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);

}
}