当我在手机上启动应用程序时，我的列表视图未显示

Question

我正在做一个 Android 蓝牙应用程序来连接到我的 hc-05 蓝牙模块，并最终控制我制作的遥控船。当我在手机上启动应用程序时，我遇到了一个问题，列表视图没有显示。（我正在 android studio 上做这个项目）

这是我在activity_main.xml 文件中的代码

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

    <LinearLayout
        android:id="@+id/topLinearLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:gravity="center_vertical"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent">

        <TextView
            android:id="@+id/textView"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Select A Pairing Device"
            android:textColor="#0033FF"
            android:textSize="16sp" />

        <Button
            android:id="@+id/button"
            style="@style/Widget.AppCompat.Button.Colored"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Pair" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        >

        <ListView
            android:id="@+id/listView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="150dp"
            android:footerDividersEnabled="false"
            tools:layout_editor_absoluteX="8dp"
            tools:layout_editor_absoluteY="8dp" />
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

这是 MainActivity 中的代码（当然还有更多内容，但这是我专门针对列表视图的代码

private void pairedDevicesList() {
        // Check if the app has the necessary permissions
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH) != PackageManager.PERMISSION_GRANTED) {
            // Permission not granted, request it
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.BLUETOOTH},
                    REQUEST_BLUETOOTH_PERMISSION);
            return; // Exit the method early, permission request is pending
        }

        // Permission is granted, proceed with listing paired devices
        Set<BluetoothDevice> pairedDevices = myBluetooth.getBondedDevices();
        ArrayList<String> list = new ArrayList<>();

        if (pairedDevices.size() > 0) {
            for (BluetoothDevice bt : pairedDevices) {
                list.add(bt.getName());
            }
        } else {
            Toast.makeText(getApplicationContext(), "No Paired Bluetooth Devices Found.", Toast.LENGTH_LONG).show();
        }
        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, list);
        devicelist.setAdapter(adapter);
        devicelist.setOnItemClickListener(myListClickListener);
    }

    private final AdapterView.OnItemClickListener myListClickListener = (parent, view, position, id) -> {
        String info = ((TextView) view).getText().toString();
        String address = info.substring(info.length()-17);

        Intent i = new Intent(MainActivity.this, BoatControl.class);
        i.putExtra(EXTRA_ADDRESS, address);
        startActivity(i);
    };

我调用onCreate()中的方法

btnPaired.setOnClickListener(v -> pairedDevicesList());

Answer 1

请保持您的代码完整。 尝试改变你的布局：

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

    <LinearLayout
        android:id="@+id/topLinearLayout"
        android:layout_width="match_parent"
        android:layout_height="?actionBarSize"
        android:orientation="horizontal"
        android:gravity="center_vertical"
        android:padding="8dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent">

        <TextView
            style="@style/TextAppearance.AppCompat.Title"
            android:id="@+id/textView"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Select A Pairing Device"
            android:textColor="#0033FF" />

        <Button
            android:id="@+id/button"
            style="@style/Widget.AppCompat.Button.Colored"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Pair" />
    </LinearLayout>

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

</LinearLayout>