Java Basics Annotations implementation in Android

The code for the activity to be posted first:

@ContentView(R.layout.activity_main) Public  class mainactivity extends appcompatactivity {    @ViewInject(R.id.text_view)PrivateTextView TextView;@OnClick(R.id.text_view)Private void OnClick(View view) {Textview.settext ("I'm textview after click."); }@Override    protected void onCreate(Bundle savedinstancestate) {Super. OnCreate (Savedinstancestate); Viewinjectutils.inject ( This); Textview.settext ("I'm the TextView in front of the click."); }}

Contentview (Class) annotation implementations:

1. Define Annotations

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

2. Implementation annotations

Private Staticvoid Injectcontentview (activity activity) { Class<? extends activity> clazz = activity. GetClass (); Contentview Contentview = clazz. getannotation (Contentview. class); if (contentview ! = null) {            //If this annotation is present on the activity, take out the value of the annotation corresponding to the previous layout file. int layoutid = Contentview.value ();Try{Method Setviewmethod = Clazz.getmethod ("Setcontentview", Int.class);            Setviewmethod.invoke (activity, LayoutID); }Catch(Exceptione) {e.printstacktrace (); }        } }

field annotation Implementation

1. Define Annotations

@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface ViewInject {    intvalue();}

2. Implementation annotations

Private Staticvoid Injectview (activity activity) { Class<? extends activity> clazz = activity. GetClass        (); Get all member variables for activity Field[]  fields = clazz. Getdeclaredfields        ();  for (field field : fields) {        //Get the viewinject annotation above each member variable and return NULL if not .Viewinject viewinject = field.getannotation (Viewinject.class);if(Viewinject! =NULL) {int viewId = Viewinject.value (); View view = Activity.findviewbyid (viewId);Try{field.setaccessible (true);                Field.set (activity, view); }Catch(Illegalaccessexception e)                {E.printstacktrace (); }            }        }    }

Interface (method) annotation implementation

1. Define Annotations

@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public @interface OnClick {    intvalue();}

2. Implementation annotations

 Public  class viewinjectutils {     Public Staticvoid inject (activity activity) {Injectcontentview (activity);        Injectview (activity);    Injectevent (activity); }Private Staticvoid Injectevent (FinalActivity activity) { Class<? extends activity> clazz = activity. GetClass        (); Method [] methods = Clazz. Getdeclaredmethods        ();  for (final Method method2 : methods) {OnClick click = Method2.getannotation (Onclick.class);if(Click! =NULL) {int[] viewId = Click.value (); Method2.setaccessible (true); Object listener = proxy.newproxyinstance (View.OnClickListener.class.getClassLoader (),New  Class[]{View.OnClickListener.class},NewInvocationhandler () {@Override PublicObject Invoke (Object proxy, Method method, object[] args) throws Throwable {returnMethod2.invoke (activity, args); }                        });Try{ for(int id:viewid)                        {View v = Activity.findviewbyid (id); Method Setclicklistener = V.getclass (). GetMethod ("Setonclicklistener", View.OnClickListener.class);                    Setclicklistener.invoke (v, listener); }                }Catch(Exceptione) {e.printstacktrace (); }            }        }    }

Java Basics Annotations implementation in Android