我正在尝试为我的应用程序创建一个已签名的apk，但在创建签名的apk对话后单击完成后出现错误。
错误：此类应提供默认构造函数（...）[Instantiatable]
public class MainActivity {
// Debugging
private static final String TAG = "BluetoothChatService";
private static final boolean D = true;
// Name for the SDP record when creating server socket
private static final String NAME = "project";
// Unique UUID for this application
private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
// Member fields
private final BluetoothAdapter mAdapter;
private final Handler mHandler;
private AcceptThread mAcceptThread;
private ConnectThread mConnectThread;
private ConnectedThread mConnectedThread;
private int mState;
// Constants that indicate the current connection state
public static final int STATE_NONE = 0; // we're doing nothing
public static final int STATE_LISTEN = 1; // now listening for incoming connections
public static final int STATE_CONNECTING = 2; // now initiating an outgoing connection
public static final int STATE_CONNECTED = 3; // now connected to a remote device
/**
* Constructor. Prepares a new BluetoothChat session.
* @param context The UI Activity Context
* @param handler A Handler to send messages back to the UI Activity
*/
public MainActivity(Context context, Handler handler) {
mAdapter = BluetoothAdapter.getDefaultAdapter();
mState = STATE_NONE;
mHandler = handler;
}
/ ** *设置聊天连接的当前状态 * @param state定义当前连接状态的整数 * /
/**
* Return the current connection state. */
public synchronized int getState() {
return mState;
}
/**
* Start the chat service. Specifically start AcceptThread to begin a
* session in listening (server) mode. Called by the Activity onResume() */
public synchronized void start() {
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Start the thread to listen on a BluetoothServerSocket
if (mAcceptThread == null) {
mAcceptThread = new AcceptThread();
mAcceptThread.start();
}
if (D) Log.d(TAG, "start");
// Cancel any thread attempting to make a connection
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Start the thread to listen on a BluetoothServerSocket
if (mAcceptThread == null) {
mAcceptThread = new AcceptThread();
mAcceptThread.start();
}
}
/**
* Start the ConnectThread to initiate a connection to a remote device.
* @param device The BluetoothDevice to connect
*/
public synchronized void connect(BluetoothDevice device) {
if (D) Log.d(TAG, "connect to: " + device);
// Cancel any thread attempting to make a connection
if (mState == STATE_CONNECTING) {
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Start the thread to connect with the given device
mConnectThread = new ConnectThread(device);
mConnectThread.start();
}
/**
* Start the ConnectedThread to begin managing a Bluetooth connection
* @param socket The BluetoothSocket on which the connection was made
* @param device The BluetoothDevice that has been connected
*/
public synchronized void connected(BluetoothSocket socket, BluetoothDevice device) {
if (D) Log.d(TAG, "connected");
// Cancel the thread that completed the connection
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Cancel the accept thread because we only want to connect to one device
if (mAcceptThread != null) {mAcceptThread.cancel(); mAcceptThread = null;}
// Start the thread to manage the connection and perform transmissions
mConnectedThread = new ConnectedThread(socket);
mConnectedThread.start();
// Send the name of the connected device back to the UI Activity
Message msg = mHandler.obtainMessage(hotlifebluetoothspp.MESSAGE_DEVICE_NAME);
Bundle bundle = new Bundle();
bundle.putString(hotlifebluetoothspp.DEVICE_NAME, device.getName());
msg.setData(bundle);
mHandler.sendMessage(msg);
}
/**
* Stop all threads
*/
public synchronized void stop() {
if (D) Log.d(TAG, "stop");
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
if (mAcceptThread != null) {mAcceptThread.cancel(); mAcceptThread = null;}
}
/**
* Write to the ConnectedThread in an unsynchronized manner
* @param out The bytes to write
* @see ConnectedThread#write(byte[])
*/
public void write(byte[] out) {
// Create temporary object
ConnectedThread r;
// Synchronize a copy of the ConnectedThread
synchronized (this) {
if (mState != STATE_CONNECTED) return;
r = mConnectedThread;
}
// Perform the write unsynchronized
r.write(out);
}
/**
* Indicate that the connection attempt failed and notify the UI Activity.
*/
/**
* Indicate that the connection was lost and notify the UI Activity.
*/
private void connectionLost() {
// Send a failure message back to the Activity
Message msg = mHandler.obtainMessage(hotlifebluetoothspp.MESSAGE_TOAST);
Bundle bundle = new Bundle();
bundle.putString(hotlifebluetoothspp.TOAST, "Device connection was lost");
msg.setData(bundle);
mHandler.sendMessage(msg);
}
/**
* This thread runs while listening for incoming connections. It behaves
* like a server-side client. It runs until a connection is accepted
* (or until cancelled).
*/
private class AcceptThread extends Thread {
// The local server socket
private final BluetoothServerSocket mmServerSocket;
public AcceptThread() {
BluetoothServerSocket tmp = null;
// Create a new listening server socket
try {
tmp = mAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
} catch (IOException e) {
Log.e(TAG, "listen() failed", e);
}
mmServerSocket = tmp;
}
public void run() {
if (D) Log.d(TAG, "BEGIN mAcceptThread" + this);
setName("AcceptThread");
BluetoothSocket socket = null;
// Listen to the server socket if we're not connected
while (mState != STATE_CONNECTED) {
try {
// This is a blocking call and will only return on a
// successful connection or an exception
socket = mmServerSocket.accept();
} catch (IOException e) {
Log.e(TAG, "accept() failed", e);
break;
}
// If a connection was accepted
if (socket != null) {
synchronized (MainActivity.this) {
switch (mState) {
case STATE_LISTEN:
case STATE_CONNECTING:
// Situation normal. Start the connected thread.
connected(socket, socket.getRemoteDevice());
break;
case STATE_NONE:
case STATE_CONNECTED:
// Either not ready or already connected. Terminate new socket.
try {
socket.close();
} catch (IOException e) {
Log.e(TAG, "Could not close unwanted socket", e);
}
break;
}
}
}
}
if (D) Log.i(TAG, "END mAcceptThread");
}
public void cancel() {
if (D) Log.d(TAG, "cancel " + this);
try {
mmServerSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of server failed", e);
}
}
}
/**
* This thread runs while attempting to make an outgoing connection
* with a device. It runs straight through; the connection either
* succeeds or fails.
*/
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public ConnectThread(BluetoothDevice device) {
mmDevice = device;
BluetoothSocket tmp = null;
// Get a BluetoothSocket for a connection with the
// given BluetoothDevice
try {
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
Log.e(TAG, "create() failed", e);
}
mmSocket = tmp;
}
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of connect socket failed", e);
}
}
public BluetoothDevice getMmDevice() {
return mmDevice;
}
}
/**
* This thread runs during a connection with a remote device.
* It handles all incoming and outgoing transmissions.
*/
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
Log.d(TAG, "create ConnectedThread");
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
Log.e(TAG, "temp sockets not created", e);
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
public void run() {
Log.i(TAG, "BEGIN mConnectedThread");
byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true) {
try {
// Read from the InputStream
bytes = mmInStream.read(buffer);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(hotlifebluetoothspp.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
connectionLost();
break;
}
}
}
/**
* Write to the connected OutStream.
* @param buffer The bytes to write
*/
public void write(byte[] buffer) {
try {
mmOutStream.write(buffer);
// Share the sent message back to the UI Activity
mHandler.obtainMessage(hotlifebluetoothspp.MESSAGE_WRITE, -1, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Log.e(TAG, "Exception during write", e);
}
}
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of connect socket failed", e);
}
}
}
}
答案 0 :(得分：2)
我建议删除您定义的构造函数，并在onCreate()方法中进行所有初始化。
删除此：
public MainActivity(Context context, Handler handler) {
mAdapter = BluetoothAdapter.getDefaultAdapter();
mState = STATE_NONE;
mHandler = handler;
}
并添加：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = BluetoothAdapter.getDefaultAdapter();
mState = STATE_NONE;
mHandler = handler;
}
<强>更新
爱立信
现在我看到你的班级不是Activity的子类。因此，MainActivity实际上不是Activity，我的建议不会为您效劳。
通常，我们使用MainActvity作为Activity的子类，如：
public MainActivity extends Activity {
}
如果没有关于项目/代码的更多详细信息，很难说明您的意图。 你能否更新你的问题？
如果MainActivity确实是正确的，而您真的不想extends Activity，那么正确的解决办法就是添加以下几行：
public MainActivity() {
}
答案 1 :(得分：0)
此类应提供默认构造函数（...）[Instantiatable]
您是否尝试过添加默认构造函数？
public MainActivity() {
}