Question

我编写了一个简单的应用程序，首先只包含一个Activity和多个其他类（不是从Activity继承）。我现在添加了一个新类HandlePrefs，它也继承自Activity并在匹配此类的清单文件中添加了一个新标记。

现在我在启动期间得到了java.lang.classcastexception错误（但仅在使用API lvl 15及更高版本时。它在较旧的API版本上运行良好。

这是清单文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="tal.game.ammelampe.classes"
  android:versionCode="3"
  android:versionName="1.2"
  android:installLocation="preferExternal">
<uses-sdk android:minSdkVersion="3" android:targetSdkVersion="8"/>
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.VIBRATE" />
<application android:icon="@drawable/icon" 
             android:label="Amme Lampe lite" 
             android:allowBackup="true">


    <provider android:name=".FeedingProvider"
              android:authorities="tal.game.ammelampe.FeedingProvider" />        

    <activity android:name="tal.game.ammelampe.classes.AmmeLampeApp"
              android:label="Amme Lampe Lite"
              android:configChanges="keyboard|keyboardHidden|orientation"
              android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity android:name="tal.game.ammelampe.classes.HandlePrefs">
    </activity>
 </application> 

 </manifest>

这是我的AndroidApp类（启动类）

package tal.game.framework.impl;


import tal.game.ammelampe.classes.HelpScreen;
import tal.game.ammelampe.classes.MainMenuScreen;
import tal.game.ammelampe.classes.Settings;
import tal.game.framework.App;
import tal.game.framework.FileIO;
import tal.game.framework.Graphics;
import tal.game.framework.Input;
import tal.game.framework.Screen;
import android.app.Activity;
import android.content.Context;
import android.content.res.Configuration;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.os.Bundle;
import android.os.PowerManager;
import android.os.Vibrator;
import android.os.PowerManager.WakeLock;
//import android.util.Log;
import android.view.KeyEvent;
import android.view.Window;
import android.view.WindowManager;


public abstract class AndroidApp extends Activity implements App {
    AndroidFastRenderView renderView;
    Graphics graphics;
    Input input;
    FileIO fileIO;
    Screen screen;
    WakeLock wakeLock;
    public static Vibrator v;


    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        //Debug.startMethodTracing();
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        boolean isLandscape = getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE;
        int frameBufferWidth = isLandscape ? 480 : 320;
        int frameBufferHeight = isLandscape ? 320 : 480;
        Bitmap frameBuffer = Bitmap.createBitmap(frameBufferWidth,
                frameBufferHeight, Config.RGB_565);

        float scaleX = (float) frameBufferWidth   /   getWindowManager().getDefaultDisplay().getWidth(); 
        float scaleY = (float) frameBufferHeight  / getWindowManager().getDefaultDisplay().getHeight();

        v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);

        renderView = new AndroidFastRenderView(this, frameBuffer);
        graphics = new AndroidGraphics(getAssets(), frameBuffer);
        fileIO = new AndroidFileIO(getAssets());

        input = new AndroidInput(this, renderView, scaleX, scaleY);
        screen = getStartScreen();
        setContentView(renderView);

        PowerManager powerManager = (PowerManager)     getSystemService(Context.POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, "GLGame");


    }

同样继承自Activity的新类：

package tal.game.ammelampe.classes;


import tal.game.ammelampe.classes.FeedingDBMetaData.FeedingTableMetaData;
import tal.game.framework.App;
import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;



public class HandlePrefs extends Activity{


// Definer keys i preferences
    private static final String INITIALIZED = "initialized"; 
    private static final String name      = "name";
private static final String dob       = "dob";
private static final String sex       = "sex";
private static final String bgColor   = "bgcolor";
private static final String onOffLamp = "onofflamp";




// This variable is set in the LoadingScreen class
public static Long currentDate;
public static Long LongDob;



public static String lName = "";            
public static String lDob;                  
public static String lSex;                  
public static String lBgColor;              
public static String lOnOffLamp;            





static SharedPreferences myPrefs;
Activity activity = this;

 @Override
 public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
 }

上面没有包含很多类中的代码，因为我确信它不会导致错误。但如果我错了，我当然会为你们提供它：）

最后是LogCat输出：

03-19 21:51:49.201: W/dalvikvm(3256): threadid=1: thread exiting with uncaught exception (group=0x40ab4228)
03-19 21:51:49.261: E/AndroidRuntime(3256): FATAL EXCEPTION: main
03-19 21:51:49.261: E/AndroidRuntime(3256): java.lang.RuntimeException: Unable to start activity ComponentInfo{tal.game.ammelampe.classes/tal.game.ammelampe.classes.AmmeLampeApp}: java.lang.ClassCastException: tal.game.ammelampe.classes.AmmeLampeApp cannot be cast to android.app.Application
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2194)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread.access$600(ActivityThread.java:139)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.os.Looper.loop(Looper.java:154)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread.main(ActivityThread.java:4945)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at java.lang.reflect.Method.invokeNative(Native Method)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at java.lang.reflect.Method.invoke(Method.java:511)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at dalvik.system.NativeStart.main(Native Method)
03-19 21:51:49.261: E/AndroidRuntime(3256): Caused by: java.lang.ClassCastException: tal.game.ammelampe.classes.AmmeLampeApp cannot be cast to android.app.Application
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.view.Window.getCompatInfo(Window.java:475)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.view.Window$LocalWindowManager.<init>(Window.java:485)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.view.Window.setWindowManager(Window.java:471)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.Activity.attach(Activity.java:4517)
03-19 21:51:49.261: E/AndroidRuntime(3256):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2135)
03-19 21:51:49.261: E/AndroidRuntime(3256):     ... 11 more
03-19 21:51:49.281: E/EmbeddedLogger(185): App crashed! Process: tal.game.ammelampe.classes
03-19 21:51:49.281: E/EmbeddedLogger(185): App crashed! Package: tal.game.ammelampe.classes v3 (1.2)
03-19 21:51:49.281: E/EmbeddedLogger(185): App crashed! Application Label: Amme Lampe lite
03-19 21:51:49.281: W/ActivityManager(185):   Force finishing activity tal.game.ammelampe.classes/.AmmeLampeApp

我尝试使用android：name =“android.app.Application”标记修改清单文件作为标记中的直接子项（如其他类似问题中所建议的那样），但仍然得到相同的错误。我在这里做错了什么？

在清单文件中使用android：name =“android.app.Application”标记的LogCat：

03-19 22:00:19.789: E/AndroidRuntime(4154): FATAL EXCEPTION: main
03-19 22:00:19.789: E/AndroidRuntime(4154): java.lang.RuntimeException: Unable to start  activity ComponentInfo{tal.game.ammelampe.classes/tal.game.ammelampe.classes.AmmeLampeApp}:   java.lang.ClassCastException: tal.game.ammelampe.classes.AmmeLampeApp cannot be cast to android.app.Application

App类：

package tal.game.framework;

import android.content.Context;

public interface App {
    public Input getInput();

    public FileIO getFileIO();

    public Graphics getGraphics();

    public void setScreen(Screen screen);

    public Screen getCurrentScreen();

    public Screen getStartScreen();

    public Context getApplicationContext();
}

Answer 1

您不需要实现App，只需像这样扩展Activity

更改：public abstract class AndroidApp extends Activity implements App {

至：public abstract class AndroidApp extends Activity {

Answer 2

您在清单中列为活动的Ammelameapp类不是从Activity派生的。您的AndroidApp类派生自Activity，但它的摘要（因此无法直接使用）并实现了一个名为App的东西，我不知道它是什么。我想你需要仔细阅读Android中的Activity和Application的含义。

每个应用都有一个Application对象。您可以使用Android默认设置，也可以扩展它并创建自己的默认设置。应用可以有一个或多个活动，这些活动是具体类，必须从活动扩展。这些活动列在应用程序内部的清单中。该列表包括类的完全限定路径或本地活动的.ClassName表单。

Answer 3

正如JBirdVegas在their comment中所说：

我不确定它是否重要，但getApplicationContext（）也是一个 Activity中继承的Context中的抽象方法。也许重命名你的方法getApplicationContext（）和你的界面App;让我们面对它的App类的命名可能更具描述性。

在启动期间在Android上获取java.lang.classcastexception

3 个答案: