ActivityManager：addAppTask (Activity activity, Intent intent, ActivityManager.TaskDescription description, Bitmap thumbnail)
1.作用
为应用创建一个新的任务，并放在任务栈的栈顶。
参数：activity ：需要被添加的Activity，用于确定进入任务栈的入口
intent ：用于启动Activity的Intent
description：携带的信息描述
thumbnail ：缩略图资源
2.源码
public int addAppTask(@NonNull Activity activity, @NonNull Intent intent,
@Nullable TaskDescription description, @NonNull Bitmap thumbnail) {
Point size;
synchronized (this) {
ensureAppTaskThumbnailSizeLocked();
size = mAppTaskThumbnailSize;
}
final int tw = thumbnail.getWidth();
final int th = thumbnail.getHeight();
if (tw != size.x || th != size.y) {
Bitmap bm = Bitmap.createBitmap(size.x, size.y, thumbnail.getConfig());
float scale;
float dx = 0, dy = 0;
if (tw * size.x > size.y * th) {
scale = (float) size.x / (float) th;
dx = (size.y - tw * scale) * 0.5f;
} else {
scale = (float) size.y / (float) tw;
dy = (size.x - th * scale) * 0.5f;
}
Matrix matrix = new Matrix();
matrix.setScale(scale, scale);
matrix.postTranslate((int) (dx + 0.5f), 0);
Canvas canvas = new Canvas(bm);
canvas.drawBitmap(thumbnail, matrix, null);
canvas.setBitmap(null);
thumbnail = bm;
}
if (description == null) {
description = new TaskDescription();
}
try {
return ActivityManagerNative.getDefault().addAppTask(activity.getActivityToken(),
intent, description, thumbnail);
} catch (RemoteException e) {
throw new IllegalStateException("System dead?", e);
}
}
3.分析及说明
我们首先来看一下ensureAppTaskThumbnailSizeLocked()
private void ensureAppTaskThumbnailSizeLocked() {
if (mAppTaskThumbnailSize == null) {
try {
mAppTaskThumbnailSize = ActivityManagerNative.getDefault().getAppTaskThumbnailSize();
} catch (RemoteException e) {
throw new IllegalStateException("System dead?", e);
}
}
}
而ActivityManagerNative.getDefault().getAppTaskThumbnailSize()返回的是一个Size，该size是确保addAppTask()中的Bitmap参数所需的Size。
其次我们来看一下addAppTask()的返回值，返回新添加的任务id应用任务,如果添加失败则返回-1；
如果创建失败了，那么极大地原因是没有更多的空间为你的应用程任务服务。
