java - 无法实例化 fragment 确保类名存在

Question

android.app.Fragment$InstantiationException: Unable to instantiate fragment: make sure class name exists, is public, and has a empty constructor that is public.

我意识到有很多关于同一错误的问题，但到目前为止没有一个对我有帮助。我正在从一本书中学习，并且之前实际上运行过准确的(99％确定)代码。全部删除并重写以供审核后，出现错误。

package com.paad.todolist;

import android.app.ListFragment;
import android.os.Bundle;

public class ToDoListFragment extends ListFragment{

    public static ToDoListFragment newInstance(int index) {
        ToDoListFragment f = new ToDoListFragment();

           Bundle args = new Bundle();
           args.putInt("index", index);
           f.setArguments(args);

           return f;
        }
    }

日志猫:

06-16 03:04:14.091: E/AndroidRuntime(836): FATAL EXCEPTION: main 06-16 03:04:14.091: E/AndroidRuntime(836): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.paad.todolist/com.paad.todolist.ToDoListActivity}: android.view.InflateException: Binary XML file line #13: Error inflating class fragment 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread.access$600(ActivityThread.java:123) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.os.Handler.dispatchMessage(Handler.java:99) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.os.Looper.loop(Looper.java:137) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread.main(ActivityThread.java:4424) 06-16 03:04:14.091: E/AndroidRuntime(836): at java.lang.reflect.Method.invokeNative(Native Method) 06-16 03:04:14.091: E/AndroidRuntime(836): at java.lang.reflect.Method.invoke(Method.java:511) 06-16 03:04:14.091: E/AndroidRuntime(836): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 06-16 03:04:14.091: E/AndroidRuntime(836): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 06-16 03:04:14.091: E/AndroidRuntime(836): at dalvik.system.NativeStart.main(Native Method) 06-16 03:04:14.091: E/AndroidRuntime(836): Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class fragment 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:697) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.rInflate(LayoutInflater.java:739) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.inflate(LayoutInflater.java:489) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.inflate(LayoutInflater.java:396) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.inflate(LayoutInflater.java:352) 06-16 03:04:14.091: E/AndroidRuntime(836): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:251) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Activity.setContentView(Activity.java:1835) 06-16 03:04:14.091: E/AndroidRuntime(836): at com.paad.todolist.ToDoListActivity.onCreate(ToDoListActivity.java:18) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Activity.performCreate(Activity.java:4466) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920) 06-16 03:04:14.091: E/AndroidRuntime(836): ... 11 more 06-16 03:04:14.091: E/AndroidRuntime(836): Caused by: android.app.Fragment$InstantiationException: Unable to instantiate fragment com.paad.todoList.ToDoListFragment: make sure class name exists, is public, and has an empty constructor that is public 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Fragment.instantiate(Fragment.java:585) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Fragment.instantiate(Fragment.java:549) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Activity.onCreateView(Activity.java:4235) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:673) 06-16 03:04:14.091: E/AndroidRuntime(836): ... 21 more 06-16 03:04:14.091: E/AndroidRuntime(836): Caused by: java.lang.ClassNotFoundException: com.paad.todoList.ToDoListFragment 06-16 03:04:14.091: E/AndroidRuntime(836): at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61) 06-16 03:04:14.091: E/AndroidRuntime(836): at java.lang.ClassLoader.loadClass(ClassLoader.java:501) 06-16 03:04:14.091: E/AndroidRuntime(836): at java.lang.ClassLoader.loadClass(ClassLoader.java:461) 06-16 03:04:14.091: E/AndroidRuntime(836): at android.app.Fragment.instantiate(Fragment.java:571) 06-16 03:04:14.091: E/AndroidRuntime(836): ... 24 more

Answer 1

发现，你的 logcat 说明了一切

 Caused by: java.lang.ClassNotFoundException: com.paad.todoList.ToDoListFragment

您的包名称不正确。使用 com.paad.todolist 而不是 com.paad.todoList

这篇文章让我想起电视节目的对话，神探夏洛克:你看到了，但你没有观察 :) :)