Allow host app to provide a way to clear all resources onStop() (#5145)

* * Integrated a way in glide to allow host app to provide a way to clear resources onStop().

* * Clear targetTracker only in case clearOnStop is true

* * Extracted a clearRequests() and re-used it in onStop() and onDestroy()

library/src/main/java/com/bumptech/glide/RequestManager.java

@@ -95,6 +95,8 @@ public void run() {
 
   private boolean pauseAllRequestsOnTrimMemoryModerate;
 
+  private boolean clearOnStop;
+
   public RequestManager(
       @NonNull Glide glide,
       @NonNull Lifecycle lifecycle,
@@ -203,6 +205,17 @@ public synchronized RequestManager setDefaultRequestOptions(
     return this;
   }
 
+  /**
+   * Clear all resources when onStop() from {@link LifecycleListener} is called.
+   *
+   * @return This request manager.
+   */
+  @NonNull
+  public synchronized RequestManager clearOnStop() {
+    clearOnStop = true;
+    return this;
+  }
+
   /**
    * Adds a default {@link RequestListener} that will be added to every request started with this
    * {@link RequestManager}.
@@ -354,12 +367,17 @@ public synchronized void onStart() {
 
   /**
    * Lifecycle callback that unregisters for connectivity events (if the
-   * android.permission.ACCESS_NETWORK_STATE permission is present) and pauses in progress loads.
+   * android.permission.ACCESS_NETWORK_STATE permission is present) and pauses in progress loads
+   * and clears all resources if {@link #clearOnStop()} is called.
    */
   @Override
   public synchronized void onStop() {
-    pauseRequests();
     targetTracker.onStop();
+    if (clearOnStop) {
+      clearRequests();
+    } else {
+      pauseRequests();
+    }
   }
 
   /**
@@ -369,10 +387,7 @@ public synchronized void onStop() {
   @Override
   public synchronized void onDestroy() {
     targetTracker.onDestroy();
-    for (Target<?> target : targetTracker.getAll()) {
-      clear(target);
-    }
-    targetTracker.clear();
+    clearRequests();
     requestTracker.clearRequests();
     lifecycle.removeListener(this);
     lifecycle.removeListener(connectivityMonitor);
@@ -703,6 +718,13 @@ public void onLowMemory() {
     // Nothing to add conditionally. See Glide#onTrimMemory for unconditional behavior.
   }
 
+  private synchronized void clearRequests() {
+    for (Target<?> target : targetTracker.getAll()) {
+      clear(target);
+    }
+    targetTracker.clear();
+  }
+
   @Override
   public void onConfigurationChanged(Configuration newConfig) {}