java - 在弹出对话框中显示配对蓝牙设备列表 - setAdapter 空指针异常

Question

我正在尝试创建一个简单的应用程序，当单击操作栏中的“连接”项时，它会在对话框中显示已配对蓝牙设备的列表。这是我正在膨胀的对话框的 XML:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/bt_list"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ListView
        android:id="@+id/BTList"
        android:layout_width="fill_parent"
        android:layout_height="200dp" >

    </ListView>

</LinearLayout>

这是 MainActivity.java 的相关部分:

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

    TextView statusText = (TextView) findViewById(R.id.textDeviceID);

    myBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

    if (myBluetoothAdapter == null) {
        statusText.setText("Bluetooth not supported on this phone");
    }
    else {
        statusText.setText("Waiting to connect");
    }
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {

    super.onOptionsItemSelected(item);

    if(item.getItemId()==R.id.connect) {
        if (!myBluetoothAdapter.isEnabled()) {
            Intent turnOnIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(turnOnIntent, REQUEST_ENABLE_BT);
        }

        showBTDialog();
    }

    else if(item.getItemId()==R.id.action_settings) {
        // TODO
    }

    return true;
}

public void showBTDialog() {

    final AlertDialog.Builder popDialog = new AlertDialog.Builder(this);
    final LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
    final View Viewlayout = inflater.inflate(R.layout.bt_list, (ViewGroup) findViewById(R.id.bt_list));

    popDialog.setTitle("Paired Bluetooth Devices");
    popDialog.setView(Viewlayout);

    // create the arrayAdapter that contains the BTDevices, and set it to a ListView
    myListView = (ListView) findViewById(R.id.BTList);
    BTArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
    myListView.setAdapter(BTArrayAdapter);

    // get paired devices
    pairedDevices = myBluetoothAdapter.getBondedDevices();

    // put it's one to the adapter
    for(BluetoothDevice device : pairedDevices)
        BTArrayAdapter.add(device.getName()+ "\n" + device.getAddress());

    // Button OK
    popDialog.setPositiveButton("Pair",
            new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }

            });

    // Create popup and show
    popDialog.create();
    popDialog.show();

}

但是当我在手机上运行它时，应用程序崩溃并且堆栈跟踪在以下位置显示空指针异常:

myListView.setAdapter(BTArrayAdapter);

当我注释掉上面的行时，“连接”按钮会显示一个空白对话框弹出窗口。我认为崩溃与“BTList”不在当前 View 的上下文中有关，但我不确定如何解决它。

感谢您的帮助。

Answer 1

您必须像这样从 showBTDialog 中的膨胀布局 ViewLayout 获取 ListView:

myListView = (ListView) ViewLayout.findViewById(R.id.BTList);

或者这不是你想要做的吗？