我有一个简单的ListView,左边有图像,右边有文字。目前我正在使用LazyAdapter根据菜肴名称从可绘制资源加载图像。
我创建了一个图像ID数组,并将其用于setImageView。
问题是,由于所有图像加载都是由主线程完成的,因此我知道滚动不顺畅。我搜索了很多关于AsyncTask的内容,它允许我们运行后台线程。我没有得到如何使用AsyncTask来实现任务,因为我在AsyncTask上看到的所有示例都有从URL下载的图像。
请帮我使用AsyncTask将图像列表从drawable加载到Bitmap。
这是我的邮件类:
ARRAY.image是一个整数数组,其图像ID用于适配器设置ImageView
package love.cookbook.FirstPage;
import com.actionbarsherlock.app.SherlockListActivity;
import com.actionbarsherlock.view.MenuItem;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.*;
import android.view.*;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.*;
public class ListViewSampleActivity extends SherlockListActivity {
LazyAdapter adapter;
public String packageName;
public int imageID;
String ingredientsImageName;
public MySqliteHelper dbHelper;
Cursor cur;
String eachIngredientsImageName [];
String listItemName;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
Intent intent = getIntent();
super.onCreate(savedInstanceState);
setContentView(R.layout.list_main);
dbHelper = new MySqliteHelper(this);
ListView list=(ListView)findViewById(android.R.id.list);
final FirstPageActivity firstPage = new FirstPageActivity();
ARRAY.dishes = intent.getStringArrayExtra("DISHES");
ARRAY.description = intent.getStringArrayExtra("DESCRIPTION");
ARRAY.timeToPrepare = intent.getStringArrayExtra("TIMETOPREPARE");
ARRAY.lock = intent.getStringArrayExtra("LOCKVALUE");
ARRAY.imageName = intent.getStringArrayExtra("IMAGENAME");
ARRAY.nonVeg = intent.getStringArrayExtra("NONVEG");
ARRAY.isFavourite = intent.getStringArrayExtra("ISFAVOURITE");
/*
* This code snippet is used to fetch the image id from the resource folder from the name fetched from database.
*/
ARRAY.image = new int[ARRAY.imageName.length];
packageName=this.getPackageName();
for(int i=0;i<ARRAY.imageName.length;i++){
ARRAY.image[i]=getResources().getIdentifier(ARRAY.imageName[i].toLowerCase(), "drawable", packageName);
}
adapter=new LazyAdapter (this, ARRAY.dishes,ARRAY.description,ARRAY.timeToPrepare,ARRAY.image,ARRAY.lock,ARRAY.nonVeg);
list.setAdapter(adapter);
list.setOnItemClickListener(new OnItemClickListener(){
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
}
});
}
}
这是我的Adapter类:
package love.cookbook.FirstPage;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private String[] dishes;
private String[] recipeDescripion;
private String[] timeToPrepare;
private String[] lock;
private String[] nonVeg;
private int [] images;
ViewHolder holder;
Bitmap bitmap;
private static LayoutInflater inflater=null;
public LazyAdapter(Activity a, String[] dishes, String[] recipeDescription,String[] timeToPrepare,int[] images,String [] lock,String [] nonVeg) {
activity = a;
this.dishes=dishes;
this.images=images;
this.bitmap = bitmap;
this.recipeDescripion=recipeDescription;
this.timeToPrepare=timeToPrepare;
this.lock=lock;
this.nonVeg=nonVeg;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public View getView(int position, View convertView, ViewGroup parent) {
//View vi=convertView;
if(convertView==null){
//vi = inflater.inflate(R.layout.item, null);
convertView = inflater.inflate(R.layout.item,parent, false);
//image = (ImageView)vi.findViewById(R.id.imageView);
holder = new ViewHolder();
holder.image = (ImageView) convertView.findViewById(R.id.imageView2);
holder.vegNonveggImageView = (ImageView) convertView.findViewById(R.id.imageView3);
holder.textView1 = (TextView)convertView.findViewById(R.id.textView1);
holder.textView2 = (TextView)convertView.findViewById(R.id.textView2);
holder.textView3 = (TextView)convertView.findViewById(R.id.textView3);
convertView.setTag(holder);
}
else
holder = (ViewHolder)convertView.getTag();
holder.textView1.setText(dishes[position]);
holder.image.setImageResource(images[position]);
holder.textView2.setText(recipeDescripion[position]);
holder.textView3.setText(timeToPrepare[position]);
if(nonVeg[position].equals("1")){
holder.vegNonveggImageView.setImageResource(R.drawable.non_veg_symbol);
}
else{
holder.vegNonveggImageView.setImageResource(R.drawable.veg_symbol);
}
return convertView;
}
public int getCount() {
return dishes.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public class ViewHolder{
ImageView image;
TextView textView1;
TextView textView2;
TextView textView3;
ImageView vegNonveggImageView;
}
}
答案 0 :(得分:0)
您的非平滑滚动问题可能是由于图像占用过多内存造成的。
您可以在Eclipse中通过查看DDMS透视图并查看分配的内存大小来查看它是否过大。
可以通过以下方式检查:
如果类型1-byte array(byte[], boolean[])
的总大小太大,则可能会导致滚动问题。
我不认为AsyncTask
会解决您的问题,因为无论如何都必须在UI(主)线程上完成更新视图。
如果您加载的图片太大,可以使用以下方法将其最小化:
Bitmap smallIcon = Bitmap.createScaledBitmap(bigIcon, width, height, false);
希望这有帮助