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Butterknife全方位解析
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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) 。
a) 首先創建一個視圖注解
b) 創建一個注解處理器，用來得到注解的屬性與所屬類
c) 解析注解，分離組合Class與屬性
d) 組合Class與屬性，生成新的Java File
APT生成的Java File ， 以及模式代碼
使用Javac ， 編譯時期生成注入類的子類
項目UML圖
簡要說明：
主要類：
VInjectProcessor —-> 注解處理器 ， 需要配置注解處理器
resources?????????-?META-INF???????????????-?services? ????????????????????-?javax.annotation.processing.Processor??Processor內容：
com.myl.viewinject.apt.VInjectProcessor???#?指定處理器全類名?? VInjectHandler —-> 注解處理類 ， 主要進行注入類與注解字段進行解析與封裝，將同類的字段使用map集合進行映射。exp: Map
自定義ButterKnife具體實現
因微信字數限制，請點擊左下角原文鏈接查看!~
本文作者：佚名 來源：51CTO
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