Android进阶(三)ButterKnife源码解析

class ExampleActivity extends Activity {
  @BindView(R.id.tv_name) EditText username;
  @BindView(R.id.tv_pwd) EditText password;
  @Override 
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    ButterKnife.bind(this);
    // TODO Use fields...
  }
}

@BindString(R.string.login_error) String loginErrorMessage;
@BindColor(R.color.color_error_text) int colorErrorText;

@OnClick(R.id.btn_login)
    void onLogin() {
        //处理登录
    }

@Retention(CLASS) @Target(FIELD)
public @interface BindView {
  /** View ID to which the field will be bound. */
  @IdRes int value();
}

public static Unbinder bind(@NonNull Activity target) {
    View sourceView = target.getWindow().getDecorView();
    return createBinding(target, sourceView);
}
public static Unbinder bind(@NonNull View target) {
    return createBinding(target, target);
}
public static Unbinder bind(@NonNull Dialog target) {
    View sourceView = target.getWindow().getDecorView();
    return createBinding(target, sourceView);

}
...

static final Map<Class<?>, Constructor<? extends Unbinder>> BINDINGS = new LinkedHashMap<>();

private static Unbinder createBinding(@NonNull Object target, @NonNull View source) {
    Class<?> targetClass = target.getClass();
    if (debug) Log.d(TAG, "Looking up binding for " + targetClass.getName());
    Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);

    if (constructor == null) {
      return Unbinder.EMPTY;
    }

    //noinspection TryWithIdenticalCatches Resolves to API 19+ only type.
    try {
      return constructor.newInstance(target, source);
    } 
    ....
}

private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {
    Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);
    if (bindingCtor != null) {
      if (debug) Log.d(TAG, "HIT: Cached in binding map.");
      return bindingCtor;
    }
    String clsName = cls.getName();
    if (clsName.startsWith("android.") || clsName.startsWith("java.")) {
      if (debug) Log.d(TAG, "MISS: Reached framework class. Abandoning search.");
      return null;
    }
    try {
      Class<?> bindingClass = cls.getClassLoader().loadClass(clsName + "_ViewBinding");
      //noinspection unchecked
      bindingCtor = (Constructor<? extends Unbinder>) bindingClass.getConstructor(cls, View.class);
      if (debug) Log.d(TAG, "HIT: Loaded binding class and constructor.");
    } catch (ClassNotFoundException e) {
      if (debug) Log.d(TAG, "Not found. Trying superclass " + cls.getSuperclass().getName());
      bindingCtor = findBindingConstructorForClass(cls.getSuperclass());
    } catch (NoSuchMethodException e) {
      throw new RuntimeException("Unable to find binding constructor for " + clsName, e);
    }
    BINDINGS.put(cls, bindingCtor);
    return bindingCtor;
}

//AutoService注解 自动生成Processor文件
@AutoService(Processor.class)
public final class ButterKnifeProcessor extends AbstractProcessor {
	@Override
	public boolean process(Set<? extends TypeElement> elements, RoundEnvironment env) {
		Map<TypeElement, BindingSet> bindingMap = findAndParseTargets(env);

		for (Map.Entry<TypeElement, BindingSet> entry : bindingMap.entrySet()) {
			TypeElement typeElement = entry.getKey();
			BindingSet binding = entry.getValue();

			JavaFile javaFile = binding.brewJava(sdk, debuggable);
			try {
				javaFile.writeTo(filer);
			} catch (IOException e) {
				error(typeElement, "Unable to write binding for type %s: %s", typeElement, e.getMessage());
			}
		}

		return false;
	}
	private Map<TypeElement, BindingSet> findAndParseTargets(RoundEnvironment env) {
		Map<TypeElement, BindingSet.Builder> builderMap = new LinkedHashMap<>();
		Set<TypeElement> erasedTargetNames = new LinkedHashSet<>();
		scanForRClasses(env);

        ...
        
		// Process each @BindView element.
		for (Element element : env.getElementsAnnotatedWith(BindView.class)) {
			// we don't SuperficialValidation.validateElement(element)
			// so that an unresolved View type can be generated by later processing rounds
			try {
				parseBindView(element, builderMap, erasedTargetNames);
			} catch (Exception e) {
				logParsingError(element, BindView.class, e);
			}
		}

		// Associate superclass binders with their subclass binders. This is a queue-based tree walk
		// which starts at the roots (superclasses) and walks to the leafs (subclasses).
		Deque<Map.Entry<TypeElement, BindingSet.Builder>> entries =
				new ArrayDeque<>(builderMap.entrySet());
		Map<TypeElement, BindingSet> bindingMap = new LinkedHashMap<>();
		while (!entries.isEmpty()) {
			Map.Entry<TypeElement, BindingSet.Builder> entry = entries.removeFirst();

			TypeElement type = entry.getKey();
			BindingSet.Builder builder = entry.getValue();

			TypeElement parentType = findParentType(type, erasedTargetNames);
			if (parentType == null) {
				bindingMap.put(type, builder.build());
			} else {
				BindingSet parentBinding = bindingMap.get(parentType);
				if (parentBinding != null) {
					builder.setParent(parentBinding);
					bindingMap.put(type, builder.build());
				} else {
					// Has a superclass binding but we haven't built it yet. Re-enqueue for later.
					entries.addLast(entry);
				}
			}
		}

		return bindingMap;
	}
}

private void parseBindView(Element element, Map<TypeElement, BindingSet.Builder> builderMap,
							   Set<TypeElement> erasedTargetNames) {
		TypeElement enclosingElement = (TypeElement) element.getEnclosingElement();

		// Assemble information on the field.
		int id = element.getAnnotation(BindView.class).value();

		BindingSet.Builder builder = builderMap.get(enclosingElement);
		QualifiedId qualifiedId = elementToQualifiedId(element, id);
		if (builder != null) {
			String existingBindingName = builder.findExistingBindingName(getId(qualifiedId));
			if (existingBindingName != null) {
				error(element, "Attempt to use @%s for an already bound ID %d on '%s'. (%s.%s)",
						BindView.class.getSimpleName(), id, existingBindingName,
						enclosingElement.getQualifiedName(), element.getSimpleName());
				return;
			}
		} else {
			builder = getOrCreateBindingBuilder(builderMap, enclosingElement);
		}
}
private BindingSet.Builder getOrCreateBindingBuilder(
	Map<TypeElement, BindingSet.Builder> builderMap, TypeElement enclosingElement) {
	BindingSet.Builder builder = builderMap.get(enclosingElement);
	if (builder == null) {
	    builder = BindingSet.newBuilder(enclosingElement);
		builderMap.put(enclosingElement, builder);
	}
	return builder;
}

static Builder newBuilder(TypeElement enclosingElement) {
    String packageName = getPackage(enclosingElement).getQualifiedName().toString();
    String className = enclosingElement.getQualifiedName().toString().substring(
        packageName.length() + 1).replace('.', '$');
    ClassName bindingClassName = ClassName.get(packageName, className + "_ViewBinding");

    boolean isFinal = enclosingElement.getModifiers().contains(Modifier.FINAL);
    return new Builder(targetType, bindingClassName, isFinal, isView, isActivity, isDialog);
}

public class MainActivity_ViewBinding implements Unbinder {
  private MainActivity target;

  @UiThread
  public MainActivity_ViewBinding(MainActivity target) {
    this(target, target.getWindow().getDecorView());
  }

  @UiThread
  public MainActivity_ViewBinding(MainActivity target, View source) {
    this.target = target;

    target.mTextView = Utils.findRequiredViewAsType(source, R.id.text_view, "field 'mTextView'", TextView.class);
  }

  @Override
  @CallSuper
  public void unbind() {
    MainActivity target = this.target;
    if (target == null) throw new IllegalStateException("Bindings already cleared.");
    this.target = null;

    target.mTextView = null;
  }
}

public static View findRequiredView(View source, @IdRes int id, String who) {
    View view = source.findViewById(id);
    if (view != null) {
      return view;
    }
    String name = getResourceEntryName(source, id);
    throw new IllegalStateException("Required view '"
        + name
        + "' with ID "
        + id
        + " for "
        + who
        + " was not found. If this view is optional add '@Nullable' (fields) or '@Optional'"
        + " (methods) annotation.");
}