ButterKnife

Introduction of ButterKnife annotation library and its all features

Transcript

1. ButterKnife 8.2.1 Himanshu Dudhat
2. Intro • Field and method binding for Android views which uses annotation processing to generate boilerplate code for you. • Eliminate findViewById calls by using @BindView on fields. • Group multiple views in a list or array. Operate on all of them at once with actions, setters, or properties. • Eliminate anonymous inner-classes for listeners by annotating methods with @OnClick and others. • Eliminate resource lookups by using resource annotations on fields.
3. Configure ButterKnife • Update Project-level build.gradle • Apply “android-apt” in module-level build.gradle buildscript { repositories { mavenCentral() } dependencies { classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' } } apply plugin: 'android-apt' android { ... } dependencies { compile 'com.jakewharton:butterknife:8.2.1' apt 'com.jakewharton:butterknife-compiler:8.2.1' }
4. Add in library module • Add Butterknife plugin to project-level build.gradle • Apply ButterKnife plugin in library module • Note: If you applied ButterKnife in library project then you neeed to use R2 class instead of R class in ButterKnife annotations. buildscript { repositories { mavenCentral() } dependencies { classpath 'com.jakewharton:butterknife-gradle-plugin:8.2.1' } } apply plugin: 'com.android.library' apply plugin: 'com.jakewharton.butterknife'
5. Features • VIEW BINDING • RESOURCE BINDING • NON-ACTIVITY BINDING • VIEW LISTS • LISTENER BINDING • BINDING RESET • OPTIONAL BINDINGS • MULTI-METHOD LISTENERS
6. VIEW BINDING • Annotate fields with @BindView and a view ID for Butter Knife to find and automatically cast the corresponding view in your layout • You can also perform binding on arbitrary objects by supplying your own view root @BindView(R.id.title) TextView title; @BindView(R.id.subtitle) TextView subtitle; @BindView(R.id.footer) TextView footer; View view = LayoutInflater.from(context).inflate(R.layout.thing, null); TextView firstName = ButterKnife.findById(view, R.id.first_name); TextView lastName = ButterKnife.findById(view, R.id.last_name); ImageView photo = ButterKnife.findById(view, R.id.phot);
7. RESOURCE BINDING • Bind pre-defined resources with @BindBool, @BindColor, @BindDimen, @BindDrawable, @BindInt, @BindString, which binds an R.bool ID (or your specified type) to its corresponding field. @BindString(R.string.title) String title; @BindDrawable(R.drawable.graphic) Drawable graphic; @BindColor(R.color.red) int red; // int or ColorStateList field @BindDimen(R.dimen.spacer) Float spacer; // int (for pixel size) or float (for exact value) field
8. VIEW LISTS • You can group multiple views into a List or array • Then apply method allows you to act on all the views in a list at once @BindViews({ R.id.first_name, R.id.middle_name, R.id.last_name }) List<EditText> nameViews; ButterKnife.apply(nameViews, DISABLE); ButterKnife.apply(nameViews, ENABLED, false);
9. Continue… • Action and Setter interfaces allow specifying simple behavior • An Android Property can also be used with the apply method. static final ButterKnife.Action<View> DISABLE = new ButterKnife.Action<View>() { @Override public void apply(View view, int index) { view.setEnabled(false); } }; static final ButterKnife.Setter<View, Boolean> ENABLED = new ButterKnife.Setter<View, Boolean>() { @Override public void set(View view, Boolean value, int index) { view.setEnabled(value); } }; ButterKnife.apply(nameViews, View.ALPHA, 0.0f);
10. LISTENER BINDING • Listeners can also automatically be configured onto methods • Specify multiple IDs in a single binding for common event handling. @OnClick(R.id.submit) public void submit(View view) { // TODO submit data to server... } @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(); } }
11. BINDING RESET • Fragments have a different view lifecycle than activities. Views should set to be null in onDestroyViews(). public class FancyFragment extends Fragment { @BindView(R.id.button1) Button button1; @BindView(R.id.button2) Button button2; private Unbinder unbinder; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fancy_fragment, container, false); unbinder = ButterKnife.bind(this, view); // TODO Use fields... return view; } @Override public void onDestroyView() { super.onDestroyView(); unbinder.unbind(); } }
12. OPTIONAL BINDINGS • For Views, it is using android defined annotation, @Nullable • For methods, it is using ButterKnife annotation - @Optional @Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere; @Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() { // TODO ... }
13. MULTI-METHOD LISTENERS • Method annotations whose corresponding listener has multiple callbacks can be used to bind to any one of them. Each annotation has a default callback that it binds to. Specify an alternate using the callback parameter. E.g. @OnItemSelected(R.id.list_view) void onItemSelected(int position) { // TODO ... } @OnItemSelected(value = R.id.maybe_missing, callback = NOTHING_SELECTED) void onNothingSelected() { // TODO ... }
14. References • http://jakewharton.github.io/butterknife • https://www.sitepoint.com/tidying-code-with-android-butterknife/ • https://guides.codepath.com/android/Reducing-View-Boilerplate-with-Butterknife
15. Questions?
16. Thanks! +HimanshuDudhat @HimanshuDudhat himanshu.dudhat@gmail.com Team Lead - Android @ Cygnet Infotech Pvt. Ltd. Sr. Software Engineer @ Cygnet Infotech Pvt. Ltd Himanshu Dudhat