ButterKnife

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