NDK 开发之“文件夹遍历”（C++文件夹遍历）

Java 层只给 JNI 层传递文件夹路径，在 JNI 中完成文件夹里的文件操作，通常都避免不了需要使用到 文件夹遍历 这个功能。那么，在 NDK 开发中怎么进行文件夹的遍历呢？

其实这就和 C++ 的文件夹遍历方式差不多。NDK 也给我们提供了 <dirent.h> 头文件，通过这个头文件中的相关方法，我们就可以完成这个功能了。

native-lib.cpp代码如下：

#include <jni.h>
#include <string.h>
#include <iostream>
#include <dirent.h>
#include "log.hpp"

extern "C" {

using namespace std;

void showAllFiles(string dir_name) {
    // check the parameter
    if (dir_name.empty()) {
        LOGE("dir_name is null !");
        return;
    }
    DIR *dir = opendir(dir_name.c_str());
    // check is dir ?
    if (NULL == dir) {
        LOGE("Can not open dir. Check path or permission!");
        return;
    }
    struct dirent *file;
    // read all the files in dir
    while ((file = readdir(dir)) != NULL) {
        // skip "." and ".."
        if (strcmp(file->d_name, ".") == 0 || strcmp(file->d_name, "..") == 0) {
            LOGV("ignore . and ..");
            continue;
        }
        if (file->d_type == DT_DIR) {
            string filePath = dir_name + "/" + file->d_name;
            showAllFiles(filePath); // 递归执行
        } else {
            // 如果需要把路径保存到集合中去，就在这里执行 add 的操作
            LOGI("filePath: %s/%s", dir_name.c_str(), file->d_name);
        }
    }
    closedir(dir);
}

JNIEXPORT void JNICALL
Java_com_afei_jnidemo_MainActivity_showDir(JNIEnv *env, jobject instance, jstring dirPath_) {
    const char *dirPath = env->GetStringUTFChars(dirPath_, 0);
    showAllFiles(string(dirPath));
    env->ReleaseStringUTFChars(dirPath_, dirPath);
}

}

MainActivirt 调用示例：

package com.afei.jnidemo;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    static {
        System.loadLibrary("native-lib");
    }

    @Override
    protected void
    onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        showDir("/sdcard/sensetime/detect/batch");
    }

    public native void showDir(String dirPath);

}

运行结果：

08-01 17:09:32.919 13820-13820/com.afei.jnidemo V/FaceAPI: ignore . and ..
    ignore . and ..
08-01 17:09:32.919 13820-13820/com.afei.jnidemo I/FaceAPI: filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.05.33_0.19583142.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.25.31_0.6432047.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.20.19_0.7755328.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.08.23_0.085364416.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.11-11.20.06_0.9677857.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.17.25_0.96264386.jpg
    filePath: /sdcard/sensetime/detect/batch/2017.12.13-11.25.30_0.9945698.jpg
08-01 17:09:32.919 13820-13820/com.afei.jnidemo V/FaceAPI: ignore . and ..
    ignore . and ..
08-01 17:09:32.919 13820-13820/com.afei.jnidemo I/FaceAPI: filePath: /sdcard/sensetime/detect/batch/q/2017.12.13-11.28.16_0.17593002.jpg
    filePath: /sdcard/sensetime/detect/batch/q/2017.12.12-11.30.46_0.6113686.jpg
    filePath: /sdcard/sensetime/detect/batch/q/2017.12.13-11.46.55_0.9884704.jpg
    filePath: /sdcard/sensetime/detect/batch/q/2017.12.13-11.30.08_0.12916178.jpg
    filePath: /sdcard/sensetime/detect/batch/q/2017.12.13-11.41.12_0.54208493.jpg
08-01 17:09:32.919 13820-13820/com.afei.jnidemo V/FaceAPI: ignore . and ..
    ignore . and ..
08-01 17:09:32.919 13820-13820/com.afei.jnidemo I/FaceAPI: filePath: /sdcard/sensetime/detect/batch/w/2017.12.12-11.28.26_0.48372716.jpg
    filePath: /sdcard/sensetime/detect/batch/w/2017.12.11-11.14.04_0.04731889.jpg
    filePath: /sdcard/sensetime/detect/batch/w/2017.12.12-11.21.32_0.456345.jpg
    filePath: /sdcard/sensetime/detect/batch/w/2017.12.13-11.46.51_0.23463911.jpg
    filePath: /sdcard/sensetime/detect/batch/w/2017.12.13-11.05.48_0.028296137.jpg
    filePath: /sdcard/sensetime/detect/batch/w/IMG_20170207_165920.JPG
08-01 17:09:32.919 13820-13820/com.afei.jnidemo V/FaceAPI: ignore . and ..
    ignore . and ..
08-01 17:09:32.919 13820-13820/com.afei.jnidemo I/FaceAPI: filePath: /sdcard/sensetime/detect/batch/e/2017.12.12-11.18.55_0.1639892.jpg
    filePath: /sdcard/sensetime/detect/batch/e/2017.12.12-11.18.53_0.011175653.jpg
    filePath: /sdcard/sensetime/detect/batch/e/2017.12.13-11.46.53_0.324961.jpg

其它：

log.hpp 的介绍在这个链接：NDK 开发之 Android log 输出的工具类封装

NDK 学习系列：Android NDK 从入门到精通（汇总篇）

NDK 开发之“文件夹遍历”（C++文件夹遍历）

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