Android butterknife（Butter Knife）框架是一个注解式编程框架，可以很好的使用@BindView代替findViewById，使用@OnClick代替setOnClickListener等事件，既节约了写代码的时间，也减少了过多的代码量，这也是Java注解式编程的好处，下面来学习一下butterknife框架吧！

1：首先在build.gradle里面导入Butter Knife的jar包，添加如下代码：

implementation 'com.jakewharton:butterknife:8.8.1'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

如果导入的butterknife版本过新，如butterknife:10.2.3版本，就会报如下错误，所以小编只使用了butterknife:8.8.1作为演示：

Duplicate class android.support.v4.app.INotificationSideChannel found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.app.INotificationSideChannel$Stub found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.app.INotificationSideChannel$Stub$Proxy found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.IResultReceiver found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.IResultReceiver$Stub found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.IResultReceiver$Stub$Proxy found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.ResultReceiver found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.ResultReceiver$1 found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.ResultReceiver$MyResultReceiver found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Duplicate class android.support.v4.os.ResultReceiver$MyRunnable found in modules classes.jar (androidx.core:core:1.0.0) and classes.jar (com.android.support:support-compat:27.1.1)

Go to the documentation to learn how to Fix dependency resolution errors.

2：可以使用@BindView注解绑定一些属性，使用@OnClick绑定点击事件，如下：

绑定属性：

class ExampleActivity extends Activity {
  @BindView(R2.id.user) EditText username;
  @BindView(R2.id.pass) EditText password;
...
}

绑定点击事件：

  @OnClick(R.id.submit) void submit() {   
   // TODO call server...
  }

当然了，你还可以同时绑定N多个点击事件，代码如下：

    @OnClick({R.id.btn_mesage, R.id.btn_image, R.id.btn_list, R.id.btn_dialog1, R.id.btn_dialog2})
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn_mesage:

                break;
            case R.id.btn_image:

                break;
            case R.id.btn_list:

                break;
            case R.id.btn_dialog1:

                break;
            case R.id.btn_dialog2:

                break;
            default:
                break;
      }

3：butterknife还有一些别的注解，如：@BindColor, @BindString, @BindAnim等，具体的用法可以自己Google一下，如图所示：