android注解实现findViewById

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.android.annotationproject.util.BindView;
import com.android.annotationproject.util.OnClick;
import com.android.annotationproject.util.WyqBind;

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.btn_action)
    private Button btnAction;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        WyqBind.bind(this);
        btnAction.setText("注解的实现依赖于java的反射机制");
    }

    @OnClick(R.id.btn_action)
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn_action:
                Toast.makeText(this, "按钮被点击了", Toast.LENGTH_SHORT).show();
                break;
        }
    }

}

import android.app.Activity;
import android.support.annotation.NonNull;
import android.support.annotation.UiThread;
import android.view.View;

import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class WyqBind {

    @NonNull
    @UiThread
    public static void bind(@NonNull Activity target) {
        findViewById(target);
        onClick(target);
    }

    private static void findViewById(Activity activity) {
        Class<? extends Activity> clazz = activity.getClass();
        Field[] declaredFields = clazz.getDeclaredFields();
        for (int i = 0; i < declaredFields.length; i++) {
            Field field = declaredFields[i];
            BindView annotation = field.getAnnotation(BindView.class);
            if (annotation != null) {
                int viewId = annotation.value();
                View view = activity.findViewById(viewId);
                try {
                    field.setAccessible(true);
                    field.set(activity, view);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private static void onClick(final Activity activity) {
        Class<?> clazz = activity.getClass();
        try {
            final Method method = clazz.getMethod("onClick", View.class);
            OnClick onClick = method.getAnnotation(OnClick.class);
            if (onClick != null) {
                int[] viewIds = onClick.value();
                for (int viewId : viewIds) {
                    final View view = activity.findViewById(viewId);
                    view.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            method.setAccessible(true);
                            try {
                                method.invoke(activity);
                            } catch (Exception e) {
                                e.printStackTrace();
                                try {
                                    method.invoke(activity, view);
                                } catch (Exception e1) {
                                    e1.printStackTrace();
                                }
                            }
                        }
                    });
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

    int[] value();

}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD) 
@Retention(RetentionPolicy.RUNTIME)
public @interface BindView {

    int value(); 

}