Question

我正在尝试构建一个扫描蓝牙设备的应用程序，并在recyclerview中显示它们。我正在使用java和kotlin中的一些应用程序编写一些应用程序。由于某种原因，我的recyclerview项目不可见。有人请帮助我找出我正在犯的错误。我发布了我的活动代码以及我的回收者视图。澄清我的问题。发现成功，找到设备，并且似乎调用了我的适配器中的所有继承方法。我在其中放置了日志消息，我仍然在recyclerview中看不到任何内容。为什么没有出现？这是我用java编写的活动：

public class ToofActivity extends AppCompatActivity implements CompoundButton.OnCheckedChangeListener {

private static final String TAG = "ToofActivity";
private static final int REQUEST_COARSE_LOCATION = 222;

private static BluetoothAdapter btAdapter;

private TextView mStatusLabel;
private Switch mStatusSwitch;
private ProgressBar mProgressBar;
private RecyclerView mDeviceRecylcer;
private static ArrayList<BluetoothDevice> mDevices = new ArrayList<>();
private DeviceAdapter mAdapter;

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

    checkLocationPermission();

    btAdapter = BluetoothAdapter.getDefaultAdapter();

    mStatusLabel = (TextView) findViewById(R.id.status_view);
    mStatusLabel.setText(btAdapter.isEnabled() ? "Active" : "Inactive");
    mStatusSwitch = (Switch) findViewById(R.id.status_switch);
    mStatusSwitch.setChecked(btAdapter.isEnabled());
    mStatusSwitch.setOnCheckedChangeListener(this);
    mProgressBar = (ProgressBar) findViewById(R.id.search_progress_bar);
    mDeviceRecylcer = (RecyclerView) findViewById(R.id.device_recycler);

    mDeviceRecylcer.setLayoutManager(new LinearLayoutManager(this));
    mAdapter = new DeviceAdapter(getApplicationContext());
    mDeviceRecylcer.setAdapter(mAdapter);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.options_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case R.id.searchOption:
            DiscoveryTask discovery = new DiscoveryTask(btAdapter, this, mProgressBar);
            discovery.setOnCompleteListener(new DiscoveryTask.OnCompletedListener() {
                @Override
                public void onComplete() {
                    mAdapter.updateItems(mDevices);
                }
            });
            discovery.execute((Void) null);
            break;
    }

    return true;
}

@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
    if (isChecked) {
        btAdapter.enable();
        mStatusLabel.setText("Active");
    } else {
        btAdapter.disable();
        mStatusLabel.setText("Inactive");
    }
}

public static void setDeviceList(ArrayList<BluetoothDevice> deviceList) {
    mDevices.clear();
    mDevices = deviceList;
}

protected void checkLocationPermission() {
    if (this.checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION)
            != PackageManager.PERMISSION_GRANTED) {

        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
                REQUEST_COARSE_LOCATION);
    }
}

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case REQUEST_COARSE_LOCATION: {
            if (grantResults.length <= 0
                    || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                checkLocationPermission();
                break;
            }
        }
    }
}
}

这是我用kotlin编写的recyclerview的代码：

class DeviceAdapter(val mContext : Context) : RecyclerView.Adapter<DeviceAdapter.DeviceHolder>(){

val mDevices = ArrayList<BluetoothDevice>()

fun updateItems(list: ArrayList<BluetoothDevice>){
    mDevices.clear()
    mDevices.addAll(list)
    Log.d(TAG, "updating items : $mDevices")
    notifyDataSetChanged()
}

override fun onBindViewHolder(holder: DeviceHolder, position: Int) {
    Log.d(TAG, "onBindViewHolder called!")
    holder.bindItems(mDevices.get(position))
}

override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): DeviceHolder{
    Log.d(TAG, "onCreateViewHolder called!")
    val v = LayoutInflater.from(mContext).inflate(R.layout.device_item, parent, false)
    return DeviceHolder(v)
}

override fun getItemCount(): Int {
    return mDevices.size
}

inner class DeviceHolder(itemView: View) : RecyclerView.ViewHolder(itemView){

        val nameView = itemView.findViewById(R.id.nameView) as TextView
        val addrView = itemView.findViewById(R.id.addressView) as TextView

    fun bindItems(btDevice: BluetoothDevice){
        Log.d(TAG, "holder created!")
        nameView.text = btDevice.name
        addrView.text = btDevice.address
    }
}

companion object {
    val TAG = "DeviceAdapter"
}

}

谢谢你的帮助。

Answer 1

您可以删除承包商适配器中的上下文，并且可以使用适配器 val v = LayoutInflater.from(mContext).inflate(R.layout.device_item, parent, false)中的上下文替换为 val v = LayoutInflater.from(parent.context).inflate(R.layout.device_item, parent, false)的这一行，或者如果您希望适配器中的上下文作为参数替换此语句，

 mAdapter = new DeviceAdapter(getApplicationContext());

到 mAdapter = new DeviceAdapter(this);

Answer 2

这里的问题是我正在使用的上下文。我的上下文是getApplicationContext()返回的不正确的上下文。现在我已将其更改为仅使用this。一旦进行了更改，所有查看者项目都可见。

android java / kotlin recyclerview项目不可见

2 个答案: