This document discusses ButterKnife, a library that reduces boilerplate code when finding and binding views in Android. It allows annotating view fields to replace findViewById calls. The library generates code at compile time to bind views, avoiding reflection. Pros include cleaner code and easier integration. Cons include slower annotation processing and needing to upgrade the dependency. Examples demonstrate how to set up dependencies and use ButterKnife to bind views in an activity.

1. ButterKnife
Jintin

2. TextView textView =
(TextView) findViewById(R.id.textView);
How to get View

3. TextView textView =
findViewById(R.id.textView);
After API 26

4. Magic Type infer
@Override
public <T extends View> T findViewById(@IdRes int id) {
return getDelegate().findViewById(id);
}
@Nullable
public final <T extends View> T findViewById(@IdRes int id) {
if (id == NO_ID) {
return null;
}
return findViewTraversal(id);
}

5. Want More?

6. ButterKnife
• Replace findViewById by
@BindView
• Generate bind file during
compile time
• No(less) reflection
• Much short, clean code

7. Install
dependencies {
implementation
'com.jakewharton:butterknife:8.8.1'
annotationProcessor
‘com.jakewharton:butterknife-compiler:8.8.1'
}

8. How to use
class ExampleActivity extends Activity {
@BindView(R.id.title) TextView title;
@BindView(R.id.subtitle) TextView subtitle;
@BindView(R.id.footer) TextView footer;
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple_activity);
ButterKnife.bind(this); // return an unbinder
// TODO Use fields...
}
}

9. Unbinder
• Return by `ButterKnife.bind()`
• Will release view reference to null
• Avoid in memory leak (mostly in Fragment case)

10. Pros & Cons
• Easy integrate
• Clean structure
• Annotation processing is slow
• One more dependency
• Upgrade
• Replace(Kotlin / databinding)

11. Demo

12. Reference
• http://jakewharton.github.io/butterknife/
• https://medium.com/@jintin/butterknife-on-
android-5b2daf60d27d