java - 如何在 Android 中的 textView 上显示除示例文本之外的值

Question

我正在制作一个 OBDII 读取器应用程序，并且希望查看文本上的(在本例中)电压，而不是我当前看到的 Logcat 中的电压。您可以在下面的代码中看到我在 while 循环中读取电压的位置。是否可以在每次循环运行时更新 textView ？

感谢任何帮助!

.java

public class BTHandler {

    public static final int STATE_NONE = 0;       // we're doing nothing
    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
    private final BluetoothAdapter mAdapter;
    private final Handler mHandler;
    BluetoothAdapter mBluetoothAdapter;
    UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    private String status;
    private BluetoothDevice mmDevice;
    private ConnectedThread mConnectedThread;
    private ConnectThread mConnectThread;
    private int pPlatform = Constants.SPA;
    private boolean connectionStatus = false;

    public BTHandler(Context context, Handler handler) { // Konstruktor
        mAdapter = BluetoothAdapter.getDefaultAdapter();
        mHandler = handler;
    }

    public void write(String s) {
        mConnectedThread.sendRawCommand(s);
        Log.v("write", "write");
    }

    public void close() {
        try {
            mConnectedThread.cancel();
        } catch (NullPointerException e) {

        }
    }

    public void connect(String deviceAddress) {
        mConnectThread = new ConnectThread(deviceAddress);
        mConnectThread.start();
    }

    private void guiHandler(int what, int arg1, String obj) {
        Message msg = mHandler.obtainMessage();
        msg.what = what;
        msg.obj = obj;
        msg.arg1 = arg1;
        msg.sendToTarget();
    }

    private class ConnectThread extends Thread {
        private final BluetoothDevice mmDevice;
        BluetoothSocket tmp = null;
        private BluetoothSocket mmSocket;

        public ConnectThread(String deviceAddress) {
            mmDevice = mAdapter.getRemoteDevice(deviceAddress);

            try {
                // MY_UUID is the app's UUID string, also used by the server code
                tmp = mmDevice.createRfcommSocketToServiceRecord(MY_UUID);
            } catch (IOException e) {
            }
            mmSocket = tmp;
        }

        public void run() {
            // Cancel discovery because it will slow down the connection
            mAdapter.cancelDiscovery();

            try {
                // Connect the device through the socket. This will block
                // until it succeeds or throws an exception
                mmSocket.connect();
            } catch (IOException connectException) {
                // Unable to connect; close the socket and get out
                try {
                    mmSocket.close();
                } catch (IOException closeException) {
                }
                guiHandler(Constants.TOAST, Constants.SHORT, "Connection Failed");
                return;
            }
            // Do work to manage the connection (in a separate thread)
            guiHandler(Constants.CONNECTION_STATUS, Constants.STATE_CONNECTED, "");
            mConnectedThread = new ConnectedThread(mmSocket);
            mConnectedThread.start();

        }
    }

    private class ConnectedThread extends Thread {
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;
        private BluetoothSocket mmSocket;
        private ObdMultiCommand multiCommand;

        public ConnectedThread(BluetoothSocket socket) {
            connectionStatus = true;
            mmSocket = socket;
            InputStream tmpIn = null;
            OutputStream tmpOut = null;


            switch (pPlatform) {
                case Constants.SPA:
                    multiCommand = new ObdMultiCommand();
                    multiCommand.add(new OdbRawCommand(SPA.VOLTAGE));
                    break;
            }

            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
                Log.v("e", "e");
            }

            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run() {
            OBDcmds();

            ModuleVoltageCommand voltageCommand = new ModuleVoltageCommand();
            //TextView textView = (TextView) findViewById(R.id.textView);

            while (!Thread.currentThread().isInterrupted()) {
                try {
                    voltageCommand.run(mmInStream, mmOutStream);
                    voltageCommand.getFormattedResult();
                    Log.d("Log", "Voltage:" + voltageCommand.getFormattedResult());
                    textView.setText(voltageCommand.getFormattedResult());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        // CALL this to MainActivity
        public void sendRawCommand(String s) {

            try {

            } catch (Exception e) {
                Log.v("sendRawCommand", "e");
            }
        }


        /*
        // Call this from the main activity to send data to the remote device
        public void write(byte[] bytes) {
            try {
                mmOutStream.write(bytes);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        */


        private void OBDcmds() { // execute commands

            try {
                new EchoOffCommand().run(mmInStream, mmOutStream);
                new LineFeedOffCommand().run(mmInStream, mmOutStream);
                new TimeoutCommand(100).run(mmInStream, mmOutStream);
                new SelectProtocolCommand(ObdProtocols.AUTO).run(mmInStream, mmOutStream);
                //ISO_15765_4_CAN

            } catch (Exception e) {
                Log.v("OBDcmds", "e");
                // handle errors
            }
        }

        /* Call this from the main activity to shutdown the connection */
        public void cancel() {
            try {
                connectionStatus = false;
                mmSocket.close();

                guiHandler(Constants.CONNECTION_STATUS, Constants.STATE_NOT_CONNECTED, "");
            } catch (IOException e) {
            }
        }
    }
}

.xml

<TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="178dp"
        android:text="Medium Text"
        android:textAppearance="?android:attr/textAppearanceMedium" />

主要 Activity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    Button b1;
    BluetoothAdapter mAdapter;
    BTHandler btHandler;

    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case Constants.MESSAGE_STATE_CHANGE:
                    switch (msg.arg1) {
                        case BTHandler.STATE_CONNECTED:
                            setContentView(R.layout.activity_connected);
                            Toast.makeText(getApplicationContext(), R.string.title_connected_to, Toast.LENGTH_SHORT).show();
                            Log.v("Log", "Connected");
                            break;
                        case BTHandler.STATE_NONE:
                            Toast.makeText(getApplicationContext(), R.string.title_not_connected, Toast.LENGTH_SHORT).show();
                            break;
                    }
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = (TextView) findViewById(R.id.textView);
        btHandler = new BTHandler(MainActivity.this, mHandler);
        b1 = (Button) findViewById(R.id.connect);
        b1.setOnClickListener(this);
        mAdapter = BluetoothAdapter.getDefaultAdapter();

        if (mAdapter == null) {
            Toast.makeText(getApplicationContext(), R.string.device_not_supported, Toast.LENGTH_LONG).show();
            finish();
        } else {
            if (!mAdapter.isEnabled()) {
                Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(intent, 1);
            }
        }
    }

    public void onClick(View v) {
        int id = v.getId();
        //String voltage = ("ATRV");

        switch (id) {
            case R.id.connect:
                onConnect(); //Operation
                Log.v("Log", "Pressed onClick");
                break;
            case R.id.getValue:
                btHandler.write(SPA.VOLTAGE);
                Log.v("getValue","" + SPA.VOLTAGE);
                break;

        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_CANCELED) {
            Toast.makeText(getApplicationContext(), R.string.enable_bluetooth, Toast.LENGTH_SHORT).show();
            finish();
        }
    }

    private void onConnect() {
        ArrayList deviceStrs = new ArrayList();
        final ArrayList<String> devices = new ArrayList();

        BluetoothAdapter mAdapter = BluetoothAdapter.getDefaultAdapter();
        Set pairedDevices = mAdapter.getBondedDevices();
        if (pairedDevices.size() > 0) {
            for (Object device : pairedDevices) {
                BluetoothDevice bdevice = (BluetoothDevice) device;
                deviceStrs.add(bdevice.getName() + "\n" + bdevice.getAddress());
                devices.add(bdevice.getAddress());
            }
        }

        // show list
        final AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);

        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.select_dialog_singlechoice,
                deviceStrs.toArray(new String[deviceStrs.size()]));

        alertDialog.setSingleChoiceItems(adapter, -1, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                int position = ((AlertDialog) dialog).getListView().getCheckedItemPosition();
                String deviceAddress = devices.get(position);

                btHandler.connect(deviceAddress);
            }
        });
        alertDialog.setTitle("Paired devices");
        alertDialog.show();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

您的对象扩展了 Thread所以我假设它会像这样开始

ConnectedThread ct = new ConnectedThread(socket);
ct.start();

在 Android 中您无法更新 View来自非 UI 线程。您需要创建一个 Handler并将数据传递给它。在你身上 Handler您可以调用 setText() 来实现更新您的方法 TextView .

查看此link有关与 UT 线程通信的更多详细信息。

更新帖子

我个人不喜欢改变 Activity 布局的想法在 Handler实现 - 我会选择 Fragment的用法。

无论如何，在调用setContentView(R.layout.activity_connected)之后在你的Handler您需要调用findViewById再次找到TextView在你的activity_connected布局:

case BTHandler.STATE_CONNECTED:
    setContentView(R.layout.activity_connected);
    Toast.makeText(getApplicationContext(), R.string.title_connected_to, Toast.LENGTH_SHORT).show();
    Log.v("Log", "Connected");
    TextView tv = (TextView)findViewById(R.id.textView);
    tv.setText("Connected");
    break;

代码 fragment 更新

ConnectedThread#run()

public void run() {
        OBDcmds();

        ModuleVoltageCommand voltageCommand = new ModuleVoltageCommand();
        //TextView textView = (TextView) findViewById(R.id.textView);

        while (!Thread.currentThread().isInterrupted()) {
            try {
                voltageCommand.run(mmInStream, mmOutStream);
                Log.d("Log", "Voltage:" + voltageCommand.getFormattedResult());
                guiHandler(Constants.VOLTAGE_STATUS, 0, voltageCommand.getFormattedResult())
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

处理程序实现私有(private)处理程序 mHandler = new Handler() { TextView textView = null;

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case Constants.MESSAGE_STATE_CHANGE:
                switch (msg.arg1) {
                    case BTHandler.STATE_CONNECTED:
                        setContentView(R.layout.activity_connected);
                        Toast.makeText(getApplicationContext(), R.string.title_connected_to, Toast.LENGTH_SHORT).show();
                        Log.v("Log", "Connected");
                        textView = (TextView)findViewById(R.id.textView);
                        break;
                    case BTHandler.STATE_NONE:
                        Toast.makeText(getApplicationContext(), R.string.title_not_connected, Toast.LENGTH_SHORT).show();
                        break;
                }
                break;
            case Constants.VOLTAGE_STATUS:
                if(msg.obj != null && textView != null){
                    textView.setText((String)msg.obj)
                }
                break;
        }
    }
};