Frage

I am new to android and java program.

I am try to write a program to remotely control switches via Android HP bluetooth.

Everything are fine only my scan for bluetooth function/activity do get random force quit. I am not sure what happen/wrong with my code hence I hope someone can help/advice me accordingly. Below are the logcat file I extract out.

08-08 17:23:40.035: D/getView(1876): WindowsCE
08-08 17:23:40.035: D/getView(1876): WindowsCE
08-08 17:23:42.949: E/BluetoothEventLoop.cpp(107): event_filter: Received signal org.bluez.Adapter:DeviceFound from /org/bluez/1610/hci0
08-08 17:23:42.953: D/BluetoothService(107): updateDeviceServiceChannelCache(00:15:A0:6B:BB:1B)
08-08 17:23:42.980: V/BluetoothEventRedirector(450): Received android.bluetooth.device.action.FOUND
08-08 17:23:42.988: D/getView(1876): WindowsCE
08-08 17:23:42.988: D/AndroidRuntime(1876): Shutting down VM
08-08 17:23:42.988: W/dalvikvm(1876): threadid=1: thread exiting with uncaught exception (group=0x40015560)
08-08 17:23:42.992: E/AndroidRuntime(1876): FATAL EXCEPTION: main
08-08 17:23:42.992: E/AndroidRuntime(1876): java.lang.NullPointerException: println needs a message
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.util.Log.println_native(Native Method)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.util.Log.d(Log.java:137)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at com.android.ui.single.ScanDeviceList.getView(ScanDeviceList.java:61)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.AbsListView.obtainView(AbsListView.java:1409)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1216)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.ListView.onMeasure(ListView.java:1127)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.View.measure(View.java:8313)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.View.measure(View.java:8313)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.View.measure(View.java:8313)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.View.measure(View.java:8313)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.View.measure(View.java:8313)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.ViewRoot.performTraversals(ViewRoot.java:839)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.os.Looper.loop(Looper.java:123)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at java.lang.reflect.Method.invokeNative(Native Method)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at java.lang.reflect.Method.invoke(Method.java:507)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at dalvik.system.NativeStart.main(Native Method)
08-08 17:23:42.999: W/ActivityManager(107):   Force finishing activity com.android/.DogActivity
08-08 17:23:43.499: W/ActivityManager(107): Activity pause timeout for HistoryRecord{408014c0 com.android/.DogActivity}


08-09 21:32:27.968: D/SurfaceFlinger(107): About to give-up screen, flinger = 0x11df90
08-09 21:41:54.546: D/SntpClient(107): request time failed: java.net.UnknownHostException: north-america.pool.ntp.org
08-09 21:41:54.554: D/SntpClient(107): request time failed: java.net.UnknownHostException: north-america.pool.ntp.org
08-09 21:41:54.554: D/SntpClient(107): request time failed: java.net.UnknownHostException: north-america.pool.ntp.org
08-09 21:41:54.617: D/skia(107): purging 201K from font cache [12 entries]

Below are my DogActivity code

package com.android;

import java.io.FileOutputStream;

import com.android.backend.data.bluetooth.BluetoothManager;
import com.android.ui.UIManager;
import com.android.ui.single.ScanDeviceList;

import android.app.Activity;
import android.app.Dialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.text.Editable;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;

public class DogActivity extends Activity {

    public BroadcastReceiver mRvc = new BroadcastReceiver(){ // The new is instantiate the class **always read from the back
                                                             // The line from the back is creating an instantiate of this class         
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                // Get the BluetoothDevice object from the Intent
                BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                // If it's already paired, skip it, because it's been listed
                // already

                // Bluetooth Manager Update

                BluetoothManager.getInstance().addDiscovered_Devices(device);
                // UI Manager Update

                UI_discovered_Devices.add(device);

            }
            if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
                uiMgr.hideScanningProgressBox();
            }
        }
    };

    public ScanDeviceList UI_discovered_Devices;
    public UIManager uiMgr = new UIManager();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.overallscanentrylayout);
        uiMgr.owner = this;
        final DogActivity tt = this;

        // set your list view
        UI_discovered_Devices = new ScanDeviceList(this,R.layout.overallscanitemlayout);
        UI_discovered_Devices.set_view(R.id.toptexto1, R.id.bottomtexto1);
        ListView discoverListView = (ListView) findViewById(R.id.clistView1);
        UI_discovered_Devices.clear(); ///////////// Testing to solve memory issue
        discoverListView.setAdapter(UI_discovered_Devices);

        discoverListView
                .setOnItemLongClickListener(new OnItemLongClickListener() {

                    @Override
                    public boolean onItemLongClick(AdapterView<?> parent,
                            View view, int position, long id) {
                        // getItem = retrieving item from UI_discovered_Devices
                        // Arraylist
                        final BluetoothDevice getItem = UI_discovered_Devices
                                .getItem((int) id);

                        final Dialog dialog_createPL = new Dialog(tt);
                        dialog_createPL.setContentView(R.layout.catdogname);

                        Button okButt = (Button) dialog_createPL
                                .findViewById(R.id.catdogok);
                        okButt.setOnClickListener(new OnClickListener() {

                            @Override
                            public void onClick(View v) {
                                EditText edit1 = (EditText) dialog_createPL
                                        .findViewById(R.id.catdogtext1);
                                Editable ret = edit1.getText();
                                String ls = ret.toString();

                                // Start activity
                                startActivity(new Intent(tt,
                                        ManualActivity.class));

                                // Write message to text
                                String msg = ls + "," + getItem.getName() + ","
                                        + getItem.getAddress();
                                writeDataToMem(msg);
                            }
                        });

                        Button cancelButt = (Button) dialog_createPL
                                .findViewById(R.id.catdogcancel);
                        cancelButt.setOnClickListener(new OnClickListener() {

                            @Override
                            public void onClick(View v) {
                                dialog_createPL.cancel();
                            }
                        });

                        dialog_createPL.setTitle("Enter Name for Bluetooth Device");
                        dialog_createPL.show();

                        return false;
                    }
                });
        discoverListView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {

                final BluetoothDevice getItem = UI_discovered_Devices
                        .getItem((int) id);


                final Dialog dialog_createPL = new Dialog(tt);
                dialog_createPL.setContentView(R.layout.catdogname);

                Button okButt = (Button) dialog_createPL
                        .findViewById(R.id.catdogok);
                okButt.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        EditText edit1 = (EditText) dialog_createPL
                                .findViewById(R.id.catdogtext1);
                        Editable ret = edit1.getText();
                        String ls = ret.toString();

                        // Start activity
                        startActivity(new Intent(tt,
                                ManualActivity.class));

                        // Write message to text
                        String msg = ls + "," + getItem.getName() + ","
                                + getItem.getAddress();
                        writeDataToMem(msg);
                    }
                });

                Button cancelButt = (Button) dialog_createPL
                        .findViewById(R.id.catdogcancel);
                cancelButt.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        dialog_createPL.cancel();
                    }
                });

                dialog_createPL.setTitle("Enter Name for Bluetooth Device");
                dialog_createPL.show();
            }
        });


        // Register for broadcasts when a device is discovered
        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);  // IntentFilter class is important to declare for below filter
        registerReceiver(mRvc,filter); //mRvc is the location of logic, filter is message identify by android


        // Register for broadcasts when discovery has finished
        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED); //Must make sure the IntentFilter is declare
        registerReceiver(mRvc,filter); //mRvc is the location of logic, filter message indetiy by android


        // // Logic
        BluetoothManager.getInstance().doDiscovery();

        uiMgr.showScanningProgressBox();
        // uiMgr.clearUIDiscovered_Devices();
    }

    public void writeDataToMem(String msg) {
        // Write playlist to database
        FileOutputStream fos;
        try {
            fos = this.openFileOutput("bone.txt", Context.MODE_PRIVATE);
            fos.write(msg.getBytes());

            Log.d("bone.txt", msg);
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            msg = msg +"\n";
            fos = this.openFileOutput("fish.txt", Context.MODE_APPEND);
            fos.write(msg.getBytes());

            Log.d("fish.txt", msg);
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    protected void onResume() { //restart bluetooth is accidently off it
        super.onResume();
        // The activity has become visible (it is now "resumed").
        BluetoothManager.getInstance().init();
        BluetoothManager.getInstance().getBluetoothAdapter().enable();

        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); // IntentFilter class is important to declare for below filter
        registerReceiver(mRvc,filter); // mRvc is the location of logic, filter is message identify by android

        filter = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED); //Must make sure the IntentFilter is declare
        registerReceiver(mRvc,filter); 
    }


    protected void onPause() {  // Clear all mac address **is a trial for memory leak
        super.onPause();
        BluetoothManager.getInstance().ccDiscovery();
        BluetoothManager.getInstance().clearDiscoveredDevices();
        uiMgr.hideScanningProgressBox();
        unregisterReceiver(mRvc);
    }

}

Below are my ScanDeviceList code

package com.android.ui.single;

//import java.util.ArrayList;

import java.util.Set;

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
//import android.widget.CompoundButton;
//import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.TextView;
//import android.widget.ToggleButton;

//import com.android.R;
//import com.android.ScanListActivity;
//import com.android.backend.data.bluetooth.BluetoothManager;

public class ScanDeviceList extends ArrayAdapter<BluetoothDevice> {
    Context context;
    int layoutResourceID;
    int topViewID;
    int bottomViewID;

    public ScanDeviceList(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
        this.context = context;
        layoutResourceID = textViewResourceId;
    }

//  public ScanDeviceList(Context context, int textViewResourceId, ArrayList<BluetoothDevice> items) {
//      super(context, textViewResourceId, items);
//      this.context = context;
//      layoutResourceID = textViewResourceId;
//  }

    public void set_view(int passtopView, int passBottomView){
        topViewID = passtopView;
        bottomViewID = passBottomView;
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null) {
            LayoutInflater vi = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(layoutResourceID, null);
        }

        TextView topView = (TextView) v.findViewById(topViewID);
        TextView bottomView = (TextView) v.findViewById(bottomViewID);

        final BluetoothDevice o = this.getItem(position);

        // Get the local Bluetooth adapter
        BluetoothAdapter mBtAdapter = BluetoothAdapter.getDefaultAdapter();

        // Get a set of currently paired devices
        Set<BluetoothDevice> pairedDevices = mBtAdapter.getBondedDevices();

        //if (o != null) 
        if (pairedDevices.size() > 0) 
        {

            if (topView != null) {
                topView.setText("Name: " + o.getName());
                Log.d("getView", o.getName());
            }

            if (bottomView != null) {
                String msg = "MAC: " + o.getAddress();
                if(o.getBondState() == BluetoothDevice.BOND_BONDED)
                    {msg = msg + "/" + "Paired";}
                else
                    {msg = msg + "/" + "Not Paired";}

                bottomView.setText(msg);
            }
        }
        return (v);
        }

}

Hope someone can advice me what are my mistake. Thank You

War es hilfreich?

Lösung

This line from your ScanDeviceList.java

if (topView != null) {
   topView.setText("Name: " + o.getName());
   Log.d("getView", o.getName());
}

o.getName() is null based on this line in your logcat:

08-08 17:23:42.992: E/AndroidRuntime(1876): FATAL EXCEPTION: main
08-08 17:23:42.992: E/AndroidRuntime(1876): java.lang.NullPointerException: println needs a message
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.util.Log.println_native(Native Method)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at android.util.Log.d(Log.java:137)
08-08 17:23:42.992: E/AndroidRuntime(1876):     at com.android.ui.single.ScanDeviceList.getView(ScanDeviceList.java:61)

The last line in the snippet of the logcat as shown above is your point where it crashes.

Solution:

if (topView != null) {
   if (o != null && o.getName() != null){
      topView.setText("Name: " + o.getName());
      Log.d("getView", o.getName());
   }else topView.setText("Name: !UNKNOWN!");
}

You will know if the UI control topView has the string "!UNKNOWN!" in there - its because the o.getName() is null.

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