Android 无法实例化活动：在路径上找不到类

我已经将项目导入到 Eclipse 中，当我尝试运行它时，会抛出以下异常：

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.polygraf/com.polygraf.activity.Dashboard}: java.lang.ClassNotFoundException: Didn't find class "com.polygraf.activity.Dashboard" on path: /data/app/com.polygraf-1.apk

我尝试清理项目，然后检查所有类名和清单是否正常，但仍然找不到发生这种情况的原因。你能帮我一点忙吗？

仪表板类：

public class Dashboard extends FragmentActivity {

private static final String WELCOME_TYPE = "WELCOME_TYPE";
private static final String HELP_TYPE = "HELP_TYPE";

public static final String ADRESS_CONTENT = "ADRESS_CONTENT";
public static final String DOC_NAME = "DOC_NAME";

private Transcript mContent;
private ISettableContent mListOfDocument;

private String mAddress;

private String mDocName;

public Dashboard() {
}

/** Called with the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.dashboard);

    boolean content = false;
    // View gc = (NoSaveStateFrameLayout)
    // findViewById(R.id.content_fragment);
    //

    Fragment frContent = getSupportFragmentManager().findFragmentById(R.id.content_fragment);
    mContent = ((IGetContent) frContent).getContent();
    TranscriptSetting cc = Polygraf.getInstance().getContentSetting();

    Fragment frDocumentsList = getSupportFragmentManager().findFragmentById(R.id.documents);
    mListOfDocument = (ISettableContent) frDocumentsList;
    cc.registerContent(mListOfDocument);

    if (getIntent().hasExtra(ADRESS_CONTENT)) {
        mAddress = getIntent().getStringExtra(ADRESS_CONTENT);
        mDocName = getIntent().getStringExtra(DOC_NAME);
        mContent.setAddress(mAddress, mDocName);
        content = true;
    } else if (getIntent().hasExtra(WELCOME_TYPE)) {
        content = true;
        prepareVisibilityBtnTranscript();
    } else if (getIntent().hasExtra(HELP_TYPE)) {
        content = true;
        mContent.showHelp();

    }

    if (content) {
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.hide(frDocumentsList);
        ft.commit();

        // because on diferent layouts for small and large device
        // some views missing, so the test is inportant
        View contentLayout = findViewById(R.id.contentLayout);
        if (contentLayout != null) {
            contentLayout.setVisibility(View.VISIBLE);
        }
        prepareVisibilityBtnWelcome();
        // cp.setContent(mContent);
    }

    cc.registerContent(mContent);
    // cp.setListener(cc);

}
    .
    .
    .
}

和清单文件：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

<uses-sdk
    android:minSdkVersion="7"
    android:targetSdkVersion="17" />

<application
    android:name=".Polygraf"
    android:allowBackup="true"
    android:hardwareAccelerated="true"
    android:icon="@drawable/icon"
    android:label="@string/skeleton_app"
    android:theme="@android:style/Theme.Black.NoTitleBar" >
    <activity
        android:name="com.polygraf.activity.Dashboard"
        android:configChanges="orientation|keyboard" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <!-- This places this activity into the main app list. -->
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.polygraf.activity.SettingActivity"
        android:label="@string/skeleton_app" />
    <activity
        android:name="com.polygraf.activity.ContentActivity"
        android:label="@string/skeleton_app" >
    </activity>
    <activity
        android:name="com.polygraf.activity.PlayVideo"
        android:configChanges="orientation|keyboard"
        android:label="@string/skeleton_app" />
</application>

我猜你正在使用 Eclipse。您的活动在那里，但 Eclipse 没有在 APK 中包含支持包...如果您在堆栈跟踪中查看上面的错误，您会注意到问题的根源：“Unable to find FragmentActivity或者您可以解压该 apk，对其进行解压，您将看到不包含兼容性包类。

要解决此问题，请右键单击您的项目、属性、构建路径，然后转到导出选项卡。那里确保“Android private libraries“已检查。清理和重建应该会让您走上正轨......