Question

我的SDCard上有一个用.nomedia隐藏的文件夹。我有这个Imageadapter，它在GridView中显示文件夹（图像和视频）的内容。它们似乎都出现了，但有时当我点击我知道的视频缩略图时，会显示图像甚至是不同的视频。有人可以告诉我这里哪里出错吗？

GridViewImageAdapter.class

package com.soboapps.todos.adapter;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.ArrayList;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.media.ThumbnailUtils;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class GridViewImageAdapter extends BaseAdapter {

    private Activity mActivity;
    private ArrayList<String> mFilePaths = new ArrayList<String>();
    private int imageWidth;

    public GridViewImageAdapter(Activity activity, ArrayList<String> filePaths, int imageWidth) {
        this.mActivity = activity;
        this.mFilePaths = filePaths;
        this.imageWidth = imageWidth;
    }

    @Override
    public int getCount() {
        return this.mFilePaths.size();
    }

    @Override
    public Object getItem(int position) {
        return this.mFilePaths.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) 
    {
        ImageView imageView;
        if (convertView == null) {
            imageView = new ImageView(mActivity);


             if(mFilePaths.get(position).contains("jpg") || mFilePaths.get(position).contains("jpeg") ||
                     mFilePaths.get(position).contains("png"))
            {
                Bitmap image = BitmapFactory.decodeFile(mFilePaths.get(position)); //Creation of Thumbnail of image
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
                imageView.setImageBitmap(image);

            }
            else if(mFilePaths.get(position).contains(".mp4") || mFilePaths.get(position).contains(".3gp"))
            {
                Bitmap video = ThumbnailUtils.createVideoThumbnail(mFilePaths.get(position), imageWidth); //Creation of Thumbnail of video
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
                imageView.setImageBitmap(video);
            }

        }
        else 
        {
            imageView = (ImageView)convertView;
        }
        return imageView;
    }


    /*
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            imageView = new ImageView(mActivity);
        } else {
            imageView = (ImageView) convertView;
        }

        // get screen dimensions
        Bitmap image = decodeFile(mFilePaths.get(position), imageWidth, imageWidth);

        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
        imageView.setImageBitmap(image);

        return imageView;
    }
    */



    public static Bitmap decodeFile(String filePath, int WIDTH, int HIGHT) {
        try {

            File f = new File(filePath);

            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f), null, o);

            final int REQUIRED_WIDTH = WIDTH;
            final int REQUIRED_HIGHT = HIGHT;
            int scale = 1;
            while (o.outWidth / scale / 2 >= REQUIRED_WIDTH
                    && o.outHeight / scale / 2 >= REQUIRED_HIGHT)
                scale *= 2;

            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        return null;
    }

}

Answer 1

在getView（）函数内部，如果convertView不为null，则不能正确设置缩略图。像这样重新排列代码来处理这种情况：

public View getView(int position, View convertView, ViewGroup parent) 
{
    ImageView imageView;
    if (convertView == null) {
        imageView = new ImageView(mActivity);
    } else {
        imageView = (ImageView) convertView;
    }

    if(mFilePaths.get(position).contains("jpg") || mFilePaths.get(position).contains("jpeg") ||
                 mFilePaths.get(position).contains("png"))
    {
        Bitmap image = BitmapFactory.decodeFile(mFilePaths.get(position));    //Creation of Thumbnail of image
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
        imageView.setImageBitmap(image);

    }
    else if(mFilePaths.get(position).contains(".mp4") || mFilePaths.get(position).contains(".3gp"))
    {
        Bitmap video = ThumbnailUtils.createVideoThumbnail(mFilePaths.get(position), imageWidth); //Creation of Thumbnail of video
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
        imageView.setImageBitmap(video);
    }

    return imageView;
}

convertView参数不是已经初始化到指定位置的视图，您可以按原样返回。它是一个用于显示不同网格元素的视图，它被回收用于不同的位置，因此您需要进行设置。

此外，如果您遇到滞后的UI问题，请考虑在AsyncTask或线程池中创建缩略图，而不是在主UI线程上创建缩略图。查看此类问题，了解有关如何执行此操作的信息：Loading images in a gridview with async task

GridView无法显示正确的缩略图

1 个答案: