我创建了一个自定义视图，它是RelativeLayout的子类。该视图是Fragment集的一部分，用于保留其实例状态。我希望在设备方向发生变化时保存状态信息（只有一个布尔值），因此我使用自定义扩展名onSaveInstanceState实现了onRestoreInstanceState和BaseSavedState。 Fragment和Activity都没有实现任何处理保存/恢复实例状态的内容。当我更改设备方向时，它会保存状态，使用已保存的状态重新创建视图，但随后再次重新创建，不用调用onRestoreInstanceState。
事件序列如下所示，showingProgress是我要保存的布尔值：
View#1 (onSaveInstanceState) showingProgress=true
View#2 (ctor) showingProgress=false
View#2 (onFinishInflate)
View#2 (onRestoreInstanceState) showingProgress=true
View#2 (showProgress)
View#2 (onSaveInstanceState) showingProgress=true
View#3 (ctor) showingProgress=false
View#3 (onFinishInflate)
之后，视图被重建，但由于onRestoreInstanceState从未被调用过View＃3，因此它始终处于初始状态。
为什么要重新创建两次视图？ 如何防止第二个视图再次重新创建，或者将保存的状态分别传递给第三个视图？
修改
活动的相关部分
private Fragment currentFragment = null;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.single_fragment);
getSupportActionBar().setDisplayShowTitleEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().show();
showLoginFragment();
}
public void showLoginFragment()
{
final FragmentTransaction t = this.getSupportFragmentManager().beginTransaction();
currentFragment = MyFragment.newInstance();
t.replace(R.id.layoutRoot, currentFragment);
t.commit();
}
布局 single_fragment.xml ：
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="@+id/layoutRoot"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
</LinearLayout>
</ScrollView>
班级 MyFragment
public class MyFragment extends RoboFragment
{
// I'm using roboguice
@InjectView(R.id.myButton) private ProgressButton myButton;
public static MyFragment newInstance()
{
Bundle arguments = new Bundle();
// no arguments for now, this comes later
MyFragment fragment = new MyFragment();
fragment.setArguments(arguments);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
setRetainInstance(true);
View result = inflater.inflate(R.layout.my_fragment, container, false);
return result;
}
}
布局 my_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<com.my.package.ProgressButton
android:id="@+id/myButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/button_caption" />
</LinearLayout>
最后是 ProgressButton
的代码/**
* A Button with an integrated progress spinner. The button can show the progress spinner while some background process
* is running to indicate it can't be clicked again.
*/
public class ProgressButton extends RelativeLayout
{
/** The view holding the button text */
private TextView textView = null;
/** The progress spinner */
private ProgressBar progressSpinner = null;
private boolean showingProgress = false;
public ProgressButton(Context context)
{
super(context);
textView = new TextView(context);
progressSpinner = new ProgressBar(context);
initView();
}
public ProgressButton(Context context, AttributeSet attrs)
{
super(context, attrs);
textView = new TextView(context, attrs);
progressSpinner = new ProgressBar(context, attrs);
initView();
}
public ProgressButton(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
textView = new TextView(context, attrs, defStyle);
progressSpinner = new ProgressBar(context, attrs, defStyle);
initView();
}
/**
* Initializes the view with all its properties.
*/
@SuppressWarnings("deprecation")
private void initView()
{
// remove the background attributes from progressbar and textview, because they should be transparent
if (Build.VERSION.SDK_INT >= 16)
{
textView.setBackground(null);
progressSpinner.setBackground(null);
}
else
{
textView.setBackgroundDrawable(null);
progressSpinner.setBackgroundDrawable(null);
}
}
@Override
protected void onFinishInflate()
{
super.onFinishInflate();
if (!isInEditMode())
{
progressSpinner.setVisibility(View.INVISIBLE);
}
RelativeLayout layout = new RelativeLayout(getContext());
layout.setId(R.id.progressButtonContainer);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
this.addView(layout, params);
params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
params.addRule(RelativeLayout.ALIGN_LEFT);
params.leftMargin = 10;
progressSpinner.setClickable(false);
progressSpinner.setId(R.id.progressButtonProgress);
layout.addView(progressSpinner, params);
params = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
params.addRule(RelativeLayout.CENTER_IN_PARENT);
textView.setClickable(false);
textView.setId(R.id.progressButtonText);
layout.addView(textView, params);
}
/**
* Disables the button and shows the progress spinner.
*/
public void showProgress()
{
this.setEnabled(false);
progressSpinner.setVisibility(View.VISIBLE);
showingProgress = true;
}
/**
* Enables the button and hides the progress spinner.
*/
public void hideProgress()
{
this.setEnabled(true);
progressSpinner.setVisibility(View.INVISIBLE);
showingProgress = false;
}
@Override
public Parcelable onSaveInstanceState()
{
Parcelable superState = super.onSaveInstanceState();
return new SavedState(superState, showingProgress);
}
@Override
public void onRestoreInstanceState(Parcelable state)
{
SavedState savedState = (SavedState) state;
super.onRestoreInstanceState(savedState.getSuperState());
showingProgress = savedState.showProgress;
if(showingProgress)
{
showProgress();
}
else
{
hideProgress();
}
}
@SuppressWarnings({ "unchecked", "rawtypes" })
@Override
protected void dispatchSaveInstanceState(SparseArray container)
{
super.dispatchFreezeSelfOnly(container);
}
@SuppressWarnings({ "unchecked", "rawtypes" })
@Override
protected void dispatchRestoreInstanceState(SparseArray container)
{
super.dispatchThawSelfOnly(container);
}
static class SavedState extends BaseSavedState
{
boolean showProgress = false;
SavedState(Parcelable superState, boolean showProgress)
{
super(superState);
this.showProgress = showProgress;
}
private SavedState(Parcel in)
{
super(in);
this.showProgress = in.readByte() == 0 ? false : true;
}
@Override
public void writeToParcel(Parcel out, int flags)
{
super.writeToParcel(out, flags);
out.writeByte((byte) (showProgress ? 1 : 0));
}
// 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];
}
};
}
}
答案 0 :(得分：0)
在Daniel Bo的有益评论之后，我很容易得到解决方案。无论是否存在保存状态，都会在活动中添加片段。这导致在初始状态下添加View＃3。在以下showLoginFragment();循环中的活动onCreate方法中包装if可以解决问题。
if(savedInstanceState == null)
{
showLoginFragment();
}