如何允許用戶在Android設備上找到要通過嵌入在應用程序中的Google雲打印服務打印的pdf文件？

Question

我正在制作一個Android應用程序，通過該應用程序，用戶可以在設備上選擇一個現有的pdf文件，並在驗證后將其發送以通過Google雲進行打印。 打印機已連接到我自己的Gmail ID，只有我有權發送打印作業。 因此，在用戶通過驗證后，打印作業將通過我的郵件ID發送。

我是一個初學者，您的建議受到贊賞。 提前致謝 ：）

Answer 1

//It´s very easy don´t forget add to manifest permissions.
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.os.CancellationSignal;
import android.os.ParcelFileDescriptor;
import android.print.PageRange;
import android.print.PrintAttributes;
import android.print.PrintDocumentAdapter;
import android.content.Context;
import android.print.PrintDocumentInfo;
import android.print.pdf.PrintedPdfDocument;
import android.graphics.pdf.PdfDocument;
import android.graphics.pdf.PdfDocument.PageInfo;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.print.PrintManager;
import android.view.View;

public class MainActivity extends AppCompatActivity {
//Your file path
String Ruta= Environment.getExternalStorageDirectory().getPath()+"/MiPdf1.pdf";
File file=new File(Ruta);

public void printDocument(View view)
{
    PrintManager printManager = (PrintManager) this
            .getSystemService(Context.PRINT_SERVICE);

    String jobName = this.getString(R.string.app_name) +
            " Document";

    printManager.print(jobName, new
                    MyPrintDocumentAdapter(this),
            null);
}

public class MyPrintDocumentAdapter extends PrintDocumentAdapter
{
    Context context;
    private int pageHeight;
    private int pageWidth;
    public PdfDocument myPdfDocument;
    public int totalpages = 4;

    private boolean pageInRange(PageRange[] pageRanges, int page)
    {
        for (int i = 0; i<pageRanges.length; i++)
        {
            if ((page >= pageRanges[i].getStart()) &&
                    (page <= pageRanges[i].getEnd()))
                return true;
        }
        return false;
    }

    public MyPrintDocumentAdapter(Context context)
    {
        this.context = context;
    }

    @Override
    public void onWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback){
        InputStream input = null;
        OutputStream output = null;

        try {

            input = new FileInputStream(file);
            output = new FileOutputStream(destination.getFileDescriptor());

            byte[] buf = new byte[1024];
            int bytesRead;

            while ((bytesRead = input.read(buf)) > 0) {
                output.write(buf, 0, bytesRead);
            }

            callback.onWriteFinished(new PageRange[]{PageRange.ALL_PAGES});

        } catch (FileNotFoundException ee){
            //Catch exception
        } catch (Exception e) {
            //Catch exception
        } finally {
            try {
                input.close();
                output.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras){

        if (cancellationSignal.isCanceled()) {
            callback.onLayoutCancelled();
            return;
        }

        //int pages = computePageCount(newAttributes);

        PrintDocumentInfo pdi = new PrintDocumentInfo.Builder("Name of file").setContentType(PrintDocumentInfo.CONTENT_TYPE_DOCUMENT).build();

        callback.onLayoutFinished(pdi, true);
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //If android version is 6.0
    if (!(ContextCompat.checkSelfPermission(this.getApplicationContext(), "android.permission.READ_EXTERNAL_STORAGE") == 0)) {
        ActivityCompat.requestPermissions(this, new String[]{ "android.permission.READ_EXTERNAL_STORAGE"}, 1);
    }
}
}