我已经实现了一个能够检测BLE信号并使用适配器将其显示为列表的应用程序。显示BLE设备后，我将每个列表的特征保存到xml文件中。当应用程序检测到设备时，它可以完美保存;我现在的问题是，如果它没有检测到任何信号，或者以另一种方式说，列表中没有项目，当它试图将其保存到xml文件时，应用程序崩溃并关闭。我试图通过检查列表中的项目数来修复它;如果它是0，它执行代码的“else”部分，如果它大于0，它将保存列表，如下所示。然而，它仍然导致同样的问题，我不知道该怎么做。
以下是我用来保存到xml文件中的代码：
public class Save {
/**
* Save the last BLE List in a XML File
*/
private BleDevicesAdapter leDeviceListAdapter;
Save(BleDevicesAdapter BLEList) {
leDeviceListAdapter = BLEList;
}
public void savedata() throws FileNotFoundException{
String filename = "BLEDevices.xml";
long dateutc = System.currentTimeMillis();
long finaldateutc = 62135596800000L + dateutc;
double frequency = 1/(0.001*SCAN_PERIOD);
long period = 200;
FileOutputStream fos = null;
File sdCard = Environment.getExternalStorageDirectory();
File directory = new File(sdCard.getAbsolutePath()+"/Mis archivos");
directory.mkdirs();
File file= new File(directory, filename);
if (leDeviceListAdapter.getDevice(0) != null) {
int size = leDeviceListAdapter.getCount();
try {
fos = new FileOutputStream(file);
//fos= openFileOutput(filename, Context.MODE_WORLD_READABLE);
XmlSerializer serializer = Xml.newSerializer();
serializer.setOutput(fos, "UTF-8");
serializer.startDocument(null, Boolean.valueOf(true));
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
serializer.startTag("", "root");
serializer.startTag("", "measurement");
serializer.attribute("", "time", String.valueOf(finaldateutc));
//serializer.attribute("", "scan period", String.valueOf(period));
for(int j = 0 ; j < size ; j++) {
BluetoothDevice devices = leDeviceListAdapter.getDevice(j);
Integer signal = leDeviceListAdapter.getRSSI(j);
serializer.startTag("", "device");
serializer.attribute("", "rssi", String.valueOf(signal));
serializer.attribute("", "mac", devices.getAddress());
serializer.attribute("", "name", devices.getName());
serializer.endTag("", "device");
}
//ObjectOutputStream out = new ObjectOutputStream(fos);
//out.writeObject(leDeviceListAdapter);
//out.close();
serializer.endDocument();
serializer.flush();
fos.close();
Toast.makeText(DeviceScanActivity.this, R.string.list_saved, Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
else {
try {
fos = new FileOutputStream(file);
//fos= openFileOutput(filename, Context.MODE_WORLD_READABLE);
XmlSerializer serializer = Xml.newSerializer();
serializer.setOutput(fos, "UTF-8");
serializer.startDocument(null, Boolean.valueOf(true));
serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
serializer.startTag("", "root");
serializer.startTag("", "measurement");
serializer.attribute("", "time", String.valueOf(finaldateutc));
serializer.endDocument();
serializer.flush();
fos.close();
Toast.makeText(DeviceScanActivity.this, R.string.list_saved, Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
}
}
这也是问题的日志：
03-18 12:51:17.081: D/BluetoothAdapter(18804): stopLeScan()
03-18 12:51:17.086: D/AndroidRuntime(18804): Shutting down VM
03-18 12:51:17.086: W/dalvikvm(18804): threadid=1: thread exiting with uncaught exception (group=0x42027700)
03-18 12:51:17.091: E/AndroidRuntime(18804): FATAL EXCEPTION: main
03-18 12:51:17.091: E/AndroidRuntime(18804): java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
03-18 12:51:17.091: E/AndroidRuntime(18804): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
03-18 12:51:17.091: E/AndroidRuntime(18804): at java.util.ArrayList.get(ArrayList.java:308)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.example.newblescan.adapter.BleDevicesAdapter.getDevice(BleDevicesAdapter.java:50)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.example.newblescan.DeviceScanActivity$Save.savedata(DeviceScanActivity.java:346)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.example.newblescan.DeviceScanActivity.onOptionsItemSelected(DeviceScanActivity.java:131)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.app.Activity.onMenuItemSelected(Activity.java:2640)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1171)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.view.menu.ActionMenuView.invokeItem(ActionMenuView.java:630)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:200)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.view.View.performClick(View.java:4475)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.view.View$PerformClick.run(View.java:18786)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.os.Handler.handleCallback(Handler.java:730)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.os.Handler.dispatchMessage(Handler.java:92)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.os.Looper.loop(Looper.java:137)
03-18 12:51:17.091: E/AndroidRuntime(18804): at android.app.ActivityThread.main(ActivityThread.java:5493)
03-18 12:51:17.091: E/AndroidRuntime(18804): at java.lang.reflect.Method.invokeNative(Native Method)
03-18 12:51:17.091: E/AndroidRuntime(18804): at java.lang.reflect.Method.invoke(Method.java:525)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
03-18 12:51:17.091: E/AndroidRuntime(18804): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
03-18 12:51:17.091: E/AndroidRuntime(18804): at dalvik.system.NativeStart.main(Native Method)
03-18 12:51:17.161: D/BluetoothAdapter(18804): stopLeScan()
03-18 12:51:17.161: D/BluetoothAdapter(18804): stopLeScan()
任何人都可以帮我解决这个问题或者说出正确的答案吗？请帮忙!!!!!
答案 0 :(得分：0)
您收到此错误的原因是因为数组列表中没有数据，大小为0.您可以做的是，您可以在BleDevicesAdapter中检查ArrayList是否为空。
public BluetoothDevice getDevice(int position) {
if(leDevices == null || leDevices.size() == 0 ) {
return null;
}
return leDevices.get(position);
}
if (leDeviceListAdapter.getDevice(0) != null)