一.什麼是APT
apt是一種註解處理工具,對源碼文件進行檢測找出其中的註解,根據註解會自動生成代碼,如果想要自定義的註解處理器能夠正常運行,必須要通過apt工具來進行處理。相信用過EventBus、ButterKnife、Dagger2的同學都會有所瞭解,因爲它們都用的是APT的技術。如果對於註解都不瞭解的,可以去看下我之前寫過的註解反射一些總結
二.用APT寫一個自己的權限框架
我們寫個簡單的權限請求的Demo來熟悉下APT的玩法。
先看看效果
在看看代碼,首先我們新建兩個JavaLib,Annotations和Compiler,一個是存放自定義註解,一個是用來對註解進行處理,
然後我們在新建一個Android的Library,這個庫的作用是提供一些權限相關的處理類,還有用反射的方式,調用APT生成的代碼。
我們先看下效果
Annotation Module的配置:
apply plugin: 'java-library'
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
}
//處理亂碼問題
tasks.withType(JavaCompile) {
options.encoding = "UTF-8"
}
sourceCompatibility = "1.8"
targetCompatibility = "1.8"
Compiler Module的配置:
apply plugin: 'java-library'
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.google.auto.service:auto-service:1.0-rc4'
// implementation 'com.google.auto.service:auto-service:1.0-rc6'
// annotationProcessor "com.google.auto.service:auto-service:1.0-rc6" //3.3.2以上需要這個
implementation project(':Annotations')
}
tasks.withType(JavaCompile) {
options.encoding = "UTF-8"
}
sourceCompatibility = "1.8"
targetCompatibility = "1.8"
Library Module的配置:
apply plugin: 'com.android.library'
android {
compileSdkVersion 28
compileOptions {
sourceCompatibility 1.8
targetCompatibility 1.8
}
defaultConfig {
minSdkVersion 19
targetSdkVersion 28
versionCode 1
versionName "1.0"
javaCompileOptions { annotationProcessorOptions { includeCompileClasspath = true } }
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:28.0.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation project(':Annotations')
}
項目中的配置:
apply plugin: 'com.android.application'
android {
compileSdkVersion 28
compileOptions {
sourceCompatibility 1.8
targetCompatibility 1.8
}
defaultConfig {
applicationId "com.seven.pemissions"
minSdkVersion 19
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
// javaCompileOptions { annotationProcessorOptions { includeCompileClasspath = true } }
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation project(':Annotations')
implementation project(':Library')
annotationProcessor project(':Compiler')
}
我們在來看看Compiler Module中的代碼:
package com.seven.permissions.compiler;
import com.google.auto.service.AutoService;
import com.seven.annotations.NeedPermissions;
import com.seven.annotations.OnNeverAskPermissions;
import com.seven.annotations.OnPermissionsDenied;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Filer;
import javax.annotation.processing.Messager;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.Elements;
import javax.lang.model.util.Types;
import javax.tools.Diagnostic;
import javax.tools.JavaFileObject;
/**
* Time:2019/12/5
* <p>
* Author:wangzhou
* <p>
* Description:
*/
@AutoService(Processor.class)
public class PermissionProcessor extends AbstractProcessor {
private Messager messager;
private Elements elementUtils;
private Filer filer;
private Types typeUtils;
@Override
public synchronized void init(ProcessingEnvironment processingEnvironment) {
super.init(processingEnvironment);
typeUtils = processingEnvironment.getTypeUtils();
elementUtils = processingEnvironment.getElementUtils();
filer = processingEnvironment.getFiler();
messager = processingEnvironment.getMessager();
}
@Override
public Set<String> getSupportedAnnotationTypes() {
Set<String> types = new LinkedHashSet<>();
types.add(NeedPermissions.class.getCanonicalName());
types.add(OnPermissionsDenied.class.getCanonicalName());
types.add(OnNeverAskPermissions.class.getCanonicalName());
return types;
}
@Override
public SourceVersion getSupportedSourceVersion() {
return SourceVersion.latest();
}
@Override
public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
messager.printMessage(Diagnostic.Kind.NOTE, "processing...");
System.out.println("start process");
Set<? extends Element> needPermissionsSet = roundEnvironment.getElementsAnnotatedWith(NeedPermissions.class);
Map<String, List<ExecutableElement>> needPermissionMap = new HashMap<>();
for (Element element : needPermissionsSet) {
ExecutableElement executableElement = (ExecutableElement) element;
String activityName = getActivityName(executableElement); //獲取類
List<ExecutableElement> list = needPermissionMap.get(activityName);
if (list == null) {
list = new ArrayList<>();
needPermissionMap.put(activityName, list);
}
list.add(executableElement);
System.out.println("NeedPermission executableElement" + element.getSimpleName().toString());
}
Set<? extends Element> onNeverAskAgainSet = roundEnvironment.getElementsAnnotatedWith(OnNeverAskPermissions.class);
Map<String, List<ExecutableElement>> onNeverAskAgainMap = new HashMap<>();
for (Element element : onNeverAskAgainSet) {
ExecutableElement executableElement = (ExecutableElement) element;
String activityName = getActivityName(executableElement);
List<ExecutableElement> list = onNeverAskAgainMap.get(activityName);
if (list == null) {
list = new ArrayList<>();
onNeverAskAgainMap.put(activityName, list);
}
list.add(executableElement);
System.out.println("NeedPermission executableElement" + element.getSimpleName().toString());
}
Set<? extends Element> onPermissionDeniedSet = roundEnvironment.getElementsAnnotatedWith(OnPermissionsDenied.class);
Map<String, List<ExecutableElement>> onPermissionDeniedMap = new HashMap<>();
for (Element element : onPermissionDeniedSet) {
ExecutableElement executableElement = (ExecutableElement) element;
String activityName = getActivityName(executableElement);
List<ExecutableElement> list = onPermissionDeniedMap.get(activityName);
if (list == null) {
list = new ArrayList<>();
onPermissionDeniedMap.put(activityName, list);
}
list.add(executableElement);
System.out.println("NeedPermission executableElement" + element.getSimpleName().toString());
}
for (String activityName : needPermissionMap.keySet()) {
List<ExecutableElement> needPermissionElements = needPermissionMap.get(activityName);
List<ExecutableElement> onNeverAskAgainElements = onNeverAskAgainMap.get(activityName);
List<ExecutableElement> onPermissionDeniedElements = onPermissionDeniedMap.get(activityName);
final String CLASS_SUFFIX = "$Permissions";
// Filer filer = processingEnv.getFiler();
try {
JavaFileObject javaFileObject = filer.createSourceFile(activityName + CLASS_SUFFIX);
String packageName = getPackageName(needPermissionElements.get(0)); //獲取註解地方的包名
Writer writer = javaFileObject.openWriter();
String activitySimpleName = needPermissionElements.get(0).getEnclosingElement()
.getSimpleName()
.toString() + CLASS_SUFFIX;
writer.write("package " + packageName + ";\n");
writer.write("import com.seven.permissions.library.listener.RequestPermission;\n");
writer.write("import com.seven.permissions.library.utils.PermissionUtils;\n");
writer.write("import android.support.v4.app.ActivityCompat;\n");
writer.write("import java.lang.ref.WeakReference;\n");
writer.write("import com.seven.permissions.library.listener.PermissionRequest;\n");
writer.write("public class " + activitySimpleName + " implements RequestPermission<" + activityName + ">{\n");
writer.write("private static final int REQUEST_CODE = 666;\n");
writer.write("private static String[] PERMISSION;\n");
writer.write("public void requestPermission(" + activityName + " target,String[] permissions) {\n");
writer.write(" PERMISSION = permissions ;\n");
writer.write(" if (PermissionUtils.hasSelfPermissions(target, permissions)) {\n");
if (needPermissionElements != null) {
for (ExecutableElement executableElement : needPermissionElements) {
String methodName = executableElement.getSimpleName().toString();
writer.write("target." + methodName + "();\n");
}
}
writer.write("}else{ ActivityCompat.requestPermissions(target, PERMISSION, REQUEST_CODE);}}\n");
writer.write("public void onRequestPermissionsResult(\n" + activityName + " target, int requestCode, int[] grantResults){");
writer.write(" switch (requestCode) {\n" + "case REQUEST_CODE:\n" + "if (PermissionUtils.verifyPermissions(grantResults)) {\n");
if (needPermissionElements != null) {
for (ExecutableElement executableElement : needPermissionElements) {
String methodName = executableElement.getSimpleName().toString();
writer.write("target." + methodName + "();\n");
}
}
writer.write("} else if (!PermissionUtils.shouldShowRequestPermissionRationale(target, PERMISSION)) {\n");
if (onNeverAskAgainElements != null) {
for (ExecutableElement executableElement : onNeverAskAgainElements) {
String methodName = executableElement.getSimpleName().toString();
writer.write("target." + methodName + "();\n");
}
}
writer.write("}else{\n");
if (onPermissionDeniedElements != null) {
for (ExecutableElement executableElement : onPermissionDeniedElements) {
String methodName = executableElement.getSimpleName().toString();
writer.write("target." + methodName + "();\n");
}
}
writer.write(" } break;\n default:\nbreak;\n}\n }\n}");
writer.flush();
writer.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return true;
}
private String getPackageName(ExecutableElement executableElement) {
TypeElement typeElement = (TypeElement) executableElement.getEnclosingElement();
String packageName = elementUtils.getPackageOf(typeElement).getQualifiedName().toString();
return packageName;
}
private String getActivityName(ExecutableElement executableElement) {
String packageName = getPackageName(executableElement);
TypeElement typeElement = (TypeElement) executableElement.getEnclosingElement();
return packageName + "." + typeElement.getSimpleName().toString();
}
}
這個就是非常笨的方式,去掃描到註解,然後拼接代碼。最終生成的代碼,會在我們的主項目的這個目錄下
代碼生成完了,我們在Library中提供兩個方法將APT生成的代碼和需要使用的地方做個綁定就可以了。代碼我就不貼了,有興趣可以去我的Git上看一看。地址:玩一玩APT
上面的純手工寫代碼是不是顯得有點不智能,不過作爲入門級玩一玩APT還是可以的,我們在來玩玩JavaPoet,Git地址是:JakeWharton大神的JavaPoet,JavaPoet是提供一些API,幫我們去生成代碼。有興趣的同學可以去看看。