在使用AsyncTaskLoader時，當手機解鎖後，會重復加載數據，代碼如下：
static class CouponShopQueryLoader extends
AsyncTaskLoader> {
private int couponId;
public CouponShopQueryLoader(Context context, int couponId) {
super(context);
this.couponId = couponId;
}
@Override
protected void onStartLoading() {
forceLoad();
}
@Override
public List loadInBackground() {
//查詢數據加載
}
}
這時候，很奇怪的現象就出來了，每次手機解鎖後，數據都會重復了，重復加載。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官方幫助文檔demo的使用方式。經修改後：
static class CouponShopQueryLoader2 extends
AsyncTaskLoader> {
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 */
@Override
public List loadInBackground() {
mData = ds.queryShopByCoupon(couponId, pageNo, PAGE_SIZE);
return mData;
}
/* Runs on the UI thread */
@Override
public 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
*/
@Override
protected void onStartLoading() {
if (mData != null) {
deliverResult(mData);
}
if (takeContentChanged() || mData == null) {
forceLoad();
}
}
/**
* Must be called from the UI thread
*/
@Override
protected void onStopLoading() {
Log.d(sss, onStopLoading);
// Attempt to cancel the current load task if possible.
cancelLoad();
}
@Override
public void onCanceled(List cursor) {
Log.d(sss, onCanceled);
}
@Override
protected void onReset() {
super.onReset();
Log.d(sss, onReset);
// Ensure the loader is stopped
onStopLoading();
mData = null;
}
}
修改後，重復加載的現象解決了，究其原因是沒有重寫
/**
* Must be called from the UI thread
*/
@Override
protected void onStopLoading() {
Log.d(sss, onStopLoading);
// Attempt to cancel the current load task if possible.
cancelLoad();
}
當手機屏幕關閉時，會調用onStopLoading（）方法，此時應該將loader取消掉，當屏幕解鎖時，會去執行onStartLoading（）方法，在onStartLoading方法中根據數據是否需要重新加載進行判斷。而如果不在onStartLoading進行loader狀態判斷的話，就導致了數據重復加載的問題！ ok---解決了！
