okhttp3实现下载进度条

以下是使用OkHttp3实现下载进度条的示例：

1. 引入依赖

在项目的build.gradle文件中添加OkHttp3依赖：

dependencies {
    implementation 'com.squareup.okhttp3:okhttp:4.9.1'
}

2. 创建OkHttpClient

OkHttpClient client = new OkHttpClient();

3. 创建Request

Request request = new Request.Builder()
        .url("http://www.example.com/file.txt")
        .build();

4. 执行请求

Call call = client.newCall(request);
Response response = call.execute();

5. 获取响应体并写入文件

if (response.isSuccessful()) {
    InputStream inputStream = response.body().byteStream();
    FileOutputStream outputStream = new FileOutputStream("file.txt");
    byte[] buffer = new byte[1024];
    int len;
    while ((len = inputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, len);
    }
    outputStream.flush();
    outputStream.close();
    inputStream.close();
}

6. 获取下载进度并更新UI

if (response.isSuccessful()) {
    InputStream inputStream = response.body().byteStream();
    FileOutputStream outputStream = new FileOutputStream("file.txt");
    byte[] buffer = new byte[1024];
    int len;
    long total = response.body().contentLength();
    long sum = 0;
    while ((len = inputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, len);
        sum += len;
        int progress = (int) (sum * 1.0f / total * 100);
        // 更新UI
        updateProgress(progress);
    }
    outputStream.flush();
    outputStream.close();
    inputStream.close();
}

其中，updateProgress方法用于更新下载进度的UI。