[移动开发]记录android开发保存文件到手机外部存储踩坑

1设置sdk版本

compileSdkVersion 30// 最高兼容版本
 minSdkVersion 23 //最低兼容版本
 targetSdkVersion 24//安装应用程序的手机系统大于设置 如果小于24页面会不兼容部分手机不会充满屏幕 设置太高获取外部存储权限不够
 

2添加权限

<uses-permission android:name=“android.permission.WRITE_EXTERNAL_STORAGE” />
<uses-permission android:name=“android.permission.READ_EXTERNAL_STORAGE” />
<application
  android:requestLegacyExternalStorage="true"
</application>

正常获取权限在android11中并不奏效需要动态获取权限贴上工具类：

 public static boolean file(Activity activity) {
        final int REQUEST_EXTERNAL_STORAGE = 1;
        String[] PERMISSIONS_STORAGE = {
                Manifest.permission.READ_EXTERNAL_STORAGE,
                Manifest.permission.WRITE_EXTERNAL_STORAGE};
        int permission = ActivityCompat.checkSelfPermission(activity,
                Manifest.permission.WRITE_EXTERNAL_STORAGE);
        if (permission != PackageManager.PERMISSION_GRANTED) {
            ToastUntil.showToast("请获取权限");
            // We don't have permission so prompt the user
            ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,
                    REQUEST_EXTERNAL_STORAGE);
            return true;
        } else {
            return false;
        }
    }

具体使用：

//外部存储路径
public final static String DOWNLOAD_DIR = Environment.getExternalStorageDirectory().getPath() + "/Download";
		//判断是否获取权限如果为true弹窗获取权限false为已获取可直接下载
				if (Authority.file(activity) == false) {
				   //android11 app包目录下可随意存储但不方便查找
                      // ContextWrapper cw = new ContextWrapper(BaseApplication.getConText());
           // File directory = cw.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS);
                            File file = new File(APIConfig.DOWNLOAD_DIR, filename);
                            if (file.exists()) {
                                file.delete();
                            }
                            try {
                                FileDownUntil.writeToLocal(file, is);                   
                           		 ToastUntil.showToast("下载成功，请到本地查看");
                            } catch (IOException e) {
                                LogUtil.e("filedownload", e.getMessage());
                              	ToastUntil.showToast("下载失败");
                                e.printStackTrace();
                            }
                        }

贴上具体下载工具类代码：

public static void writeToLocal(File destination, InputStream input)
            throws IOException {
        int index;
        byte[] bytes = new byte[1024];
        FileOutputStream downloadFile = new FileOutputStream(destination);
        while ((index = input.read(bytes)) != -1) {
            downloadFile.write(bytes, 0, index);
            downloadFile.flush();
        }
        input.close();
        downloadFile.close();
    }