android - 使用 java.lang.ClassNotFoundException 扩展布局时出错

Question

现在我知道这个问题已经在 SO 上被问过好几次了，但没有一个答案对我有用。

我正在尝试为我的项目创建自定义首选项。更具体地说，它是对 HorizontalListView 的偏好。直接附在它下面。我基本上是通过修改 this code 创建的对于 SeekBarPreference(我也在使用并且工作正常)。我的 ListViewPreference 与 SeelkBarPreference 位于完全相同的文件夹中(正如我所说的那样没有问题)，但我不断收到 ClassNotFoundException(请参阅下面的 logcat)。这是我的 ListViewPreference 类:

package com.example.ebookreader;

import android.content.Context;
import android.content.res.TypedArray;
import android.preference.Preference;
import android.util.AttributeSet;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.ViewParent;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class ListViewPreference extends Preference {

    private final String TAG = getClass().getName();

    private static final String ROBOBUNNYNS = "http://robobunny.com";
    private static final int DEFAULT_VALUE = 50;

    private int mCurrentValue;
    private String mUnitsLeft = "";
    private String mUnitsRight = "";

    private HorizontalListView mListView;

    private TextView mStatusText;

    public ListViewPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        initPreference(context, attrs);
    }

    public ListViewPreference(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initPreference(context, attrs);
    }

    private void initPreference(Context context, AttributeSet attrs) {
        setValuesFromXml(attrs);

        mListView = new HorizontalListView(context, attrs);
        LayoutParams params = mListView.getLayoutParams();
        params.width = LayoutParams.MATCH_PARENT;
        params.height = LayoutParams.WRAP_CONTENT;
        mListView.setLayoutParams(params);
    }

    private void setValuesFromXml(AttributeSet attrs) {
        mUnitsLeft = getAttributeStringValue(attrs, ROBOBUNNYNS, "unitsLeft",
                "");
        String units = getAttributeStringValue(attrs, ROBOBUNNYNS, "units", "");
        mUnitsRight = getAttributeStringValue(attrs, ROBOBUNNYNS, "unitsRight",
                units);
    }

    private String getAttributeStringValue(AttributeSet attrs,
            String namespace, String name, String defaultValue) {
        String value = attrs.getAttributeValue(namespace, name);

        if (value == null)
            value = defaultValue;

        return value;
    }

    @Override
    protected View onCreateView(ViewGroup parent) {
        RelativeLayout layout = null;

        try {
            LayoutInflater mInflater = (LayoutInflater) getContext()
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            layout = (RelativeLayout) mInflater.inflate(
                    R.layout.horizontal_list_view_preference, parent, false);
        } catch (Exception e) {
            Log.e(TAG, "Error creating seek bar preference", e);
        }

        return layout;
    }

    @Override
    public void onBindView(View view) {
        super.onBindView(view);

        try {
            // move our seekbar to the new view we've been given
            ViewParent oldContainer = mListView.getParent();
            ViewGroup newContainer = (ViewGroup) view
                    .findViewById(R.id.listViewPrefBarContainer);

            if (oldContainer != newContainer) {
                // remove the seekbar from the old view
                if (oldContainer != null) {
                    ((ViewGroup) oldContainer).removeView(mListView);
                }
                // remove the existing seekbar (there may not be one) and add
                // ours
                newContainer.removeAllViews();
                newContainer.addView(mListView,
                        ViewGroup.LayoutParams.FILL_PARENT,
                        ViewGroup.LayoutParams.WRAP_CONTENT);
            }
        } catch (Exception ex) {
            Log.e(TAG, "Error binding view: " + ex.toString());
        }

        updateView(view);
    }

    /**
    * Update a SeekBarPreference view with our current state
    * 
    * @param view
    */
    protected void updateView(View view) {
        try {
            RelativeLayout layout = (RelativeLayout) view;

            mStatusText = (TextView) layout
                    .findViewById(R.id.listViewPrefValue);
            mStatusText.setText(String.valueOf(mCurrentValue));
            mStatusText.setMinimumWidth(30);

            TextView unitsRight = (TextView) layout
                    .findViewById(R.id.listViewPrefUnitsRight);
            unitsRight.setText(mUnitsRight);

            TextView unitsLeft = (TextView) layout
                    .findViewById(R.id.listViewPrefUnitsLeft);
            unitsLeft.setText(mUnitsLeft);
        } catch (Exception e) {
            Log.e(TAG, "Error updating seek bar preference", e);
        }
    }

    @Override
    protected Object onGetDefaultValue(TypedArray ta, int index) {
        int defaultValue = ta.getInt(index, DEFAULT_VALUE);
        return defaultValue;
    }

    @Override
    protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
        if (restoreValue) {
            mCurrentValue = getPersistedInt(mCurrentValue);
        } else {
            int temp = 0;
            try {
                temp = (Integer) defaultValue;
            } catch (Exception ex) {
                Log.e(TAG, "Invalid default value: " + defaultValue.toString());
            }

            persistInt(temp);
            mCurrentValue = temp;
        }
    }
}

对于大多数人来说，这个问题是由于没有带有参数 Context 和 AttributeSet 的构造函数造成的，但正如您所见，我显然有。

这是错误不断发生的 XML 文件:

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res/com.example.ebookreader"
    android:background="@drawable/wallpaper" >

    <android:PreferenceCategory
        android:key="device_settings"
        android:title="Device Settings" >

        <android:CheckBoxPreference
            android:key="wifi"
            android:summary="Enable or Disable Wi-Fi"
            android:title="Wi-Fi" />

        <android:CheckBoxPreference
            android:key="bluetooth"
            android:summary="Enable or Disable Bluetooth"
            android:title="Bluetooth" />

        <android:CheckBoxPreference
            android:key="autosync"
            android:summary="Enable or Disable AutoSync"
            android:title="AutoSync" />

        <custom:SeekBarPreference
            android:id="@+id/brightness_adjust"
            android:defaultValue="100"
            android:key="brightness"
            android:max="200"
            android:summary="Adjust Brightness Levels"
            android:title="Brightness" />
    </android:PreferenceCategory>

    <android:PreferenceCategory
        android:key="account_settings"
        android:title="Account Settings" >

        <custom:ListViewPreference> <!-- Error happens here -->
                android:id="@+id/font_selector"
                android:key="font"
                android:title="Font"
                android:summary="Edit Font"     
            />
        </custom:ListViewPreference>
    </android:PreferenceCategory>

</PreferenceScreen>

下面是我的完整 Logcat:

03-14 17:53:14.290: E/AndroidRuntime(449): FATAL EXCEPTION: main
03-14 17:53:14.290: E/AndroidRuntime(449): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ebookreader/com.example.ebookreader.SettingsActivity}: android.view.InflateException: Binary XML file line #40: Error inflating class ListViewPreference
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1736)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1752)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread.access$1500(ActivityThread.java:123)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:993)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.os.Looper.loop(Looper.java:126)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread.main(ActivityThread.java:3997)
03-14 17:53:14.290: E/AndroidRuntime(449):  at java.lang.reflect.Method.invokeNative(Native Method)
03-14 17:53:14.290: E/AndroidRuntime(449):  at java.lang.reflect.Method.invoke(Method.java:491)
03-14 17:53:14.290: E/AndroidRuntime(449):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
03-14 17:53:14.290: E/AndroidRuntime(449):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
03-14 17:53:14.290: E/AndroidRuntime(449):  at dalvik.system.NativeStart.main(Native Method)
03-14 17:53:14.290: E/AndroidRuntime(449): Caused by: android.view.InflateException: Binary XML file line #40: Error inflating class ListViewPreference
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.createItemFromTag(GenericInflater.java:441)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.rInflate(GenericInflater.java:481)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.rInflate(GenericInflater.java:493)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.inflate(GenericInflater.java:326)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.inflate(GenericInflater.java:263)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:269)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.PreferenceActivity.addPreferencesFromResource(PreferenceActivity.java:1333)
03-14 17:53:14.290: E/AndroidRuntime(449):  at com.example.ebookreader.SettingsActivity.onCreate(SettingsActivity.java:31)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1700)
03-14 17:53:14.290: E/AndroidRuntime(449):  ... 11 more
03-14 17:53:14.290: E/AndroidRuntime(449): Caused by: java.lang.ClassNotFoundException: android.preference.ListViewPreference in loader dalvik.system.PathClassLoader[/data/app/com.example.ebookreader-2.apk]
03-14 17:53:14.290: E/AndroidRuntime(449):  at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:251)
03-14 17:53:14.290: E/AndroidRuntime(449):  at java.lang.ClassLoader.loadClass(ClassLoader.java:548)
03-14 17:53:14.290: E/AndroidRuntime(449):  at java.lang.ClassLoader.loadClass(ClassLoader.java:508)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.createItem(GenericInflater.java:375)
03-14 17:53:14.290: E/AndroidRuntime(449):  at android.preference.GenericInflater.onCreateItem(GenericInflater.java:417)
03-14 17:53:14.290: E/AndroidRuntime(449):  at    android.preference.GenericInflater.createItemFromTag(GenericInflater.java:428)
03-14 17:53:14.290: E/AndroidRuntime(449):  ... 20 more

如有任何帮助，我们将不胜感激。

Answer 1

但是你为什么写

 <custom:ListViewPreference 

应该是

 <com.example.ebookreader.ListViewPreference

作为你的包，放置类的地方，叫做