Android Loader使用時，螢幕解鎖後，重複載入

Android Loader使用時，螢幕解鎖後，重複載入

在使用AsyncTaskLoader時，當手機解鎖後，會重複載入資料，代碼如下：

 

static class CouponShopQueryLoader extendsAsyncTaskLoader> {private int couponId;public CouponShopQueryLoader(Context context, int couponId) {super(context);this.couponId = couponId;}@Overrideprotected void onStartLoading() {forceLoad();}@Overridepublic List loadInBackground() {//查詢資料載入}}

這時候，很奇怪的現象就出來了，每次手機解鎖後，資料都會重複了，重複載入。經查閱CursorLoader源碼後發現，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。經修改後：

 

 

static class CouponShopQueryLoader2 extendsAsyncTaskLoader> {private List 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 loadInBackground() {mData = ds.queryShopByCoupon(couponId, pageNo, PAGE_SIZE);return mData;}/* Runs on the UI thread */@Overridepublic void deliverResult(List 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 cursor) {Log.d(sss, onCanceled);}@Overrideprotected void onReset() {super.onReset();Log.d(sss, onReset);// Ensure the loader is stoppedonStopLoading();mData = null;}}

修改後，重複載入的現象解決了，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，會去執行onStartLoading（）方法，在onStartLoading方法中根據資料是否需要重新載入進行判斷。而如果不在onStartLoading進行loader狀態判斷的話，就導致了資料重複載入的問題！ ok---解決了！