ListView中的ImageView。获取AlbumArt

Question

我试着把AlbumArt放在ImageView里，放在ListView里。我不知道为什么第一个例子是有效的，我可以把位图放在其他片段的ImageView中，但我不能把位图放在列表视图中。

BookFragment.mAlbumArt.setImageBitmap(bitmap);'  

正在工作，而'BookFragment‘是其他片段

ivListAlbumArt.setImageBitmap(bitmap); 

不起作用

代码

public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.library, parent, false);

    ListView lvLibList = (ListView)view.findViewById(R.id.lvLibList);
    ImageButton btAddItem = (ImageButton)view.findViewById(R.id.btAddItem);
    lvLibList.setAdapter(adapter);
    final ImageView ivListAlbumArt = (ImageView)view.findViewById(R.id.ivListAlbumArt);
    mBooks = BookLib.get(getActivity()).getBooks();

    lvLibList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {

            Book b = (Book)parent.getAdapter().getItem(position);
            String fn = b.getBookFileName();
            Log.d(LOG_TAG, fn);

            musicSrv.releaseMedia();
            musicSrv.initMediaPlayer();
            musicSrv.setMedia(fn);
            musicSrv.createMedia();
            musicSrv.playNewMedia();
            BookFragment.mFileName.setText(musicSrv.getMediaTitle());


            byte[] art = musicSrv.getMediaAlbumArt();
            if(art != null)
            {
                Bitmap bitmap = BitmapFactory.decodeByteArray(art, 0, art.length);
                BookFragment.mAlbumArt.setImageBitmap(bitmap); 
                BookFragment.mAlbumArt.setAdjustViewBounds(true);
                BookFragment.mAlbumArt.setLayoutParams(new LinearLayout.LayoutParams(800, 800));

                ivListAlbumArt.setImageBitmap(bitmap); 
                ivListAlbumArt.setAdjustViewBounds(true);
                ivListAlbumArt.setLayoutParams(new LinearLayout.LayoutParams(80, 80));
            }
            else
            {
                BookFragment.mAlbumArt.setImageResource(R.drawable.thevoice); 
                BookFragment.mAlbumArt.setAdjustViewBounds(true);
                BookFragment.mAlbumArt.setLayoutParams(new LinearLayout.LayoutParams(800, 800));

                ivListAlbumArt.setImageResource(R.drawable.thevoice); 
                ivListAlbumArt.setAdjustViewBounds(true);
                ivListAlbumArt.setLayoutParams(new LinearLayout.LayoutParams(80, 80));
            }
         }
    });

    BookAdapter bookAdapter = new BookAdapter(mBooks);
    lvLibList.setAdapter(bookAdapter);

    btAddItem.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            OpenFileDialog fileDialog = new OpenFileDialog(getActivity());
            fileDialog.show();
        }
    });

    return view;
}

更新:适配器代码。我可以在适配器中添加更新ImageView的代码吗？

private class BookAdapter extends ArrayAdapter<Book> {
    public BookAdapter(ArrayList<Book> books) {
        super(getActivity(),0,books);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = getActivity().getLayoutInflater().inflate(R.layout.list_item, null);
        }
        Book b = getItem(position);
        TextView tvTitle = (TextView)convertView.findViewById(R.id.tvFileName);
        TextView tvPath = (TextView)convertView.findViewById(R.id.tvFilePath);
        TextView tvListDuration = (TextView)convertView.findViewById(R.id.tvListDuration);
        ImageView ivListAlbumArt = (ImageView)convertView.findViewById(R.id.ivListAlbumArt);
        tvTitle.setText(b.getTitle());
        tvPath.setText(b.getBookAutor());
        return convertView;
    }
}

适配器XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>


<ImageView
    android:layout_width="54dp"
    android:layout_height="54dp"
    android:layout_weight="0"
    android:id="@+id/ivListAlbumArt"
    android:padding="3dp"
    android:src="@drawable/logo" />

 <TextView
    android:id="@+id/tvFileName"
    android:text="FileName will be here"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="0"
    android:padding="5dp"
    android:textStyle="bold"
    android:layout_toRightOf="@id/ivListAlbumArt"
    android:layout_gravity="center_horizontal"/>

<TextView
    android:id="@+id/tvListDuration"
    android:text="0:00"
    android:layout_weight="0"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="5dp"
    android:layout_alignParentRight="true" />

<TextView
    android:id="@+id/tvFilePath"
    android:text="FilePath will be here"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:layout_below="@id/tvFileName"
    android:layout_toRightOf="@id/ivListAlbumArt"
    android:padding="5dp"/>

</RelativeLayout>

更新: LogCat输出

11-14 07:08:31.742    5943-5943/ru.app.a_book W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4159aba8)
11-14 07:08:31.742    5943-5943/ru.app.a_book E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: ru.app.a_book, PID: 5943
java.lang.NullPointerException
        at ru.app.a_book.TabLibrary$2.onItemClick(TabLibrary.java:182) // code: ivListAlbumArt.setImageBitmap(bitmap);
        at android.widget.AdapterView.performItemClick(AdapterView.java:299)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1113)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:2911)
        at android.widget.AbsListView$3.run(AbsListView.java:3645)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5001)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

您尚未初始化ivListAlbumArt anywhere，这就是您收到空指针异常的原因

在setOnItemClickListener中初始化ivListAlbumArt：

 lvLibList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
             ivListAlbumArt =  (ImageView) view.findViewById(R.id.ivListAlbumArt);
        }
 });