com.d4a.tobias.Book.onCreateView上的java.lang.NullPointerException

您好，我正在开发一个应用程序，当我测试它时，启动时会崩溃

这是我的日志：

    11-29 00:16:19.582: E/memtrack(1549): Couldn't load memtrack module (No such file or directory)
11-29 00:16:19.582: E/android.os.Debug(1549): failed to load memtrack module: -2
11-29 00:16:28.782: E/memtrack(1609): Couldn't load memtrack module (No such file or directory)
11-29 00:16:28.782: E/android.os.Debug(1609): failed to load memtrack module: -2
11-29 00:16:29.462: E/AndroidRuntime(1620): FATAL EXCEPTION: main
11-29 00:16:29.462: E/AndroidRuntime(1620): Process: com.d4a.tobias, PID: 1620
11-29 00:16:29.462: E/AndroidRuntime(1620): java.lang.NullPointerException
11-29 00:16:29.462: E/AndroidRuntime(1620):     at com.d4a.tobias.Book.onCreateView(Book.java:55)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:622)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1416)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:431)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:139)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.view.ViewPager.populate(ViewPager.java:804)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.View.measure(View.java:16458)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.View.measure(View.java:16458)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.View.measure(View.java:16458)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.View.measure(View.java:16458)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.View.measure(View.java:16458)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.Choreographer.doFrame(Choreographer.java:532)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.os.Handler.handleCallback(Handler.java:733)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.os.Handler.dispatchMessage(Handler.java:95)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.os.Looper.loop(Looper.java:137)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at java.lang.reflect.Method.invokeNative(Native Method)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at java.lang.reflect.Method.invoke(Method.java:515)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-29 00:16:29.462: E/AndroidRuntime(1620):     at dalvik.system.NativeStart.main(Native Method)
11-29 00:16:38.902: E/WindowManager(494): Starting window AppWindowToken{42e4abd8 token=Token{42681aa0 ActivityRecord{42311100 u0 com.d4a.tobias/.MainActivity t33}}} timed out

---

下面是Book.java：

    package com.d4a.tobias;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.List;

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.res.AssetManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import com.actionbarsherlock.app.SherlockFragment;
import com.d4a.tobias.R;
import com.sibext.android_shelf.ImportBooks;
import com.sibext.android_shelf.adapter.ShelfAdapter;

public class Book extends SherlockFragment {

    Button bt1;
     //Shelf
        private static final String TARGET_DIRECTORY = "mnt/sdcard/shelf/";
        private ListView list;



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Get the view from fragmenttab1.xml
        View v=inflater.inflate(R.layout.fragmenttab1, container, false);


        // shelf
        File dir = new File(TARGET_DIRECTORY);
        if(!dir.exists()){
            dir.mkdirs();
            //past here
            addBooksFromAssetsToCard();
        }else{
            String files[] = dir.list();
            // line 55 if(files.length == 0){
                //past here
                addBooksFromAssetsToCard();
            }
        }

        list = (ListView) v. findViewById(R.id.list);

        ShelfAdapter adapter = new ShelfAdapter(this,TARGET_DIRECTORY);
        adapter.setToListView(list);

        //Intent in =  new Intent(v.getContext(), com.sibext.android_shelf.MainActivityShelf.class);
        //startActivity(in);

        //Toast.makeText(v.getContext(), "Did you see the toast msg?",Toast.LENGTH_LONG).show();

        //buttons for toolbelt do not take out!!

          v. findViewById(R.id.button10).setOnClickListener(new OnClickListener()

   {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub



                String url = "http://www.google.com";
                Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
                startActivity(browserIntent);
            }
        });


   v. findViewById(R.id.button11).setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub



                //  String url = "http://www.google.com";
                //  Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            //      startActivity(browserIntent);



            Intent i=new Intent(getActivity().getApplicationContext(),Launchalot.class);

            startActivity(i);


        }

   });


   v. findViewById(R.id.tools).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub



            //  String url = "http://www.google.com";
            //  Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        //      startActivity(browserIntent);



                Intent intent = new Intent(Intent.ACTION_MAIN);
                intent.setComponent(new ComponentName("com.d4a.stz","com.d4a.stz.ToolsHome"));
                intent.putExtra("grace", "Hi");
                startActivity(intent);


    }

});



    v. findViewById(R.id.googleplay).setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub



            //  String url = "http://www.google.com";
            //  Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            //      startActivity(browserIntent);



            Intent intent = new Intent(Intent.ACTION_VIEW);
            intent.setData(Uri.parse("http://play.google.com/store/apps"));
            startActivity(intent);


        }

    });

    v. findViewById(R.id.youtube).setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub


            //  String url = "http://www.google.com";
            //  Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            //      startActivity(browserIntent);


            Intent videoClient = new Intent(Intent.ACTION_VIEW);
            videoClient.setClassName("com.google.android.youtube", "com.google.android.youtube.WatchActivity");
            startActivity(videoClient);


        }

    });

    v. findViewById(R.id.email).setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub


            Intent intent = new Intent(Intent.ACTION_MAIN);
            intent.setComponent(new ComponentName("com.d4a.eMailTime","com.fsck.k9.activity.Accounts"));
            intent.putExtra("grace", "Hi");
            startActivity(intent);




        }

    });

        //shelf
        //ShelfAdapter adapter = new ShelfAdapter(this, TARGET_DIRECTORY);
        //adapter.setToListView(list);
        return v;

    }



    public void addBooksFromAssetsToCard(){
        List<String> books;
        try {
            books = getBooksFromAsset(getActivity());

            for(String book : books){
                copyFromAssets(book);
            }

        } catch (Exception e) {
        }
    }

    public List<String> getBooksFromAsset(Context ctx) throws Exception
    {
        AssetManager assetManager =ctx.getAssets();
        String[] files = assetManager.list("books");
        List<String> it=Arrays.asList(files);
        return it;
    }

    public void copyFromAssets(String book)
    {
        AssetManager assetManager = getActivity().getAssets();
        String[] files = null;
        InputStream in = null;
        OutputStream out = null;
        //String filename = "filename.ext";
        try
        {
            in = assetManager.open("books/"+book);
            out = new FileOutputStream(Environment.getExternalStorageDirectory()+File.separator+"/shelf/"+book);
            Log.d("Copying...", ""+book);
            copyFile(in, out); 
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
        }
        catch(Exception e)
        { 
            Log.e("tag", "Failed to copy asset file: " + book, e);
        }      
    }
    public void copyFile(InputStream in, OutputStream out) throws Exception
    {
        byte[] buffer = new byte[1024];
        int read;
        while((read = in.read(buffer)) != -1)
        {
            out.write(buffer, 0, read);
        }
        Log.d("Copy_State", "Done...");
    }

    public void onImportClicked(View v){
        Toast.makeText(getActivity(), "Please Wait", Toast.LENGTH_LONG)
         .show();
        Intent in = new Intent(getActivity(), ImportBooks.class);
        startActivity(in);











        return;

    }













}

我已经尝试了所有的方法，谷歌搜索logcat错误，询问一个对java很好的朋友，但仍然没有结果

任何帮助都将是惊人的

提前谢谢

---

Chris

dir.list（），此方法要么返回Null，要么返回文件夹中的文件列表，确保您引用的文件夹中有一些文件，否则您将获得NPE。您能指出第55行是什么吗？Kailash Daphi我在第55行添加了一条注释，请检查：）如果Techfist的解决方案不起作用，尝试在onCreateView中设置断点并逐步完成代码。此外，我不认为这是导致错误的原因，但您永远不应该像这样大写您的包名：com.d4a.eMailTime。如果EmailTime是java类名，请尝试com.d4a.EmailTime；如果不是，请尝试com.d4a.EmailTime。

    11-29 00:29:29.662: E/AndroidRuntime(2710): java.lang.NullPointerException
11-29 00:29:29.662: E/AndroidRuntime(2710):     at com.d4a.tobias.Book.onCreateView(Book.java:55)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:622)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1416)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:431)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:139)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.view.ViewPager.populate(ViewPager.java:804)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.View.measure(View.java:16458)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.View.measure(View.java:16458)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.View.measure(View.java:16458)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.View.measure(View.java:16458)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2289)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.View.measure(View.java:16458)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1914)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1111)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1293)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5582)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.Choreographer.doFrame(Choreographer.java:532)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.os.Handler.handleCallback(Handler.java:733)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.os.Handler.dispatchMessage(Handler.java:95)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.os.Looper.loop(Looper.java:137)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at android.app.ActivityThread.main(ActivityThread.java:4998)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at java.lang.reflect.Method.invokeNative(Native Method)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at java.lang.reflect.Method.invoke(Method.java:515)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-29 00:29:29.662: E/AndroidRuntime(2710):     at dalvik.system.NativeStart.main(Native Method)
11-29 00:29:38.802: E/WindowManager(494): Starting window AppWindowToken{429fc770 token=Token{42516cc8 ActivityRecord{426874a8 u0 com.d4a.tobias/.MainActivity t38}}} timed out