Butterknife全方位解析
zvci3409
8年前
<h2>概述</h2> <p>Butterknife是供职于Square公司的JakeWharton大神开发的开源库，使用这个库，在AS中搭配 <a href="/misc/goto?guid=4959671792203787710" rel="nofollow,noindex">Android</a> ButterKnife Zelezny插件，可以大大提高开发的效率，从此摆脱繁琐的findViewById(int id)，也不用自己手动@bind(int id) ， 直接用插件生成即可。本篇文章将对Butterknife进行深入解析。</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/eac77eea8e60f3d81fe3f490e325daba.png"></p> <p>ButterKnife有以下优点：</p> <p>1、强大的View绑定和Click事件处理功能，简化代码，提升开发效率</p> <p>2、方便的处理Adapter里的ViewHolder绑定问题</p> <p>3、运行时不会影响APP效率，使用配置方便</p> <p>4、代码清晰，可读性强</p> <h2>如何导入ButterKnife</h2> <p>在项目的build.grade文件中进行如下配置：</p> <pre> <code class="language-java">buildscript { repositories { jcenter() mavenCentral() maven { url "https://plugins.gradle.org/m2/" } } dependencies { classpath 'com.android.tools.build:gradle:2.2.0' //这里配置 apt 供butterknife使用 classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' } }</code></pre> <p>例如：</p> <pre> <code class="language-java">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 }</code></pre> <p>在app的build.grade文件中进行如下配置：</p> <pre> <code class="language-java">apply plugin: 'com.android.application' apply plugin: 'com.neenbedankt.android-apt' android{...} dependencies { //视图绑定 butterknife compile 'com.jakewharton:butterknife:8.4.0' apt 'com.jakewharton:butterknife-compiler:8.4.0' }</code></pre> <p>例如：</p> <pre> <code class="language-java">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' }</code></pre> <h2>如何使用ButterKnife</h2> <p>1) 由于每次都要在Activity中的onCreate绑定Activity，所以个人建议写一个BaseActivity完成绑定，子类继承即可</p> <p>注：ButterKnife.bind(this)；绑定Activity 必须在setContentView之后：</p> <p>实现如下（FragmentActivity 实现一样）：</p> <pre> <code class="language-java">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);//解除绑定，官方文档只对fragment做了解绑 } }</code></pre> <p>2) 绑定fragment</p> <pre> <code class="language-java">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);//绑定framgent this.context = getActivity(); initAllMembersView(savedInstanceState); return mRootView; } protected abstract void initAllMembersView(Bundle savedInstanceState); @Override public void onDestroyView() { super.onDestroyView(); ButterKnife.unbind(this);//解绑 } }</code></pre> <p>3) 控件id 注解： @BindView（）</p> <pre> <code class="language-java">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 的修饰类型不能是：private 或者 static 。 否则会报错：错误: @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); //绑定activity ButterKnife.bind( this ) ; button1.setText( "I am a button "); } }</code></pre> <p>4) 多个控件id 注解： @BindViews（）</p> <pre> <code class="language-java">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 "); } }</code></pre> <p>5) @BindString() ：绑定string 字符串</p> <pre> <code class="language-java">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 ) //绑定button 控件 public Button button1 ; @BindString( R.string.app_name ) //绑定string 字符串 String meg; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_butterknife); //绑定activity ButterKnife.bind( this ) ; button1.setText( meg ); } }</code></pre> <p>6) @BindArray() : 绑定string里面array数组</p> <pre> <code class="language-java"><resources> <string name="app_name">校园助手</string> <string-array name="city"> <item>东莞市</item> <item>广州市</item> <item>珠海市</item> <item>肇庆市</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 ) //绑定button 控件 public Button button1 ; @BindArray(R.array.city ) //绑定string里面array数组 String [] citys ; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_butterknife); //绑定activity ButterKnife.bind( this ) ; button1.setText( citys[0] ); } }</code></pre> <p>7) @BindBitmap( ) : 绑定Bitmap 资源</p> <pre> <code class="language-java">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 ) //绑定ImageView 控件 public ImageView imageView ; @BindBitmap( R.mipmap.wifi ) //绑定Bitmap 资源 public Bitmap wifi_bitmap ; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_butterknife); //绑定activity ButterKnife.bind( this ) ; imageView.setImageBitmap( wifi_bitmap ); } }</code></pre> <p>8) @BindColor( ) : 绑定一个颜色值</p> <pre> <code class="language-java">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 ) //绑定一个控件 public Button button1 ; @BindColor( R.color.colorAccent ) int black ; //绑定一个颜色值 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_butterknife); //绑定activity ButterKnife.bind( this ) ; button1.setTextColor( black ); } }</code></pre> <p>9) Adapter ViewHolder 绑定</p> <pre> <code class="language-java">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); } } }</code></pre> <p>10) 点击事件的绑定：不用声明view，不用setOnClickLisener（）就可以绑定点击事件</p> <p>a. 直接绑定一个方法</p> <pre> <code class="language-java">@OnClick(R.id.submit) public void submit(View view) { // TODO submit data to server... }</code></pre> <p>b. 所有监听方法的参数是可选的</p> <pre> <code class="language-java">@OnClick(R.id.submit) public void submit() { // TODO submit data to server... }</code></pre> <p>c. 定义一个特定类型，它将自动被转换</p> <pre> <code class="language-java">@OnClick(R.id.submit) public void sayHi(Button button) { button.setText("Hello!"); }</code></pre> <p>d. 多个view统一处理同一个点击事件，很方便，避免抽方法重复调用的麻烦</p> <pre> <code class="language-java">@OnClick({ R.id.door1, R.id.door2, R.id.door3 }) public void pickDoor(DoorView door) { if (door.hasPrizeBehind()) { Toast.makeText(this, "You win!", LENGTH_SHORT).show(); } else { Toast.makeText(this, "Try again", LENGTH_SHORT).show(); } }</code></pre> <p>e. 自定义view可以绑定自己的监听，不指定id</p> <pre> <code class="language-java">public class FancyButton extends Button { @OnClick public void onClick() { // TODO do something! } }</code></pre> <p>f. 给EditText加addTextChangedListener（即添加多回调方法的监听的使用方法），利用指定回调，实现想回调的方法即可，哪个注解不会用点进去看下源码上的注释</p> <pre> <code class="language-java">@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) { }</code></pre> <h2>代码混淆</h2> <pre> <code class="language-java">-keep class butterknife.** { *; } -dontwarn butterknife.internal.** -keep class **$$ViewBinder { *; } -keepclasseswithmembernames class * { @butterknife.* <fields>; } -keepclasseswithmembernames class * { @butterknife.* <methods>; }</code></pre> <h2>Zelezny插件的使用</h2> <p>在AndroidStudio->File->Settings->Plugins->搜索Zelezny下载添加就行 ，可以快速生成对应组件的实例对象，不用手动写。使用时，在要导入注解的Activity 或 Fragment 或 ViewHolder的layout资源代码上，右键——>Generate——Generate ButterKnife Injections，然后就出现如图的选择框。</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/84b66a1c0caee9c008da2a266095c9a7.gif"></p> <h2>ButterKnife实现原理</h2> <p>对ButterKnife有过了解人 ， 注入字段的方式是使用注解@BindView(R.id.tv_account_name)，但首先我们需要在Activity声明注入ButterKnife.bind(Activity activity) 。我们知道，注解分为好几类， 有在源码生效的注解，有在类文件生成时生效的注解，有在运行时生效的注解。分别为RetentionPolicy.SOURCE，RetentionPolicy.CLASS，RetentionPolicy.RUNTIME ，其中以RetentionPolicy.RUNTIME最为消耗性能。而ButterKnife使用的则是编译器时期注入，在使用的时候，需要配置classpath ‘com.neenbedankt.gradle.plugins:android-apt:1.8’ ， 这个配置说明，在编译的时候，进行注解处理。要对注解进行处理，则需要继承AbstractProcessor ， 在boolean process(Set</p> <h2>ButterKnife实现方式</h2> <p>知晓了注解可以在编译的时候进行处理，那么，我们就可以得到注解的字段属性与所在类 ， 进而生成注入文件，生成一个注入类的内部类，再进行字段处理 ， 编译之后就会合并到注入类中，达到植入新代码段的目的。例如：我们注入@VInjector(R.id.tv_show) TextView tvShow;我们就可以得到tvShow这个变量与R.id.tv_show这个id的值，然后进行模式化处理injectObject.tvShow = injectObject.findViewById(R.id.tv_show); ，再将代码以内部类的心事加入到组件所在的类中 ， 完成一次DI（注入） 。</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/6ce06e3e9ea439a97486fdc5b8e8f96a.png"></p> <p>a) 首先创建一个视图注解</p> <p>b) 创建一个注解处理器，用来得到注解的属性与所属类</p> <p>c) 解析注解，分离组合Class与属性</p> <p>d) 组合Class与属性，生成新的Java File</p> <p>APT生成的Java File ， 以及模式代码</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/6f304007bc677577257a8d2be23048bb.png"></p> <p>使用Javac ， 编译时期生成注入类的子类</p> <h2>项目UML图</h2> <p><img src="https://simg.open-open.com/show/a259b207364b403398cf160ea3d4802a.jpg"></p> <p>简要说明：</p> <p>主要类：</p> <p>VInjectProcessor —-> 注解处理器 ， 需要配置注解处理器</p> <pre> <code class="language-java">resources - META-INF - services - javax.annotation.processing.Processor</code></pre> <p>Processor内容：</p> <pre> <code class="language-java">com.myl.viewinject.apt.VInjectProcessor # 指定处理器全类名</code></pre> <p style="text-align:center"><img src="https://simg.open-open.com/show/4aa2c4137eabe620bc33a042827a96ac.png"></p> <p>VInjectHandler —-> 注解处理类 ， 主要进行注入类与注解字段进行解析与封装，将同类的字段使用map集合进行映射。exp: Map</p> <h2>自定义ButterKnife具体实现</h2> <p>一 ， 创建注解 , 对视图进行注解，R.id.xxx ， 所以注解类型是int类型</p> <pre> <code class="language-java">/** * Created by myl on 2016/11/21. * * View inject * 字段注入注解，可以新建多个注解，再通过AnnotationProcessor进行注解处理 * RetentionPolicy.CLASS ，在编译的时候进行注解 。我们需要在生成.class文件的时候需要进行处理 */ @Retention(RetentionPolicy.CLASS) @Target(ElementType.FIELD) public @interface VInjector { int value(); }</code></pre> <p>二， 注解处理器 关于注解处理器配置，上面已经做了说明</p> <pre> <code class="language-java">/** * Created by myl on 2016/11/21. * * Inject in View annotation processor * * 需要在配置文件中指定处理类 resources/META-INF/services/javax.annotation.processing.Processor * com.myl.viewinject.apt.VInjectProcessor */ @SupportedAnnotationTypes("com.myl.viewinject.annotation.VInjector") @SupportedSourceVersion(SourceVersion.RELEASE_6) public class VInjectProcessor extends AbstractProcessor { List<IAnnotationHandler> mAnnotationHandler = new ArrayList<>(); Map<String,List<VariableElement>> mHandleAnnotationMap = new HashMap<>(); private IGenerateAdapter mGenerateAdapter; @Override public synchronized void init(ProcessingEnvironment processingEnv) { super.init(processingEnv); // init annotation handler , add handler registerHandler(new VInjectHandler()); // init generate adapter mGenerateAdapter = new ViewGenerateAdapter(processingEnv); } /*可以有多个处理*/ protected void registerHandler(IAnnotationHandler handler) { mAnnotationHandler.add(handler); } // annotation into process run @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { for (IAnnotationHandler handler : mAnnotationHandler) { // attach environment , 关联环境 handler.attachProcessingEnvironment(processingEnv); // handle annotation 处理注解 ，得到注解类的属性列表 mHandleAnnotationMap.putAll(handler.handleAnnotation(roundEnv)); } // 生成辅助类 mGenerateAdapter.generate(mHandleAnnotationMap); // 表示处理 return true; } }</code></pre> <p>对得到的注解进行处理 ， 主要是进行注解类型与属性进行分离合并处理，因为一个类有多个属性，所以采用map集合，进行存储，数据结构为：Map</p> <pre> <code class="language-java">/** * Created by myl on 2016/11/21. * * 注解处理实现 , 解析VInjector注解属性 */ public class VInjectHandler implements IAnnotationHandler { private ProcessingEnvironment mProcessingEnvironment; @Override public void attachProcessingEnvironment(ProcessingEnvironment environment) { this.mProcessingEnvironment = environment; } @Override public Map<String, List<VariableElement>> handleAnnotation(RoundEnvironment roundEnvironment) { Map<String,List<VariableElement>> map = new HashMap<>(); /*获取一个类中带有VInjector注解的属性列表*/ Set<? extends Element> elements = roundEnvironment.getElementsAnnotatedWith(VInjector.class); for (Element element : elements) { VariableElement variableElement = (VariableElement) element; /*获取类名 ，将类目与属性配对，一个类，对于他的属性列表*/ String className = getFullClassName(variableElement); List<VariableElement> cacheElements = map.get(className); if (cacheElements == null) { cacheElements = new ArrayList<>(); map.put(className,cacheElements); } cacheElements.add(variableElement); } return map; } /** * 获取注解属性的完整类名 * @param variableElement */ private String getFullClassName(VariableElement variableElement) { TypeElement typeElement = (TypeElement) variableElement.getEnclosingElement(); String packageName = AnnotationUtils.getPackageName(mProcessingEnvironment,typeElement); return packageName+"."+typeElement.getSimpleName().toString(); } }</code></pre> <p>生成Java File ， 根据获取的属性与类，创建一个注入类的内部类</p> <pre> <code class="language-java">/** * Created by myl on 2016/11/21. * * 生成View注解辅助类 */ public class ViewGenerateAdapter extends AbstractGenerateAdapter { public ViewGenerateAdapter(ProcessingEnvironment processingEnvironment) { super(processingEnvironment); } @Override protected void generateImport(Writer writer, InjectInfo injectInfo) throws IOException { writer.write("package "+injectInfo.packageName+";"); writer.write("\n\n"); writer.write("import com.zeno.viewinject.adapter.IVInjectorAdapter;"); writer.write("\n\n"); writer.write("import com.zeno.viewinject.utils.ViewFinder;"); writer.write("\n\n\n"); writer.write("/* This class file is generated by ViewInject , do not modify */"); writer.write("\n"); writer.write("public class "+injectInfo.newClassName+" implements IVInjectorAdapter<"+injectInfo.className+"> {"); writer.write("\n\n"); writer.write("public void injects("+injectInfo.className+" target) {"); writer.write("\n"); } @Override protected void generateField(Writer writer, VariableElement variableElement, InjectInfo injectInfo) throws IOException { VInjector vInjector = variableElement.getAnnotation(VInjector.class); int resId = vInjector.value(); String fieldName = variableElement.getSimpleName().toString(); writer.write("\t\ttarget."+fieldName+" = ViewFinder.findViewById(target,"+resId+");"); writer.write("\n"); } @Override protected void generateFooter(Writer writer) throws IOException { writer.write(" \t}"); writer.write("\n\n"); writer.write("}"); } }</code></pre> <p> </p> <p>来自：http://www.androidchina.net/6082.html</p> <p> </p>