UPDATES ：即使我没有从缓存中检索图像，我也尝试通过Drawable检索，其中我将所有18个图像存储在“drawable-mdpi”文件夹中。仍然显示空白屏幕。
我能够从服务器检索图像并将图像（.GIF）保存到缓存中。但是，当我需要从缓存加载该图像时，图像不会显示在屏幕上。以下是完成工作的代码：
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);
}
}
用于存储图像名称的ArrayList： smallMapImageNames （图片名称也可以在URL中找到）
用于存储图像网址的ArrayList： mapPiecesURL
总结一下，我有2个问题 1）如何从缓存加载图像？ 2）关于bitmap.compress（），来自服务器的图像是.GIF格式，但我应用了Bitmap.CompressFormat.PNG。那么这会有什么问题吗？
有人可以帮我解决这个问题吗？
这两项功能
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;
}
}
我实际上试图显示18张（3X6）图像以形成平面图。因此，为了显示图像，我使用两个for循环来显示它。两个.GIF图像，ERLab-1_1.GIF和ERLab-4_1.GIF是每组的中心部分。例如，第一行将是ERLab-0_0.GIF，ERLab-1_0.GIF，ERLab-2_0.GIF，ERLab-3_0.GIF，ERLab-4_0.GIF，ERLab-5_0.GIF。第二行是第三行的XXX-X_1.GIF和XXX-X_2.GIF。
最后，
Bitmap resultMap = getBitMap(this.getContext());
bmLargeImage = Bitmap.createBitmap(1029 , 617, Bitmap.Config.ARGB_8888);
bmLargeImage = resultMap;
然后在onDraw函数中将图像绘制到画布上。
答案 0 :(得分：2)
我刚刚解决了自己的问题。
在这一行中，canvas.drawBitmap(puzzle.get(cnt), srcRect, dstRect,null);在每个for循环中，我用它来将位图绘制到画布上，我需要将ArrayList中的每个项目（拼图）转换为Bitmap。只有这样才能显示图像。
我认为如果ArrayList是明确的，那么ArrayList<Bitmap> puzzle = new ArrayList<Bitmap>(); ArrayList中的每个项都是Bitmap类型。但这不总是如此吗？