Question

我正在尝试创建一个图库应用，只是为了向用户显示图片。

该应用已经在运行，但网格滚动缓慢且不流畅。

我不知道我还能做些什么才能让表现更好。我已经使用LruCache和Async任务来加载图片。

GridAdapter

package abcde.xyz;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.support.v4.util.LruCache;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;

import java.util.ArrayList;

/**
 * Created by Lucas on 25/03/2017.
 */

public class GridImagesAdapter extends ArrayAdapter {


    private Context context;
    private int layoutResourceId;
    private ArrayList data = new ArrayList();
    public static LruCache<Integer, Bitmap> mMemoryCache;

    public GridImagesAdapter(Context context, int layoutResourceId, ArrayList<Integer> data) {
        super(context, layoutResourceId, data);
        this.layoutResourceId = layoutResourceId;
        this.context = context;
        this.data = data;


        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);

        final int cacheSize = maxMemory / 4;
        if(mMemoryCache == null){
            mMemoryCache = new LruCache<Integer, Bitmap>(cacheSize) {
                @Override
                protected int sizeOf(Integer key, Bitmap bitmap) {
                    return bitmap.getByteCount() / 1024;
                }
            };
        }
        mMemoryCache.evictAll();

    }

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

        if (row == null) {
            LayoutInflater inflater = ((Activity) context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);

            ImageView image = (ImageView)row.findViewById(R.id.image);
            final Integer item = (Integer)data.get(position);


            image.setImageBitmap(null);
            ImageGridHandler handler = new ImageGridHandler(context, image);
            handler.execute(item);
        }

        return row;
    }
}

ImageGridHandler

package abcde.xyz;

import android.content.Context;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.provider.MediaStore;
import android.util.Log;
import android.widget.ImageView;

import java.lang.ref.WeakReference;

/**
 * Created by Lucas on 29/03/2017.
 */

public class ImageGridHandler extends AsyncTask<Integer, Void, Bitmap> {
    private final WeakReference<ImageView> imageViewReference;
    private Context context;
    public ImageGridHandler(Context context, ImageView img){
        imageViewReference = new WeakReference<ImageView>(img);
        this.context = context;
    }

    @Override
    protected Bitmap doInBackground(Integer... params) {

        return loadBitmap(params[0]);

    }

    @Override
    protected void onPostExecute(Bitmap result) {
        final ImageView imageView = imageViewReference.get();

        if(imageView != null) {
            //imageView.setScaleType(ImageView.ScaleType.CENTER);
            imageView.setImageBitmap(result);
        }
    }


    public void addBitmapToMemoryCache(Integer key, Bitmap bitmap) {
        if (getBitmapFromMemCache(key) == null) {
            GridImagesAdapter.mMemoryCache.put(key, bitmap);
        }
    }

    public Bitmap getBitmapFromMemCache(Integer key) {
        return GridImagesAdapter.mMemoryCache.get(key);
    }

    public Bitmap loadBitmap(Integer resId) {


        Bitmap bitmap = getBitmapFromMemCache(resId);
        if (bitmap == null) {

           Log.d("ImageGridHandler", "Loading: " + resId);
            if(resId != null) {
                bitmap = MediaStore.Images.Thumbnails.getThumbnail(
                        context.getContentResolver(), resId,
                        MediaStore.Images.Thumbnails.MICRO_KIND,
                        null);
                if(bitmap != null) {
                    addBitmapToMemoryCache(resId, bitmap);
                }
            }

            Log.d("GRIDADAPTER", "ImageLoaded");
        }

        return bitmap;
    }


}

布局

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="umdev.images24.MainActivity"
    tools:showIn="@layout/activity_main">
    <android.support.v4.widget.SwipeRefreshLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/swipeRefresh"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        tools:layout_editor_absoluteY="8dp"
        tools:layout_editor_absoluteX="8dp">

     <GridView
         android:id="@+id/gridView"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_margin="0dp"
         android:drawSelectorOnTop="true"
         android:gravity="center"
         android:columnWidth="100dp"
         android:numColumns="auto_fit"
         android:stretchMode="columnWidth"
         android:verticalSpacing="0dp"
         android:focusable="true"
         android:clickable="true"
         android:fastScrollEnabled="true"/>

    </android.support.v4.widget.SwipeRefreshLayout>
</android.support.constraint.ConstraintLayout>

grid_item_layout.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="2dp"
    android:background="#fff">

    <ImageView
        android:id="@+id/image"
        android:layout_width="120dp"
        android:layout_height="120dp" />

</LinearLayout>

Answer 1

它并不快速而顺畅，因为你不是在缓存。我有同样的问题，我使用Universal Image loader，使用此库在网格视图中调整图像大小。

Git-Hub Universal Image Loader

它使用url获取图像，然后将其转换为位图，然后调整大小。因此，如果您只想创建一个简单的图库。然后你可以像你一样获取SD卡图像并将其传递给通用图像加载器的方法 ImageLoader（）

例如 -

String path="file://"+String.valueOf(wholeList.get(i));//Your Image path

    ImageLoader.getInstance().displayImage(path,holder.image,options,new SimpleImageLoadingListener() {
        @Override
        public void onLoadingStarted(String imageUri, View view) {
            holder.progressBar.setProgress(0);
            holder.progressBar.setVisibility(View.VISIBLE);
        }

        @Override
        public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
            holder.progressBar.setVisibility(View.GONE);
        }

        @Override
        public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
            holder.progressBar.setVisibility(View.GONE);
        }
    }, new ImageLoadingProgressListener() {
        @Override
        public void onProgressUpdate(String imageUri, View view, int      current, int total) {
            holder.progressBar.setProgress(Math.round(100.0f * current / total));
        }});

    return convertView;
}
private static class ViewHolder {
    ImageView image;
    ProgressBar progressBar;
}

**注意：这不是完整的代码，它只是它的一部分，我建议你先检查一下Git hub链接** - GitHub Universal Image Loader

Answer 2

您可以使用Glide，Picassa或ImageLoader加载图像并避免使用由于在图像中加载图像所花费的时间而发生的滚动问题图

例如在Glide中

Glide.with(getActivity()).load(Uri.fromFile(new File(String.valueOf(getItem(position))))).into(ivPhoto);

Answer 3

在加载图像之前，我们必须调整它以避免ImageView缩放。

将缩小版本加载到内存中

https://developer.android.com/topic/performance/graphics/load-bitmap.html

谢谢@GT

Gridview滚动慢

3 个答案: