package com.example.ele_me.util; 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;
}
//mActicity本身擁有獨立的變量，並賦值給class Injector，然而我們也可透過修改activity去改變mActivity。
/**
* 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()
//inject等待被另一個Java檔召喚。
{
for (Field field : mActivity.getClass().getDeclaredFields())
//Field是一個對象類型，其作用等同於findViewById一樣，在於捕捉其對象。而下面的for迴圈則為了去捕捉對象所需要運用到的算式。
{
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);
}
}
}
}
}
}
這是一個必須複製的編碼。我們必須重新開一個Java檔案去讓injectView運行，injectView本身並不會獨自地去尋找對象，而是透過injectView Inject()去運算，並且尋找對象。