踩坑-复用RemoteView导致内存泄漏总结

复用RemoteView导致内存泄漏总结

关于RemoteView

RemoteView是一个提供跨进程控制的View，主要用在通知栏或者小部件的开发上。例如音乐类APP自定义的通知栏样式就是通过RemoteView实现的。如果你之前没有听说过RemoteView，可以在这里简单了解一下：

https://www.jianshu.com/p/23041852bd85

RemoteView中可以使用的布局和控件是受限制的，能用的布局有：

• AdapterViewFlipper
• FrameLayout
• GridLayout
• GridView
• LinearLayout
• ListView
• RelativeLayout
• StackView
• ViewFlipper

可以用的控件有:

• AnalogClock
• Button
• Chronometer
• ImageButton
• ImageView
• ProgressBar
• TextClock
• TextView

遇到的问题

最近开发了一个音乐类的App，播放音乐时会在通知栏常驻一个自定义样式的通知，其中通知栏有一个头像是通过setImageViewBitmap(int viewId, Bitmap bitmap)方法进行设置的：

RemoteViews mRemoteView;  // 全局变量

mRemoteView = new RemoteViews(Application.getInstance().getPackageName(), resId);

// 每次调用setImageViewBitmap来更新通知栏的头像
mRemoteView.setImageViewBitmap(R.id.cover, bitmap);

后来发现如果App连续放歌在3个小时左右时就会OOM崩掉，通过Profile检查内存后，发现是头像的bitmap没有销毁导致的，但是这里的bitmap对象每次使用完都会recycle掉，为什么还会内存泄漏呢？经过一番排查，发现是使用同一个RemoteVIew对象setImageViewBitmap(R.id.cover, bitmap)导致的。

在RemoteView的源码中我们可以看到一个mActions变量，这是一个Action的列表：

/**
     * An array of actions to perform on the view tree once it has been
     * inflated
     */
private ArrayList<Action> mActions;

而Action是其内部定义的一个可序列化的类:

private abstract static class Action implements Parcelable 

通过跟踪setImageViewBitmap(int viewId, Bitmap bitmap)中bitmap的去向，发现最终调用了setBitmap()方法:

public void setBitmap(int viewId, String methodName, Bitmap value) {
    addAction(new BitmapReflectionAction(viewId, methodName, value));
}

private class BitmapReflectionAction extends Action {
        int bitmapId;
        Bitmap bitmap;
        String methodName;

        BitmapReflectionAction(int viewId, String methodName, Bitmap bitmap) {
            this.bitmap = bitmap;
           ...
        }
		...
            
        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeInt(TAG);
            dest.writeInt(viewId);
            dest.writeString(methodName);
            dest.writeInt(bitmapId);
        }

     	...
    }

可以看出，每次setImageViewBitmap()，都会将Bitmap做成一个BitmapReflectionAction，并添加到mActions列表里，这里的BitmapReflectionAction是继承Action的一个可序列化的类，Bitmap在里面作为被序列化成了一组值最终存到了mActions列表中。在源码中，mActions列表只看到有添加操作，并没有看到remove或者clear操作，导致了内存泄漏。

解决

不要复用RemoteView，更新通知栏icon时，new一个新的RemoteView给NotificationCompat.Builder

参考

So internally RemoteViews is simply a set of actions that are “serialized” and sent to another process. Each time you make a call to something like setDouble(), you’re adding an additional action to RemoteViews’ internal list.

Because there isn’t a way of clearing these actions from a RemoteViews object, all of your successive setImageViewBitmap() calls, along with their Bitmaps, remain in the internal list, and are actually “serialized” and applied each time your send it. :( In this case it’s best to just create a new RemoteViews object every time.

https://github.com/rojdes/AngryDict/blob/master/app/src/main/java/me/rds/angrydictionary/widget/BinaryClockWidget.java

https://blog.csdn.net/u013989732/article/details/78501462