Android调用@hide系统隐藏类的几种方法

调用android系统隐藏的API的几种方法（以调SystemProperties这个类为例）： 

1、用反射：

//获取系统属性
public static  String getProperty(String key, String defaultValue) {
    String value = defaultValue;
    try {
        Class c = Class.forName("android.os.SystemProperties");
        Method get = c.getMethod("get", String.class, String.class);
        value = (String)(get.invoke(c, key, "unknown" ));
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        return value;
    }
}
//设置系统属性
public static void setProperty(String key, String value) {
    try {
        Class c = Class.forName("android.os.SystemProperties");
        Method set = c.getMethod("set", String.class, String.class);
        set.invoke(c, key, value );
    } catch (Exception e) {
        e.printStackTrace();
    }
}

注意：编译时要注释掉  //implementation fileTree(include: ['*.jar'],dir: 'libs')

2、添加系统framework.jar

在目录下out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/classes.jar改名得到 framework.jar 把jar包添加到lib目录并add as library，修改项目的build.gradle文件，在repositories里加入如下代码

allprojects {
    repositories {
        jcenter()
        google()
    }
    gradle.projectsEvaluated {
        tasks.withType(JavaCompile){
options.compilerArgs.add(-Xbootclasspath/p:app\\libs\\framework.jar')
        }
    }
}

在app的build.gradle中添加依赖

dependencies {
    provided files('libs/framework.jar')
//    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:25.4.0'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
} 
// 作用域改为provided

3、添加layoutlib.jar依赖

修改app中gradle.build文件添加默认的layoutlib.jar（或是指定sdk添加）即可调用隐藏的api，配置如下

修改app中的build.gradle,注意在android{}之后添加如下代码

def getLayoutLibPath() {
    return "${android.getSdkDirectory().getAbsolutePath()}" + "/platforms/" +
            android.compileSdkVersion +"/data/layoutlib.jar"
}
//String SDK_DIR = System.getenv("ANDROID_SDK_HOME")
//if (SDK_DIR == null){
//    java.util.Properties prop = new Properties()
//    prop.load(new FileInputStream(project.rootProject.file("local.properties")))
//    SDK_DIR = prop.get("sdk.dir")
//}
dependencies {
    provided files(getLayoutLibPath())
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
//    provided files("${SDK_DIR}/platforms/android-21/data/layoutlib.jar")
}