我想从网络上的照片创建一个位图。
首先我尝试使用BitmapFactory.decodeStream
但由于存在错误而返回null(http://code.google.com/p/android/issues/detail?id=6066)。
现在我正在使用BitmapFactory.decodeFile
保存图像,但它仍然返回null。
任何想法是错误的还是其他解决方法?
谢谢!
try {
URL uri = new URL("http://www.witzigundkraus.de/wp-content/uploads/2008/04/scooter-dj-munchen.jpg");
URLConnection connection = uri.openConnection();
Log.i(TAG, "connecting...");
connection.connect();
InputStream is = connection.getInputStream();
//BufferedInputStream bis = new BufferedInputStream(is, 8 * 1024);
File myfile = new File(getApplicationContext().getCacheDir(), "wallpaper.tmp");
myfile.createNewFile();
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(myfile));
byte buf[]=new byte[1024];
int len;
while((len=is.read(buf))>0)
out.write(buf,0,len);
out.close();
is.close();
Log.d(TAG, String.valueOf(myfile.exists()));
Bitmap bmp = BitmapFactory.decodeFile(myfile.getName());
//Bitmap bmp = BitmapFactory.decodeStream(bis);
Log.i(TAG, "setting bitmap");
Matrix matrix = new Matrix();
int scale = canvas.getWidth()/bmp.getWidth();
matrix.postScale(scale, scale, bmp.getWidth(), bmp.getHeight());
//matrix.postScale(0.5F, canvas.getWidth()/bmp.getWidth());
Bitmap bmp2 = Bitmap.createScaledBitmap(bmp, canvas.getWidth(), canvas.getHeight(), true);
Paint p = new Paint();
p.setFilterBitmap(true);
try{
canvas.drawBitmap(bmp2, matrix, p);
}catch(NullPointerException exc){
//why do we get this??
Log.d(TAG, "NullPointerException drawing canvas. why?");
return;
}
} catch (MalformedURLException exc){
Log.e(TAG, exc.toString());
return;
} catch (IOException exc){
Log.e(TAG, exc.toString());
return;
}
6-30 17:16:14.558 2253 2253 E AndroidRuntime: java.lang.NullPointerException
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.localfotos.MyWallpaperService$CubeEngine.drawCube(MyWallpaperService.java:212)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.localfotos.MyWallpaperService$CubeEngine.drawFrame(MyWallpaperService.java:159)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.localfotos.MyWallpaperService$CubeEngine.onSurfaceChanged(MyWallpaperService.java:109)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.service.wallpaper.WallpaperService$Engine.updateSurface(WallpaperService.java:543)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.service.wallpaper.WallpaperService$Engine.attach(WallpaperService.java:591)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.service.wallpaper.WallpaperService$IWallpaperEngineWrapper.executeMessage(WallpaperService.java:787)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:45)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.os.Looper.loop(Looper.java:136)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:4425)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:521)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
06-30 17:16:14.558 2253 2253 E AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分:1)
盖伊,我也在我的应用程序中从互联网上下载图像,它的工作正常。我用来下载的功能是:
public Bitmap download_Image(String url) {
Bitmap bm = null;
try {
URL aURL = new URL(url);
URLConnection conn = aURL.openConnection();
conn.connect();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
bm = BitmapFactory.decodeStream(bis);
bis.close();
is.close();
} catch (IOException e) {
Log.e("Hub","Error getting the image from server : " + e.getMessage().toString());
}
return bm;
}
我设置另一个线程来下载图像,以便UI线程继续可用。我使用了AsyncTask(参见here),以便(简化的)doInBackground
函数类似于:
@Override
protected Void doInBackground(String... urls) {
return download_Image(urls[0]);
}
我认为Android博客上的this page解释了与此问题相关的一些内容。