Question

我创建了一个包含3页的viewpager。目前其中一个有一个按钮，但是当我尝试向按钮添加一个按钮监听器时，应用程序崩溃但调试没有报告任何错误。除了断开连接到虚拟机。最初视图被夸大了，听众在案例陈述中添加了内容，但这也没有用。

如果Android有问题，控制台不应该说些什么吗？

片段及其行为如下应用程序在setOnClickListener上崩溃。有任何想法吗？谢谢

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity$PlaceholderFragment">

    <TextView
        android:id="@+id/section_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/activity_vertical_margin"
        android:layout_marginEnd="@dimen/activity_horizontal_margin"
        android:layout_marginStart="@dimen/activity_horizontal_margin"
        android:layout_marginTop="@dimen/activity_vertical_margin"
        android:text="@string/app_name"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="@+id/constraintLayout"
        tools:layout_constraintLeft_creator="1"
        tools:layout_constraintTop_creator="1" />

    <android.support.v7.widget.AppCompatCheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/activity_vertical_margin"
        android:layout_marginEnd="@dimen/activity_horizontal_margin"
        android:layout_marginStart="@dimen/activity_horizontal_margin"
        android:layout_marginTop="@dimen/activity_vertical_margin"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageButton
        android:id="@+id/imageButton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@android:drawable/ic_media_play"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintVertical_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {

            View rootView;
            View mainView = inflater.inflate(R.layout.fragment_main, container, false);
            button= (Button) getActivity().findViewById(R.id.imageButton2);
            button.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // Code here executes on main thread after user presses button
                    TextView textView = (TextView)getActivity().findViewById(R.id.section_label);
                    textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
                }
            });

            int page=getArguments().getInt(ARG_SECTION_NUMBER);
            switch (page)
            {
                case 1:
                    rootView=mainView;

                    break;
                case 2:
                    rootView = inflater.inflate(R.layout.activity_options, container, false);
                    break;
                case 3:
                    rootView = inflater.inflate(R.layout.activity_request, container, false);
                    break;
                    default:
                        rootView = inflater.inflate(R.layout.fragment_main, container, false);
                        break;

            }


            return rootView;
        }

Answer 1

错误 findViewById

试试这个

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {

            View rootView;
            View mainView= inflater.inflate(R.layout.fragment_main, container, false);
          ImageButton  button= (ImageButton) mainView.findViewById(R.id.imageButton2);
            button.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // Code here executes on main thread after user presses button
                    TextView textView = (TextView)mainView.findViewById(R.id.section_label);
                    textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
                }
            });

            int page=getArguments().getInt(ARG_SECTION_NUMBER);
            switch (page)
            {
                case 1:
                    rootView=mainView;

                    break;
                case 2:
                    rootView = inflater.inflate(R.layout.activity_options, container, false);
                    break;
                case 3:
                    rootView = inflater.inflate(R.layout.activity_request, container, false);
                    break;
                    default:
                        rootView = inflater.inflate(R.layout.fragment_main, container, false);
                        break;

            }


            return rootView;
        }

Answer 2

可能会出现多个出错的情况，其中一个我认为ImageButton无法转换为Button。如果不是这种情况，请尝试使用调试器来查看null（最可能是null）

Answer 3

更改以下内容

button= (Button) getActivity().findViewById(R.id.imageButton2);

到

button= (Button) mainView.findViewById(R.id.imageButton2);

并在充气视图后初始化button。因为它可能不会在初始化时产生问题，但如果您的视图更改了实际按钮的位置，则会崩溃。

Answer 4

由于上面的答案解决方案是改变一行从 button =（Button）getActivity（）。findViewById（R.id.imageButton2）; 到

ImageButton button = mainView.findViewById（R.id.imageButton2）;

向viewpager添加按钮监听器会崩溃应用程序

4 个答案: