com.bumptech.glide.request.target

Class ViewTarget<T extends View,Z>

java.lang.Object

com.bumptech.glide.request.target.BaseTarget<Z>

com.bumptech.glide.request.target.ViewTarget<T,Z>

Type Parameters:

T - The specific subclass of view wrapped by this target.

Z - The resource type this target will receive.

All Implemented Interfaces:

LifecycleListener, Target<Z>

Direct Known Subclasses:

ImageViewTarget

public abstract class ViewTarget<T extends View,Z>
extends BaseTarget<Z>

A base Target for loading Bitmaps into Views that provides default implementations for most most methods and can determine the size of views using a ViewTreeObserver.OnDrawListener.

To detect View reuse in ListView or any ViewGroup that reuses views, this class uses the View.setTag(Object) method to store some metadata so that if a view is reused, any previous loads or resources from previous loads can be cancelled or reused.

Any calls to View.setTag(Object)} on a View given to this class will result in excessive allocations and and/or IllegalArgumentExceptions. If you must call View.setTag(Object) on a view, consider using BaseTarget or SimpleTarget instead.

Subclasses must call super in onLoadCleared(Drawable)

Field Summary

Fields

Modifier and Type	Field and Description
protected T	view

Fields inherited from interface com.bumptech.glide.request.target.Target

SIZE_ORIGINAL

Constructor Summary

Constructors

Constructor and Description
ViewTarget(T view) Constructor that defaults waitForLayout to false.
ViewTarget(T view, boolean waitForLayout) Deprecated. Use waitForLayout() instead.

Method Summary

Modifier and Type	Method and Description
ViewTarget<T,Z>	clearOnDetach() Clears the View's Request when the View is detached from its Window and restarts the Request when the View is re-attached from its Window.
Request	getRequest() Returns any stored request using View.getTag().
void	getSize(SizeReadyCallback cb) Determines the size of the view by first checking View.getWidth() and View.getHeight().
T	getView() Returns the wrapped View.
void	onLoadCleared(Drawable placeholder) A lifecycle callback that is called when a load is cancelled and its resources are freed.
void	onLoadStarted(Drawable placeholder) A lifecycle callback that is called when a load is started.
void	removeCallback(SizeReadyCallback cb) Removes the given callback from the pending set if it's still retained.
void	setRequest(Request request) Stores the request using View.setTag(Object).
static void	setTagId(int tagId) Sets the android resource id to use in conjunction with View.setTag(int, Object) to store temporary state allowing loads to be automatically cancelled and resources re-used in scrolling lists.
String	toString()
ViewTarget<T,Z>	waitForLayout() Indicates that Glide should always wait for any pending layout pass before checking for the size an View.

Methods inherited from class com.bumptech.glide.request.target.BaseTarget

onDestroy, onLoadFailed, onStart, onStop

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.bumptech.glide.request.target.Target

onResourceReady

Field Detail

view

protected final T extends View view

Constructor Detail

ViewTarget

public ViewTarget(T view)

Constructor that defaults waitForLayout to false.

ViewTarget

@Deprecated
public ViewTarget(T view,
                              boolean waitForLayout)

Deprecated. Use waitForLayout() instead.

Parameters:

waitForLayout - If set to true, Glide will always wait for any pending layout pass before checking for the size a View. If set to false Glide will only wait for a pending layout pass if it's unable to resolve the size from layout parameters or an existing View size. Because setting this parameter to true forces Glide to wait for the layout pass to occur before starting the load, setting this parameter to true can cause flashing in some cases and should be used sparingly. If layout parameters are set to fixed sizes, they will still be used instead of the View's dimensions even if this parameter is set to true. This parameter is a fallback only.

Method Detail

clearOnDetach

public final ViewTarget<T,Z> clearOnDetach()

Clears the View's Request when the View is detached from its Window and restarts the Request when the View is re-attached from its Window.

This is an experimental API that may be removed in a future version.

Using this method can save memory by allowing Glide to more eagerly clear resources when transitioning screens or swapping adapters in scrolling views. However it also substantially increases the odds that images will not be in memory if users subsequently return to a screen where images were previously loaded. Whether or not this happens will depend on the number of images loaded in the new screen and the size of the memory cache. Increasing the size of the memory cache can improve this behavior but it largely negates the memory benefits of using this method.

Use this method with caution and measure your memory usage to ensure that it's actually improving your memory usage in the cases you care about.

waitForLayout

public final ViewTarget<T,Z> waitForLayout()

Indicates that Glide should always wait for any pending layout pass before checking for the size an View.

By default, Glide will only wait for a pending layout pass if it's unable to resolve the size from the ViewGroup.LayoutParams or valid non-zero values for View.getWidth() and View.getHeight().

Because calling this method forces Glide to wait for the layout pass to occur before starting loads, setting this parameter to true can cause Glide to asynchronous load an image even if it's in the memory cache. The load will happen asynchronously because Glide has to wait for a layout pass to occur, which won't necessarily happen in the same frame as when the image is requested. As a result, using this method can resulting in flashing in some cases and should be used sparingly.

If the ViewGroup.LayoutParams of the wrapped View are set to fixed sizes, they will still be used instead of the View's dimensions even if this method is called. This parameter is a fallback only.

onLoadStarted

@CallSuper
public void onLoadStarted(@Nullable
                                     Drawable placeholder)

Description copied from interface: Target

A lifecycle callback that is called when a load is started.

Note - This may not be called for every load, it is possible for example for loads to fail before the load starts (when the model object is null).

Note - This method may be called multiple times before any other lifecycle method is called. Loads can be paused and restarted due to lifecycle or connectivity events and each restart may cause a call here.

You must ensure that any current Drawable received in Target.onResourceReady(Object, Transition) is no longer displayed before redrawing the container (usually a View) or changing its visibility.

Specified by:

onLoadStarted in interface Target<Z>

Overrides:

onLoadStarted in class BaseTarget<Z>

Parameters:

placeholder - The placeholder drawable to optionally show, or null.

getView

public T getView()

Returns the wrapped View.

getSize

@CallSuper
public void getSize(SizeReadyCallback cb)

Determines the size of the view by first checking View.getWidth() and View.getHeight(). If one or both are zero, it then checks the view's ViewGroup.LayoutParams. If one or both of the params width and height are less than or equal to zero, it then adds an ViewTreeObserver.OnPreDrawListener which waits until the view has been measured before calling the callback with the view's drawn width and height.

Parameters:

cb - The callback that must be called when the size of the target has been determined

removeCallback

@CallSuper
public void removeCallback(SizeReadyCallback cb)

Description copied from interface: Target

Removes the given callback from the pending set if it's still retained.

Parameters:

cb - The callback to remove.

onLoadCleared

@CallSuper
public void onLoadCleared(Drawable placeholder)

Description copied from interface: Target

A lifecycle callback that is called when a load is cancelled and its resources are freed.

You must ensure that any current Drawable received in Target.onResourceReady(Object, Transition) is no longer displayed before redrawing the container (usually a View) or changing its visibility.

Specified by:

onLoadCleared in interface Target<Z>

Overrides:

onLoadCleared in class BaseTarget<Z>

Parameters:

placeholder - The placeholder drawable to optionally show, or null.

setRequest

public void setRequest(@Nullable
                       Request request)

Stores the request using View.setTag(Object).

Specified by:

setRequest in interface Target<Z>

Overrides:

setRequest in class BaseTarget<Z>

Parameters:

request -

getRequest

@Nullable
public Request getRequest()

Returns any stored request using View.getTag().

For Glide to function correctly, Glide must be the only thing that calls View.setTag(Object). If the tag is cleared or put to another object type, Glide will not be able to retrieve and cancel previous loads which will not only prevent Glide from reusing resource, but will also result in incorrect images being loaded and lots of flashing of images in lists. As a result, this will throw an IllegalArgumentException if View.getTag()} returns a non null object that is not an Request.

Specified by:

getRequest in interface Target<Z>

Overrides:

getRequest in class BaseTarget<Z>

toString

public String toString()

Overrides:

toString in class Object

setTagId

public static void setTagId(int tagId)

Sets the android resource id to use in conjunction with View.setTag(int, Object) to store temporary state allowing loads to be automatically cancelled and resources re-used in scrolling lists.

If no tag id is set, Glide will use View.setTag(Object).

Warning: prior to Android 4.0 tags were stored in a static map. Using this method prior to Android 4.0 may cause memory leaks and isn't recommended. If you do use this method on older versions, be sure to call RequestManager.clear(View) on any view you start a load into to ensure that the static state is removed.

Parameters:

tagId - The android resource to use.