java - 在 Cordova-Android 上扫描网络打印机

Question

我正在尝试在cordova上构建一个插件，它可以找到蓝牙、USB和网络打印机并打印文本、图像、二维码、条形码...我在网络打印机扫描时遇到问题，需要一些帮助接着就，随即。我下面有这段代码，可以搜索连接到 wifi 的网络打印机。它适用于 android 7 和 6，但在 android 5 的情况下，它无法返回回调。这可能是由于线程限制或 android 5 上的某些原因

 scanWifi(ips, new OnIPScanningCallback() {
            @Override
            public void onScanningComplete(List<String> results) {
                Log.d("TAG", "onScanningComplete: " + results.size()+" : "+results.toString());
                Printers printerList =null;
                for(String printerIps:results) {
                    String mac = getHardwareAddress(printerIps);
                    printerList = new Printers(printerIps, mac);
                    printers.put(printerIps);
                    list.add(printerList);
                }
                Log.d(TAGS,"The List of all wifi Printers : "+list);
            }
        });
        isStart = false;
    }

private static void scanWifi(final List<String> ips, final 
OnIPScanningCallback callback) {
    final Vector<String> results = new Vector<String>();
    final int totalSize = ips.size();
    final int splitSize = 10;
    final int[] index = {0};
    final long start = System.currentTimeMillis();
    for (int i = 0; i < totalSize; i += splitSize) {
        final List<String> child = new ArrayList<String>(ips.subList(i, Math.min(totalSize, i + splitSize)));

        new Thread() {
            @Override
            public void run() {
                for (String ip : child) {
                    Log.d("TAG", " scanning : " + index[0] + ", ip: " + ip);
                    boolean isPrinter = connect(ip);
                    if (isPrinter) {
                        results.add(ip);
                    }
                    if (index[0] == ips.size() - 1) {
                        long end = System.currentTimeMillis();
                        Log.d("TAG", "scanning time: " + (end - start) / 1000);
                        callback.onScanningComplete(results);
                    } else {
                        index[0]++;
                    }
                }

            }
        }.start();
    }
}
  public interface OnIPScanningCallback {
    void onScanningComplete(List<String> results);
  }

我也尝试过异步任务，它适用于所有版本的 Android，但问题是该过程需要 170 到 193 秒，这对于上面的代码来说太长了，它能够在 20 秒内完成相同的任务

 scanWifi(ips, new PrintingPlugin.OnIPScanningCallback() {
            @Override
            public void onScanningComplete(List<String> results) {
                Log.d(TAGS, "onScanningComplete: " + results.size() + " : " + results.toString());
                Printers printerList;
                for (String printerIps : results) {
                    String mac = getHardwareAddress(printerIps);
                    printerList = new Printers(printerIps, mac);
                    printers.put(printerIps);
                    list.add(printerList);
                }
                Log.d(TAGS, "The List of all wifi Printers : " + list);

            }
        });
        isStart = false;
    } catch (Exception e) {
        Log.e(TAGS, "Error while scanning for wifi"+e.getMessage());
    }
    return printers;
}

private  Integer index = 0;

void resetIndex() {
    index = 0;
}

private  void scanWifi(final List<String> ips, final PrintingPlugin.OnIPScanningCallback callback) {
    Log.d(TAGS, " scanWifi" );
    final Vector<String> results = new Vector<String>();
    final int totalSize = ips.size();
    final int splitSize = 10;
    resetIndex();
    final long start = System.currentTimeMillis();
    for (int i = 0; i < totalSize; i += splitSize) {
        final List<String> child = new ArrayList<String>(ips.subList(i, Math.min(totalSize, i + splitSize)));
        executeTask(new AsyncTask() {
            @Override
            protected Object doInBackground(Object[] objects) {
                synchronized (index) {
                    for (String ip : child) {
                        Log.d(TAGS, " scanning : " + index + ", ip: " + ip);
                        boolean isPrinter = connect(ip);
                        if (isPrinter) {
                            results.add(ip);
                        }
                        if (index == ips.size() - 1) {
                            long end = System.currentTimeMillis();
                            Log.d(TAGS, "scanning time: " + (end - start) / 1000);
                            callback.onScanningComplete(results);
                        } else {
                            index++;
                        }
                    }
                }

                return null;
            }

        });
    }

   public void executeTask(AsyncTask asyncTask) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        asyncTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
    } else {
        asyncTask.execute();
    }
}

这是我在 android 5 上运行时收到的消息。

D/ConnectivityManager.CallbackHandler: CM callback handler got msg 524290

任何帮助让这个东西以任何方式工作(在 android 5 上工作的第一个代码或以更快、更有效的方式工作的第二个代码)将受到深深的赞赏。我已经查看了与此相关的问题，但我不想使用打印服务。

Answer 1

由于索引值是未发送回调的原因，因此要解决此问题，只需在发现网络打印机后立即发送回调并将其存储在 var(在我的情况下为 JSONArray )中即可为您提供列表打印机及其有效性。