您可以通过实现View#onSaveInstanceState
和View#onRestoreInstanceState
并扩展View.BaseSavedState
类来实现这一点.
public class CustomView extends View {
private int stateToSave;
...
@Override
public Parcelable onSaveInstanceState() {
//begin boilerplate code that allows parent classes to save state
Parcelable superState = super.onSaveInstanceState();
SavedState ss = new SavedState(superState);
//end
ss.stateToSave = this.stateToSave;
return ss;
}
@Override
public void onRestoreInstanceState(Parcelable state) {
//begin boilerplate code so parent classes can restore state
if(!(state instanceof SavedState)) {
super.onRestoreInstanceState(state);
return;
}
SavedState ss = (SavedState)state;
super.onRestoreInstanceState(ss.getSuperState());
//end
this.stateToSave = ss.stateToSave;
}
static class SavedState extends BaseSavedState {
int stateToSave;
SavedState(Parcelable superState) {
super(superState);
}
private SavedState(Parcel in) {
super(in);
this.stateToSave = in.readInt();
}
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeInt(this.stateToSave);
}
//required field that makes Parcelables from a Parcel
public static final Parcelable.Creator<SavedState> CREATOR =
new Parcelable.Creator<SavedState>() {
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}
工作在视图和视图的SavedState类之间拆分.你应该做SavedState
班Parcel
人的所有读写工作.然后,您的View类可以执行提取状态成员的工作,并执行使类返回有效状态所需的工作.
Notes: View#onSavedInstanceState
and View#onRestoreInstanceState
are called automatically for you if View#getId
returns a value >= 0. This happens when you give it an id in xml or call setId
manually. Otherwise you have to call View#onSaveInstanceState
and write the Parcelable returned to the parcel you get in Activity#onSaveInstanceState
to save the state and subsequently read it and pass it to View#onRestoreInstanceState
from Activity#onRestoreInstanceState
.
另一个简单的例子是CompoundButton