Question

您好，

我想

将文件转换为字节[]
在Access数据库中写入byte []
从DB
从

1。

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"
    defaultConfig {
        applicationId "com.aitrich.android.modern.photo"
        minSdkVersion 14
        targetSdkVersion 25
        multiDexEnabled true
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}


apply plugin: 'com.neenbedankt.android-apt'
apply plugin: 'org.greenrobot.greendao'

ext {
    supportLibraryVersion = '25.0.1'
    playServicesVersion = '9.0.2'
    retrofitVersion = '2.1.0'
}

greendao {
    schemaVersion 1
}

apt {
    arguments {
        stagGeneratedPackageName "com.aitrich.android.modern.stag.generated"
        stagDebug true
    }
}


dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'

    compile "com.android.support:design:$supportLibraryVersion"
    compile "com.android.support:support-v13:$supportLibraryVersion"
    compile "com.android.support:cardview-v7:$supportLibraryVersion"
    compile 'org.greenrobot:eventbus:3.0.0'
    compile 'org.greenrobot:greendao:3.2.0'
    compile 'com.jakewharton:butterknife:8.4.0'
    compile 'com.intuit.sdp:sdp-android:1.0.3'
    compile 'me.zhanghai.android.materialprogressbar:library:1.3.0'
    compile 'com.mobsandgeeks:android-saripaar:2.0.3'
    compile "com.squareup.retrofit2:retrofit:$retrofitVersion"
    compile "com.squareup.retrofit2:converter-gson:$retrofitVersion"
    compile 'com.squareup.okhttp3:logging-interceptor:3.4.1'
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'com.vimeo.stag:stag-library:2.0.2'
    compile 'com.github.hotchemi:permissionsdispatcher:2.2.0'
    compile 'com.tapadoo.android:alerter:1.0.6'
    compile 'ch.halcyon:squareprogressbar:1.6.0'
    compile 'com.yalantis:ucrop:2.2.0'
    compile 'com.yalantis:ucrop:2.2.0-native'
    compile 'com.evernote:android-job:1.1.8'
    compile('com.github.silvestrpredko:dot-progress-bar:1.1') {
        exclude group: 'com.android.support', module: 'appcompat-v7'
    }
    compile('com.github.StevenDXC:DxLoadingButton:1.5') {
        exclude group: 'com.android.support', module: 'appcompat-v7'
    }
    compile('com.redmadrobot:chronos:1.0.7') {
        exclude module: 'eventbus:2.4.0'
    }
    compile ('co.infinum:materialdatetimepicker-support:3.1.3') {
        exclude group: 'com.android.support', module: 'design'
        exclude group: 'com.android.support', module: 'support-v4'
        exclude group: 'com.android.support', module: 'support-v13'
    }
    compile 'com.android.support:multidex:1.0.1'


    apt 'com.jakewharton:butterknife-compiler:8.4.0'
    apt 'com.vimeo.stag:stag-library-compiler:2.0.2'
    apt 'com.github.hotchemi:permissionsdispatcher-processor:2.2.0'
}

2

byte[] bytes = System.IO.File.ReadAllBytes(@"C:\Users\user\Docs\1.pdf");

3。

AccessConnector.WriteByteArrayToID(122, bytes);

    public static void WriteByteArrayToID(int aID, byte[] aFile)
    {
        conn.Open();
        dbCommand = new OleDbCommand("UPDATE Belege SET Datei = @file WHERE(ID = @ID)", conn);

        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
        dbCommand.Parameters.Add("@file", OleDbType.VarBinary).Value = aFile.ToString();

        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        dbCommand.ExecuteNonQuery();

        conn.Close();
    }

4。

        DataTable table = AccessConnector.GetFileByteArrayByID(122);
        DataRow row = table.Rows[0];

        System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();

        byte[] newbytes = enc.GetBytes(row.ItemArray[0].ToString());

问题是，newbytes比字节小，新文件不可访问。 Access DB单元格就像中文字母。我已经尝试过使用其他编码。没有。任何人都可以解释为什么它这么小（23000个字符到400个字符）。谢谢。

更新为其他功能添加了代码

            System.IO.File.WriteAllBytes(@"C:\Users\user\Documents\Docs\a.pdf", newbytes);

Answer 1

dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
dbCommand.Parameters.Add("@ID", OleDbType.VarBinary).Value = aFile;

您永远不会为@file参数分配值。

此外，在读取数据时无需转换为字符串，这应该可以改为：

byte[] newbytes = (byte[])table.Rows[0][0];

Answer 2

解决方案

    public static void WriteByteArrayToID(int aID, byte[] aFile)
    {
        conn.Open();

        dbCommand = new OleDbCommand("UPDATE Belege SET Datei = @file WHERE(ID = @ID)", conn);

        string tmp = Convert.ToBase64String(aFile);

        dbCommand.Parameters.Add("@file", OleDbType.VarChar).Value = tmp;
        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;

        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        dbCommand.ExecuteNonQuery();

        conn.Close();
    }

    public static DataTable GetFileByteArrayByID(int aID)
    {
        conn.Open();

        dbCommand = new OleDbCommand("SELECT Datei FROM Belege WHERE (ID = @ID)", conn);

        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        DataTable resultDataTable = new DataTable();
        dbDataAdapter.Fill(resultDataTable);

        conn.Close();
        return resultDataTable;
    } 

        //-----------------------------------------------------------------------------------------------------------------

        byte[] bytes = System.IO.File.ReadAllBytes(@"C:\Users\user\Music\1.pdf");

        AccessConnector.WriteByteArrayToID(122, bytes);

        DataTable table = AccessConnector.GetFileByteArrayByID(122);

        string file = table.Rows[0][0] as string;

        System.IO.File.WriteAllBytes(@"C:\Users\user\Documents\Dokumente\a.pdf", Convert.FromBase64String(file));

        //-----------------------------------------------------------------------------------------------------------------

将文件转换为字节数组，保存在Access-DB中，从数据库读取并创建文件

2 个答案: