如何从一个特定的位置,光标阅读的jpg文件 [英] How to read jpg file from a specific location with the cursor
问题描述
我想知道我怎么能使用游标JPG文件在SD卡中指定的文件夹中。我试图用光标选择特定文件夹中的JPG文件,我试图这样的:
这是code:
公共静态乌里getRandomImage(ContentResolver的解析器){ 的String [] =投影新的String [] {
BaseColumns._ID,
}; 字符串的文件夹=/ SD卡/ DCIM /墙纸/;
文件夹= +%;
URI URI = Media.EXTERNAL_CONTENT_URI;
的String [] = whereArgs新的String [] {}文件夹; 光标光标= resolver.query(URI,投影,空,whereArgs,MediaColumns._ID); 如果(光标==空|| cursor.getCount()&下; = 0){
返回null;
} cursor.moveToPosition(新随机()nextInt(cursor.getCount())。); 返回Uri.withAppendedPath(URI,cursor.getString(0));
}
但这种code给我的错误。
下面是logcat的:
E / AndroidRuntime(11986):致命异常:主要
E / AndroidRuntime(11986):android.database.sqlite.SQLiteException:绑定或列索引超出范围:办理0x26a490
E / AndroidRuntime(11986):在android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:158)
E / AndroidRuntime(11986):在android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:114)
E / AndroidRuntime(11986):在android.content.ContentProviderProxy.bulkQueryInternal(ContentProviderNative.java:330)
E / AndroidRuntime(11986):在android.content.ContentProviderProxy.query(ContentProviderNative.java:366)
E / AndroidRuntime(11986):在android.content.ContentResolver.query(ContentResolver.java:245)
E / AndroidRuntime(11986):在it.bisemanuDEV.slidepuzzle.SelectImage preference.getRandomImage(SelectImage preference.java:126)
E / AndroidRuntime(11986):在it.bisemanuDEV.slidepuzzle.TileView.newGame(TileView.java:156)
E / AndroidRuntime(11986):在it.bisemanuDEV.slidepuzzle.SlidePuzzleActivity.onOptionsItemSelected(SlidePuzzleActivity.java:377)
E / AndroidRuntime(11986):在android.app.Activity.onMenuItemSelected(Activity.java:2762)
E / AndroidRuntime(11986):在com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:730)
E / AndroidRuntime(11986):在com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:143)
E / AndroidRuntime(11986):在com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:855)
E / AndroidRuntime(11986):在com.android.internal.view.menu.IconMenuView.invokeItem(IconMenuView.java:532)
E / AndroidRuntime(11986):在com.android.internal.view.menu.IconMenuItemView.performClick(IconMenuItemView.java:122)
E / AndroidRuntime(11986):在android.view.View $ PerformClick.run(View.java:8819)
E / AndroidRuntime(11986):在android.os.Handler.handleCallback(Handler.java:603)
E / AndroidRuntime(11986):在android.os.Handler.dispatchMessage(Handler.java:92)
E / AndroidRuntime(11986):在android.os.Looper.loop(Looper.java:123)
E / AndroidRuntime(11986):在android.app.ActivityThread.main(ActivityThread.java:4627)
E / AndroidRuntime(11986):在java.lang.reflect.Method.invokeNative(本机方法)
E / AndroidRuntime(11986):在java.lang.reflect.Method.invoke(Method.java:521)
E / AndroidRuntime(11986):在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:868)
E / AndroidRuntime(11986):在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
E / AndroidRuntime(11986):在dalvik.system.NativeStart.main(本机方法)
从你有例外:
cursor.moveToPosition(新的随机()nextInt(cursor.getCount()));
更多precisly:
新的随机()。nextInt(cursor.getCount())
将返回cursor.getCount(),它是光标的范围之外。
从随机()nextInt(N)
的Java文档:
返回半开区间[0伪随机均匀分布INT,N)。
这意味着它可以返回否。所以,如果你想使你的code的工作,尝试新的随机()。nextInt(cursor.getCount()-1)
既然你已经测试了 cursor.getCount()> 0
I would like to understand how I can use a cursor to jpg files in a folder specified in the sdcard. I'm trying to select with a cursor the jpg files in a specific folder, and I tried this:
This is the code:
public static Uri getRandomImage(ContentResolver resolver) {
String[] projection = new String[] {
BaseColumns._ID,
};
String folder = "/sdcard/DCIM/Wallpaper/";
folder = folder + "%";
Uri uri = Media.EXTERNAL_CONTENT_URI;
String[] whereArgs = new String[]{folder};
Cursor cursor = resolver.query(uri, projection, null, whereArgs, MediaColumns._ID);
if (cursor == null || cursor.getCount() <= 0) {
return null;
}
cursor.moveToPosition(new Random().nextInt(cursor.getCount()));
return Uri.withAppendedPath(uri, cursor.getString(0));
}
but this code gives me error.
Here is the logcat:
E/AndroidRuntime(11986): FATAL EXCEPTION: main
E/AndroidRuntime(11986): android.database.sqlite.SQLiteException: bind or column index out of range: handle 0x26a490
E/AndroidRuntime(11986): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:158)
E/AndroidRuntime(11986): at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:114)
E/AndroidRuntime(11986): at android.content.ContentProviderProxy.bulkQueryInternal(ContentProviderNative.java:330)
E/AndroidRuntime(11986): at android.content.ContentProviderProxy.query(ContentProviderNative.java:366)
E/AndroidRuntime(11986): at android.content.ContentResolver.query(ContentResolver.java:245)
E/AndroidRuntime(11986): at it.bisemanuDEV.slidepuzzle.SelectImagePreference.getRandomImage(SelectImagePreference.java:126)
E/AndroidRuntime(11986): at it.bisemanuDEV.slidepuzzle.TileView.newGame(TileView.java:156)
E/AndroidRuntime(11986): at it.bisemanuDEV.slidepuzzle.SlidePuzzleActivity.onOptionsItemSelected(SlidePuzzleActivity.java:377)
E/AndroidRuntime(11986): at android.app.Activity.onMenuItemSelected(Activity.java:2762)
E/AndroidRuntime(11986): at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:730)
E/AndroidRuntime(11986): at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:143)
E/AndroidRuntime(11986): at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:855)
E/AndroidRuntime(11986): at com.android.internal.view.menu.IconMenuView.invokeItem(IconMenuView.java:532)
E/AndroidRuntime(11986): at com.android.internal.view.menu.IconMenuItemView.performClick(IconMenuItemView.java:122)
E/AndroidRuntime(11986): at android.view.View$PerformClick.run(View.java:8819)
E/AndroidRuntime(11986): at android.os.Handler.handleCallback(Handler.java:603)
E/AndroidRuntime(11986): at android.os.Handler.dispatchMessage(Handler.java:92)
E/AndroidRuntime(11986): at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(11986): at android.app.ActivityThread.main(ActivityThread.java:4627)
E/AndroidRuntime(11986): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(11986): at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime(11986): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
E/AndroidRuntime(11986): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
E/AndroidRuntime(11986): at dalvik.system.NativeStart.main(Native Method)
From the exception you have:
cursor.moveToPosition(new Random().nextInt(cursor.getCount()));
more precisly :
new Random().nextInt(cursor.getCount())
is returning cursor.getCount() which is outside of the range of the cursor.
From Random().nextInt(n)
java doc:
Returns a pseudo-random uniformly distributed int in the half-open range [0, n).
This means it can return n. So if you want to make your code work, try new Random().nextInt(cursor.getCount() -1)
since you already tested that cursor.getCount() > 0
这篇关于如何从一个特定的位置,光标阅读的jpg文件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!