java - java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“int java.io.InputStream.read(byte[])”
问题描述
我正在尝试使用 WiFip2p 创建一个聊天应用程序。一切都在这个应用程序中完成。在发送和接收消息应用程序运行良好之前。之后,我得到了这个错误。当我连接到另一台设备时出现此错误。它显示一个空对象引用。我不知道为什么我需要一个解决方案,任何人都可以帮助我,谢谢。
public class WiFi_Activity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_wi_fi_);
FINDVIEWBYID();
CLICKLISTINER();
}
Handler handler=new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {
switch (msg.what)
{
case MESSAGE_READ:
byte[] readbuffer=(byte[])msg.obj;
String tempmez=new String(readbuffer,0,msg.arg1);
txt_message.setText(tempmez);
break;
}
return true;
}
});
private void FINDVIEWBYID() {
btn_onoff=findViewById(R.id.onOff);
btn_discover=findViewById(R.id.discover);
btn_send=findViewById(R.id.sendButton);
listView=findViewById(R.id.peerListView);
txt_connectionsts=findViewById(R.id.connectionStatus);
txt_message=findViewById(R.id.readMsg);
edit_message=findViewById(R.id.writeMsg);
wifiManager= (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
wifiP2pManager= (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
channel=wifiP2pManager.initialize(this,getMainLooper(),null);
broadcastReceiver=new Wifi_broadcast_reciever(wifiP2pManager,channel,this);
intentFilter=new IntentFilter();
intentFilter.addAction(wifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
intentFilter.addAction(wifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
intentFilter.addAction(wifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
intentFilter.addAction(wifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
}
private void CLICKLISTINER() {
btn_onoff.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (wifiManager.isWifiEnabled())
{
wifiManager.setWifiEnabled(false);
btn_onoff.setText("ON");
}
else
{
wifiManager.setWifiEnabled(true);
btn_onoff.setText("OFF");
}
}
});
btn_discover.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
wifiP2pManager.discoverPeers(channel, new WifiP2pManager.ActionListener() {
@Override
public void onSuccess() {
txt_connectionsts.setText("Discovery Started");
}
@Override
public void onFailure(int reason) {
txt_connectionsts.setText("Discovery starting failuree"+String.valueOf(reason));
}
});
}
});
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
final WifiP2pDevice wifiP2pDevice=devicearray[position];
WifiP2pConfig config=new WifiP2pConfig();
config.deviceAddress=wifiP2pDevice.deviceAddress;
wifiP2pManager.connect(channel, config, new WifiP2pManager.ActionListener() {
@Override
public void onSuccess() {
Toast.makeText(WiFi_Activity.this, "Connect with"+ wifiP2pDevice.deviceName, Toast.LENGTH_SHORT).show();
}
@Override
public void onFailure(int reason) {
Toast.makeText(WiFi_Activity.this, "Not connected", Toast.LENGTH_SHORT).show();
}
});
}
});
btn_send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String msz=edit_message.getText().toString();
sendRecieve.write(msz.getBytes());
}
});
}
WifiP2pManager.PeerListListener peerListListener=new WifiP2pManager.PeerListListener() {
@Override
public void onPeersAvailable(WifiP2pDeviceList peerslist) {
if (!peerslist.getDeviceList().equals(peers));
{
peers.clear();
peers.addAll(peerslist.getDeviceList());
devicename_array=new String[peerslist.getDeviceList().size()];
devicearray=new WifiP2pDevice[peerslist.getDeviceList().size()];
int index= 0;
for (WifiP2pDevice device:peerslist.getDeviceList())
{
devicename_array[index]=device.deviceName;
devicearray[index]=device;
index++;
}
ArrayAdapter<String> arrayAdapter=new ArrayAdapter<String>(getApplicationContext(),R.layout.support_simple_spinner_dropdown_item,devicename_array);
listView.setAdapter(arrayAdapter);
}
if (peers.size()==0)
{
Toast.makeText(WiFi_Activity.this, "No discover show", Toast.LENGTH_SHORT).show();
}
}
};
WifiP2pManager.ConnectionInfoListener connectionInfoListener=new WifiP2pManager.ConnectionInfoListener() {
@Override
public void onConnectionInfoAvailable(WifiP2pInfo info) {
final InetAddress owneraddress= info.groupOwnerAddress;
if (info.groupFormed && info.isGroupOwner)
{
txt_connectionsts.setText("Host");
serverclass=new Serverclass();
serverclass.start();
}
else if (info.groupFormed)
{
txt_connectionsts.setText("Client");
clientclass = new Clientclass(owneraddress);
clientclass.start();
}
}
};
@Override
protected void onResume() {
super.onResume();
registerReceiver(broadcastReceiver,intentFilter);
}
@Override
protected void onPause() {
super.onPause();
unregisterReceiver(broadcastReceiver);
}
public class Serverclass extends Thread
{
Socket socket;
ServerSocket serverSocket;
@Override
public void run() {
try {
serverSocket=new ServerSocket(1111);
socket=serverSocket.accept();
sendRecieve=new SendRecieve(socket);
sendRecieve.start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class Clientclass extends Thread
{
Socket socket;
String host_address;
public Clientclass(InetAddress hostaddress){
host_address=hostaddress.getHostAddress();
socket=new Socket();
sendRecieve=new SendRecieve(socket);
sendRecieve.start();
}
@Override
public void run() {
try {
socket.connect(new InetSocketAddress(host_address,1111),500);
} catch (IOException e) {
e.printStackTrace();
}
}
}
private class SendRecieve extends Thread
{
private Socket socket;
private InputStream inputStream;
private OutputStream outputStream;
public SendRecieve(Socket skt)
{
socket=skt;
try {
inputStream=socket.getInputStream();
outputStream=socket.getOutputStream();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void run() {
byte[] buffer=new byte[2048];
int bytes;
while (socket!=null)
{
try {
bytes=inputStream.read(buffer);
if (bytes>0)
{
handler.obtainMessage(MESSAGE_READ,bytes,-1,buffer).sendToTarget();
}
} catch (IOException e) {
Log.d("error",e.getMessage());
}
}
}
public void write(byte[] bytes)
{
try {
outputStream.write(bytes);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
我在这部分代码上收到此错误:-
@Override
public void run() {
byte[] buffer=new byte[2048];
int bytes;
while (socket!=null)
{
try {
bytes=inputStream.read(buffer);
if (bytes>0)
{
handler.obtainMessage(MESSAGE_READ,bytes,-1,buffer).sendToTarget();
}
} catch (IOException e) {
Log.d("error",e.getMessage());
}
}
}
解决方案
我唯一能看到的一个问题是你正在从getInputStream()
and捕获(并忽略)错误getOutputStream()
。异常是停止执行,所以如果getInputStream()
出错,它不会被设置。您的两个流都将为空。
由于您至少要打印堆栈跟踪,因此请在实际崩溃之前检查其他堆栈跟踪。它可能会告诉你更多关于哪里出了问题。
为了解决这个问题,我建议不要捕获异常,而是让构造函数 throw IOException
。如果你早点发现它,它会在以后给你带来更少的问题。
编辑:我看了你的课多一点,我发现你没有及时设置地址Socket
。在获得数据流之前执行此操作。不使用这些字段将起作用。
private Socket socket;
public SendRecieve(Socket skt) {
this.socket = skt;
}
@Override
public void run() {
try {
InputStream in = socket.getInputStream();
... etc
} ...
}
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