系统打印服务框架代码位于android.printservice包中。系统并没有实现具体打印功能,需要打印机厂商制作插件接入系统打印服务之后,自行实现
主要类:
PrintDocument:表示待打印文件
PrintDiscoverySession:用于发现打印机和打印机状态更新
PrintJob:代表打印任务
PrintService:接入系统打印Service
打印机发现过程:
当用户在设置里开启你的打印服务插件和进入系统打印服务界面时,系统会调用 PrinterDiscoverySession 里的 onStartPrinterDiscovery(List priorityList) 函数,通知你的插件查找打印机。具体查找方式需要自己实现,可能是查找USB接口,可能是搜索网络。系统只管结果,你通过调用其父类的 addPrinters() 方法将打印机添加进去。打印机是放在List数组里传入。
打印机选择过程
当用户通过一些有打印功能的APP调用系统打印服务时,如果选择了你的插件的打印机,那么系统会调用 PrinterDiscoverySession 里的 onStartPrinterStateTracking(PrinterId printerId) 方法。这里系统主要希望得到打印机的 PrinterCapabilitiesInfo 和状态,里面包括打印机支持的纸张大小,以及色彩等详细功能参数。
打印过程:
当用户在刚刚的系统打印服务界面点击右上角的打印按钮时,系统会调用打印机所属的 PrintService 里的 onPrintJobQueued(PrintJob printJob) 方法,插件需要处理该 PrintJob 。首先需要通过 PrintJob.isQueued() 判断,该PrintJob是否准备好打印,返回true代表可以打印。然后可以通过 PrintJob.getDocument() 获得要打印的文档,这里面的数据可以通过 PrintDocument.getData() 读取。开始打印的时候,调用PrintJob.start()标记开始状态。当打印成功时,调用 PrintJob.complete() 标记打印成功。或者打印失败时,调用 PrintJob.fail( String) 标记失败。
打印服务需要添加的权限:
<uses-permission android:name="android.permission.START_PRINT_SERVICE_CONFIG_ACTIVITY" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
打印类:
public class MyPrintService extends PrintService {
private static final String TAG = "MyPrintService";
@Override
protected PrinterDiscoverySession onCreatePrinterDiscoverySession() {
Log.d(TAG, "onCreatePrinterDiscoverySession()");
return new MyPrintDiscoverySession(this);
}
@Override
protected void onRequestCancelPrintJob(PrintJob printJob) {
Log.d(TAG, "onRequestCancelPrintJob()");
printJob.cancel();
}
@Override
protected void onPrintJobQueued(PrintJob printJob) {
Log.d(TAG, "onPrintJobQueued()");
PrintJobInfo printjobinfo = printJob.getInfo();
PrintDocument printdocument = printJob.getDocument();
if (printJob.isQueued()) {
return;
}
printJob.start();
String filename = "docu.pdf";
File outfile = new File(this.getFilesDir(), filename);
outfile.delete();
FileInputStream file = new ParcelFileDescriptor.AutoCloseInputStream(printdocument.getData());
//创建一个长度为1024的内存空间
byte[] bbuf = new byte[1024];
//用于保存实际读取的字节数
int hasRead = 0;
//使用循环来重复读取数据
try {
FileOutputStream outStream = new FileOutputStream(outfile);
while ((hasRead = file.read(bbuf)) > 0) {
//将字节数组转换为字符串输出
//System.out.print(new String(bbuf, 0, hasRead));
outStream.write(bbuf);
}
outStream.close();
} catch (IOException e) {
e.printStackTrace();
}finally {
//关闭文件输出流,放在finally块里更安全
try {
file.close();
} catch (IOException e) {
e.printStackTrace();
}
}
printJob.complete();
}
}
PrinterDiscoverySession实现类编写:
public class MyPrintDiscoverySession extends PrinterDiscoverySession {
private static final String TAG = "MyPrintDiscoverySession";
private final MyPrintService myPrintService;
public MyPrintDiscoverySession(MyPrintService myPrintService) {
Log.d(TAG, "MyPrintDiscoverySession()");
this.myPrintService = myPrintService;
}
@Override
public void onStartPrinterDiscovery(List<PrinterId> priorityList) {
Log.d(TAG, "onStartPrinterDiscovery()");
List<PrinterInfo> printers = this.getPrinters();
String name = "printer1";
PrinterInfo myprinter = new PrinterInfo
.Builder(myPrintService.generatePrinterId(name), name, PrinterInfo.STATUS_IDLE)
.build();
printers.add(myprinter);
addPrinters(printers);
}
@Override
public void onStopPrinterDiscovery() {
Log.d(TAG, "onStopPrinterDiscovery()");
}
/**
* 确定这些打印机存在
* @param printerIds
*/
@Override
public void onValidatePrinters(List<PrinterId> printerIds) {
Log.d(TAG, "onValidatePrinters()");
}
/**
* 选择打印机时调用该方法更新打印机的状态,能力
* @param printerId
*/
@Override
public void onStartPrinterStateTracking(PrinterId printerId) {
Log.d(TAG, "onStartPrinterStateTracking()");
PrinterInfo printer = findPrinterInfo(printerId);
if (printer != null) {
PrinterCapabilitiesInfo capabilities =
new PrinterCapabilitiesInfo.Builder(printerId)
.setMinMargins(new PrintAttributes.Margins(200, 200, 200, 200))
.addMediaSize(PrintAttributes.MediaSize.ISO_A4, true)
//.addMediaSize(PrintAttributes.MediaSize.ISO_A5, false)
.addResolution(new PrintAttributes.Resolution("R1", "200x200", 200, 200), false)
.addResolution(new PrintAttributes.Resolution("R2", "300x300", 300, 300), true)
.setColorModes(PrintAttributes.COLOR_MODE_COLOR
| PrintAttributes.COLOR_MODE_MONOCHROME,
PrintAttributes.COLOR_MODE_MONOCHROME)
.build();
printer = new PrinterInfo.Builder(printer)
.setCapabilities(capabilities)
.setStatus(PrinterInfo.STATUS_IDLE)
// .setDescription("fake print 1!")
.build();
List<PrinterInfo> printers = new ArrayList<PrinterInfo>();
printers.add(printer);
addPrinters(printers);
}
}
@Override
public void onStopPrinterStateTracking(PrinterId printerId) {
Log.d(TAG, "onStopPrinterStateTracking()");
}
@Override
public void onDestroy() {
Log.d(TAG, "onDestroy()");
}
private PrinterInfo findPrinterInfo(PrinterId printerId) {
List<PrinterInfo> printers = getPrinters();
final int printerCount = getPrinters().size();
for (int i = 0; i < printerCount; i++) {
PrinterInfo printer = printers.get(i);
if (printer.getId().equals(printerId)) {
return printer;
}
}
return null;
}
}