如果在蓝牙扫描期间滚动，则出现 java.lang.IllegalStateException

Question

我正在尝试制作一个应用程序来扫描蓝牙设备。如果我在扫描过程中滚动，应用程序就会崩溃。否则，如果我将其保留为 scan_period，它就可以正常工作。

这是我的主要 Activity :

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter mBluetoothAdapter;
    private BluetoothLeScanner mBluetoothLeScanner;

    private boolean mScanning;

    private static final int ENABLE_BLUETOOTH = 1;
    private static final int ENABLE_LOCATION = 255;

    Button btnScan;
    ListView listViewLE;

    List<BluetoothDevice> listBluetoothDevice;
    ListAdapter adapterLeScanResult;

    private Handler mHandler;
    private static final long SCAN_PERIOD = 7500;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //check BLE supported on this device or not
        if(!getPackageManager().hasSystemFeature(getPackageManager().FEATURE_BLUETOOTH_LE)){
            Toast.makeText(this,"Bluetooth Low Energy is not supported.", Toast.LENGTH_SHORT).show();
            finish();
        }

        //get bluetooth adapter and le scanner
        btAdapterAndleScanner();

        //check if bluetooth is supported on this device
        if(mBluetoothAdapter == null){
            Toast.makeText(this, "Bluetooth is not supported.", Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        //check for location permission
        locationPermission();

        btnScan = (Button)findViewById(R.id.scan_button);
        btnScan.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                scanLeDevice(true);
                btnScan.setVisibility(View.GONE);
            }
        });

        listViewLE = (ListView)findViewById(R.id.device_list);

        listBluetoothDevice = new ArrayList<BluetoothDevice>();
        adapterLeScanResult = new ArrayAdapter<BluetoothDevice>(this,android.R.layout.simple_expandable_list_item_1, listBluetoothDevice);
        listViewLE.setAdapter(adapterLeScanResult);
        listViewLE.setOnItemClickListener(scanResultOnItemClickListener);

        mHandler = new Handler();

    }

    AdapterView.OnItemClickListener scanResultOnItemClickListener = new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            final BluetoothDevice device = (BluetoothDevice) parent.getItemAtPosition(position);

            //TODO: Add bondstate to check whether the device is bonded or not.
            String msg = "Address: " + device.getAddress() + "\n"  + "Type: " +  getBTDeviceType(device);

            new AlertDialog.Builder(MainActivity.this)
                    .setTitle("Name: " + device.getName())
                    .setMessage(msg)
                    .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {

                        }
                    })
                    .show();
        }
    };

    private String getBTDeviceType(BluetoothDevice d){
        String type = "";

        switch (d.getType()){
            case BluetoothDevice.DEVICE_TYPE_CLASSIC:
                type = "Classic";
                break;
            case BluetoothDevice.DEVICE_TYPE_DUAL:
                type = "Dual";
                break;
            case BluetoothDevice.DEVICE_TYPE_LE:
                type = "Low Energy";
                break;
            case BluetoothDevice.DEVICE_TYPE_UNKNOWN:
                type = "Unknown";
                break;
            default:
                type = "unknown...";
        }

        return type;
    }

    @Override
    protected void onResume(){
        super.onResume();

        //TODO: use if condition twice to check how it differes from using it from the first time.
            if (!mBluetoothAdapter.isEnabled()) {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, ENABLE_BLUETOOTH);
            }

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data){

        if(requestCode == ENABLE_BLUETOOTH && resultCode == Activity.RESULT_CANCELED){
            finish();
            return;
        }

        //TODO: get bluetooth adapter and lescan function to see what happens. go without it first.

        //TODO: check bluetooth supported or not. no idea why!!!

        super.onActivityResult(requestCode, resultCode, data);
    }

    private void btAdapterAndleScanner(){
        final BluetoothManager mBluetoothManager = (BluetoothManager)getSystemService(Context.BLUETOOTH_SERVICE);

        mBluetoothAdapter = mBluetoothManager.getAdapter();
        mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

        mScanning = false;
    }

    private void scanLeDevice(final boolean enable){
        if (enable){
            listBluetoothDevice.clear();
            listViewLE.invalidateViews();

            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mBluetoothLeScanner.stopScan(scanCallback);
                    listViewLE.invalidateViews();

                    Toast.makeText(MainActivity.this, "Scan timeout", Toast.LENGTH_SHORT).show();

                    mScanning = false;
                    btnScan.setEnabled(true);
                }
            },SCAN_PERIOD);

            mBluetoothLeScanner.startScan(scanCallback);
            mScanning = true;
            btnScan.setEnabled(false);
        } else {
            mBluetoothLeScanner.stopScan(scanCallback);
            mScanning = false;
            btnScan.setEnabled(true);
        }
    }

    private ScanCallback scanCallback = new ScanCallback() {
        @Override
        public void onScanResult(int callbackType, ScanResult result) {
            super.onScanResult(callbackType, result);
            addBluetoothDevice(result.getDevice());

        }

        @Override
        public void onBatchScanResults(List<ScanResult> results) {
            super.onBatchScanResults(results);
            for (ScanResult result : results){
                addBluetoothDevice(result.getDevice());
            }
        }

        @Override
        public void onScanFailed(int errorCode) {
            super.onScanFailed(errorCode);
            Toast.makeText(MainActivity.this, "onScanFailed: " + String.valueOf(errorCode),Toast.LENGTH_LONG).show();
        }
        private void addBluetoothDevice(BluetoothDevice device){
            if(!listBluetoothDevice.contains(device)){
                listBluetoothDevice.add(device);
                listViewLE.invalidateViews();
            }
        }
    };

    @TargetApi(23)
    private void locationPermission() {
        if (ContextCompat.checkSelfPermission(this, ACCESS_COARSE_LOCATION) != PERMISSION_GRANTED) {
            requestPermissions(new String[]{ACCESS_COARSE_LOCATION}, ENABLE_LOCATION);
        }
    }

}

这是我的 xml 文件:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/device_list"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Scan"
        android:id="@+id/scan_button"
        android:layout_alignParentBottom="true"/>


</RelativeLayout>

这是日志猫:

2019-09-30 15:38:29.036 2786-2786/com.example.v_daq_re E/InputEventReceiver: Exception dispatching input event.
2019-09-30 15:38:29.037 2786-2786/com.example.v_daq_re E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
2019-09-30 15:38:29.043 2786-2786/com.example.v_daq_re E/MessageQueue-JNI: java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. Make sure your adapter calls notifyDataSetChanged() when its content changes. [in ListView(2131230812, class android.widget.ListView) with Adapter(class android.widget.ArrayAdapter)]
        at android.widget.ListView.layoutChildren(ListView.java:1810)
        at android.widget.AbsListView.onTouchMove(AbsListView.java:6514)
        at android.widget.AbsListView.onTouchEvent(AbsListView.java:6368)
        at android.widget.ListView.onTouchEvent(ListView.java:1705)
        at android.view.View.dispatchTouchEvent(View.java:13484)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3216)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2888)
        at android.widget.AbsListView.dispatchTouchEvent(AbsListView.java:6285)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:697)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1879)
        at android.app.Activity.dispatchTouchEvent(Activity.java:3487)
        at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
        at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:655)
        at android.view.View.dispatchPointerEvent(View.java:13732)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6119)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5897)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5399)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5365)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5524)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5373)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5581)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5399)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5365)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5373)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8408)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8341)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:8294)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8523)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:198)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:326)
        at android.os.Looper.loop(Looper.java:181)
        at android.app.ActivityThread.main(ActivityThread.java:7037)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494
2019-09-30 15:38:29.043 2786-2786/com.example.v_daq_re D/AndroidRuntime: Shutting down VM
2019-09-30 15:38:29.045 2786-2786/com.example.v_daq_re E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.v_daq_re, PID: 2786
    java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. Make sure your adapter calls notifyDataSetChanged() when its content changes. [in ListView(2131230812, class android.widget.ListView) with Adapter(class android.widget.ArrayAdapter)]
        at android.widget.ListView.layoutChildren(ListView.java:1810)
        at android.widget.AbsListView.onTouchMove(AbsListView.java:6514)
        at android.widget.AbsListView.onTouchEvent(AbsListView.java:6368)
        at android.widget.ListView.onTouchEvent(ListView.java:1705)
        at android.view.View.dispatchTouchEvent(View.java:13484)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3216)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2888)
        at android.widget.AbsListView.dispatchTouchEvent(AbsListView.java:6285)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3222)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2904)
        at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:697)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1879)
        at android.app.Activity.dispatchTouchEvent(Activity.java:3487)
        at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
        at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:655)
        at android.view.View.dispatchPointerEvent(View.java:13732)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6119)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5897)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5399)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5365)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5524)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5373)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5581)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5399)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5365)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5373)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5346)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8408)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8341)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:8294)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8523)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:198)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:326)
        at android.os.Looper.loop(Looper.java:181)
        at android.app.ActivityThread.main(ActivityThread.java:7037)
2019-09-30 15:38:29.045 2786-2786/com.example.v_daq_re E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)

应用程序本身运行良好。唯一的问题是当我在扫描过程中向下滚动时。如果有人能找出问题并让我知道如何解决它，那将会很有帮助。谢谢!!!

Answer 1

The content of the adapter has changed but ListView did not receive a notification.

Make sure the content of your adapter is not modified from a background thread, but only from the UI thread.

Make sure your adapter calls notifyDataSetChanged() when its content changes.

编辑:正如 @Codo 评论的那样，在这种情况下，只有 notifyDataSetChanged() 没有被调用。

修改listBluetoothDevice后在适配器上调用notifyDataSetChanged()

如果从另一个线程更改listBluetoothDevice。用 runOnUiThread 包装它并调用 notifyDataSetChanged()

runOnUiThread(new Runnable() {
        @Override
        public void run() {
            //...
        }
    });