使用 Navigation 访问 onClick 形成 Android 片段

Question

我无法在片段中为我的按钮设置 onClick 侦听器。可能是上下文错了，但是我看不到。

请在下方提供帮助我认为我正在做所有事情好吗？我虽然理解上下文的工作原理，但在我看来，今天有用的东西明天就不行了？

片段xml:

    <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout 
    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:background="@color/colorPrimary"
    tools:context=".OBWelcomeFragment">

    <ImageView
        android:id="@+id/imageView3"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:src="@drawable/logo_main"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.08" />

    <ScrollView
        android:id="@+id/scrollView3"
        android:layout_width="324dp"
        android:layout_height="333dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.494"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView3"
        app:layout_constraintVertical_bias="0.594">

        <TextView
            android:id="@+id/tv_description_heading"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="@string/ob_welcome_text"
            android:textColor="@color/cardview_light_background"
            android:textSize="18sp" />

    </ScrollView>

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="@string/app"
        android:textColor="@color/cardview_light_background"
        android:textSize="36sp"
        app:layout_constraintBottom_toTopOf="@+id/scrollView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView3"
        app:layout_constraintVertical_bias="0.18" />

    <Button
        android:id="@+id/oBlocationButton"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginLeft="32dp"
        android:layout_marginEnd="32dp"
        android:layout_marginRight="32dp"
        android:layout_marginBottom="32dp"
        android:onClick="onClick"
        android:text="Next"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/scrollView2" />
    </androidx.constraintlayout.widget.ConstraintLayout>

对应片段

    import android.os.Bundle;

    import androidx.appcompat.app.AppCompatActivity;
    import androidx.fragment.app.Fragment;
    import androidx.fragment.app.FragmentActivity;
    import androidx.navigation.NavDirections;
    import androidx.navigation.Navigation;

    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;


    public class OBWelcomeFragment extends Fragment implements View.OnClickListener {

    public OBWelcomeFragment() {
        // Required empty public constructor
    }

    public static OBWelcomeFragment newInstance(String param1, String param2) {
    OBWelcomeFragment fragment = new OBWelcomeFragment();
    return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_o_b_welcome, container, false);
    }

    @Override
    public void onClick(View v) {

        NavDirections action = 
    OBWelcomeFragmentDirections.actionOBWelcomeFragmentToOBLocationFragment3();
        Navigation.findNavController(v).navigate(action);

    }
    }

错误

    2020-02-27 12:43:50.375 15523-15523/com.app E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.app, PID: 15523
    java.lang.IllegalStateException: Could not find method onClick(View) in a parent or ancestor 
    Context for android:onClick attribute defined on view class 
    androidx.appcompat.widget.AppCompatButton with id 'oBlocationButton'
        at 
androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatView 
    Inflater.java:436)
        at 
androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflat .er.java:393)
        at android.view.View.performClick(View.java:7259)
        at android.view.View.performClickInternal(View.java:7236)
        at android.view.View.access00(View.java:801)
        at android.view.View$PerformClick.run(View.java:27892)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

如果您还需要什么，请告诉我？

Answer 1

问题是您正在执行这两项操作（虽然两者都不完整...），实施 OnClickListener 并在 xml 中定义了一个方法。做其中任何一项。

我会指定这两个，如果只在 xml 中执行，你必须在 xml 中指定你的 onClick() 方法，而不是

<Button
    android:id="@+id/oBlocationButton"
    ....
    android:onClick="onClick"/>

在您的片段中只需创建此方法：（不要实现侦听器）

public class OBWelcomeFragment extends Fragment {

    ....

    // notice -> no override here..
    public void onClick(View v) {


    }
}

或者反过来：这次不在xml中指定onClick，而是找到按钮并设置监听器。

public class OBWelcomeFragment extends Fragment implements View.OnClickListener {

    .....

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Button btn = view.findViewById(R.id.oBlocationButton);
        btn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        NavDirections action = OBWelcomeFragmentDirections.actionOBWelcomeFragmentToOBLocationFragment3();
        Navigation.findNavController(v).navigate(action);
    }
}

使用 Navigation 访问 onClick 形成 Android 片段

Accessing onClick form an Android fragment using Navigation

android

android-fragments

android-navigation