ButterKnife配置与使用

ゝ一世哀愁。 2022-09-27 04:58 312阅读 0赞

ButterKnife是我很欣赏的国外大神JakeWharton的作品，是一个专注于Android系统的View注入框架,可以减少大量的findViewById以及setOnClickListener代码，通过Android Studio 插件可以可视化一键生成。

下面是Readme所述 的功能  
\- 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.

apply plugin: 'com.android.library'
    apply plugin: 'com.jakewharton.butterknife'
    
    
    dependencies {
      compile 'com.jakewharton:butterknife:8.5.1'
        apt 'com.jakewharton:butterknife-compiler:8.5.1'
    }

同时也要在buile.gradle(project)中配置依赖。

buildscript {
      repositories {
        mavenCentral()
       }
      dependencies {
        classpath 'com.jakewharton:butterknife-gradle-plugin:8.5.1'
      }
    }

然后就可以在代码中使用butterKnife了

## 绑定View ##

@BindView(R.id.toolbar)
        Toolbar tb_toolbar;
        @BindView(R.id.toolbar_layout)
        CollapsingToolbarLayout ct_toolbarLayout;
        @BindView(R.id.app_bar)
        AppBarLayout ab_appBar;
        @BindView(R.id.content_main)
        NestedScrollView ns_contentMain;

## 绑定资源文件 ##

class ExampleActivity extends Activity {
        
      @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
      // ...
    }

## Fragment绑定view ##

public class FancyFragment extends Fragment {
        
      @BindView(R.id.button1) Button button1;
      @BindView(R.id.button2) Button button2;
    
      @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fancy_fragment, container, false);
        ButterKnife.bind(this, view);
        // TODO Use fields...
        return view;
      }
    }

## ViewHolder ##

public class MyAdapter extends BaseAdapter {
        
      @Override public View getView(int position, View view, ViewGroup parent) {
        ViewHolder holder;
        if (view != null) {
          holder = (ViewHolder) view.getTag();
        } else {
          view = inflater.inflate(R.layout.whatever, parent, false);
          holder = new ViewHolder(view);
          view.setTag(holder);
        }
    
        holder.name.setText("John Doe");
        // etc...
    
        return view;
      }
    
      static class ViewHolder {
        @BindView(R.id.title) TextView name;
        @BindView(R.id.job_title) TextView jobTitle;
    
        public ViewHolder(View view) {
          ButterKnife.bind(this, view);
        }
      }
    }

## 生成相同类型的View集合，并统一控制他们的属性 ##

通过Action和Setter接口定义一个控件简单的行为，然后将这个行为应用到一组控件中。

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);
      }
    };

@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);

## Listener监听 ##

通过@OnClick注解绑定监听方法

@OnClick(R.id.submit)
    public void submit(View view) {
      // TODO submit data to server...
    }

方法的参数是可以改变的 ，如果是特殊的对象，它将会自动转化

@OnClick(R.id.submit)
    public void sayHi(Button button) {
      button.setText("Hello!");
    }

当然对于同类型控件的通用事件处理，我们也可以把它们写在一起

@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();
      }
    }

## 取消绑定操作 ##

Fragment的生命周期不同于Activity，我们在onCreateView中绑定一个布局的时候，必须在onDestroyView将View设为null，我们可以调用unbinder.unbind()方法来取消绑定

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();
      }
    }

默认情况下，如果找不到资源id，会抛出异常，但是我们可以使用@Nullable和@Optional注解来防止程序崩溃。

@Nullable @BindView(R.id.might_not_be_there) TextView mightNotBeThere;
    
    @Optional @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {
      // TODO ...
    }

# **最后的彩蛋~** #

ButterKnife额外的提供了findById 方法给我们进行绑定操作。。。。。我满怀期待的查看了源码，却发现。。

/** Simpler version of {@link View#findViewById(int)} which infers the target type. */
      @SuppressWarnings({ "unchecked", "UnusedDeclaration" }) // Checked by runtime cast. Public API.
      @CheckResult
      public static <T extends View> T findById(@NonNull View view, @IdRes int id) {
        return (T) view.findViewById(id);
      }
    
      /** Simpler version of {@link Activity#findViewById(int)} which infers the target type. */
      @SuppressWarnings({ "unchecked", "UnusedDeclaration" }) // Checked by runtime cast. Public API.
      @CheckResult
      public static <T extends View> T findById(@NonNull Activity activity, @IdRes int id) {
        return (T) activity.findViewById(id);
      }
    
      /** Simpler version of {@link Dialog#findViewById(int)} which infers the target type. */
      @SuppressWarnings({ "unchecked", "UnusedDeclaration" }) // Checked by runtime cast. Public API.
      @CheckResult
      public static <T extends View> T findById(@NonNull Dialog dialog, @IdRes int id) {
        return (T) dialog.findViewById(id);
      }
    }

发现JakeWharton大神仅仅是帮我们用泛型的方法自动转化了类型-.-  
真的是意想不到的彩蛋啊，哈哈哈哈~

**参考文章**  
[Butterknife使用指南][Butterknife]  
[Android Butterknife 8.4.0 使用方法总结][Android Butterknife 8.4.0]

[Butterknife]: http://jakewharton.github.io/butterknife/
[Android Butterknife 8.4.0]: http://www.cnblogs.com/zhaoyanjun/p/6016341.html