理解为接口回调方式中接口的定义

mFunctions.invokeFunction 是调用抽象方法

public class BaseFragment extends Fragment{    protected Functions mFunctions;    protected BaseActivity mBaseActivity;    /**     * activity调用此方法进行设置Functions     * @param functions     */    public void setFunctions(Functions functions){        this.mFunctions = functions;    }    @Override    public void onAttach(Context context) {        super.onAttach(context);        if(context instanceof BaseActivity){            mBaseActivity = (BaseActivity)context;            mBaseActivity.setFunctionsForFragment(getTag());        }    }}

public class MainFragment extends BaseFragment {    public static final String FUNCTION_WPAR = "MAIN_FUNCTION_WITH_PARAM_AND_RESULT";    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.fragment_main, null);        return view;    }    @Override    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {        super.onViewCreated(view, savedInstanceState);        Button btn1 = (Button) view.findViewById(R.id.button1);        final TextView tv1 = (TextView) view.findViewById(R.id.textview1);        btn1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                try {                    String result = mFunctions.invokeFunction(FUNCTION_WPAR,                            String.class, "来自MainFragment参数");                    tv1.setText(result);                } catch (NoFunctionException e) {                    e.printStackTrace();                }            }        });    }}

MainActivity

其中new Functions.FunctionWithParamAndResult相当于接口方式里的实现接口

public class MainActivity extends BaseActivity {    private Functions mFunctions = new Functions();    private FragmentManager mFragmentManager;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }    @Override    public void setFunctionsForFragment(String fragmentTAG) {        mFragmentManager = getSupportFragmentManager();        if("fragment_main".equals(fragmentTAG)){            BaseFragment mainFragment = (BaseFragment)mFragmentManager.findFragmentByTag(fragmentTAG);            mainFragment.setFunctions(mFunctions);            mFunctions.addFunction(new Functions.FunctionWithParamAndResult<String,                    String>(MainFragment.FUNCTION_WPAR) {                @Override                public String function(String str) {                    Toast.makeText(MainActivity.this,                            "收到MainFragment参数:" + str,                            Toast.LENGTH_SHORT).show();                    return "Activty处理参数:" + str;                }            });        } else if("fragment_second".equals(fragmentTAG)){            BaseFragment secondFragment = (BaseFragment)mFragmentManager.findFragmentByTag(fragmentTAG);            secondFragment.setFunctions(mFunctions);            mFunctions.addFunction(new Functions.FunctionWithParamAndResult<String,                    String>(SecondFragment.FUNCTION_WPAR) {                @Override                public String function(String str) {                    Toast.makeText(MainActivity.this,                            "收到SecondFragment参数:" + str,                            Toast.LENGTH_SHORT).show();                    return "Activty处理参数:" + str;                }            });        }    }}

如果使用这种方式来代替接口实现Activity与Fragment的通信，会使代码的阅读性变差，假如一个Fragment中有两个参数和返回类型相同，但是名字不同的方法，需要定义两个方法名字，阅读代码的时候，你就需要频繁查看调用处对应的方法名。

代码地址

参考文章：

Android：Activity与Fragment通信(99%)完美解决方案

其实个人觉得也没有特别完美，使用接口的方式，代码会更直观。