Thứ Bảy, 14 tháng 7, 2012

Implement Android Gallery widget with scale-down bitmap

In the exercise of "Android Gallery widget", the bitmap are loaded in Gallery widget without re-size. If you load with big picture, error of java.lang.OutOfMemoryError will be thrown.

Last post "Scale bitmap Efficiently" explain how to scale-down bitmap. It will be apply in the Gallery.

Android Gallery widget with scale-down bitmap

package com.example.androidgallery;

import java.util.ArrayList;

import android.os.Bundle;
import android.os.Environment;
import android.content.Context;
import android.view.Gravity;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast;

public class MainActivity extends Activity {

public class GalleryBaseAdapter extends BaseAdapter {

ArrayList<String> GalleryFileList;
Context context;

GalleryBaseAdapter(Context cont){
context = cont;
GalleryFileList = new ArrayList<String>();

public int getCount() {
return GalleryFileList.size();

public Object getItem(int position) {
return GalleryFileList.get(position);

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

public View getView(int position, View convertView, ViewGroup parent) {
//Bitmap bm = BitmapFactory.decodeFile(GalleryFileList.get(position));
Bitmap bm = decodeSampledBitmapFromUri(GalleryFileList.get(position), 200, 200);

LinearLayout layout = new LinearLayout(context);
layout.setLayoutParams(new Gallery.LayoutParams(250, 250));

ImageView imageView = new ImageView(context);
imageView.setLayoutParams(new Gallery.LayoutParams(200, 200));

return layout;


public void add(String newitem){


GalleryBaseAdapter myGalleryBaseAdapter;
Gallery myPhotoGallery;

public void onCreate(Bundle savedInstanceState) {
myPhotoGallery = (Gallery)findViewById(;

myGalleryBaseAdapter = new GalleryBaseAdapter(this);

String ExternalStorageDirectoryPath = Environment

String targetPath = ExternalStorageDirectoryPath + "/test/";

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

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


public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(, menu);
return true;

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;


The layout refer "Android Gallery widget".

Download the files.

- Caching Bitmaps with LruCache

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