android 快速开发利器 ButterKnife 使用介绍

介绍

程序员一般都比较懒，遇到一些机械化的事情，总是能想到一些方法自动化的帮助我们减轻工作量，通过　ButterKnife 开源库能让我们从　大量的 findViewById ,setOnClickListener 中解放出来.并且对程序性能的影响微乎其微
（其自定义注解的实现都是限定为RetentionPolicy.CLASS，也就是到编译出.class文件为止有效，在运行时不额外消耗性能，其是通过java注解自动生成java代码的形式来完成工作）

如果，按照平常的用法，通过　findViewById　等一系列方法，给控件设置监听等，将会让代码显得非常丑陋，比如:

public class ButterActivity extends AppCompatActivity {

    TextView ansTextView;
    EditText par1,par2;
    Button cal;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_butter);
        ansTextView=(TextView)findViewById(R.id.tv_ans);
        par1=(EditText)findViewById(R.id.edt_par1);
        par2=(EditText)findViewById(R.id.edt_par2);
        cal=(Button)findViewById(R.id.btn_add);
        cal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String x=par1.getText().toString();
                String y=par2.getText().toString();
                ansTextView.setText(x+y);
            }
        });

    }
}

而使用　ButterKnife 之后

public class ButterActivity extends AppCompatActivity {

    @Bind(R.id.tv_ans)TextView ansTextView;
    @Bind(R.id.edt_par1)EditText par1;
    @Bind(R.id.edt_par2)EditText par2;
    @Bind(R.id.btn_add)Button cal;
    @Nullable  @OnClick(R.id.btn_add)void add(View view){
       String x=par1.getText().toString();
       String y=par2.getText().toString();
       ansTextView.setText(x+y);
   }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_butter);
        ButterKnife.bind(this);
      }

这样写，代码是不是清晰了很多，变得非常优雅.下面是具体用法:

使用　android studio 在　build.gradle 添加这句: compile ‘com.jakewharton:butterknife:7.0.1’

  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      compile 'com.android.support:appcompat-v7:23.1.1'
      compile 'com.jakewharton:butterknife:7.0.1'
  }

项目地址:https://github.com/JakeWharton/butterknife

基本用法

class ExampleActivity extends Activity {
  @Bind(R.id.title) TextView title;
  @Bind(R.id.subtitle) TextView subtitle;
  @Bind(R.id.footer) TextView footer;

  @Override public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.simple_activity);
    ButterKnife.bind(this);
    // TODO Use fields...
  }
}

资源绑定

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

public class FancyFragment extends Fragment {
  @Bind(R.id.button1) Button button1;
  @Bind(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;
  }
}

Adapter

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 {
    @Bind(R.id.title) TextView name;
    @Bind(R.id.job_title) TextView jobTitle;

    public ViewHolder(View view) {
      ButterKnife.bind(this, view);
    }
  }
}

View List

  //可以将多个view 设置到一个list 或　array

  @Bind({ R.id.first_name, R.id.middle_name, R.id.last_name })
  List<EditText> nameViews;

  //给　view list 一致动作或者设置

  ButterKnife.apply(nameViews, DISABLE);
  ButterKnife.apply(nameViews, ENABLED, false);
  Action and Setter interfaces allow specifying simple behavior.

  //
  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);
    }
  };

  //设置属性
  ButterKnife.apply(nameViews, View.ALPHA, 0.0f);

监听器

  //注册普通的按钮监听

  @OnClick(R.id.submit)
  public void submit(View view) {
    // TODO submit data to server...
  }
  //监听方法中的所有参数都是可选的

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

  //对监听器中的参数指定具体的类型，会自动转换

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

  //给定多个 id ，为它们指定共同的处理方法

  @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();
    }
  }
  //view 类型的内部指定监听器，可以不用指定id

  public class FancyButton extends Button {
    @OnClick
    public void onClick() {
      // TODO do something!
    }
  }


  //防止因为没找到该控件设置监听而抛出异常
  @Nullable @Bind(R.id.might_not_be_there) TextView mightNotBeThere;

  @Nullable @OnClick(R.id.maybe_missing) void onMaybeMissingClicked() {
  // TODO ...
  }

绑定重置

Fragment 的生命周期与Activity 不一样，可以这样

public class FancyFragment extends Fragment {
  @Bind(R.id.button1) Button button1;
  @Bind(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;
  }

  @Override public void onDestroyView() {
    super.onDestroyView();
    ButterKnife.unbind(this);
  }
}

一个例子

public class MainActivity extends AppCompatActivity {

    @BindString(R.string.action_settings)String title;

    @Bind(R.id.input_edit1)EditText input1;
    @Bind(R.id.input_edit2)EditText input2;

    @Bind({R.id.input_edit1,R.id.input_edit2})
    List<EditText> editTextList;

    @Bind(R.id.ans_text)TextView outText;
    @Bind(R.id.cal_button)Button button;

    @OnClick(R.id.cal_button)void calculate(View view){
        String x=input1.getText().toString();
        String y=input2.getText().toString();
        outText.setText(x + y);
        Intent intent=new Intent(MainActivity.this,ListActivity.class);
        startActivity(intent);
    }

    static  final ButterKnife.Action<EditText>SIZE=new ButterKnife.Action<EditText>(){
        @Override
        public void apply(EditText view, int index) {
                view.setTextSize(10+index*5);
        }
    };

    static  final  ButterKnife.Setter<View,Integer>COLOR=new ButterKnife.Setter<View,Integer>(){
        @Override
        public void set(View view, Integer value, int index) {
                    view.setBackgroundColor(value);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        ButterKnife.apply(editTextList, View.ALPHA, 0.5f);
        ButterKnife.apply(editTextList,COLOR,0xbbccaaff);
        ButterKnife.apply(editTextList,SIZE);

    }
}