Kotlin反射访问androidx.collection.LruCache类私有变量

àì夳堔傛蜴生んèń 2023-10-14 16:57 44阅读 0赞

androidx.collection.LruCache类中定义了一个名为map的LinkedHashMap，map存储了所有LruCache的数据，有时候需要遍历访问该LinkedHashMap，取出里面的值，但是LruCache代码实现中，map为private私有，且无get方法返回，所以需要通过反射访问。

![502bcbecf2e743eab78324f5351c5749.png][]

比如：

import java.lang.reflect.Field
    
    fun main() {
        val myLruCache = make()
        val lruCache = myLruCache as LruCache<Any, Any>
        lruCache::class.members.forEach {
            //println("${it.name}")
        }
    
        //寻找LruCache类中名为 map 的private私有变量。
        var privateField: Field = LruCache::class.java.getDeclaredField("map")
        //改变private属性，变成可访问。
        privateField.setAccessible(true)
    
        var obj: Any? = privateField.get(lruCache)
        var map = obj as HashMap<Any, Any>
        println(map)
    }
    
    fun make(): MyLruCache {
        var cache = MyLruCache(100)
        cache.put("year", 2023)
        cache.put(1, "fly")
        return cache
    }
    
    class MyLruCache(size: Int) : LruCache<Any, Any>(size) {
    
    }

> \{year=2023, 1=fly\}

Android官方的androidx.collection.LruCache源代码：

[https://android.googlesource.com/platform/frameworks/support/+/f2e05c341382db64d127118a13451dcaa554b702/collection/collection/src/main/java/androidx/collection/LruCache.java![icon-default.png_t_N6B9][]https://android.googlesource.com/platform/frameworks/support/+/f2e05c341382db64d127118a13451dcaa554b702/collection/collection/src/main/java/androidx/collection/LruCache.java][https_android.googlesource.com_platform_frameworks_support_f2e05c341382db64d127118a13451dcaa554b702_collection_collection_src_main_java_androidx_collection_LruCache.java_icon-default.png_t_N6B9_https_android.googlesource.com_platform_frameworks_support_f2e05c341382db64d127118a13451dcaa554b702_collection_collection_src_main_java_androidx_collection_LruCache.java]

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[Java反射改变Android属性\_zhangphil的博客-CSDN博客Java反射改变Android属性在某些情况下，Android体系里面的某些对象没有对外提供针对某个属性或者类，方法公开的get或者set方法，但是项目需要对这些需要修改和调整。就需要使用Java的反射机制修改Android的属性。举一个简单的例子，通过Java反射机制改变Android ListView分割线的高度值。Android的ListView本身有分割线，并对外提供了公开设置分割线高度的![favicon32.ico][]https://blog.csdn.net/zhangphil/article/details/80138465][Java_Android_zhangphil_-CSDN_Java_Android_Android_get_set_Java_Android_Java_Android ListView_Android_ListView_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_80138465]

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[https_android.googlesource.com_platform_frameworks_support_f2e05c341382db64d127118a13451dcaa554b702_collection_collection_src_main_java_androidx_collection_LruCache.java_icon-default.png_t_N6B9_https_android.googlesource.com_platform_frameworks_support_f2e05c341382db64d127118a13451dcaa554b702_collection_collection_src_main_java_androidx_collection_LruCache.java]: https://android.googlesource.com/platform/frameworks/support/+/f2e05c341382db64d127118a13451dcaa554b702/collection/collection/src/main/java/androidx/collection/LruCache.java
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[Java_private_Map_zhangphil_-CSDN_Java_Android_Android_get_set_Java_Android_Java_Class_Method_Fieldimport com.orhanobut.logger.Logger_Java_Class_Method_Field_zhangphil_-CSDN_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_131935002]: https://blog.csdn.net/zhangphil/article/details/131935002
[Java_Android_zhangphil_-CSDN_Java_Android_Android_get_set_Java_Android_Java_Android ListView_Android_ListView_favicon32.ico_https_blog.csdn.net_zhangphil_article_details_80138465]: https://blog.csdn.net/zhangphil/article/details/80138465