如何在我的应用程序中停止 UI 线程，直到其他线程完成打印

Question

说明：

• 在我的应用程序中，我需要使用蓝牙打印机打印数据。
• UI 线程必须等到另一个线程处理打印 完成任务
• 打印线程设置一个值是否可以打印

问题：应用程序中的 UI 线程没有等待，它立即获得默认状态 false

我在下面的代码中哪里出错了？

界面线程：

private void printingStatus()
{
    if(printData.isPrintFinished())
        // do something
    else
        // do something
}

// 在不同线程中执行打印的 PrintData 类

    private boolean printFinished = false;
// UI thread asks this method whether printing is success or failure
public boolean isPrintFinished() {
    return printed;
}

public void setPrintFinished(boolean printed) {
    this.printed = printed;
}

public static interface IPrintFinished {
    public void onPrintFinished(boolean success);
}

public void printData() {
    sendDataToPrinter(context, contentToPrint, new IPrintFinished() {
        @Override
        public void setPrintFinished(boolean success) {
            if (success) {
                setPrintFinished(true);
                Logger.e("inside if success - printed"+printed);
            }
            setPrintFinished(false);
            Logger.e("printed outside if" + printed);
        }
    });
}
public static void sendDataToPrinter(final Context context, final contentDefinition contentToPrint, final IPrintFinished listener) {
    new Thread(new Runnable() {
    @Override
    public void run() {
        Looper.prepare();
        // starts here the actual printing and gets a result
        int tmpResult;
          try {
              DataPrinter.getInstance().print(contentToPrint);
              try {
                  Thread.sleep(2000);
              } catch (InterruptedException e) {
                  Logger.e("exceptpion:" + e);
              }
              tmpResult =  STATUS_PRINTED;
          } catch (TechnicalException e) {
              Logger.e("exceptpion:" + e);
              if (e.getMessage() != null && DataPrinter.ERROR_BLUETOOH_IS_DISABLED.equals(e.getMessage()))
                  tmpResult = STATUS_BLUETOOTH_DISABLED;
              else
                  tmpResult = STATUS_ERROR;
          }


          final int result = tmpResult;
          Logger.e("print result:"+result);
          new Handler(Looper.getMainLooper()).post(new Runnable() {

              @Override
              public void run() {

                  if(result == STATUS_PRINTED) {
                      if (listener != null) {
                          Logger.e("inside the listener status printed");
                          listener.onPrintFinished(true);
                      }
                  } else if (result == STATUS_BLUETOOTH_DISABLED) {
                      SimpleToast.showToast("bluetooth disabled");
                      if (listener != null) {
                          listener.onPrintFinished(false);
                      }
                  } else {
                      SimpleToast.showToast("cannot connect to printer");
                      if (listener != null) {
                          listener.onPrintFinished(false);
                      }
                  }
              }
          });

                Looper.loop();
            }
        }).start();
    }

Answer 1

您不能暂时保留您的 UI 线程。这将导致ANR 状态。它是处理 UI 组件的主线程。