编译时注解点击此处～～～
运行时注解
以 @BindView 为例。下面是实现步骤
- 新建一个 apt-annotation 的 java-library ，然后在库中新建一个注解，传入一个 int 参数用来传入viewId
@Target(ElementType.FIELD)
public @interface BindView {
int value();
}
- 新建一个Java 库 apt-processor 并添加依赖
BindViewProcessor 继承 AbstractProcessor
@AutoService(Processor.class)
public class BindViewProcessor extends AbstractProcessor {
private Messager mMessager;
private Elements mElementUtils;
private Map<String, ClassCreatorProxy> mProxyMap = new HashMap<>();
@Override
public synchronized void init(ProcessingEnvironment processingEnv) {
super.init(processingEnv);
mMessager = processingEnv.getMessager();
mElementUtils = processingEnv.getElementUtils();
}
@Override
public Set<String> getSupportedAnnotationTypes() {
HashSet<String> supportTypes = new LinkedHashSet<>();
supportTypes.add(BindView.class.getCanonicalName());
return supportTypes;
}
@Override
public SourceVersion getSupportedSourceVersion() {
return SourceVersion.latestSupported();
}
@Override
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
mMessager.printMessage(Diagnostic.Kind.NOTE, "processing...");
mProxyMap.clear();
Set<? extends Element> elements = roundEnvironment.getElementsAnnotatedWith(BindView.class);
for (Element element : elements) {
VariableElement variableElement = (VariableElement) element;
TypeElement classElement = (TypeElement) variableElement.getEnclosingElement();
String fullClassName = classElement.getQualifiedName().toString();
ClassCreatorProxy proxy = mProxyMap.get(fullClassName);
if (proxy == null) {
proxy = new ClassCreatorProxy(mElementUtils, classElement);
mProxyMap.put(fullClassName, proxy);
}
BindView bindAnnotation = variableElement.getAnnotation(BindView.class);
int id = bindAnnotation.value();
proxy.putElement(id, variableElement);
}
for (String key : mProxyMap.keySet()) {
ClassCreatorProxy proxyInfo = mProxyMap.get(key);
JavaFile javaFile = JavaFile.builder(proxyInfo.getPackageName(), proxyInfo.generateJavaCode2()).build();
try {
javaFile.writeTo(processingEnv.getFiler());
} catch (IOException e) {
e.printStackTrace();
}
}
mMessager.printMessage(Diagnostic.Kind.NOTE, "process finish ...");
return true;
}
}
public class ClassCreatorProxy {
private String mBindingClassName;
private String mPackageName;
private TypeElement mTypeElement;
private Map<Integer, VariableElement> mVariableElementMap = new HashMap<>();
public ClassCreatorProxy(Elements elementUtils, TypeElement classElement) {
this.mTypeElement = classElement;
PackageElement packageElement = elementUtils.getPackageOf(mTypeElement);
String packageName = packageElement.getQualifiedName().toString();
String className = mTypeElement.getSimpleName().toString();
this.mPackageName = packageName;
this.mBindingClassName = className + "_ViewBinding";
}
public void putElement(int id, VariableElement element) {
mVariableElementMap.put(id, element);
}
private void generateMethods(StringBuilder builder) {
builder.append("public void bind(" + mTypeElement.getQualifiedName() + " host ) {\n");
for (int id : mVariableElementMap.keySet()) {
VariableElement element = mVariableElementMap.get(id);
String name = element.getSimpleName().toString();
String type = element.asType().toString();
builder.append("host." + name).append(" = ");
builder.append("(" + type + ")(((android.app.Activity)host).findViewById( " + id + "));\n");
}
builder.append(" }\n");
}
public String getProxyClassFullName() {
return mPackageName + "." + mBindingClassName;
}
public TypeElement getTypeElement() {
return mTypeElement;
}
public TypeSpec generateJavaCode2() {
TypeSpec bindingClass = TypeSpec.classBuilder(mBindingClassName)
.addModifiers(Modifier.PUBLIC)
.addMethod(generateMethods2())
.build();
return bindingClass;
}
private MethodSpec generateMethods2() {
ClassName host = ClassName.bestGuess(mTypeElement.getQualifiedName().toString());
MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder("bind")
.addModifiers(Modifier.PUBLIC)
.returns(void.class)
.addParameter(host, "host");
for (int id : mVariableElementMap.keySet()) {
VariableElement element = mVariableElementMap.get(id);
String name = element.getSimpleName().toString();
String type = element.asType().toString();
methodBuilder.addCode("host." + name + " = " + "(" + type + ")(((android.app.Activity)host).findViewById( " + id + "));");
}
return methodBuilder.build();
}
public String getPackageName() {
return mPackageName;
}
}
- BindViewTools 类绑定Activity 通过反射调用初始化View的方法
public class BindViewTools {
public static void bind(Activity activity) {
Class clazz = activity.getClass();
try {
Class bindViewClass = Class.forName(clazz.getName() + "_ViewBinding");
Method method = bindViewClass.getMethod("bind", activity.getClass());
method.invoke(bindViewClass.newInstance(), activity);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
}
- 调用如下：
public class MainActivity extends AppCompatActivity {
@BindView(R.id.tv)
TextView mTextView;
@BindView(R.id.btn)
Button mButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BindViewTools.bind(this);
mTextView.setText("Hello World");
mButton.setText("success");
}
}
- 整个项目执行流程为：
编译器通过扫描我们在ActivityView中使用的@BindeView注解，然后回调到 BindViewProcessor 的 process() 方法，然后在Build中生成 app/build/intermediates/classes/debug/com/example/gavin/apttest/MainActivity_ViewBinding.class ，接着通过 BindViewTools.bind(this); 反射调用到 MainActivity_ViewBinding.class 的 bind 方法，从而初始化View完成。下面是生成的 MainActivity_ViewBinding.class 代码。
public class MainActivity_ViewBinding {
public MainActivity_ViewBinding() {
}
public void bind(MainActivity host) {
host.mButton = (Button)((Button)host.findViewById(2131165218));
host.mTextView = (TextView)((TextView)host.findViewById(2131165321));
}
}
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