如何创建 json 文件及其内容

Question

我正在react-native中创建一个Android模块

我从未使用过 Java 或用 Java 编写代码

如何完成下面的代码？

我想要什么

1-查看并验证目录是否存在，如果存在则将其删除。

2- 重新创建目录。

3- 创建一个 json 文件并添加其内容。

这是我目前得到的结果

@ReactMethod
public string write(string content) {
    var folder = "NovelManager";
    File path = Paths.get(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), folder);
    var fullPath = Paths.get(path, "NovelManager.backup.json");

    makeDir(path);
    File file = new File(path, "NovelManager.backup.json");
    if (!file.exists())
        file = file.createNewFile();

    BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), StandardCharsets.UTF_8));

    out.write(content);
    out.close();

    return file.getAbsolutePath();
}

private void makeDir(string dirPath){
    var dir = new File(dirPath);
    if (!dir.exists())
    dir.mkdir();
}

更新及解决方案

经过艰苦的努力，这对我来说确实有用。

这里是任何有类似问题的人的完整代码。

// DownloadFileModule.java
package com.novelmanager;

import android.view.View;
import android.app.Activity;

import java.io.BufferedWriter;
import java.io.Console;
import java.io.File;
import java.io.FileWriter;
import android.os.Environment;
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;
import java.nio.charset.StandardCharsets;

import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContext;
import com.facebook.react.bridge.UiThreadUtil;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;

public class DownloadFileModule extends ReactContextBaseJavaModule {
    @Override
    public String getName() {
        return "DownloadFileModule";
    }

    @ReactMethod(isBlockingSynchronousMethod = true)
    public String write(String content) {
        if (content == null || content == "")
            return "";
        try {

            String folder = "NovelManager";
            String fileName = "NovelManager.backup.json";
            String downloadFolderPath = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)
                    .getPath();
            String dirPath = compine(downloadFolderPath, folder);
            File dir = new File(dirPath);
            if (!dir.exists())
                dir.mkdir();

            String path = compine(downloadFolderPath, folder, fileName);

            File file = new File(path);
            if (!file.exists())
                file.createNewFile();

            BufferedWriter out = new BufferedWriter(
                    new OutputStreamWriter(new FileOutputStream(file), StandardCharsets.UTF_8));

            out.write(content);
            out.close();
            return file.getPath();
        } catch (Exception e) {
            return e.getMessage();
        }

    }

    private String compine(String... more) {
        String url = more[0];

        for (int i = 1; i < more.length; i++) {
            String str = more[i];
            if (str.startsWith("/"))
                str = str.substring(1);
            if (str.endsWith("/"))
                str = str.substring(0, str.length() - 1);

            if (url.endsWith("/"))
                url = url.substring(0, url.length() - 1);

            url = url + "/" + str; // relative url
        }

        return url; // relative url
    }

    DownloadFileModule(ReactApplicationContext reactContext) {
        super(reactContext);
    }
}

Answer 1

删除目录

public boolean deleteDirectory(Path pathToBeDeleted) throws IOException {
    Files.walk(pathToBeDeleted)
      .sorted(Comparator.reverseOrder())
      .map(Path::toFile)
      .forEach(File::delete);
    
    return !Files.exists(pathToBeDeleted);
}

写入文件

public void writeToFile(String content, File file) throws IOException {
    Files.write(file.toPath(), content.getBytes());
}

Answer 2

您可以使用 Apache FileUtils 执行所有必需的操作，例如

参考：https://commons.apache.org/proper/commons-io/javadocs/api-2.5/index.html?org/apache/commons/io/FileUtils.html

    FileUtils.cleanDirectory(path); //clean out directory (this is optional)
    FileUtils.forceDelete(path); //delete directory
    FileUtils.forceMkdir(path); //create directory
    FileUtils.touch(file)); //create new file