实现 Android Pdf Viewer 库

Question

它似乎是唯一不依赖于 MuPDF 的免费 android pdf 阅读器。

我正在尝试证明这一点，我有 downloaded the project 但运行它时出现异常：

01-17 13:45:03.960: E/AndroidRuntime(13631): FATAL EXCEPTION: main
01-17 13:45:03.960: E/AndroidRuntime(13631): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{net.sf.andpdf.pdfviewer/net.sf.andpdf.pdfviewer.PdfViewerActivity}: java.lang.InstantiationException: can't instantiate class net.sf.andpdf.pdfviewer.PdfViewerActivity
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1894)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread.access$600(ActivityThread.java:128)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.os.Looper.loop(Looper.java:137)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread.main(ActivityThread.java:4514)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at java.lang.reflect.Method.invokeNative(Native Method)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at java.lang.reflect.Method.invoke(Method.java:511)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at dalvik.system.NativeStart.main(Native Method)
01-17 13:45:03.960: E/AndroidRuntime(13631): Caused by: java.lang.InstantiationException: can't instantiate class net.sf.andpdf.pdfviewer.PdfViewerActivity
01-17 13:45:03.960: E/AndroidRuntime(13631):    at java.lang.Class.newInstanceImpl(Native Method)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at java.lang.Class.newInstance(Class.java:1319)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.Instrumentation.newActivity(Instrumentation.java:1027)
01-17 13:45:03.960: E/AndroidRuntime(13631):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1885)

在项目的自述文件中，最后一步我看不懂。

6) 使用以下代码调用派生的 PdfViewActivity：

 Intent intent = new Intent(this, YourPdfViewerActivity.class);
 intent.putExtra(PdfViewerActivity.EXTRA_PDFFILENAME, "PATH TO PDF GOES HERE");
 startActivity(intent);

谁能解释一下这一步是什么？或者更重要的是：有人可以使用这个 pdf 阅读器吗？

谢谢

Answer 1

问题是您尝试在Intent 中实例化的PdfViewerActivity 是abstract class 并且无法实例化（类here 的链接）。您需要创建一个扩展 PdfViewerActivity 的 Activity，实现该类具有的任何抽象方法。像这样的：

public class MyPdfViewerActivity extends PdfViewerActivity {

   //Your implementation code here.
}