一、概念

ButterKnife是一个专注于Android系统的View注入框架。
使用ButterKnife对性能基本没有损失，因为ButterKnife用到的注解并不是在运行时使用反射，而是在编译时生成新的类。
项目集成以及使用都特别简单。

二、使用

//build.gradle（project）
// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

//build.gradle（module）
apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.0"
    defaultConfig {
        applicationId "com.example.sourcecodetest"
        minSdkVersion 19
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    // Butterknife requires Java 8.
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

    implementation 'com.jakewharton:butterknife:10.2.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:10.2.1'
}

//strings.xml
<resources>
    <string name="app_name">SourceCodeTest</string>

    <string-array name="city">
        <item>北京</item>
        <item>上海</item>
        <item>广州</item>
    </string-array>
</resources>

//colors.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#008577</color>
    <color name="colorPrimaryDark">#00574B</color>
    <color name="colorAccent">#D81B60</color>
</resources>

//activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button1"/>
    <Button
        android:id="@+id/btn2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/btn1"
        android:text="Button2"/>
    <Button
        android:id="@+id/btn3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/btn2"
        android:text="Button3"/>
    <TextView
        android:id="@+id/tv1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/btn3"
        android:text="TextView1"/>
</RelativeLayout>

//MainActivity
public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";

    @BindViews({ R.id.btn1, R.id.btn2,  R.id.btn3})
    public List<Button> buttonList ;

    @BindView(R.id.tv1)
    public TextView textView;

    @BindString(R.string.app_name)
    String str;

    @BindArray(R.array.city)
    String[] arr;

    @BindColor(R.color.colorAccent)
    int color;

    @BindBitmap(R.drawable.ic_launcher)
    Bitmap bitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(TAG, "zwm, onCreate");
        ButterKnife.bind(this);

        buttonList.get(0).setText("ButterKnife Button1");
        buttonList.get(1).setText("ButterKnife Button2");
        buttonList.get(2).setText("ButterKnife Button3");
        textView.setText("ButterKnife TextView1");

        Log.d(TAG, "zwm, str: " + str);
        if(arr != null && arr.length > 0) {
            for(String item : arr) {
                Log.d(TAG, "zwm, item: " + item);
            }
        }

        textView.setBackgroundColor(color);
        Log.d(TAG, "zwm ,bitmap: " + bitmap);
    }

    @OnClick(R.id.btn1)
    public void showShortClickToast() {
        Toast.makeText(this, "This is a short click", Toast.LENGTH_SHORT).show();
    }

    @OnLongClick(R.id.btn1)
    public void showLongClickToast() {
        Toast.makeText(this, "This is a long click", Toast.LENGTH_SHORT).show();
    }

    @OnClick({R.id.btn2, R.id.btn3})
    public void onViewClick(View view) {
        switch (view.getId()) {
            case R.id.btn2:
                Toast.makeText(this, "This is a btn2 click", Toast.LENGTH_SHORT).show();
                break;
            case R.id.btn3:
                Toast.makeText(this, "This is a btn3 click", Toast.LENGTH_SHORT).show();
                break;
        }
    }
}

//输出log
2020-01-13 11:44:39.543 12202-12202/com.example.sourcecodetest D/MyApplication: zwm, onCreate
2020-01-13 11:44:41.331 12202-12202/com.example.sourcecodetest D/MainActivity: zwm, onCreate
2020-01-13 11:44:41.336 12202-12202/com.example.sourcecodetest D/MainActivity: zwm, str: SourceCodeTest
2020-01-13 11:44:41.337 12202-12202/com.example.sourcecodetest D/MainActivity: zwm, item: 北京
2020-01-13 11:44:41.337 12202-12202/com.example.sourcecodetest D/MainActivity: zwm, item: 上海
2020-01-13 11:44:41.337 12202-12202/com.example.sourcecodetest D/MainActivity: zwm, item: 广州
2020-01-13 11:44:41.337 12202-12202/com.example.sourcecodetest D/MainActivity: zwm ,bitmap: android.graphics.Bitmap@a645210