我实现了使用SQLiteDatabase作为其后备数据源的Content Provider。
通过调用getContentResolver().applyBatch(operations)
来写入DB的一个活动,该活动应该是原子的。
protected void onPause() {
new Thread(){
@Override
public void run() {
ArrayList<ContentProviderOperation> ops = new ArrayList<>();
ContentProviderOperation.Builder builder;
for (Tag tag: mTopicAdapter.getTags()) {
builder = ContentProviderOperation.newUpdate(QuizProvider.TAG_URI);
builder.withValue(Tag.Table.SELECTED, tag.getSelectionStatus());
builder.withSelection(Tag.Table._ID + " = " + tag.getId(), null);
ops.add(builder.build());
}
try {
ContentProviderResult[] res = getContentResolver().applyBatch(QuizProvider.AUTHORITY, ops);
Timber.d("Update result: %d", res.length);
getContentResolver().notifyChange(QuizProvider.TAG_URI, null);
getContentResolver().notifyChange(QuizProvider.QUESTION_URI, null);
} catch (RemoteException e) {
e.printStackTrace();
} catch (OperationApplicationException e) {
e.printStackTrace();
}
}
}.start();
super.onPause();
}
在Cursor Loader的帮助下从DB读取的第二个活动,有时会获取旧数据(竞争条件)。
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
Uri randQuestionUri = QuizProvider.QUESTION_URI
.buildUpon()
.appendPath("rand").appendPath(Integer.toString(QUIZ_SIZE))
.build();
return new CursorLoader(this, randQuestionUri, null, null, null, null);
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
if (DEBUG) Timber.d("load finished: %d", data.hashCode());
mPagerAdapter.swapCursor(data);
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
mPagerAdapter.swapCursor(null);
}
完整项目here。
日志输出:
NSA:QuizProvider:138: update db: selected=false _id = 4
NSA:QuizProvider:138: update db: selected=false _id = 5
NSA:QuizProvider:138: update db: selected=false _id = 26
NSA:QuizProvider:138: update db: selected=false _id = 19
NSA:QuizProvider:138: update db: selected=false _id = 28
NSA:QuizProvider:138: update db: selected=false _id = 10
NSA:QuizProvider:138: update db: selected=false _id = 12
NSA:QuizProvider:138: update db: selected=false _id = 15
NSA:QuizProvider:138: update db: selected=false _id = 18
NSA:QuizProvider:138: update db: selected=false _id = 25
NSA:QuizProvider:138: update db: selected=false _id = 16
NSA:QuizProvider:138: update db: selected=false _id = 17
NSA:QuizProvider:138: update db: selected=false _id = 8
NSA:QuizProvider:138: update db: selected=false _id = 3
NSA:QuizProvider:138: update db: selected=false _id = 20
NSA:QuizProvider:138: update db: selected=false _id = 29
NSA:QuizProvider:138: update db: selected=false _id = 24
NSA:QuizProvider:138: update db: selected=false _id = 23
NSA:QuizProvider:138: update db: selected=false _id = 30
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuizProvider:103: query db: content://doit.study.droi question/ran 280 null null
NSA:QuizProvider:138: update db: selected=false _id = 6
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuizProvider:138: update db: selected=false _id = 1
NSA:QuizProvider:138: update db: selected=false _id = 14
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuizProvider:138: update db: selected=false _id = 7
NSA:QuizProvider:138: update db: selected=false _id = 27
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuestionsActivity:84: load finished: 154982045
NSA:QuestionsPagerAdapter:66: swap cursor, cnt: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:35: instantiateItem, pos=0
NSA:QuestionsPagerAdapter:25: getItem, pos=0
NSA:QuestionsPagerAdapter:35: instantiateItem, pos=1
NSA:QuestionsPagerAdapter:25: getItem, pos=1
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuizProvider:138: update db: selected=false _id = 2
NSA:QuizProvider:138: update db: selected=false _id = 11
NSA:QuizProvider:138: update db: selected=false _id = 22
NSA:QuizProvider:138: update db: selected=false _id = 9
NSA:QuizProvider:138: update db: selected=false _id = 31
NSA:QuizProvider:138: update db: selected=false _id = 21
NSA:QuizProvider:138: update db: selected=false _id = 32
NSA:QuizProvider:138: update db: selected=false _id = 13
NSA:QuizProvider:138: update db: selected=false _id = 4
W/FragmentManager: moveToState: Fragment state for QuestionFragment{5c25e01 #0 id=0x7f0f00e5} not updated inline; expected state 3 found 2
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:52: title pos: 0, questions: tags: [User Interfaces]
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:52: title pos: 1, questions: tags: [User Interfaces]
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuizProvider:103: query db: content://doit.study.droi tag null null
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuestionsPagerAdapter:42: counter: 104
NSA:QuizProvider:138: update db: selected=false _id = 5
NSA:QuizProvider:138: update db: selected=false _id = 26
NSA:QuizProvider:103: query db: content://doit.study.droi tag null null
NSA:QuizProvider:138: update db: selected=false _id = 19
NSA:QuizProvider:138: update db: selected=false _id = 28
NSA:QuizProvider:138: update db: selected=false _id = 10
NSA:QuizProvider:138: update db: selected=false _id = 12
NSA:QuizProvider:138: update db: selected=false _id = 15
NSA:QuizProvider:138: update db: selected=false _id = 18
NSA:QuizProvider:138: update db: selected=false _id = 25
NSA:QuizProvider:138: update db: selected=false _id = 16
NSA:QuizProvider:138: update db: selected=false _id = 17
NSA:QuizProvider:138: update db: selected=false _id = 8
NSA:QuizProvider:138: update db: selected=false _id = 3
NSA:QuizProvider:138: update db: selected=false _id = 20
NSA:QuizProvider:138: update db: selected=false _id = 29
NSA:QuizProvider:138: update db: selected=false _id = 24
NSA:QuizProvider:138: update db: selected=false _id = 23
NSA:QuizProvider:138: update db: selected=false _id = 30
NSA:QuizProvider:138: update db: selected=false _id = 6
NSA:QuizProvider:138: update db: selected=false _id = 1
NSA:QuizProvider:138: update db: selected=false _id = 14
NSA:QuizProvider:138: update db: selected=false _id = 7
NSA:QuizProvider:138: update db: selected=false _id = 27
NSA:QuizProvider:138: update db: selected=false _id = 2
NSA:QuizProvider:138: update db: selected=false _id = 11
NSA:QuizProvider:138: update db: selected=false _id = 22
NSA:QuizProvider:138: update db: selected=false _id = 9
NSA:QuizProvider:138: update db: selected=false _id = 31
NSA:QuizProvider:138: update db: selected=false _id = 21
NSA:QuizProvider:138: update db: selected=false _id = 32
NSA:QuizProvider:138: update db: selected=false _id = 13
NSA:QuizProvider:103: query db: content://doit.study.droi question/ran 280 null null
NSA:QuestionsActivity:84: load finished: 19434496
NSA:QuestionsPagerAdapter:66: swap cursor, cnt: 0
NSA:QuestionsPagerAdapter:42: counter: 0
NSA:QuestionsPagerAdapter:42: counter: 0
日志显示applyBatch未完成,Cursor Loader获得部分修改的数据(光标计数器= 104,应为0或280)。
一些资源(抱歉,无法添加两个以上的链接):
_http://developer.android.com/guide/topics/providers/content-provider-basics.html#Batch
_http://www.androiddesignpatterns.com/2012/10/sqlite-contentprovider-thread-safety.html
_http://stackoverflow.com/questions/8104832/sqlite-simultaneous-reading-and-writing
_http://www.grokkingandroid.com/better-performance-with-contentprovideroperation/
你有什么想法吗?
答案 0 :(得分:4)
这里基本上要考虑三件事:
notifyChange()
电话移至您的ContentProvider。这样,您可以确保无论何时进行更改都会调用它们。换句话说:你可能忘记在其他地方这样做。客户不应对此负责 - 它不属于此。applyBatch()
方法实际使用了交易。只有这样你才能获得所需的性能优势,只有锁才能以你需要的方式使用。applyBatch()
运行时,不会发出任何通知。否则你的Loader会被频繁调用。你绝对想避免这种情况。您可以看到符合这些规则的内容提供商cpsample project。