安卓按钮。performclick（）java。lang.NullPointerException

Question

我正在尝试修改应用程序以添加其他功能。我有一个像这样的函数

public class MainActivity extends Activity implements RadioGroup.OnCheckedChangeListener {
    private static final int REQUEST_SELECT_DEVICE = 1;
    private static final int REQUEST_ENABLE_BT = 2;
    public static final String TAG = "nRFUART";
    private static final String TAG1 = "smsTAG";
    private static final int UART_PROFILE_CONNECTED = 20;
    private static final int UART_PROFILE_DISCONNECTED = 21;
    public static String content = null;
    private int mState = UART_PROFILE_DISCONNECTED;
    private UartService mService = null;
    private BluetoothDevice mDevice = null;
    private BluetoothAdapter mBtAdapter = null;
    private ListView messageListView;
    private ArrayAdapter<String> listAdapter;
    public Button btnConnectDisconnect,btnSend;
    private EditText edtMessage;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();
        if (mBtAdapter == null) {
            Toast.makeText(this, "Bluetooth is not available", Toast.LENGTH_LONG).show();
        }else{

            btnConnectDisconnect=(Button) findViewById(R.id.btn_select);
            btnSend=(Button) findViewById(R.id.sendButton);
            edtMessage = (EditText) findViewById(R.id.sendText);
            mBtAdapter = BluetoothAdapter.getDefaultAdapter();
            messageListView = (ListView) findViewById(R.id.listMessage);
            listAdapter = new ArrayAdapter<String>(this, R.layout.message_detail);
            messageListView.setAdapter(listAdapter);
            messageListView.setDivider(null);
            //Call receiveBroadCast like this
            receiveBroadCast(getIntent().getStringExtra("message"));
            service_init();
        }

    ...

        // Handle Send button
        btnSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                EditText editText = (EditText) findViewById(R.id.sendText);
//              String message = editText.getText().toString();
                String message = content;
                byte[] value;
                try {
                    //send data to service
                    value = message.getBytes("UTF-8");
                    mService.writeRXCharacteristic(value);
                    //Update the log with time stamp
                    String currentDateTimeString = DateFormat.getTimeInstance().format(new Date());
                    listAdapter.add("["+currentDateTimeString+"] TX: "+ message);
                    messageListView.smoothScrollToPosition(listAdapter.getCount() - 1);
                    edtMessage.setText("");
                    Log.i(TAG1, "success, value: " + value + " message: " + message);
                } catch (UnsupportedEncodingException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Log.i(TAG1, "fail" + e.toString());
                }
            }
        });

        ...

    }

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    public void receiveBroadCast(String text) {
        btnSend=(Button) findViewById(R.id.sendButton);
        Log.i(TAG1, "test " + text);
        try {
            Log.i(TAG1, "success " + text);
            content = text;
            btnSend.performClick();
        } catch (Exception e) {
            Log.i(TAG1, "fail " + e.toString());
        }
    }
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

但是当我运行代码时，我得到了错误

java.lang.NullPointerException: Attempt to invoke virtual method '安卓.view.View 安卓.view.Window.findViewById(int)' on a null object reference

这是主要的。包含我的按钮的xml文件

        <Button
            安卓:id="@+id/sendButton"
            安卓:layout_width="wrap_content"
            安卓:layout_height="wrap_content"
            安卓:layout_alignParentRight="true"
            安卓:layout_alignParentBottom="true"
            安卓:layout_marginRight="0dp"
            安卓:layout_marginBottom="0dp"
            安卓:enabled="false"
            安卓:text="Send" />

知道是什么导致了这个错误吗

每次我向receiveBroadcast提供字符串时，我都试图使我的receiveBroadcast自动单击Send按钮

这是我用来调用receiveBroadcast的SMSReceiver类：

public class SmsReceiver extends BroadcastReceiver {
    private static final String TAG = "MyBroadcastReceiver";
    @Override
    public void onReceive(Context context, Intent intent) {
        if(intent.getAction().equals("安卓.provider.Telephony.SMS_RECEIVED")) {
            Bundle bundle = intent.getExtras();
            SmsMessage[] msgs = null;
            if (bundle != null){
                try{
                    Object[] pdus = (Object[]) bundle.get("pdus");
                    msgs = new SmsMessage[pdus.length];
                    for(int i=0; i<msgs.length; i++){
                        msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
                        String msgBody = msgs[i].getMessageBody();
                        Log.i(TAG, " success " + msgBody);
                        MainActivity Text = new MainActivity();
                        Text.receiveBroadCast(msgBody);
                        Intent intentsms = new Intent(context, MainActivity.class);
                        intentsms.putExtra("message", msgBody);
                        context.startActivity(intentsms);
                    }
                } catch(Exception e) {
                    Log.i(TAG, e.toString());
                }
            }
        }
    }
}

Answer 1

For that thing to work for you. You will have to send the LocalBroadCastManager to MainActivity and there you will have to get that data to perform your Action.

检查以下实现：

public class MainActivity extends Activity implements RadioGroup.OnCheckedChangeListener {
    private static final int REQUEST_SELECT_DEVICE = 1;
    private static final int REQUEST_ENABLE_BT = 2;
    public static final String TAG = "nRFUART";
    private static final String TAG1 = "smsTAG";
    private static final int UART_PROFILE_CONNECTED = 20;
    private static final int UART_PROFILE_DISCONNECTED = 21;
    public static String content = null;
    private int mState = UART_PROFILE_DISCONNECTED;
    private UartService mService = null;
    private BluetoothDevice mDevice = null;
    private BluetoothAdapter mBtAdapter = null;
    private ListView messageListView;
    private ArrayAdapter<String> listAdapter;
    public Button btnConnectDisconnect,btnSend;
    private EditText edtMessage;


    private BroadcastReceiver myMessageRec = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            // Get extra data included in the Intent
            String message = intent.getStringExtra("message");
            Log.d("receiver", "Got message: " + message);
            receiveBroadCast(message);
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LocalBroadcastManager.getInstance(MainActivity.this).registerReceiver(myMessageRec,
                new IntentFilter("myMessage"));
        btnConnectDisconnect = (Button) findViewById(R.id.btn_select);
        btnSend = (Button) findViewById(R.id.sendButton);
        edtMessage = (EditText) findViewById(R.id.sendText);
        mBtAdapter = BluetoothAdapter.getDefaultAdapter();
        messageListView = (ListView) findViewById(R.id.listMessage);
        listAdapter = new ArrayAdapter<String>(this, R.layout.message_detail);
        messageListView.setAdapter(listAdapter);
        messageListView.setDivider(null);
        service_init();

        // Handle Send button
        btnSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                EditText editText = (EditText) findViewById(R.id.sendText);
//              String message = editText.getText().toString();
                String message = content;
                byte[] value;
                try {
                    //send data to service
                    value = message.getBytes("UTF-8");
                    mService.writeRXCharacteristic(value);
                    //Update the log with time stamp
                    String currentDateTimeString = DateFormat.getTimeInstance().format(new Date());
                    listAdapter.add("[" + currentDateTimeString + "] TX: " + message);
                    messageListView.smoothScrollToPosition(listAdapter.getCount() - 1);
                    edtMessage.setText("");
                    Log.i(TAG1, "success, value: " + value + " message: " + message);
                } catch (UnsupportedEncodingException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Log.i(TAG1, "fail" + e.toString());
                }
            }
        });

    }

    public void receiveBroadCast(String text) {
        Log.i(TAG1, "test " + text);
        try {
            Log.i(TAG1, "success " + text);
            content = text;
            btnSend.performClick();
        } catch (Exception e) {
            Log.i(TAG1, "fail " + e.toString());
        }
    }

    @Override
    protected void onDestroy() {
        // Unregister since the activity is about to be closed.
        LocalBroadcastManager.getInstance(MainActivity.this).unregisterReceiver(myMessageRec);
        super.onDestroy();
    }


}

SmsReceiver will look like this:

public class SmsReceiver extends BroadcastReceiver {
        private static final String TAG = "MyBroadcastReceiver";
        @Override
        public void onReceive(Context context, Intent intent) {
            if(intent.getAction().equals("android.provider.Telephony.SMS_RECEIVED")) {
                Bundle bundle = intent.getExtras();
                SmsMessage[] msgs = null;
                String str = "";
                if (bundle != null) {
                    Object[] pdus = (Object[]) bundle.get("pdus");
                    msgs = new SmsMessage[pdus.length];
                    for (int i=0; i<msgs.length; i++){
                        msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
                        str += "SMS from " + msgs[i].getOriginatingAddress();
                        str += " :";
                        str += msgs[i].getMessageBody().toString();
                        str += "\n";
                    }
                }
                Intent intentsms = new Intent("myMessage");
                intentsms.putExtra("message", str);
                LocalBroadcastManager.getInstance(context).sendBroadcast(intentsms);
            }
        }
    }