Butterknife全方位解析

概述

Butterknife是供職于Square公司的JakeWharton大神開發的開源庫，使用這個庫，在AS中搭配Android ButterKnife Zelezny插件，可以大大提高開發的效率，從此擺脫繁瑣的findViewById(int id)，也不用自己手動@bind(int id) ，直接用插件生成即可。本篇博客將對Butterknife進行深入解析。

項目地址：?JakeWharton/butterknife

ButterKnife有以下優點：

1、強大的View綁定和Click事件處理功能，簡化代碼，提升開發效率

2、方便的處理Adapter里的ViewHolder綁定問題

3、運行時不會影響APP效率，使用配置方便

4、代碼清晰，可讀性強

如何導入ButterKnife

在項目的build.grade文件中進行如下配置：

buildscript?{?
????repositories?{?
????????jcenter()?
????????mavenCentral()?
????????maven?{?
????????????url?"https://plugins.gradle.org/m2/"?
????????}?
????}?
????dependencies?{?
????????classpath?'com.android.tools.build:gradle:2.2.0'?
????????//這里配置?apt?供butterknife使用?
????????classpath?'com.neenbedankt.gradle.plugins:android-apt:1.8'?
?
????}?
}??

例如：

buildscript?{?
????repositories?{?
????????jcenter()?
????????mavenCentral()?
????????maven?{?
????????????url?"https://plugins.gradle.org/m2/"?
????????}?
?
????}?
?
????dependencies?{?
????????classpath?'com.android.tools.build:gradle:2.2.2'?
????????classpath?'com.neenbedankt.gradle.plugins:android-apt:1.8'?
????}?
}?
?
allprojects?{?
????repositories?{?
????????jcenter()?
????}?
}?
?
task?clean(type:?Delete)?{?
????delete?rootProject.buildDir?
}??

在app的build.grade文件中進行如下配置：

apply?plugin:?'com.android.application'?
apply?plugin:?'com.neenbedankt.android-apt'?
?
android{...}?
?
dependencies?{?
????//視圖綁定?butterknife?
????compile?'com.jakewharton:butterknife:8.4.0'?
????apt?'com.jakewharton:butterknife-compiler:8.4.0'?
}??

例如：

apply?plugin:?'com.android.application'?
apply?plugin:?'android-apt'?
?
android?{?
????compileSdkVersion?24?
????buildToolsVersion?"24.0.3"?
?
????defaultConfig?{?
?
????????minSdkVersion?14?
????????targetSdkVersion?24?
????????versionCode?1?
????????versionName?"1.0"?
????}?
????buildTypes?{?
????????release?{?
????????????minifyEnabled?false?
????????????proguardFiles?getDefaultProguardFile('proguard-android.txt'),?'proguard-rules.pro'?
????????}?
????}?
}?
?
dependencies?{?
????compile?fileTree(dir:?'libs',?include:?['*.jar'])?
?
????compile?'com.jakewharton:butterknife:8.4.0'?
????apt?'com.jakewharton:butterknife-compiler:8.4.0'?
}??

如何使用ButterKnife

1) 由于每次都要在Activity中的onCreate綁定Activity，所以個人建議寫一個BaseActivity完成綁定，子類繼承即可

注：ButterKnife.bind(this);綁定Activity 必須在setContentView之后：

實現如下(FragmentActivity 實現一樣)：

public?abstract?class?BaseActivity?extends?Activity?{???
????public?abstract?int?getContentViewId();???
?
????@Override???
????protected?void?onCreate(Bundle?savedInstanceState)?{???
????????super.onCreate(savedInstanceState);???
????????setContentView(getContentViewId());???
????????ButterKnife.bind(this);???
????????initAllMembersView(savedInstanceState);???
????}???
?
????protected?abstract?void?initAllMembersView(Bundle?savedInstanceState);???
?
????@Override???
????protected?void?onDestroy()?{???
????????super.onDestroy();???
????????ButterKnife.unbind(this);//解除綁定，官方文檔只對fragment做了解綁???
????}???
}????

2) 綁定fragment

public?abstract?class?BaseFragment?extends?Fragment?{???
????public?abstract?int?getContentViewId();???
????protected?Context?context;???
????protected?View?mRootView;???
?
????@Nullable???
????@Override???
????public?View?onCreateView(LayoutInflater?inflater,?@Nullable?ViewGroup?container,?@Nullable?Bundle?savedInstanceState)?{???
????????mRootView?=inflater.inflate(getContentViewId(),container,false);???
????????ButterKnife.bind(this,mRootView);//綁定framgent???
????????this.context?=?getActivity();???
????????initAllMembersView(savedInstanceState);???
????????return?mRootView;???
????}???
?
????protected?abstract?void?initAllMembersView(Bundle?savedInstanceState);???
?
????@Override???
????public?void?onDestroyView()?{???
????????super.onDestroyView();???
????????ButterKnife.unbind(this);//解綁???
????}???
}????

3) 控件id 注解： @BindView()

package?com.myl.test;?
?
import?android.support.v7.app.AppCompatActivity;?
import?android.os.Bundle;?
import?android.widget.Button;?
?
import?butterknife.BindView;?
import?butterknife.ButterKnife;?
?
public?class?ButterknifeActivity?extends?AppCompatActivity?{?
?
????@BindView(?R.id.button1?)?
????public?Button?button1?;?
?
????//?注意：button?的修飾類型不能是：private?或者?static?。?否則會報錯：錯誤:?@BindView?fields?must?not?be?private?or?static.?(com.myl.test.ButterknifeActivity.button1)?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_butterknife);?
????????//綁定activity?
????????ButterKnife.bind(?this?)?;?
?
????????button1.setText(?"I?am?a?button?");?
????}?
}??

4) 多個控件id 注解： @BindViews()

package?com.myl.test;?
?
import?android.support.v7.app.AppCompatActivity;?
import?android.os.Bundle;?
import?android.widget.Button;?
import?java.util.List;?
import?butterknife.BindViews;?
import?butterknife.ButterKnife;?
?
public?class?Main2Activity?extends?AppCompatActivity?{?
?
????@BindViews({?R.id.button1??,?R.id.button2?,??R.id.button3?})?
????public?List<Button>?buttonList?;?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_main2);?
?
????????ButterKnife.bind(this);?
?
????????buttonList.get(?0?).setText(?"hello?1?");?
????????buttonList.get(?1?).setText(?"hello?2?");?
????????buttonList.get(?2?).setText(?"hello?3?");?
????}?
}??

5) @BindString() ：綁定string 字符串

package?com.myl.test;?
?
import?android.os.Bundle;?
import?android.support.v7.app.AppCompatActivity;?
import?android.widget.Button;?
?
import?butterknife.BindString;?
import?butterknife.BindView;?
import?butterknife.ButterKnife;?
?
public?class?ButterknifeActivity?extends?AppCompatActivity?{?
?
????@BindView(?R.id.button1?)?//綁定button?控件?
????public?Button?button1?;?
?
????@BindString(?R.string.app_name?)??//綁定string?字符串?
????String?meg;?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_butterknife);?
?
????????//綁定activity?
????????ButterKnife.bind(?this?)?;?
?
????????button1.setText(?meg?);?
????}?
}??

6) @BindArray() : 綁定string里面array數組

<resources>?
????<string?name="app_name">校園助手</string>?
?
????<string-array?name="city">?
????????<item>東莞市</item>?
????????<item>廣州市</item>?
????????<item>珠海市</item>?
????????<item>肇慶市</item>?
????????<item>深圳市</item>?
????</string-array>?
?
</resources>?
-----------------------------------------------------------------?
package?com.myl.test;?
?
import?android.os.Bundle;?
import?android.support.v7.app.AppCompatActivity;?
import?android.widget.Button;?
?
import?butterknife.BindArray;?
import?butterknife.BindView;?
import?butterknife.ButterKnife;?
?
public?class?ButterknifeActivity?extends?AppCompatActivity?{?
?
????@BindView(?R.id.button1?)?//綁定button?控件?
????public?Button?button1?;?
?
????@BindArray(R.array.city?)??//綁定string里面array數組?
????String?[]?citys?;?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_butterknife);?
?
????????//綁定activity?
????????ButterKnife.bind(?this?)?;?
?
????????button1.setText(?citys[0]?);?
????}?
}??

7) @BindBitmap( ) : 綁定Bitmap 資源

package?com.myl.test;?
?
import?android.graphics.Bitmap;?
import?android.os.Bundle;?
import?android.support.v7.app.AppCompatActivity;?
import?android.widget.ImageView;?
?
import?butterknife.BindBitmap;?
import?butterknife.BindView;?
import?butterknife.ButterKnife;?
?
public?class?ButterknifeActivity?extends?AppCompatActivity?{?
?
????@BindView(?R.id.imageView?)?//綁定ImageView?控件?
????public?ImageView?imageView?;?
?
????@BindBitmap(?R.mipmap.wifi?)??//綁定Bitmap?資源?
????public?Bitmap?wifi_bitmap?;?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_butterknife);?
?
????????//綁定activity?
????????ButterKnife.bind(?this?)?;?
?
????????imageView.setImageBitmap(?wifi_bitmap?);?
????}?
}??

8) @BindColor( ) : 綁定一個顏色值

package?com.myl.test;?
?
import?android.os.Bundle;?
import?android.support.v7.app.AppCompatActivity;?
import?android.widget.Button;?
?
import?butterknife.BindColor;?
import?butterknife.BindView;?
import?butterknife.ButterKnife;?
?
public?class?ButterknifeActivity?extends?AppCompatActivity?{?
?
????@BindView(?R.id.button1?)??//綁定一個控件?
????public?Button?button1?;?
?
????@BindColor(?R.color.colorAccent?)?int?black?;??//綁定一個顏色值?
?
????@Override?
????protected?void?onCreate(Bundle?savedInstanceState)?{?
????????super.onCreate(savedInstanceState);?
????????setContentView(R.layout.activity_butterknife);?
?
????????//綁定activity?
????????ButterKnife.bind(?this?)?;?
?
????????button1.setTextColor(??black?);?
?
????}?
}??

9) Adapter ViewHolder 綁定

public?class?TestAdapter?extends?BaseAdapter?{???
????private?List<String>?list;???
????private?Context?context;???
?
????public?TestAdapter(Context?context,?List<String>?list)?{???
????????this.list?=?list;???
????????this.context?=?context;???
????}???
?
????@Override???
????public?int?getCount()?{???
????????return?list==null???0?:?list.size();???
????}???
?
????@Override???
????public?Object?getItem(int?position)?{???
????????return?list.get(position);???
????}???
?
????@Override???
????public?long?getItemId(int?position)?{???
????????return?position;???
????}???
?
????@Override???
????public?View?getView(int?position,?View?convertView,?ViewGroup?parent)?{???
????????ViewHolder?holder;???
????????if?(convertView?==?null)?{???
????????????convertView?=?LayoutInflater.from(context).inflate(R.layout.layout_list_item,?null);???
????????????holder?=?new?ViewHolder(convertView);???
????????????convertView.setTag(holder);???
????????}?else?{???
????????????holder?=?(ViewHolder)?convertView.getTag();???
????????}???
????????holder.textview.setText("item====="?+?position);???
????????return?convertView;???
????}???
?
????static?class?ViewHolder?{???
????????@Bind(R.id.hello_world)???
????????TextView?textview;???
?
????????public?ViewHolder(View?view)?{???
????????????ButterKnife.bind(this,?view);???
????????}???
????}???
}????

10) 點擊事件的綁定：不用聲明view，不用setOnClickLisener()就可以綁定點擊事件

a. 直接綁定一個方法

@OnClick(R.id.submit)???
public?void?submit(View?view)?{???
??//?TODO?submit?data?to?server...???
}????

b. 所有監聽方法的參數是可選的

@OnClick(R.id.submit)???
public?void?submit()?{???
??//?TODO?submit?data?to?server...???
}???

c. 定義一個特定類型，它將自動被轉換

@OnClick(R.id.submit)???
public?void?sayHi(Button?button)?{???
??button.setText("Hello!");???
}????

d. 多個view統一處理同一個點擊事件，很方便，避免抽方法重復調用的麻煩

@OnClick(R.id.submit)???
public?void?sayHi(Button?button)?{???
??button.setText("Hello!");???
}???

e. 自定義view可以綁定自己的監聽，不指定id

public?class?FancyButton?extends?Button?{???
??@OnClick???
??public?void?onClick()?{???
????//?TODO?do?something!???
??}???
}????

f. 給EditText加addTextChangedListener(即添加多回調方法的監聽的使用方法)，利用指定回調，實現想回調的方法即可，哪個注解不會用點進去看下源碼上的注釋

@OnTextChanged(value?=?R.id.mobileEditText,?callback?=?OnTextChanged.Callback.BEFORE_TEXT_CHANGED)???
void?beforeTextChanged(CharSequence?s,?int?start,?int?count,?int?after)?{???
?
}???
@OnTextChanged(value?=?R.id.mobileEditText,?callback?=?OnTextChanged.Callback.TEXT_CHANGED)???
void?onTextChanged(CharSequence?s,?int?start,?int?before,?int?count)?{???
?
}???
@OnTextChanged(value?=?R.id.mobileEditText,?callback?=?OnTextChanged.Callback.AFTER_TEXT_CHANGED)???
void?afterTextChanged(Editable?s)?{???
?
}??

代碼混淆

-keep?class?butterknife.**?{?*;?}???
-dontwarn?butterknife.internal.**???
-keep?class?**$$ViewBinder?{?*;?}???
?
-keepclasseswithmembernames?class?*?{???
????@butterknife.*?<fields>;???
}???
?
-keepclasseswithmembernames?class?*?{???
????@butterknife.*?<methods>;???
}????

Zelezny插件的使用

在AndroidStudio->File->Settings->Plugins->搜索Zelezny下載添加就行，可以快速生成對應組件的實例對象，不用手動寫。使用時，在要導入注解的Activity 或 Fragment 或 ViewHolder的layout資源代碼上，右鍵——>Generate——Generate ButterKnife Injections，然后就出現如圖的選擇框。

ButterKnife實現原理

對ButterKnife有過了解人，注入字段的方式是使用注解@BindView(R.id.tv_account_name)，但首先我們需要在Activity聲明注入ButterKnife.bind(Activity activity) 。我們知道，注解分為好幾類，有在源碼生效的注解，有在類文件生成時生效的注解，有在運行時生效的注解。分別為RetentionPolicy.SOURCE，RetentionPolicy.CLASS，RetentionPolicy.RUNTIME ，其中以RetentionPolicy.RUNTIME最為消耗性能。而ButterKnife使用的則是編譯器時期注入，在使用的時候，需要配置classpath ‘com.neenbedankt.gradle.plugins:android-apt:1.8’ ，這個配置說明，在編譯的時候，進行注解處理。要對注解進行處理，則需要繼承AbstractProcessor ，在boolean process(Set

ButterKnife實現方式

知曉了注解可以在編譯的時候進行處理，那么，我們就可以得到注解的字段屬性與所在類，進而生成注入文件，生成一個注入類的內部類，再進行字段處理，編譯之后就會合并到注入類中，達到植入新代碼段的目的。例如：我們注入@VInjector(R.id.tv_show) TextView tvShow;我們就可以得到tvShow這個變量與R.id.tv_show這個id的值，然后進行模式化處理injectObject.tvShow = injectObject.findViewById(R.id.tv_show); ，再將代碼以內部類的心事加入到組件所在的類中，完成一次DI(注入) 。