butterKnife源码解析 (butterknife-7.0.1.jar)
简单使用
下面就是针对这段代码进行解析
package com.syntc.deletedemo;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
import butterknife.BindString;
import butterknife.BindView;
import butterknife.ButterKnife;
import butterknife.OnClick;
import butterknife.Unbinder;
public class MainActivity extends AppCompatActivity {
@BindView(R.id.image)
ImageView username;
@BindView((R.id.button))
Button button;
@BindString(R.string.app_name)
String message;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Unbinder unbinder = ButterKnife.bind(this);
unbinder.unbind();
}
@OnClick(R.id.button)
public void doWork(){
Toast.makeText(this, "do work", Toast.LENGTH_SHORT).show();
}
}
从 Unbinder unbinder = ButterKnife.bind(this); 开始
@NonNull @UiThread
public static Unbinder bind(@NonNull Activity target) {
View sourceView = target.getWindow().getDecorView();
return createBinding(target, sourceView); //这里注意两个重要的对象 当前的activity和 当前的DecorView
}
然后(重点方法)
private static Unbinder createBinding(@NonNull Object target, @NonNull View source) {
Class<?> targetClass = target.getClass(); //获取当前Activity的 Class类型
Constructor<? extends Unbinder> constructor = findBindingConstructorForClass(targetClass);
// 重点，根据当前Activity的Class类型获取 javapoet-1.7.0.jar生成的代码即为和当前Activity配对的MainActivity_ViewBinding类 (后面讲到)
if (constructor == null) {
return Unbinder.EMPTY;
}
return constructor.newInstance(target, source); // 把Activity(this)和当前的DecorView对象传入
}
查找 MainActivity_ViewBinding(代码生成的类)的构造器，如果第一次查找，放入缓存中，如果已经查找过，从缓存中取出(这是因为用户可能多次调用bind()方法，而且bind有很多构造方法，不需要每次都去查找一遍)
static final Map<Class<?>, Constructor<? extends Unbinder>> BINDINGS = new LinkedHashMap<>();//缓存
private static Constructor<? extends Unbinder> findBindingConstructorForClass(Class<?> cls) {
Constructor<? extends Unbinder> bindingCtor = BINDINGS.get(cls);
if (bindingCtor != null) {
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 = Class.forName(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;
}
生成的代码如下
// Generated code from Butter Knife. Do not modify!
package com.syntc.deletedemo;
import android.content.res.Resources;
import android.support.annotation.CallSuper;
import android.support.annotation.UiThread;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import butterknife.Unbinder;
import butterknife.internal.DebouncingOnClickListener;
import butterknife.internal.Utils;
import java.lang.IllegalStateException;
import java.lang.Override;
//需要注意一点就是 我们发现下面泛型T target 也能调用 target.username等属性是因为 <T extends MainActivity>
public class MainActivity_ViewBinding<T extends MainActivity> implements Unbinder {
protected T target;
private View view2131427412;
@UiThread
public MainActivity_ViewBinding(final T target, View source) {
this.target = target;
View view;
// 就是 View view = source.findViewById(R.id.image);和 return (T)view; 其中T 由 target.username指定了这里必须填ImageView.class
target.username = Utils.findRequiredViewAsType(source, R.id.image, "field 'username'", ImageView.class);
// 就是 仅仅View view = source.findViewById(R.id.R.id.button); 不带类型转换
view = Utils.findRequiredView(source, R.id.button, "field 'button' and method 'doWork'");
// 就是 仅仅 转换类型
target.button = Utils.castView(view, R.id.button, "field 'button'", Button.class);
view2131427412 = view;
view.setOnClickListener(new DebouncingOnClickListener() {
@Override
public void doClick(View p0) {
target.doWork();
}
});
Resources res = source.getResources();
target.message = res.getString(R.string.app_name);
}
@Override
@CallSuper
public void unbind() {
T target = this.target;
if (target == null) throw new IllegalStateException("Bindings already cleared.");
target.username = null;
target.button = null;
view2131427412.setOnClickListener(null);
view2131427412 = null;
this.target = null;
}
}
最后 关于代码的生成和apt请单独查阅理解
相关知识点
自定义注解
Apt
autoService
javapoet-1.7.0.jar
注
关于这些源码还是自己直接跟踪查看，测试最好理解
别人的文章如上面的几大知识点杂烩在一起则很难搞清楚
相关知识点后期抽空放在git上面，一看就明白了
