Java怎么使用反射和动态代理实现一个View注解绑定库

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使用反射结合动态代理实现一个View注解绑定库，支持View和事件绑定，代码简洁，使用简单，扩展性强。

支持的功能

• @ContentView 绑定layout 替代setContentView()

• @BindView 绑定View 替代findViewById()

• @OnClick 绑定点击事件 替代setOnClickListener()

• @OnLongClick 绑定长按事件 替代setOnLongClickListener()

代码

注解类

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface ContentView {    int value();}

@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface BindView {    int value();}

@Target(ElementType.ANNOTATION_TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface OnEvent {    //订阅方式    String setCommonListener();    //事件源对象    Class commonListener();}

@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)@OnEvent(setCommonListener = "setOnClickListener",        commonListener = View.OnClickListener.class)public @interface OnClick {    int value();}

@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)@OnEvent(setCommonListener = "setOnLongClickListener",        commonListener = View.OnLongClickListener.class)public @interface OnLongClick {    int value();}

实现类

public class MsInjector {    public static void inject(Object object) {        injectContentView(object);        injectView(object);        injectEvent(object);    }    private static void injectContentView(Object object) {        Class clazz = object.getClass();        //获取到ContentView注解        ContentView contentView = clazz.getAnnotation(ContentView.class);        if (contentView == null) {            return;        }        //获取到注解的值，也就是layoutResID        int layoutResID = contentView.value();        try {            //反射出setContentView方法并调用            Method method = clazz.getMethod("setContentView", int.class);            method.invoke(object, layoutResID);        } catch (Exception e) {            e.printStackTrace();        }    }    private static void injectView(Object object) {        Class clazz = object.getClass();        //获取到所有字段并遍历        Field[] fields = clazz.getDeclaredFields();        for (Field field : fields) {            field.setAccessible(true);            //获取字段上的BindView注解            BindView bindView = field.getAnnotation(BindView.class);            if (bindView == null) {                continue;            }            //获取到viewId            int viewId = bindView.value();            try {                //通过反射调用findViewById得到view实例对象                Method method = clazz.getMethod("findViewById", int.class);                Object view = method.invoke(object, viewId);                //赋值给注解标注的对应字段                field.set(object, view);            } catch (Exception e) {                e.printStackTrace();            }        }    }    private static void injectEvent(Object object) {        Class clazz = object.getClass();        //获取到当前页年所有方法并遍历        Method[] declaredMethods = clazz.getDeclaredMethods();        for (Method declaredMethod : declaredMethods) {            declaredMethod.setAccessible(true);            //获取方法上的所有注解并遍历            Annotation[] annotations = declaredMethod.getDeclaredAnnotations();            for (Annotation annotation : annotations) {                //获取注解本身                Class annotationType = annotation.annotationType();                //获取注解上的OnEvent注解                OnEvent onEvent = annotationType.getAnnotation(OnEvent.class);                if (onEvent == null) {                    continue;                }                //拿到注解中的元素                String setCommonListener = onEvent.setCommonListener();                Class commonListener = onEvent.commonListener();                try {                    //由于上边没有明确获取是哪个注解，所以这里需要使用反射获取viewId                    Method valueMethod = annotationType.getDeclaredMethod("value");                    valueMethod.setAccessible(true);                    int viewId = (int) valueMethod.invoke(annotation);                    //通过反射findViewById获取到对应的view                    Method findViewByIdMethod = clazz.getMethod("findViewById", int.class);                    Object view = findViewByIdMethod.invoke(object, viewId);                    //通过反射获取到view中对应的setCommonListener方法                    Method viewMethod = view.getClass().getMethod(setCommonListener, commonListener);                    //使用动态代理监听回调                    Object proxy = Proxy.newProxyInstance(                            clazz.getClassLoader(),                            new Class[]{commonListener},                            new InvocationHandler() {                                @Override                                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                                    //最终执行被标注的方法                                    return declaredMethod.invoke(object, null);                                }                            }                    );                    //调用view的setCommonListener方法                    viewMethod.invoke(view, proxy);                } catch (Exception e) {                    e.printStackTrace();                }            }        }    }}

使用

@ContentView(R.layout.activity_main)public class MainActivity extends AppCompatActivity {    @BindView(R.id.button1)    private Button button1;    @BindView(R.id.button2)    Button button2;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        MsInjector.inject(this);    }    @OnClick(R.id.button1)    public void clickButton1() {        Toast.makeText(this, "click button1", Toast.LENGTH_SHORT).show();    }    @OnClick(R.id.button2)    public void clickButton2() {        Toast.makeText(this, "click button2", Toast.LENGTH_SHORT).show();    }    @OnLongClick(R.id.button1)    public boolean longClickButton1() {        Toast.makeText(this, "long click button1", Toast.LENGTH_SHORT).show();        return false;    }    @OnLongClick(R.id.button2)    public boolean longClickButton2() {        Toast.makeText(this, "long click button2", Toast.LENGTH_SHORT).show();        return false;    }}

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