Java使用反射和动态代理实现一个View注解绑定库

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<? extends annotation> 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();
                }
            }
        }
    }
}
复制代码

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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