download：2021助理高薪-拉钩产品经理高薪训练营
运用反射和动态代理完成一个View注解绑定库
支持的功用
@ContentView 绑定layout 替代setContentView()
@BindView 绑定View 替代findViewById()
@OnClick 绑定点击事情 替代setOnClickListener()
@OnLongClick 绑定长按事情 替代setOnLongClickListener()
代码
注解类
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface ContentView {
int value();}
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@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface BindView {
int value();}
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@Target(ElementType.ANNOTATION_TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface OnEvent {
//订阅方式
String setCommonListener();
//事情源对象
Class commonListener();}
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@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@OnEvent(setCommonListener = "setOnClickListener",
commonListener = View.OnClickListener.class)public @interface OnClick {
int value();}
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@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@OnEvent(setCommonListener = "setOnLongClickListener",
commonListener = View.OnLongClickListener.class)public @interface OnLongClick {
int value();}
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完成类
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办法并调用
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();
//获取到一切字段并遍历
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 {
//经过反射调用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();
//获取到当前页年一切办法并遍历
Method[] declaredMethods = clazz.getDeclaredMethods();
for (Method declaredMethod : declaredMethods) {
declaredMethod.setAccessible(true);
//获取办法上的一切注解并遍历
Annotation[] annotations = declaredMethod.getDeclaredAnnotations();
for (Annotation annotation : annotations) {
//获取注解自身
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 {
//由于上边没有明白获取是哪个注解，所以这里需求运用反射获取viewId
Method valueMethod = annotationType.getDeclaredMethod("value");
valueMethod.setAccessible(true);
int viewId = (int) valueMethod.invoke(annotation);
//经过反射findViewById获取到对应的view
Method findViewByIdMethod = clazz.getMethod("findViewById", int.class);
Object view = findViewByIdMethod.invoke(object, viewId);
//经过反射获取到view中对应的setCommonListener办法
Method viewMethod = view.getClass().getMethod(setCommonListener, commonListener);
//运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 {
//最终执行被标注的办法
return declaredMethod.invoke(object, null);
}
}
);
//调用view的setCommonListener办法
viewMethod.invoke(view, proxy);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}}
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运用
@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;
}}