新版android sdk问题

Question

就在今天，我下载了eclipse并为android开发进行了设置。当创建一个新的android项目时，它会创建主项目引用的appcompat_v7库项目。问题是两者都显示错误。我甚至试图从问题列表中删除错误，但这并没有帮助。运行时错误被抛出 -

04-25 15:07:51.521: E/AndroidRuntime(1348): FATAL EXCEPTION: main 
04-25 15:07:51.521: E/AndroidRuntime(1348): Process: com.example.demo, PID: 1348 
04-25 15:07:51.521: E/AndroidRuntime(1348): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.demo/com.example.demo.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.example.demo.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.demo-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.demo-1, /system/lib]] 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread.access$800(ActivityThread.java:135) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.os.Handler.dispatchMessage(Handler.java:102) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.os.Looper.loop(Looper.java:136) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread.main(ActivityThread.java:5017) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at java.lang.reflect.Method.invoke(Method.java:515) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at dalvik.system.NativeStart.main(Native Method) 
04-25 15:07:51.521: E/AndroidRuntime(1348): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.demo.MainActivity" on path: DexPathList[[zip file "/data/app/com.example.demo-1.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.demo-1, /system/lib]] 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at java.lang.ClassLoader.loadClass(ClassLoader.java:497) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at java.lang.ClassLoader.loadClass(ClassLoader.java:457) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.Instrumentation.newActivity(Instrumentation.java:1061) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112) 
04-25 15:07:51.521: E/AndroidRuntime(1348):  ... 11 more 

现在如何使用开发环境。显然我无法创建一个新项目。但老年人工作得很好。提前致谢。

编辑：我追加，是由在IDE中创建的第一个活动源 -

package com.example.demo; 

import android.support.v7.app.ActionBarActivity; 
import android.support.v7.app.ActionBar; 
import android.support.v4.app.Fragment; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.os.Build; 

public class MainActivity extends ActionBarActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     if (savedInstanceState == null) { 
      getSupportFragmentManager().beginTransaction() 
        .add(R.id.container, new PlaceholderFragment()) 
        .commit(); 
     } 
    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 

     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 
     if (id == R.id.action_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    /** 
    * A placeholder fragment containing a simple view. 
    */ 
    public static class PlaceholderFragment extends Fragment { 

     public PlaceholderFragment() { 
     } 

     @Override 
     public View onCreateView(LayoutInflater inflater, ViewGroup container, 
       Bundle savedInstanceState) { 
      View rootView = inflater.inflate(R.layout.fragment_main, container, false); 
      return rootView; 
     } 
    } 

} 

Answer 1

我复制了Android的支持 - 从v4.jar libs文件夹到appcompat_v7/bin文件夹和错误得到解决。该应用程序运行得很好。