@InjectView的实例化

这里是一个官方例子，轻量级的处理，灵感来自于强大的开源项目RoboGuice,可以通过wiki文档了解。
https://github.com/roboguice/roboguice/wiki

基于反射的injectview:

Android的findViewById真是太烦人了，模板似的方法，要写在每个Activity，Fragment，Adapter里面。声明View和findView总是间隔着未知的行距；setOnClickListener之后，总是要寻找对应的onClick方法在何处。

难道Android就不能智能的把layout中的View相应的与对应field绑定起来？

答案是：Android本身不支持，但是我们可以通过一些hack达到目的。

这是提供一个实例化对象来实现：

package com.lsj.utils;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;

import android.app.Activity;

/** * Very lightweight form of injection, inspired by RoboGuice, for injecting common ui elements. * <p> * Usage is very simple. In your Activity, define some fields as follows: * * <pre class="code"> * @InjectView(R.id.fetch_button) * private Button mFetchButton; * @InjectView(R.id.submit_button) * private Button mSubmitButton; * @InjectView(R.id.main_view) * private TextView mTextView; * </pre> * <p> * Then, inside your Activity's onCreate() method, perform the injection like this: * * <pre class="code"> * setContentView(R.layout.main_layout); * Injector.get(this).inject(); * </pre> * <p> * See the {@link #inject()} method for full details of how it works. Note that the fields are * fetched and assigned at the time you call {@link #inject()}, consequently you should not do this * until after you've called the setContentView() method. */
public final class Injector {
    private final Activity mActivity;

    private Injector(Activity activity) {
        mActivity = activity;
    }

    /** * Gets an {@link Injector} capable of injecting fields for the given Activity. */
    public static Injector get(Activity activity) {
        return new Injector(activity);
    }

    /** * Injects all fields that are marked with the {@link InjectView} annotation. * <p> * For each field marked with the InjectView annotation, a call to * {@link Activity#findViewById(int)} will be made, passing in the resource id stored in the * value() method of the InjectView annotation as the int parameter, and the result of this call * will be assigned to the field. * * @throws IllegalStateException if injection fails, common causes being that you have used an * invalid id value, or you haven't called setContentView() on your Activity. */
    public void inject() {
        for (Field field : mActivity.getClass().getDeclaredFields()) {
            for (Annotation annotation : field.getAnnotations()) {
                if (annotation.annotationType().equals(InjectView.class)) {
                    try {
                        Class<?> fieldType = field.getType();
                        int idValue = InjectView.class.cast(annotation).value();
                        field.setAccessible(true);
                        Object injectedValue = fieldType.cast(mActivity.findViewById(idValue));
                        if (injectedValue == null) {
                            throw new IllegalStateException("findViewById(" + idValue
                                    + ") gave null for " +
                                    field + ", can't inject");
                        }
                        field.set(mActivity, injectedValue);
                        field.setAccessible(false);
                    } catch (IllegalAccessException e) {
                        throw new IllegalStateException(e);
                    }
                }
            }
        }
    }
}

以上的injector，接下的是injectview

package com.lsj.utils;

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

/** * Use this annotation to mark the fields of your Activity as being injectable. * <p> * See the {@link Injector} class for more details of how this operates. */  
@Target({ ElementType.FIELD })  
@Retention(RetentionPolicy.RUNTIME)  
public @interface InjectView {  
    /** * The resource id of the View to find and inject. */  
    public int value();  
}  

接着按照规定格式，你就可以放心地使用@injectview了。
用师兄的一句话说就是：省时省力，高效开发。