public View getView(int position, View convertView, ViewGroup parent) { if(convertView==null){ LayoutInflater inflater = LayoutInflater.from(context); convertView = inflater.inflate(R.layout.photo_item, null); holder = new ViewHolder(); holder.photo = (ImageView) convertView.findViewById(R.id.photo_item_image); holder.photoTitle = (TextView) convertView.findViewById(R.id.photo_item_title); holder.photoDate = (TextView) convertView.findViewById(R.id.photo_item_date); convertView.setTag(holder); }else { holder = (ViewHolder) convertView.getTag(); } cursor.moveToPosition(position); Bitmap current = dateCache.get(position); if(current != null){//如果缓存中已解码该图片,则直接返回缓存中的图片 holder.photo.setImageBitmap(current); }else { current = bitmapDecoder.getPhotoItem(cursor.getString(1), 2) ; holder.photo.setImageBitmap(current); dateCache.put(position, current); } holder.photoTitle.setText(cursor.getString(2)); holder.photoDate.setText(cursor.getString(4)); return convertView; } public View getView(int position, View convertView, ViewGroup parent) { if(convertView==null){ LayoutInflater inflater = LayoutInflater.from(context); convertView = inflater.inflate(R.layout.photo_item, null); holder = new ViewHolder(); holder.photo = (ImageView) convertView.findViewById(R.id.photo_item_image); holder.photoTitle = (TextView) convertView.findViewById(R.id.photo_item_title); holder.photoDate = (TextView) convertView.findViewById(R.id.photo_item_date); convertView.setTag(holder); }else { holder = (ViewHolder) convertView.getTag(); } cursor.moveToPosition(position); Bitmap current = dateCache.get(position); if(current != null){//如果缓存中已解码该图片,则直接返回缓存中的图片 holder.photo.setImageBitmap(current); }else { current = bitmapDecoder.getPhotoItem(cursor.getString(1), 2) ; holder.photo.setImageBitmap(current); dateCache.put(position, current); } holder.photoTitle.setText(cursor.getString(2)); holder.photoDate.setText(cursor.getString(4)); return convertView; } }
BitmapDecoder.class
package com.wuyi.bestjoy; import java.io.FileNotFoundException; import java.io.FileOutputStream; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Matrix; public class BitmapDecoder { private static final String TAG = "BitmapDecoder"; private Context context; public BitmapDecoder(Context context) { this.context = context; } public Bitmap getPhotoItem(String filepath,int size) { BitmapFactory.Options options = new BitmapFactory.Options(); options.inSampleSize=size; Bitmap bitmap = BitmapFactory.decodeFile(filepath,options); bitmap=Bitmap.createScaledBitmap(bitmap, 180, 251, true);//预先缩放,避免实时缩放,可以提高更新率 return bitmap; } } package com.wuyi.bestjoy; import java.io.FileNotFoundException; import java.io.FileOutputStream; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Matrix; public class BitmapDecoder { private static final String TAG = "BitmapDecoder"; private Context context; public BitmapDecoder(Context context) { this.context = context; } public Bitmap getPhotoItem(String filepath,int size) { BitmapFactory.Options options = new BitmapFactory.Options(); options.inSampleSize=size; Bitmap bitmap = BitmapFactory.decodeFile(filepath,options); bitmap=Bitmap.createScaledBitmap(bitmap, 180, 251, true);//预先缩放,避免实时缩放,可以提高更新率 return bitmap; } }
2.由于Gallery控件的特点,总有一个item处于当前选择状态,我们利用此时进行dataCache中额外不用的bitmap的清理,来释放内存。
@Override public void onItemSelected(AdapterView<?> parent, View view, int position,long id) { releaseBitmap(); Log.v(TAG, "select id:"+ id); } private void releaseBitmap(){ //在这,我们分别预存储了第一个和最后一个可见位置之外的3个位置的bitmap //即dataCache中始终只缓存了(M=6+Gallery当前可见view的个数)M个bitmap int start = mGallery.getFirstVisiblePosition()-3; int end = mGallery.getLastVisiblePosition()+3; Log.v(TAG, "start:"+ start); Log.v(TAG, "end:"+ end); //释放position<start之外的bitmap资源 Bitmap delBitmap; for(int del=0;del<start;del++){ delBitmap = dateCache.get(del); if(delBitmap != null){ //如果非空则表示有缓存的bitmap,需要清理 Log.v(TAG, "release position:"+ del); //从缓存中移除该del->bitmap的映射 dateCache.remove(del); delBitmap.recycle(); } } freeBitmapFromIndex(end); } /** * 从某一位置开始释放bitmap资源 * @param index */ private void freeBitmapFromIndex(int end) { //释放之外的bitmap资源 Bitmap delBitmap; for(int del =end+1;del<dateCache.size();del++){ delBitmap = dateCache.get(del); if(delBitmap != null){ dateCache.remove(del); delBitmap.recycle(); Log.v(TAG, "release position:"+ del); } } } @Override public void onItemSelected(AdapterView<?> parent, View view, int position,long id) { releaseBitmap(); Log.v(TAG, "select id:"+ id); } private void releaseBitmap(){ //在这,我们分别预存储了第一个和最后一个可见位置之外的3个位置的bitmap //即dataCache中始终只缓存了(M=6+Gallery当前可见view的个数)M个bitmap int start = mGallery.getFirstVisiblePosition()-3; int end = mGallery.getLastVisiblePosition()+3; Log.v(TAG, "start:"+ start); Log.v(TAG, "end:"+ end); //释放position<start之外的bitmap资源 Bitmap delBitmap; for(int del=0;del<start;del++){ delBitmap = dateCache.get(del); if(delBitmap != null){ //如果非空则表示有缓存的bitmap,需要清理 Log.v(TAG, "release position:"+ del); //从缓存中移除该del->bitmap的映射 dateCache.remove(del); delBitmap.recycle(); } } freeBitmapFromIndex(end); } /** * 从某一位置开始释放bitmap资源 * @param index */ private void freeBitmapFromIndex(int end) { //释放之外的bitmap资源 Bitmap delBitmap; for(int del =end+1;del<dateCache.size();del++){ delBitmap = dateCache.get(del); if(delBitmap != null){ dateCache.remove(del); delBitmap.recycle(); Log.v(TAG, "release position:"+ del); } } }