Question

在为第二个广播组注册第二个侦听器时出现问题。
XML：

 <RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="124dp"
    android:layout_height="123dp"
    android:layout_marginTop="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.014">

    <RadioButton
        android:id="@+id/WhiteLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/whiteLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/BlueLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/blueLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/RedLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/redLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/InfraredLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/irLed"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/OffLight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:checked="true"
        android:text="@string/offLed"
        android:textColor="@color/colorWhite" />
</RadioGroup>

<SeekBar
    android:id="@+id/seekBar5"
    style="@style/Widget.AppCompat.SeekBar.Discrete"
    android:layout_width="258dp"
    android:layout_height="67dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="56dp"
    android:layout_marginEnd="8dp"
    android:max="20"
    android:progress="0"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toEndOf="@+id/radioGroup"
    app:layout_constraintTop_toTopOf="parent" />

<RadioGroup
    android:layout_width="210dp"
    android:layout_height="120dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginBottom="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.043"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/seekBar5"
    app:layout_constraintVertical_bias="0.112">

    <RadioButton
        android:id="@+id/HDMI1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:checked="true"
        android:text="@string/Camera1"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera2"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera3"
        android:textColor="@color/colorWhite" />

    <RadioButton
        android:id="@+id/HDMI4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/Camera4"
        android:textColor="@color/colorWhite" />
</RadioGroup>

Java（从onCreate（）复制）：

    final RadioGroup LEDGroup = findViewById(R.id.radioGroup);
    final SeekBar LEDIntensity = findViewById((R.id.seekBar5));
    final RadioGroup CameraGroup = findViewById((R.id.cameraGroup)) ;

    LEDGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected
            //LEDIntensity.setProgress (2);
            Toast.makeText(MainActivity.this, "This is LED select",
                    Toast.LENGTH_LONG).show();
            //send selected LED to USB port where checkedId is teh selected LED
        }
    });

    CameraGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener(){
        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected
            Toast.makeText(MainActivity.this, "This is Camera select",
                    Toast.LENGTH_LONG).show();
            //send selected camera to USB port where checkId is the selected camera
        }
    });

当我开始调试代码时，在CamerGroup.setOnCheckedChangeListener行上收到NullPointerException。当我注释掉那部分代码时，我的应用程序正确启动。实际上是否可以有两个单独的onCheckedChanged注册，还是我必须创建一个侦听器并弄清楚哪个RadioGroup在侦听器本身中调用该侦听器。
我所有的搜索都显示了仅使用一个RadioGroup的示例，而且我似乎想不起我曾经使用过的任何应用程序一次具有多个RadioGroup。

Answer 1

为您的第二个广播组提供此ID：

android:id="@+id/cameraGroup"

您忘记了。

所以这行：

final RadioGroup CameraGroup = findViewById((R.id.cameraGroup)) ;

由于找不到cameraGroup，使得CameraGroup null
而CameraGroup.setOnCheckedChangeListener()则抛出NPE。

是的，您可以拥有与广播组一样多的听众。

为2个单独的RadioGroup注册OnCheckedChangeListeners

1 个答案: