Android（五十一）：文件读写

文件读写

var fileName = FindViewById<EditText>(Resource.Id.file_name);           // 文件名 
var fileContent = FindViewById<EditText>(Resource.Id.file_content);     // 文件内容
var writeFileBtn = FindViewById<Button>(Resource.Id.write_file_btn);    // 写入按钮
var readFileBtn = FindViewById<Button>(Resource.Id.read_file_btn);      // 读取按钮

// 写入
if (writeFileBtn != null)
    writeFileBtn.Click += delegate
    {
        var outputStream = OpenFileOutput(fileName.Text, FileCreationMode.Private);
        try
        {
            var writeBytes = Encoding.ASCII.GetBytes(fileContent.Text);
            outputStream?.Write(writeBytes, 0, writeBytes.Length);
            Toast.MakeText(this, "写入成功", ToastLength.Short)?.Show();
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
            Toast.MakeText(this, "写入失败", ToastLength.Short)?.Show();
        }
        finally
        {
            outputStream?.Close();
        }
    };

// 读取
if (readFileBtn != null)
    readFileBtn.Click += delegate
    {
        try
        {
            var inputStream = OpenFileInput(fileName.Text);
            var stringBuilder = new StringBuilder("");
            var readBytes = new byte[2];
            while (inputStream?.Read(readBytes) > 0)
            {
                stringBuilder.Append(Encoding.ASCII.GetString(readBytes, 0, readBytes.Length));
            }
            fileContent.Text = stringBuilder.ToString();
            inputStream?.Close();
            Toast.MakeText(this, "读取成功", ToastLength.Short)?.Show();
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
            Toast.MakeText(this, "读取失败", ToastLength.Short)?.Show();
        }
    };

文件读写（SD卡）

<!-- Properties/AndroidManifest.xml -->
<!--SDCard写入数据权限-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<!--SDCard读取数据权限-->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

var fileName = FindViewById<EditText>(Resource.Id.file_name);
var fileContent = FindViewById<EditText>(Resource.Id.file_content);
var writeFileBtn = FindViewById<Button>(Resource.Id.write_file_btn);
var readFileBtn = FindViewById<Button>(Resource.Id.read_file_btn);

// 写入
if (writeFileBtn != null)
    writeFileBtn.Click += delegate
    {
        // 肯定 Permission.Granted 否定 Permission.Denied
        if (CheckSelfPermission(Manifest.Permission.WriteExternalStorage) == Permission.Denied)
        {
            RequestPermissions(new[] { Manifest.Permission.WriteExternalStorage }, 1);
            return;
        }

        if (Environment.ExternalStorageState == Environment.MediaMounted)
        {
            var filePath = $"{Environment.ExternalStorageDirectory.CanonicalPath}/{fileName.Text}";
            var fileOutputStream = new FileOutputStream(filePath);
            fileOutputStream.Write(Encoding.ASCII.GetBytes(fileContent.Text));
            fileOutputStream.Close();
            Toast.MakeText(this, filePath, ToastLength.Short)?.Show();
        }
        else
            Toast.MakeText(this, "SD卡不存在或者不可读写", ToastLength.Short)?.Show();
    };

// 读取
if (readFileBtn != null)
    readFileBtn.Click += delegate
    {
        // 肯定 Permission.Granted 否定 Permission.Denied
        if (CheckSelfPermission(Manifest.Permission.ReadExternalStorage) == Permission.Denied)
        {
            RequestPermissions(new[] { Manifest.Permission.ReadExternalStorage }, 2);
            return;
        }

        if (Environment.ExternalStorageState == Environment.MediaMounted)
        {
            var filePath = $"{Environment.ExternalStorageDirectory.CanonicalPath}/{fileName.Text}";
            var fileInputStream = new FileInputStream(filePath);
            var stringBuilder = new StringBuilder("");
            var readBytes = new byte[2];
            while (fileInputStream.Read(readBytes) > 0)
            {
                stringBuilder.Append(Encoding.ASCII.GetString(readBytes, 0, readBytes.Length));
            }
            fileContent.Text = stringBuilder.ToString();
            fileInputStream.Close();
        }
        else
            Toast.MakeText(this, "SD卡不存在或者不可读写", ToastLength.Short)?.Show();
    };