ButterKnife 基本使用
implementation 'com.jakewharton:butterknife:8.8.0'
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.0'
public class MainActivity extends AppCompatActivity {
@BindView(R.id.tv_main_show)
TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
textView.setText("Butter-Knife-Test");
}
}
ButterKnife 实现--反射
BindView
/**
* 查找控件ID的注解
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface BindView {
int value() default -1;
}
InjectLayout
/**
* 给Activity注入布局文件的注解
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface InjectLayout {
int value() default -1;
}
OnClick
/**
* 给View设置监听事件的注解
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface OnClick {
int[] value();
}
BindProcessor
/**
* 使用注解注入布局文件省去setContentView
* 使用注解省去findViewById
* 使用注解省去setOnClickListener
* 参考资料：
* https://blog.csdn.net/qq_20521573/article/details/82054088
*/
public class BindProcessor {
/**
* 供Activity调用，用于绑定注解逻辑
*
* @param activity
*/
public static void bind(Activity activity) {
injectLayout(activity);
bindView(activity);
onClick(activity);
}
private static void injectLayout(Activity activity) {
Class<?> activityCls = activity.getClass();
if (activityCls.isAnnotationPresent(InjectLayout.class)) {
InjectLayout layout = activityCls.getAnnotation(InjectLayout.class);
int layoutId = layout.value();
try {
Method setContentView = activityCls.getMethod("setContentView", int.class);
setContentView.setAccessible(true);
setContentView.invoke(activity, layoutId);
} catch (Exception e) {
e.printStackTrace();
}
}
}
private static void bindView(Activity activity) {
Class<?> activityCls = activity.getClass();
Field[] fields = activityCls.getDeclaredFields();
for (Field field : fields) {
if (field.isAnnotationPresent(BindView.class)) {
BindView bindView = field.getAnnotation(BindView.class);
int viewId = bindView.value();
try {
Method findViewById = activityCls.getMethod("findViewById", int.class);
findViewById.setAccessible(true);
Object view = findViewById.invoke(activity, viewId);
field.setAccessible(true);
field.set(activity, view);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
private static void onClick(final Activity activity) {
Class<?> activityCls = activity.getClass();
Method[] methods = activityCls.getMethods();
for (final Method method : methods) {
if (method.isAnnotationPresent(OnClick.class)) {
OnClick onclick = method.getAnnotation(OnClick.class);
int[] viewIdArray = onclick.value();
for (int viewId : viewIdArray) {
final View view = activity.findViewById(viewId);
if (view == null) {
continue;
}
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
method.setAccessible(true);
method.invoke(activity, view);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}
}
}
}
使用 MyButterKnife
/**
* 自定义butterknife
* 通过注解和反射，来绑定view
*/
@InjectLayout(R.layout.activity_main)
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
@BindView(R.id.tv_main)
TextView tv_main;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main);
BindProcessor.bind(this);
tv_main.setText("注解绑定View");
Log.i(TAG, "MainActivity onCreate");
}
@OnClick({R.id.btn_main_click1, R.id.btn_main_click2})
public void onClickView(View view) {
int viewId = view.getId();
if (viewId == R.id.btn_main_click1) {
Toast.makeText(this, "Btn01", Toast.LENGTH_SHORT).show();
} else if (viewId == R.id.btn_main_click2) {
Toast.makeText(this, "Btn02", Toast.LENGTH_SHORT).show();
} else {
Log.i(TAG, "onClickView unknown");
}
}
}
ButterKnife 实现--APT
使用 APT，需要使用 annotationProcessor 依赖 APT 编译自动生成Java代码 需要分别创建两个 module；annotation_compile 存放 APT 源码，annotation_lib 存放要使用的注解
annotationProcessor project(path: ':annotation_compile')
implementation project(path: ':annotation_lib')
annotation_lib
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.SOURCE)
public @interface BindView {
int value();
}
annotation_compile
/**
* 注解处理器，用于生成Java代码
*/
@AutoService(Processor.class)
public class AnnotationCompiler extends AbstractProcessor {
/**
* 用来生成文件的对象
*/
private Filer mFiler;
/**
* 支持的 Java 版本
*/
@Override
public SourceVersion getSupportedSourceVersion() {
return SourceVersion.latestSupported();
}
/**
* 当前APT处理的注解类型
*/
@Override
public Set<String> getSupportedAnnotationTypes() {
Set<String> types = new HashSet<>();
types.add(BindView.class.getCanonicalName());
return types;
}
/**
* 获取用来生成文件的对象：Filer
* 通过 Filer 生成源文件
*/
@Override
public synchronized void init(ProcessingEnvironment processingEnvironment) {
super.init(processingEnvironment);
mFiler = processingEnvironment.getFiler();
}
/**
* 注解处理逻辑
* 生成的代码在 app/build/generated/ap_generated_sources
*/
@Override
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
// 获取所有的 BindView 注解元素；将所有的 BindView 注解都获取到 Set 集合
Set<? extends Element> elementsAnnotatedWith = roundEnvironment.getElementsAnnotatedWith(BindView.class);
// 对所有的 BindView 注解元素分类；相同的Activity中的 BindView 元素放在一起
Map<String, List<VariableElement>> map = new HashMap<>();
for (Element element : elementsAnnotatedWith) {
VariableElement variableElement = (VariableElement) element;
// 得到 VariableElement 所在的 activity 名称
String activityName = variableElement.getEnclosingElement().getSimpleName().toString();
// 用 List 保存所在 activity 的 VariableElement
List<VariableElement> variableElementList = map.get(activityName);
if (variableElementList == null) {
variableElementList = new ArrayList<>();
map.put(activityName, variableElementList);
}
variableElementList.add(variableElement);
}
// 对 Map 中的元素进行解析，拼接成Java文件
if (map.size() > 0) {
Writer writer = null;
Iterator<String> iterator = map.keySet().iterator();
while (iterator.hasNext()) {
String activityName = iterator.next();
List<VariableElement> variableElementList = map.get(activityName);
// 获取包名
TypeElement typeElement = (TypeElement) variableElementList.get(0).getEnclosingElement();
String packageName = processingEnv.getElementUtils().getPackageOf(typeElement).toString();
// 写入文件
try {
// 创建文件
JavaFileObject sourceFile = mFiler.createSourceFile(
packageName + "." + activityName + "_ViewBinding");
// 创建输入流
writer = sourceFile.openWriter();
// 写入具体内容
writer.write("package " + packageName + ";\n");
writer.write("import " + packageName + ".IBinder;\n");
writer.write("public class " + activityName +
"_ViewBinding implements IBinder<"
+ packageName + "." + activityName + ">{\n");
writer.write("@Override\n");
writer.write("public void bind("
+ packageName + "." + activityName + " target){\n");
for (VariableElement element : variableElementList) {
// 获取被 BindView 注解的变量名称
String variableName = element.getSimpleName().toString();
// 获取 BindView 注解的 id
int id = element.getAnnotation(BindView.class).value();
// 获取被 BindView 注解的变量类型
TypeMirror typeMirror = element.asType();
writer.write("target." + variableName
+ " = (" + typeMirror + ") target.findViewById(" + id + ");\n");
}
writer.write("\n}\n}");
} catch (Exception e) {
e.printStackTrace();
} finally {
if (writer != null) {
try {
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
return false;
}
}
app module
IBinder
annotation_compile 中生成的 xxx_ViewBinding 类实现了 IBinder
/**
* 用户绑定activity
*/
public interface IBinder<T> {
void bind(T target);
}
MyButterKnife
/**
* 用于给用户绑定
*/
public class MyButterKnife {
public static void bind(Activity activity) {
String viewBindingName = activity.getClass().getName() + "_ViewBinding";
try {
Class<?> viewBindingClass = Class.forName(viewBindingName);
// 执行 xxx_ViewBinding 类中的 bind 方法
IBinder iBinder = (IBinder) viewBindingClass.newInstance();
iBinder.bind(activity);
} catch (Exception e) {
e.printStackTrace();
}
}
}
使用 MyButterKnife
public class MainActivity extends AppCompatActivity {
@BindView(R.id.btn_main)
Button btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MyButterKnife.bind(this);
btn.setText("MyButterKnife");
}
}
