5

我创建了一个采用者来显示特定文件夹中的视频图像缩略图，但是当我滚动它时它会有点滞后，但这是为什么呢？

下面是代码：

主要活动课

public class TestvideolistingActivity extends ListActivity {

    String filename = null;
    String filePath = null;
    String dirNameSlash = "/videotest/";
    String dirName = "videotest";
    String path = Environment.getExternalStorageDirectory() + dirNameSlash ;
    String[] values;
    String deleteFile ;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // getting the own adapter
        getInit();
    }

    @Override
    protected void onResume() {
        getInit();
        super.onResume();
    }
    public void getInit() {

        deleteFile = null;
        values = getFilesArrayFromSdCard();
        setListAdapter(new MyAdapter(this, values));
    }

    protected void onListItemClick(ListView l, View v, int position, long id) {
        String item = (String) getListAdapter().getItem(position);
        Intent intentToPlayVideo = new Intent(Intent.ACTION_VIEW);
        intentToPlayVideo.setDataAndType(Uri.parse(path + item), "video/*");
        startActivity(intentToPlayVideo);
    }

    public String[] getFilesArrayFromSdCard() {
        String[] fileList = null;
        File videoFiles = new File(path);
        if (videoFiles.isDirectory()) {
            fileList = videoFiles.list();
        }
        return fileList;
    }
}

this the adopter class which show;s the text and the thumbnail 



public class MyAdapter extends ArrayAdapter<String> {

    private final Activity context;
    private final String[] names;
    private String filePath = null;
    private Bitmap bmThumbnail;

    private String dateFormat = "dd/MM/yyyy HH:mm:ss";
    private SimpleDateFormat formatter;
    private String filename;
    String dirNameSlash = "/videotest/";

    static class ViewHolder {
        // value for the name of the file
        public TextView text;
        // video file thumbnail
        public ImageView image;
    }

    public MyAdapter(Activity context, String[] names) {
        super(context, R.layout.rowlayout, names);
        this.context = context;
        this.names = names;
        filePath = Environment.getExternalStorageDirectory() + dirNameSlash;
        formatter = new SimpleDateFormat(dateFormat);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View rowView = convertView;
        if (rowView == null) {
            LayoutInflater inflater = context.getLayoutInflater();
            rowView = inflater.inflate(R.layout.rowlayout, null);
            ViewHolder viewHolder = new ViewHolder();
            viewHolder.text = (TextView) rowView.findViewById(R.id.label);
            viewHolder.image = (ImageView) rowView.findViewById(R.id.icon);
            rowView.setTag(viewHolder);
        }

        ViewHolder holder = (ViewHolder) rowView.getTag();
        // Video file name
        String s = names[position];

        holder.text.setText(s);

        bmThumbnail = ThumbnailUtils.createVideoThumbnail(filename, Thumbnails.MICRO_KIND);
        holder.image.setImageBitmap(bmThumbnail);

        return rowView;
    }
}

这是使用 Akhil 代码的错误

    04-04 18:09:59.078: E/AndroidRuntime(10625): FATAL EXCEPTION: main
04-04 18:09:59.078: E/AndroidRuntime(10625): java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
04-04 18:09:59.078: E/AndroidRuntime(10625):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at java.util.ArrayList.get(ArrayList.java:311)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at com.koders.testvideolisting.MyPerformanceArrayAdapter.getView(MyPerformanceArrayAdapter.java:111)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.AbsListView.obtainView(AbsListView.java:1315)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.ListView.makeAndAddView(ListView.java:1727)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.ListView.fillDown(ListView.java:652)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.ListView.fillFromTop(ListView.java:709)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.ListView.layoutChildren(ListView.java:1580)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.AbsListView.onLayout(AbsListView.java:1147)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.View.layout(View.java:7034)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.View.layout(View.java:7034)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1249)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1125)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1042)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.View.layout(View.java:7034)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.widget.FrameLayout.onLayout(FrameLayout.java:333)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.View.layout(View.java:7034)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.ViewRoot.performTraversals(ViewRoot.java:1049)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1744)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.os.Looper.loop(Looper.java:144)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at android.app.ActivityThread.main(ActivityThread.java:4937)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at java.lang.reflect.Method.invokeNative(Native Method)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at java.lang.reflect.Method.invoke(Method.java:521)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-04 18:09:59.078: E/AndroidRuntime(10625):    at dalvik.system.NativeStart.main(Native Method)
4

2 回答 2

8

列表视图滞后，因为您每次都在 getView()中创建新的缩略图。只是没有缓存或重用。当使用向上/向下滚动时，会调用 getView() 并且会发生创建缩略图的耗时过程，因此会出现滞后。您也将很快运行。 Out of Memory

创建并保留一个位图数组，其长度与数据源中元素的数量相同，并将缩略图存储在数组中。从数组中取出该特定位置的位图getView()。这应该会大大提高性能。

编辑我添加了一个 Hasmap 位图来演示重用。

 public MyAdapter(Activity context, String[] names) {
    super(context, R.layout.rowlayout, names);
    this.context = context;
    this.names = names;
    filePath = Environment.getExternalStorageDirectory() + dirNameSlash;
    formatter = new SimpleDateFormat(dateFormat);
cacheBitmap = new HashMap<String, Bitmap>(names.length);
initCacheBitmap();
}

private void initCacheBitmap() {
    for(String string:names)
        cacheBitmap.put(string, ThumbnailUtils.createVideoThumbnail(filePath+string, Thumbnails.MICRO_KIND));

}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    View rowView = convertView;
    if (rowView == null) {
        LayoutInflater inflater = context.getLayoutInflater();
        rowView = inflater.inflate(R.layout.rowlayout, null);
        ViewHolder viewHolder = new ViewHolder();
        viewHolder.text = (TextView) rowView.findViewById(R.id.label);
        viewHolder.image = (ImageView) rowView.findViewById(R.id.icon);
        rowView.setTag(viewHolder);
    }

    ViewHolder holder = (ViewHolder) rowView.getTag();
    // Video file name
    String s = names[position];

    holder.text.setText(s);


    holder.image.setImageBitmap(cacheBitmap.get(s));

    return rowView;
}}
于 2012-04-04T05:49:09.963 回答
3

由于您在 getView() 中为视频创建缩略图，因此会减慢滚动速度。

因此，您必须将位图保存在 Arrarys 中并在滚动时列出它。试试这个示例，因为这将真正帮助您快速滚动。此示例包含图像，您必须在 Media Content Providers 中更改视频。快速滚动示例

于 2012-04-04T06:07:57.653 回答