ViewHolder GridView 滞后

Question

我第一次使用 ViewHolder 和 GridView，我是 android/java 新手 与ImageView 相比，它的效果要好得多。

但我最大的问题是滚动很慢。 我有两个问题：

第一个：我能做些什么来提高性能？ 第二个：我可以用BitmapWorkerTask/AsyncTask怎么用？

我尝试的是android:scrollingCache="false"，因为每个人都在写，但似乎android:scrollingCache="true" 的性能对我来说要好一些。

代码：

布局

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
                  android:orientation="vertical"  
                  android:layout_width="fill_parent"  
                  android:layout_height="fill_parent"  
                  android:padding="10dp">  
    <ImageView android:id="@+id/ic_launcher"
    android:contentDescription="@string/desc"  
    android:layout_width="match_parent" 
    android:layout_height="match_parent"
    android:columnWidth="90dp"
    android:numColumns="4"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:stretchMode="columnWidth"
    android:gravity="center"
    android:fastScrollEnabled="true"
    android:persistentDrawingCache="scrolling"
    android:scrollingCache="true"
    android:animationCache="false"
    android:smoothScrollbar="true"
    /> 

    </LinearLayout> 

图像适配器

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;



public class ImageAdapter extends BaseAdapter {
    private Context mContext;
    private LayoutInflater mInflater; 


    // Keep all Images in array about 600
    public Integer[] mThumbIds = {

};
// Constructor
    public ImageAdapter(Context c) {   
        mInflater = LayoutInflater.from(c);  
           mContext = c;
    }

    @Override
    public int getCount() {
        return mThumbIds.length;
    }

    @Override
    public Object getItem(int position) {
        return mThumbIds[position];
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }



 // create a new ImageView for each item referenced by the     
    public View getView(int position, View convertView, ViewGroup parent) {     
     ViewHolder holder;
       if (convertView == null) {  // if it's not recycled,     
             convertView = mInflater.inflate(R.layout.categorycontent, null);  
           convertView.setLayoutParams(new GridView.LayoutParams(130, 130));  
          holder = new ViewHolder();  
             holder.icon = (ImageView )convertView.findViewById(R.id.ic_launcher);  
             convertView.setTag(holder);  
         } else {  
             holder = (ViewHolder) convertView.getTag();

         }  
holder.icon.setAdjustViewBounds(true);  
holder.icon.setScaleType(ImageView.ScaleType.CENTER_INSIDE);     
holder.icon.setImageResource(mThumbIds[position]);  
return convertView;     
    }     
    class ViewHolder {  
        ImageView icon;  
    }  }

希望各位大侠给我一些建议:)

NewCodewithErrors

    }

    class ViewHolder {  
        ImageView icon;  
    } 

 // create a new ImageView for each item referenced by the     
    public View getView(int position, View convertView, ViewGroup parent) {     
     ViewHolder holder;
       if (convertView == null) {  // if it's not recycled,     
             convertView = mInflater.inflate(R.layout.categorycontent, null);  
           convertView.setLayoutParams(new GridView.LayoutParams(130, 130));  
          holder = new ViewHolder();  
             holder.icon = (ImageView )convertView.findViewById(R.id.ic_launcher);  
             convertView.setTag(holder);  
         } else {  
             holder = (ViewHolder) convertView.getTag();

         }  
holder.icon.setAdjustViewBounds(true);  
holder.icon.setScaleType(ImageView.ScaleType.CENTER_INSIDE);     
holder.icon.setImageResource(mThumbIds[position]);

//Here i have the errors:
//The constructor ImageAdapter.LoadImage() is undefine ImageAdapter.java
//The method execute(Integer...) in the type AsyncTask<Integer,Void,Bitmap> is not 
//applicable for the arguments (View) ImageAdapter.java

new LoadImage().execute(convertView);

return convertView;     
    }   


    private class LoadImage extends AsyncTask<Integer, Void, Bitmap> {

        private ImageView imv;

        public LoadImage(ImageView imv) {
            this.imv = imv;
        }

        @Override
        protected void onPostExecute(Bitmap result) {

            if (result != null && imv != null) {
                imv.setVisibility(View.VISIBLE);
                imv.setImageBitmap(result);
            } else {
                imv.setVisibility(View.GONE);
            }
        }

        @Override
        protected Bitmap doInBackground(Integer... params) {
            Bitmap bitmap = null;
            bitmap = BitmapFactory.decodeResource(mContext.getResources(),
                    params[0]);
            return bitmap;
        }

    }}

Answer 1

首先在您的适配器中获取内部类，例如..

private class LoadImage extends AsyncTask<Integer, Void, Bitmap> {

    private ImageView imv;

    public LoadImage(ImageView imv) {
        this.imv = imv;
    }

    @Override
    protected void onPostExecute(Bitmap result) {

        if (result != null && imv != null) {
            imv.setVisibility(View.VISIBLE);
            imv.setImageBitmap(result);
        } else {
            imv.setVisibility(View.GONE);
        }
    }

    @Override
    protected Bitmap doInBackground(Integer... params) {
        Bitmap bitmap = null;
        bitmap = BitmapFactory.decodeResource(mContext.getResources(),
                params[0]);
        return bitmap;
    }

}

并在上面调用它 return convertView

new LoadImage(holder.icon).execute(mThumbIds[position]);