从高速缓存在Android中使用BitmapFactory.de codeStream（）导入图像 [英] Loading image from cache using BitmapFactory.decodeStream() in Android
问题描述
更新：即使我不检索缓存图片，我想通过我的地方存储所有的18幅图像中的绘制，MDPI文件夹中可绘制对象来检索。尽管如此，黑屏是显示器。
UPDATES: Even if i don't retrieve images from cache, i tried to retrieve via Drawable where i stored all the 18 images in the "drawable-mdpi" folder. Still, a blank screen was display.
我能够检索到的图像从服务器和图像（.GIF）保存到缓存中。但是，当我需要加载从缓存中的图像，图像不会在屏幕上显示出来。这是C $ CS的$该做的工作：
I was able to retrieved images from the server and save the image (.GIF) into the cache. However, when i need to load that image from cache, the image doesn't show up on screen. Here is the codes that does the work:
File cacheDir = context.getCacheDir();
File cacheMap = new File(cacheDir, smallMapImageNames.get(i).toString());
if(cacheMap.exists()){
FileInputStream fis = null;
try {
fis = new FileInputStream(cacheMap);
Bitmap local = BitmapFactory.decodeStream(fis);
puzzle.add(local);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}else{
Drawable smallMap = LoadImageFromWebOperations(mapPiecesURL.get(i).toString());
if(i==0){
height1 = smallMap.getIntrinsicHeight();
width1 = smallMap.getIntrinsicWidth();
}
if (smallMap instanceof BitmapDrawable) {
Bitmap bitmap = ((BitmapDrawable)smallMap).getBitmap();
FileOutputStream fos = null;
try {
cacheMap.createNewFile();
fos = new FileOutputStream(cacheMap);
bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);
fos.flush();
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
puzzle.add(bitmap);
}
}
ArrayList中存储的图像名称： smallMapImageNames （图像名称也可以在网址中找到）
ArrayList to store the image names: smallMapImageNames (The image names can also be found in the URL)
ArrayList中存储的图像的URL： mapPiecesURL
ArrayList to store the URL of the images: mapPiecesURL
要概括起来讲，我有2个问题 1）如何从缓存中加载的图片？ 2）关于bitmap.com preSS（），从服务器的映像是。GIF格式，但我申请Bitmap.Com pressFormat.PNG。那么，有没有打算与此有任何问题？
To sum it up i have 2 questions 1) how to load images from cache? 2) regarding the bitmap.compress(), the images from the server is .GIF format but i apply Bitmap.CompressFormat.PNG. So is there going to be any problem with this?
任何人都可以请帮我这个？
Can anyone please help me with this?
这两个函数
private Bitmap getBitMap(Context context) {
// TODO Auto-generated method stub
WifiPositioningServices wifiPositioningServices = new WifiPositioningServices();
String[] mapURLandCalibratedPoint1 = wifiPositioningServices.GetMapURLandCalibratedPoint("ERLab-1_1.GIF","ERLab"); //list of map pieces url in the first 9 pieces
String[] mapURLandCalibratedPoint2 = wifiPositioningServices.GetMapURLandCalibratedPoint("ERLab-4_1.GIF","ERLab"); //list of map pieces url in the last 9 pieces
ArrayList<String> smallMapImageNames = new ArrayList<String>();
ArrayList<String> mapPiecesURL = new ArrayList<String>();
for(int i=0; i<mapURLandCalibratedPoint1.length; i++){
if(mapURLandCalibratedPoint1[i].length()>40){ //image url
int len = mapURLandCalibratedPoint1[i].length();
int subStrLen = len-13;
smallMapImageNames.add(mapURLandCalibratedPoint1[i].substring(subStrLen, len-3)+"JPEG");
mapPiecesURL.add(mapURLandCalibratedPoint1[i]);
}
else{
//perform other task
}
}
for(int i=0; i<mapURLandCalibratedPoint2.length; i++){
if(mapURLandCalibratedPoint2[i].length()>40){ //image url
int len = mapURLandCalibratedPoint2[i].length();
int subStrLen = len-13;
smallMapImageNames.add(mapURLandCalibratedPoint2[i].substring(subStrLen, len-3)+"JPEG");
mapPiecesURL.add(mapURLandCalibratedPoint2[i]);
}
else{
//perform other task
}
}
Bitmap result = Bitmap.createBitmap(1029, 617, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(result);
ArrayList<Bitmap> puzzle = new ArrayList<Bitmap>();
int height1 = 0 ;
int width1 = 0;
File cacheDir = context.getCacheDir();
for(int i=0; i<18; i++){
File cacheMap = new File(cacheDir, smallMapImageNames.get(i).toString());
if(cacheMap.exists()){
//retrieved from cached
try {
FileInputStream fis = new FileInputStream(cacheMap);
Bitmap bitmap = BitmapFactory.decodeStream(fis);
puzzle.add(bitmap);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else{
//retrieve from server and cached it
Drawable smallMap = LoadImageFromWebOperations(mapPiecesURL.get(i).toString());
if(i==0){
height1 = smallMap.getIntrinsicHeight();
width1 = smallMap.getIntrinsicWidth();
}
if (smallMap instanceof BitmapDrawable) {
Bitmap bitmap = ((BitmapDrawable)smallMap).getBitmap();
FileOutputStream fos = null;
try {
cacheMap.createNewFile();
fos = new FileOutputStream(cacheMap);
bitmap.compress(CompressFormat.JPEG, 100, fos);
fos.flush();
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
puzzle.add(bitmap);
}
}
}
Rect srcRect;
Rect dstRect;
int cnt =0;
for (int j = 0; j < 3; j++) {
int newHeight = height1 * (j % 3);
for (int k = 0; k < 3; k++) {
if (j == 0 && k == 0) {
srcRect = new Rect(0, 0, width1, height1);
dstRect = new Rect(srcRect);
} else {
int newWidth = width1 * k;
srcRect = new Rect(0, 0, width1, height1);
dstRect = new Rect(srcRect);
dstRect.offset(newWidth, newHeight);
}
canvas.drawBitmap(puzzle.get(cnt), srcRect, dstRect,null);
cnt++;
}
}
for(int a=0; a<3; a++){
int newHeight = height1 * (a % 3);
for (int k = 3; k < 6; k++) {
if (a == 0 && k == 0) {
srcRect = new Rect(0, 0, width1*3, height1);
dstRect = new Rect(srcRect);
} else {
int newWidth = width1 * k;
srcRect = new Rect(0, 0, width1, height1);
dstRect = new Rect(srcRect);
dstRect.offset(newWidth, newHeight);
}
canvas.drawBitmap(puzzle.get(cnt), srcRect, dstRect,
null);
cnt++;
}
}
return result;
}
private Drawable LoadImageFromWebOperations(String url) {
// TODO Auto-generated method stub
try
{
InputStream is = (InputStream) new URL(url).getContent();
Drawable d = Drawable.createFromStream(is, "src name");
return d;
}catch (Exception e) {
System.out.println("Exc="+e);
return null;
}
}
我其实是想显示18张图像的（3X6），形成了一个平面布置图。因此，为了显示图像，我使用两个for循环来显示它。两个.gif图片，ERLab-1_1.GIF和ERLab-4_1.GIF是中心部分各组。例如，第一行是ERLab-0_0.GIF，ERLab-1_0.GIF，ERLab-2_0.GIF，ERLab-3_0.GIF，ERLab-4_0.GIF，ERLab-5_0.GIF。第二排是XXX-X_1.GIF和XXX-X_2.GIF的第三排。
I am actually trying to display 18 pieces (3X6) of images to form up a floorplan. So to display the images, i use two for-loop to display it. the two .GIF images, ERLab-1_1.GIF and ERLab-4_1.GIF are the center piece of each group. For example, the first row of would be ERLab-0_0.GIF, ERLab-1_0.GIF, ERLab-2_0.GIF, ERLab-3_0.GIF, ERLab-4_0.GIF, ERLab-5_0.GIF. Second row would be XXX-X_1.GIF and XXX-X_2.GIF for the third row.
最后，
Bitmap resultMap = getBitMap(this.getContext());
bmLargeImage = Bitmap.createBitmap(1029 , 617, Bitmap.Config.ARGB_8888);
bmLargeImage = resultMap;
然后在OnDraw函数将图像绘制在画布上。
Then in the onDraw function would be drawing the image onto the canvas.
推荐答案
我刚刚解决了我的问题。
I just solved my own question.
在这一行， canvas.drawBitmap（puzzle.get（CNT），srcRect，dstRect，NULL）; 在每一个for循环中，我正在使用它绘制位图到画布上，我需要投中的ArrayList（拼图）的每个项目为位图。只有这样，图像得到显示。
In this line, canvas.drawBitmap(puzzle.get(cnt), srcRect, dstRect,null); within each of the for-loop which i am using it to draw the bitmap onto the canvas, i need to cast the each item in the ArrayList (puzzle) to Bitmap. Only then will the image get display.
我想，如果ArrayList中是明确的，例如，的ArrayList＆LT;位图＆GT;拼图=新的ArrayList＆LT;位图＆GT;（）; ArrayList中的每个项目将位图型。但并非总是如此吗？
I thought that if the ArrayList is definite as such, ArrayList<Bitmap> puzzle = new ArrayList<Bitmap>(); each items in the ArrayList would be of Bitmap type. But isn't that always true?
这篇关于从高速缓存在Android中使用BitmapFactory.de codeStream（）导入图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
