大家，我遇到一个问题，我使用 listView 显示来自本地资源的数百张图像，并且我将图像设置为全屏。每个列表项中有一个带有 imageView 和 TextView 的项目。但是当我滑动到下一项，不太顺利。我使用ImageFactory.options调整图像的比例。但问题仍然存在。我想也许我应该使用异步任务加载和图像缓存来解决这个问题。这是我的代码，希望你们能指出我的问题。非常感谢。
package com.jafir.project.adapter;
import java.util.List;
import java.util.Map;
import com.jafir.project.porunacabeza.R;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView.RecyclerListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class PicListViewAdapter extends BaseAdapter {
private Context context;
private Resources resources;
private LayoutInflater inflater;
private ViewHolder holder;
private List<Map<String, Object>> list;
public PicListViewAdapter(Context context,List<Map<String, Object>> list) {
this.list = list;
this.context = context;
this.inflater = LayoutInflater.from(context);
resources = context.getResources();
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int arg0) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null) {
convertView = inflater.inflate(R.layout.item_pic, null);
holder = new ViewHolder();
holder.imageView = (ImageView) convertView.findViewById(R.id.img_pic);
holder.textView = (TextView) convertView.findViewById(R.id.txt_pic);
convertView.setTag(holder);
}else {
holder = (ViewHolder) convertView.getTag();
}
int resID = (Integer) list.get(position).get("image");
String text = (String) list.get(position).get("text");
holder.imageView.setImageBitmap(decodeBitmap(resources, resID, holder.imageView.getWidth(), holder.imageView.getHeight()));
holder.textView.setText(text);
notifyDataSetChanged();
return convertView;
}
public Bitmap decodeBitmap(Resources res,int id,int width,int height){
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res,id,options);
options.inSampleSize = getInSampleSize(options,width,height);
options.inJustDecodeBounds = false;
return BitmapFactory.decodeResource(res,id,options);
}
public int getInSampleSize(BitmapFactory.Options options,int reqWidth,int reqHeight){
final int width = options.outWidth;
final int height = options.outHeight;
int inSampleSize = 1;
if(height > reqHeight || width > reqWidth) {
int radioWidth = Math.round((float)width/(float)reqWidth);
int radioHeight = Math.round((float)height/(float)reqHeight);
inSampleSize = radioHeight < radioWidth ?radioHeight:radioWidth;
}
return inSampleSize;
}
final static class ViewHolder{
ImageView imageView;
TextView textView;
}
}
这是为了活动：
private void init() {
listView = (ListView) getActivity().findViewById(R.id.lst_pic);
list = new ArrayList<Map<String,Object>>();
for(int i=0;i < texts.length;i++){
Map<String, Object> map = new HashMap<String, Object>();
map.put("image", R.drawable.img0+ i);
map.put("text", texts[i]);
list.add(map);
}
listView.setAdapter(new PicListViewAdapter(getActivity(), list));
}
这是针对 item.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:orientation="vertical"
>
<ImageView android:id="@+id/img_pic"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
/>
<TextView android:id="@+id/txt_pic"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="15dp"
android:gravity="center_horizontal"
android:layout_gravity="center_horizontal"
/>
</LinearLayout>