如何在Android应用中实现文件上传到服务器的功能？

Android上传给服务器

在Android应用开发中，与服务器进行数据交互是常见的需求，本文将详细介绍如何在Android应用中实现文件上传功能，包括选择文件、压缩文件（可选）、上传文件到服务器以及处理服务器响应，以下是详细的步骤和代码示例：

准备工作

1.1 添加依赖

在项目的build.gradle文件中添加必要的依赖，例如用于网络请求的OkHttp库和用于JSON解析的Gson库。

dependencies {
    implementation 'com.squareup.okhttp3:okhttp:4.9.0'
    implementation 'com.google.code.gson:gson:2.8.6'
}

1.2 权限声明

在AndroidManifest.xml中声明必要的权限，例如互联网访问权限和读写存储权限。

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

选择文件

使用Intent让用户从设备中选择一个文件。

private void chooseFile() {
    Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    intent.setType("*/*");
    intent.addCategory(Intent.CATEGORY_OPENABLE);
    try {
        startActivityForResult(Intent.createChooser(intent, "Select a File to Upload"), FILE_SELECT_CODE);
    } catch (android.content.ActivityNotFoundException ex) {
        // Potentially handle the error here
    }
}

压缩文件（可选）

如果需要对文件进行压缩，可以使用ZipOutputStream类。

private File compressFile(File file) throws IOException {
    File zipFile = new File(file.getParent(), file.getName() + ".zip");
    try (ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(zipFile))) {
        zos.putNextEntry(new ZipEntry(file.getName()));
        byte[] bytes = new byte[1024];
        int length;
        try (FileInputStream fis = new FileInputStream(file)) {
            while ((length = fis.read(bytes)) >= 0) {
                zos.write(bytes, 0, length);
            }
        }
        zos.closeEntry();
    }
    return zipFile;
}

上传文件到服务器

使用OkHttp库上传文件到服务器。

private void uploadFile(File file) {
    // Create a multipart request body
    RequestBody filePart = RequestBody.create(MediaType.parse("application/octet-stream"), file);
    MultipartBody requestBody = new MultipartBody.Builder()
            .setType(MultipartBody.FORM)
            .addFormDataPart("file", file.getName(), filePart)
            .build();
    // Create the request
    Request request = new Request.Builder()
            .url("https://yourserver.com/upload")
            .post(requestBody)
            .build();
    // Add the request to the client and execute it
    OkHttpClient client = new OkHttpClient();
    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, Response response) {
            // Handle the failure
        }
        @Override
        public void onResponse(Call call, Response response) throws IOException {
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
            // Handle the response
        }
    });
}

处理服务器响应

根据服务器返回的数据格式，解析响应并更新UI。

client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, Response response) {
        // Handle the failure
    }
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
        // Assuming the server returns a JSON response
        String jsonData = response.body().string();
        // Parse the JSON data using Gson or any other library
    }
});

完整示例代码

以下是一个完整的示例代码，展示了如何实现上述功能。

public class MainActivity extends AppCompatActivity {
    private static final int FILE_SELECT_CODE = 1;
    private OkHttpClient client = new OkHttpClient();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.btnChooseFile).setOnClickListener(v -> chooseFile());
    }
    private void chooseFile() {
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("*/*");
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        try {
            startActivityForResult(Intent.createChooser(intent, "Select a File to Upload"), FILE_SELECT_CODE);
        } catch (android.content.ActivityNotFoundException ex) {
            // Potentially handle the error here
        }
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, int data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == FILE_SELECT_CODE && resultCode == RESULT_OK && data != null) {
            Uri fileUri = data.getData();
            try {
                File file = new File(requireNotNull(fileUri).getPath());
                File compressedFile = compressFile(file); // Compress if needed
                uploadFile(compressedFile);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    private File compressFile(File file) throws IOException {
        File zipFile = new File(file.getParent(), file.getName() + ".zip");
        try (ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(zipFile))) {
            zos.putNextEntry(new ZipEntry(file.getName()));
            byte[] bytes = new byte[1024];
            int length;
            try (FileInputStream fis = new FileInputStream(file)) {
                while ((length = fis.read(bytes)) >= 0) {
                    zos.write(bytes, 0, length);
                }
            }
            zos.closeEntry();
        }
        return zipFile;
    }
    private void uploadFile(File file) {
        RequestBody filePart = RequestBody.create(MediaType.parse("application/octet-stream"), file);
        MultipartBody requestBody = new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
                .addFormDataPart("file", file.getName(), filePart)
                .build();
        Request request = new Request.Builder()
                .url("https://yourserver.com/upload")
                .post(requestBody)
                .build();
        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, Response response) {
                // Handle the failure
            }
            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
                String jsonData = response.body().string();
                // Parse the JSON data using Gson or any other library
            }
        });
    }
}