网格视图滚动和图像加载非常慢

Question

我使用下面的代码用图像填充网格视图，网格视图中的图像加载速度很慢，网格视图滚动很慢并且卡在某个点上。我不确定我做错了什么。

logcat中没有写入错误消息

package com.dbprox.tagpic;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

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

public class imagegallery extends AppCompatActivity {

    private class ImageAdapter extends BaseAdapter {

        private Context mContext;
        ArrayList<String> itemList = new ArrayList<String>();

        public ImageAdapter(Context c) {
            mContext = c;
        }

        void add(String path){
            itemList.add(path);
        }

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

        @Override
        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new GridView.LayoutParams(185, 185));
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(5, 5, 5, 5);

            } else {
                imageView = (ImageView) convertView;
            }

            Bitmap bm = decodeSampledBitmapFromUri(itemList.get(position), 185, 185);

            if(bm!=null){
                imageView.setImageBitmap(bm);
            }

            return imageView;
        }

        public Bitmap decodeSampledBitmapFromUri(String path, int reqWidth, int reqHeight) {

            Bitmap bm = null;
            // First decode with inJustDecodeBounds=true to check dimensions
            final BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            BitmapFactory.decodeFile(path, options);

            // Calculate inSampleSize
            options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

            // Decode bitmap with inSampleSize set
            options.inJustDecodeBounds = false;
            bm = BitmapFactory.decodeFile(path, options);

            return bm;
        }

        public int calculateInSampleSize(

                BitmapFactory.Options options, int reqWidth, int reqHeight) {
            // Raw height and width of image
            final int height = options.outHeight;
            final int width = options.outWidth;
            int inSampleSize = 1;

            if (height > reqHeight || width > reqWidth) {
                if (width > height) {
                    inSampleSize = Math.round((float)height / (float)reqHeight);
                } else {
                    inSampleSize = Math.round((float)width / (float)reqWidth);
                }
            }

            return inSampleSize;
        }

    }

    ImageAdapter myImageAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_imagegallery);

        GridView gridview = (GridView) findViewById(R.id.imagegridview);
        gridview.setFastScrollEnabled(true);
        myImageAdapter = new ImageAdapter(this);
        gridview.setAdapter(myImageAdapter);


        String ExternalStorageDirectoryPath = Environment
                .getExternalStorageDirectory()
                .getAbsolutePath();

        String targetPath =Environment.getExternalStorageDirectory().toString()+"/Pictures"; //ExternalStorageDirectoryPath + "/Pictures";

       // Toast.makeText(getApplicationContext(), targetPath, Toast.LENGTH_LONG).show();
        File targetDirector = new File(targetPath);

        File[] files = targetDirector.listFiles();
        for (File file : files){

            try {

                myImageAdapter.add(file.getAbsolutePath());
            }catch(Exception e) {
                Log.d("TAG", "Error is " + e);}
        }
    }

}

Answer 1

您正在执行的所有与图像相关的操作都在阻塞UI的主线程上完成。您需要将所有这些工作推送到工作线程。

或者使用像Glide或Picasso这样的图书馆来为你做所有繁重的工作。

Answer 2

我有同样的问题。使用Picasso - Square加载图像，应用程序将比以往更顺畅地运行。适用于从服务器获取的两个图像以及可绘制的资源。