我不知道ImagaeCatche.params中的错误到底是什么，它显示了空指针异常，我在行尾指出了错误编号。
堆栈跟踪：
E/AndroidRuntime(1464): FATAL EXCEPTION: main
E/AndroidRuntime(1464): Process: com.gems.android, PID: 1464
E/AndroidRuntime(1464): java.lang.NullPointerException
E/AndroidRuntime(1464): at com.sit.fth.util.ImageCache.getDiskCacheDir(ImageCache.java:514)
E/AndroidRuntime(1464): at com.sit.fth.util.ImageCache$ImageCacheParams.<init>(ImageCache.java:463)
E/AndroidRuntime(1464): at com.sit.fth.frgment.HomeFragment.onCreateView(HomeFragment.java:82)
E/AndroidRuntime(1464): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
E/AndroidRuntime(1464): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
E/AndroidRuntime(1464): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
E/AndroidRuntime(1464): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
E/AndroidRuntime(1464): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
E/AndroidRuntime(1464): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
E/AndroidRuntime(1464): at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
E/AndroidRuntime(1464): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
E/AndroidRuntime(1464): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
E/AndroidRuntime(1464): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
E/AndroidRuntime(1464): at android.view.View.measure(View.java:16497)
E/AndroidRuntime(1464): at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
E/AndroidRuntime(1464): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
E/AndroidRuntime(1464): at android.view.View.measure(View.java:16497)
E/AndroidRuntime(1464): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
E/AndroidRuntime(1464): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
E/AndroidRuntime(1464): at android.view.View.measure(View.java:16497)
E/AndroidRuntime(1464): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
E/AndroidRuntime(1464): at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
E/AndroidRuntime(1464): at android.view.View.measure(View.java:16497)
E/AndroidRuntime(1464): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
E/AndroidRuntime(1464): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
E/AndroidRuntime(1464): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
E/AndroidRuntime(1464): at android.view.View.measure(View.java:16497)
E/AndroidRuntime(1464): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
E/AndroidRuntime(1464): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
E/AndroidRuntime(1464): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
E/AndroidRuntime(1464): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
E/AndroidRuntime(1464): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
E/AndroidRuntime(1464): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
E/AndroidRuntime(1464): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
: E/AndroidRuntime(1464): at android.view.Choreographer.doFrame(Choreographer.java:544)
E/AndroidRuntime(1464): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
E/AndroidRuntime(1464): at android.os.Handler.handleCallback(Handler.java:733)
E/AndroidRuntime(1464): at android.os.Handler.dispatchMessage(Handler.java:95)
E/AndroidRuntime(1464): at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime(1464): at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime(1464): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(1464): at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime(1464): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
E/AndroidRuntime(1464): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
E/AndroidRuntime(1464): at dalvik.system.NativeStart.main(Native Method)
ImageCatche.java：
package com.sit.fth.util;
public class ImageCache {
private static final String TAG = "ImageCache";
// Default memory cache size in kilobytes
private static final int DEFAULT_MEM_CACHE_SIZE = 1024 * 5; // 5MB
// Default disk cache size in bytes
private static final int DEFAULT_DISK_CACHE_SIZE = 1024 * 1024 * 10; // 10MB
// Compression settings when writing images to disk cache
private static final CompressFormat DEFAULT_COMPRESS_FORMAT = CompressFormat.JPEG;
private static final int DEFAULT_COMPRESS_QUALITY = 70;
private static final int DISK_CACHE_INDEX = 0;
// Constants to easily toggle various caches
private static final boolean DEFAULT_MEM_CACHE_ENABLED = true;
private static final boolean DEFAULT_DISK_CACHE_ENABLED = true;
private static final boolean DEFAULT_INIT_DISK_CACHE_ON_CREATE = false;
private DiskLruCache mDiskLruCache;
private LruCache<String, BitmapDrawable> mMemoryCache;
private ImageCacheParams mCacheParams;
private final Object mDiskCacheLock = new Object();
private boolean mDiskCacheStarting = true;
private HashSet<SoftReference<Bitmap>> mReusableBitmaps;
private ImageCache(ImageCacheParams cacheParams) {
init(cacheParams);
}
public static ImageCache getInstance(
FragmentManager fragmentManager, ImageCacheParams cacheParams) {
// Search for, or create an instance of the non-UI RetainFragment
final RetainFragment mRetainFragment = findOrCreateRetainFragment(fragmentManager);
// See if we already have an ImageCache stored in RetainFragment
ImageCache imageCache = (ImageCache) mRetainFragment.getObject();
// No existing ImageCache, create one and store it in RetainFragment
if (imageCache == null) {
imageCache = new ImageCache(cacheParams);
mRetainFragment.setObject(imageCache);
}
return imageCache;
}
public static class ImageCacheParams {
public int memCacheSize = DEFAULT_MEM_CACHE_SIZE;
public int diskCacheSize = DEFAULT_DISK_CACHE_SIZE;
public File diskCacheDir;
public CompressFormat compressFormat = DEFAULT_COMPRESS_FORMAT;
public int compressQuality = DEFAULT_COMPRESS_QUALITY;
public boolean memoryCacheEnabled = DEFAULT_MEM_CACHE_ENABLED;
public boolean diskCacheEnabled = DEFAULT_DISK_CACHE_ENABLED;
public boolean initDiskCacheOnCreate = DEFAULT_INIT_DISK_CACHE_ON_CREATE;
public ImageCacheParams(Context context, String diskCacheDirectoryName) {
diskCacheDir = getDiskCacheDir(context, diskCacheDirectoryName); <-- 375th Error
}
public void setMemCacheSizePercent(float percent) {
if (percent < 0.05f || percent > 0.8f) {
throw new IllegalArgumentException("setMemCacheSizePercent - percent must be "
+ "between 0.05 and 0.8 (inclusive)");
}
memCacheSize = Math.round(percent * Runtime.getRuntime().maxMemory() / 1024);
}
}
private static boolean canUseForInBitmap(
Bitmap candidate, BitmapFactory.Options targetOptions) {
int width = targetOptions.outWidth / targetOptions.inSampleSize;
int height = targetOptions.outHeight / targetOptions.inSampleSize;
return candidate.getWidth() == width && candidate.getHeight() == height;
}
public static File getDiskCacheDir(Context context, String uniqueName) {
// Check if media is mounted or storage is built-in, if so, try and use external cache dir
// otherwise use internal cache dir
final String cachePath =
Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) ||
!isExternalStorageRemovable() ? getExternalCacheDir(context).getPath() : <---402nd Error
context.getCacheDir().getPath();
return new File(cachePath + File.separator + uniqueName);
}
}
HomeFragment.java：
package com.sit.fth.frgment;
public class HomeFragment extends BaseFragment {
private View view;
private ExpandableListView expListView;
private ArrayList<String> childArrayList;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild = new HashMap<String, List<String>>();
private int lastExpandedPosition = -1;
int lastExpandedGroupPosition;
private int mImageThumbSize;
private ImageFetcher mImageFetcher;
private LinearLayout loadingLayout;
private TextView invisible;
private List<ImgGallery> imggalleries;
private LinearLayout listlayout;
private int collapse = 1;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.home_fragment, null);
// mTabHost = (TabHost) mRoot.findViewById(android.R.id.tabhost);
mImageThumbSize = getResources().getDimensionPixelSize(
R.dimen.image_thumbnail_size);
((TextView) view.findViewById(R.id.txt_header)).setText("HOME");
ImageCacheParams cacheParams = new ImageCacheParams(getActivity(),
AppConstants.IMAGE_CACHE_DIR); <---82nd Line Error
cacheParams.setMemCacheSizePercent(0.25f); // Set memory cache to 25% of
// app memory
}
如果您知道如何解决这些问题，任何人都可以帮助我。谢谢。
最佳答案
AppConstants.IMAGE_CACHE_DIR的值及其引用在函数中：
public static File getDiskCacheDir(Context context, String uniqueName) {
// Check if media is mounted or storage is built-in, if so, try and use external cache dir
// otherwise use internal cache dir
final String cachePath =
Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) ||
!isExternalStorageRemovable() ? getExternalCacheDir(context).getPath() : <---402nd Error
context.getCacheDir().getPath();
return new File(cachePath + File.separator + uniqueName);
}
将其用于仿真器，电话时，情况有所不同。即sdCard上的路径访问。
因此，您需要检查在哪种设备上遇到此错误的情况。
关于android - NullPointerException在ImageCatche，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24121307/