標籤:
正在使用AsyncTaskLoader時間。當手機被解鎖,重複載入資料,碼,如以下:
static class CouponShopQueryLoader extendsAsyncTaskLoader<List<CouponStore>> {private int couponId;public CouponShopQueryLoader(Context context, int couponId) {super(context);this.couponId = couponId;}@Overrideprotected void onStartLoading() {forceLoad();}@Overridepublic List<CouponStore> loadInBackground() {//查詢資料載入}}
這時候,非常奇怪的現象就出來了,每次手機解鎖後,資料都會反覆了,反覆載入。經查閱CursorLoader原始碼後發現,原來還是自己太嫩了,loader使用時。沒有嚴格遵守android官方協助文檔demo的使用方式。
經改動後:
static class CouponShopQueryLoader2 extendsAsyncTaskLoader<List<CouponStore>> {private List<CouponStore> mData;private int couponId;public CouponShopQueryLoader2(Context context, int couponId) {super(context);this.couponId = couponId;}// final ForceLoadContentObserver mObserver;/* Runs on a worker thread */@Overridepublic List<CouponStore> loadInBackground() {mData = ds.queryShopByCoupon(couponId, pageNo, PAGE_SIZE);return mData;}/* Runs on the UI thread */@Overridepublic void deliverResult(List<CouponStore> data) {if (isReset()) {return;}if (isStarted()) {super.deliverResult(data);}}/** * Starts an asynchronous load of the contacts list data. When the * result is ready the callbacks will be called on the UI thread. If a * previous load has been completed and is still valid the result may be * passed to the callbacks immediately. * * Must be called from the UI thread */@Overrideprotected void onStartLoading() {if (mData != null) {deliverResult(mData);}if (takeContentChanged() || mData == null) {forceLoad();}}/** * Must be called from the UI thread */@Overrideprotected void onStopLoading() {Log.d("sss", "onStopLoading");// Attempt to cancel the current load task if possible.cancelLoad();}@Overridepublic void onCanceled(List<CouponStore> cursor) {Log.d("sss", "onCanceled");}@Overrideprotected void onReset() {super.onReset();Log.d("sss", "onReset");// Ensure the loader is stoppedonStopLoading();mData = null;}}
改動後。反覆載入的現象攻克了,究其原因是沒有重寫
/** * Must be called from the UI thread */@Overrideprotected void onStopLoading() {Log.d("sss", "onStopLoading");// Attempt to cancel the current load task if possible.cancelLoad();}
當手機螢幕關閉時,會調用onStopLoading()方法,此時應該將loader取消掉,當螢幕解鎖時,會去運行onStartLoading()方法,在onStartLoading方法中依據資料是否須要又一次載入進行推斷。而假設不在onStartLoading進行loader狀態推斷的話。就導致了資料反覆載入的問題! ok---攻克了!
提示:在學習android開發中。官方文檔事實上是非常好的,遵守他們的編寫規範,能夠使自己少走好多彎路。
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Android Loader使用,螢幕解鎖,重複荷載