我正在尝试创建一个使用Jack Wharton的ViewPager库（here）的应用程序，仅使用每个页面的图像（类似于Prixing（here）主屏幕）。 一切正常，除了片段中的saveInstance。
在Jack Wharton的例子中，他将文本存储在名为mContent的String变量中，并在onCreate中恢复它，但在我的情况下，我该怎么办？保存/恢复位图？！任何客观的答案都会非常感激！
我对使用应用程序的Fragment很新，因为我看到的每个例子都只提供了基础知识，并且在更复杂的问题上变得越来越困难。
PS。如果有用的知道，我正在使用CirclePageIndicator。
目前的片段代码：
public final class SpecialOfferFragment extends Fragment {
private int imageResourceId;
public static SpecialOfferFragment newInstance(int i) {
//probably I'll use a bitmap(downloaded) as parameter instead of using static images
SpecialOfferFragment fragment = new SpecialOfferFragment();
fragment.imageResourceId = i;
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// if ((savedInstanceState != null) { }
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ImageView image = new ImageView(getActivity());
image.setImageResource(imageResourceId);
image.setScaleType(ScaleType.FIT_XY);
LinearLayout layout = new LinearLayout(getActivity());
layout.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
LayoutParams.FILL_PARENT));
layout.setGravity(Gravity.CENTER);
layout.addView(image);
return layout;
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
//smth to save here..
}
}
在应用程序的当前状态中，我得到以下异常：
04-12 07:28:17.760: E/AndroidRuntime(31903): FATAL EXCEPTION: main
04-12 07:28:17.760: E/AndroidRuntime(31903): java.lang.NullPointerException
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.support.v4.app.FragmentManagerImpl.saveFragmentBasicState(FragmentManager.java:1576)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.support.v4.app.FragmentManagerImpl.saveAllState(FragmentManager.java:1617)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.support.v4.app.FragmentActivity.onSaveInstanceState(FragmentActivity.java:481)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.Activity.performSaveInstanceState(Activity.java:1113)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.Instrumentation.callActivityOnSaveInstanceState(Instrumentation.java:1188)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.ActivityThread.performStopActivityInner(ActivityThread.java:2804)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.ActivityThread.handleStopActivity(ActivityThread.java:2862)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.ActivityThread.access$900(ActivityThread.java:127)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1175)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.os.Handler.dispatchMessage(Handler.java:99)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.os.Looper.loop(Looper.java:137)
04-12 07:28:17.760: E/AndroidRuntime(31903): at android.app.ActivityThread.main(ActivityThread.java:4511)
04-12 07:28:17.760: E/AndroidRuntime(31903): at java.lang.reflect.Method.invokeNative(Native Method)
04-12 07:28:17.760: E/AndroidRuntime(31903): at java.lang.reflect.Method.invoke(Method.java:511)
04-12 07:28:17.760: E/AndroidRuntime(31903): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
04-12 07:28:17.760: E/AndroidRuntime(31903): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
04-12 07:28:17.760: E/AndroidRuntime(31903): at dalvik.system.NativeStart.main(Native Method)
每当我暂停/停止包含此片段的活动时都会发生这种情况，例如按下主页按钮。
**
**
public class MainMenu extends FragmentActivity {
//private List<CategoriesHolder> categoriesList = new ArrayList<CategoriesHolder>();
//private CategoriesAdapter categoriesAdapter = null;
//private GridView gv_mainmenu_categories;
SpecialOfferFragmentAdapter mAdapter;
ViewPager mPager;
PageIndicator mIndicator;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mainmenu);
linkUI();
setAction();
// just for testing
String[] imagesUrls = null;
mAdapter = new SpecialOfferFragmentAdapter(getSupportFragmentManager(),
this, imagesUrls);
//categoriesAdapter = new CategoriesAdapter(this, categoriesList);
// used for Categories GridView
//gv_mainmenu_categories.setAdapter(categoriesAdapter);
// used for ViewPager
mPager.setAdapter(mAdapter);
mIndicator.setViewPager(mPager);
}
private void linkUI() {
mPager = (ViewPager) findViewById(R.id.vp_mainmenu_special_offers);
mIndicator = (CirclePageIndicator) findViewById(R.id.indicator);
//gv_mainmenu_categories = (GridView) findViewById(R.id.gv_mainmenu_categories);
}
private void setAction() {
}
}
public class SpecialOfferFragmentAdapter extends FragmentPagerAdapter implements
IconPagerAdapter {
private int[] mCarouselImages = new int[] { R.drawable.pic1,
R.drawable.pic2, R.drawable.pic3, R.drawable.pic4, R.drawable.pic5
};
private String[] imagesUrls;
private Context context;
public static final int[] ICONS = new int[] {
R.drawable.perm_group_calendar, R.drawable.perm_group_camera,
R.drawable.perm_group_device_alarms, R.drawable.perm_group_location };
private int mCount = mCarouselImages.length;
public SpecialOfferFragmentAdapter(FragmentManager fm, Context context,
String[] imagesUrls) {
super(fm);
this.context = context;
this.imagesUrls = imagesUrls;
}
@Override
public Fragment getItem(int position) {
return SpecialOfferFragment.newInstance(mCarouselImages[position]);
}
@Override
public int getCount() {
return mCount;
}
@Override
public int getIconResId(int index) {
return ICONS[index % ICONS.length];
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
}
答案 0 :(得分：10)
要实现您想要的东西，您应该使用整数值来存储ViewPager中的当前位置，然后使用此值将正确的位置设置为ViewPager。
例如，在FragmentActivity：
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putInt("mMyCurrentPosition", mPager.getPosition());
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
mMyCurrentPosition = savedInstanceState.getInt("mMyCurrentPosition");
// where mMyCurrentPosition should be a public value in your activity.
}
将保存您的ViewPager的最后位置。然后在您的onResume()中，您可以检查
if(mMyCurrentPosition != 0){
mPager.setCurrentItem(mMyCurrentPosition);
}
我认为这应该可行，在捆绑中保存图像/位图并不是一个好习惯（我认为你无法做到这一点）。
答案 1 :(得分：2)
好的，首先想要清除一些可能解决你对saveinstancestate的困惑的事情。 Savedinstancestate只能处理原语（int，double，float，byte ..）和String对象。这应该是您所需要的，但在某些情况下，您还希望保存其他对象的实例。为此，您需要一些其他模式来完成工作，例如工厂模式包含所有位图的数组。 比如创建一个类ImageFactory，它包含一个静态的位图ArrayList。 无论何时旋转设备，都会再次调用oncreateview和onactivitycreated方法，这是检查是否要从工厂检索信息的时刻。例如
if（savedInstanceState！= null）{//我们有一个savedinstancestate 可能有保存的图像ImageFactory.getBMPs（）; }
希望你能用这些信息做些什么。祝你好运
答案 2 :(得分：2)
这对我来说在你的主要活动中简单易行
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
onCreate(savedInstanceState);
}
并在你的清单
中
<activity
android:configChanges="orientation|screenSize"/>
答案 3 :(得分：1)
我在使用SharedPreference更改标签时创建了自己保存片段数据的方法：
方法如：
public void saveData() {
Log.d("msg", "Save Instance");
SharedPreferences.Editor outState = getActivity().getSharedPreferences("order", Context.MODE_APPEND).edit();
orderDate = orderDateEditText.getText().toString();
orderBy = orderByEditText.getText().toString();
orderMobileNo = orderMobileNoEditText.getText().toString();
orderTransport = orderTransportEditText.getText().toString();
orderInvoicePer = orderInvoicePerEditText.getText().toString();
orderCharge = orderChargeEditText.getText().toString();
orderGoodsDispatch = orderGoodsDispatchEditText.getText().toString();
orderOthers = orderOthersEditText.getText().toString();
orderIsDirect = orderIsDirectCheckBox.isChecked() ? 1 : 0;
outState.putBoolean("saved", true);
outState.putString("orderDate", orderDate);
outState.putString("orderBy", orderBy);
outState.putString("orderMobileNo", orderMobileNo);
outState.putString("orderTransport", orderTransport);
outState.putString("orderInvoicePer", orderInvoicePer);
outState.putString("orderCharge", orderCharge);
outState.putString("orderGoodsDispatch", orderGoodsDispatch);
outState.putString("orderOthers", orderOthers);
outState.putInt("orderIsDirect", orderIsDirect);
outState.commit();
}
时调用此方法
@Override
public void onStop() {
// TODO Auto-generated method stub
super.onStop();
saveData();
}
使用 EditText 替换已保存的数据：
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
/***** PUT DATA IN EDITTEXT is ITS AVAILABLE IN BUNDLE *****/
SharedPreferences orderData = getActivity().getSharedPreferences("order", Context.MODE_APPEND);
Log.d("msg", ""+orderData.getBoolean("saved", false));
if(orderData.getBoolean("saved", false))
{
orderDate = orderData.getString("orderDate", "");
orderBy = orderData.getString("orderBy", "");
orderMobileNo = orderData.getString("orderMobileNo", "");
orderTransport = orderData.getString("orderTransport", "");
orderInvoicePer = orderData.getString("orderInvoicePer", "");
orderCharge = orderData.getString("orderCharge", "");
orderGoodsDispatch = orderData.getString("orderGoodsDispatch", "");
orderOthers = orderData.getString("orderOthers", "");
orderIsDirect = orderData.getInt("orderIsDirect", 0);
orderDateEditText.setText(orderDate);
orderByEditText.setText(orderBy);
orderMobileNoEditText.setText(orderMobileNo);
orderTransportEditText.setText(orderTransport);
orderInvoicePerEditText.setText(orderInvoicePer);
orderChargeEditText.setText(orderCharge);
orderGoodsDispatchEditText.setText(orderGoodsDispatch);
orderOthersEditText.setText(orderOthers);
if(orderIsDirect == 0)
orderIsDirectCheckBox.setChecked(false);
else
orderIsDirectCheckBox.setChecked(true);
}
}
愿这段代码对你有帮助......
...谢谢
答案 4 :(得分：1)
我不太确定这个问题是否仍然困扰着你，因为已经有好几个月了。但我想分享一下我是如何处理这个问题的。 这是源代码：
int FLAG = 0;
private View rootView;
private LinearLayout parentView;
/**
* The fragment argument representing the section number for this fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
/**
* Returns a new instance of this fragment for the given section number.
*/
public static Fragment2 newInstance(Bundle bundle) {
Fragment2 fragment = new Fragment2();
Bundle args = bundle;
fragment.setArguments(args);
return fragment;
}
public Fragment2() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
Log.e("onCreateView","onCreateView");
if(FLAG!=12321){
rootView = inflater.inflate(R.layout.fragment_create_new_album, container, false);
changeFLAG(12321);
}
parentView=new LinearLayout(getActivity());
parentView.addView(rootView);
return parentView;
}
/* (non-Javadoc)
* @see android.support.v4.app.Fragment#onDestroy()
*/
@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
Log.e("onDestroy","onDestroy");
}
/* (non-Javadoc)
* @see android.support.v4.app.Fragment#onStart()
*/
@Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
Log.e("onstart","onstart");
}
/* (non-Javadoc)
* @see android.support.v4.app.Fragment#onStop()
*/
@Override
public void onStop() {
// TODO Auto-generated method stub
super.onStop();
if(false){
Bundle savedInstance=getArguments();
LinearLayout viewParent;
viewParent= (LinearLayout) rootView.getParent();
viewParent.removeView(rootView);
}
parentView.removeView(rootView);
Log.e("onStop","onstop");
}
@Override
public void onPause() {
super.onPause();
Log.e("onpause","onpause");
}
@Override
public void onResume() {
super.onResume();
Log.e("onResume","onResume");
}
这是MainActivity：
/**
* Fragment managing the behaviors, interactions and presentation of the
* navigation drawer.
*/
private NavigationDrawerFragment mNavigationDrawerFragment;
/**
* Used to store the last screen title. For use in
* {@link #restoreActionBar()}.
*/
public static boolean fragment2InstanceExists=false;
public static Fragment2 fragment2=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager()
.findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
// Set up the drawer.
mNavigationDrawerFragment.setUp(R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
switch(position){
case 0:
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, Fragment1.newInstance(position+1)).commit();
break;
case 1:
Bundle bundle=new Bundle();
bundle.putInt("source_of_create",CommonMethods.CREATE_FROM_ACTIVITY);
if(!fragment2InstanceExists){
fragment2=Fragment2.newInstance(bundle);
fragment2InstanceExists=true;
}
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, fragment2).commit();
break;
case 2:
fragmentTransaction.addToBackStack(null);
fragmentTransaction.replace(R.id.container, FolderExplorerFragment.newInstance(position+1)).commit();
break;
default:
break;
}
}
parentView是关键点。 通常，在onCreateView上，我们只使用return rootView。但是现在，我将rootView添加到parentView，然后返回parentView。防止＆＃34;指定的孩子已经有父母。你必须在...＆＃34;上调用removeView（）。错误，我们需要调用＆＃34; parentView.removeView（rootView）＆＃34;，或者我提供的方法是无用的。 我也想分享我是如何找到它的。首先，我设置一个布尔值来指示实例是否存在。当实例存在时，rootView将不会再次膨胀。但是后来，logcat给孩子已经有了父东西，所以我决定用另一个父亲作为中间父视图。这是它的工作原理。 希望它对您有所帮助。
答案 5 :(得分：0)
让我写下我的方法来处理这个问题。我在Activity中保留了一个片段对象变量，以便以后进行交互。在onCreate（）方法中，我检查是否存在savedInstanceState（由屏幕旋转或其他原因引起）。
public class MainActivity extends AppCompatActivity {
PlaceAddFragment mFragment;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(savedInstanceState == null) {
mFragment = new PlaceAddFragment();
mFragment.setProfileImages(incomingPics);
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.form_fragment_holder, mFragment, PlaceAddFragment.TAG)
.commit();
}else{
mFragment = (PlaceAddFragment) getSupportFragmentManager().findFragmentByTag(PlaceAddFragment.TAG);
}
}
在我的fragment类中，我重写onSaveInstanceState方法，并在其中添加setRetainInstance（true），如下所示：
public class PlaceAddFragment extends Fragment {
public static final String TAG = ".PlaceAddFragment";
private ProfileImageAdapter mAdapter;
private List<ProfileImage> mProfileImages;
private Context mContext;
public PlaceAddFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mContext = getContext();
View view = inflater.inflate(R.layout.fragment_place_add, container, false);
RecyclerView mRecyclerView = (RecyclerView) view.findViewById(R.id.hw_pictures_holder);
mRecyclerView.setLayoutManager(new LinearLayoutManager(mContext, LinearLayoutManager.HORIZONTAL, false));
mAdapter = new ProfileImageAdapter(mContext, mProfileImages);
mRecyclerView.setAdapter(mAdapter);
return view;
}
@Override
public void onSaveInstanceState(final Bundle outState) {
super.onSaveInstanceState(outState);
setRetainInstance(true);
}
@Override
public void onDestroy() {
super.onDestroy();
mAdapter = null;
mProfileImages = null;
}
public void setProfileImages(List<ProfileImage> incomingPics) {
this.mProfileImages = incomingPics;
}
public List<ProfileImage> getProfileImages() {
return this.mProfileImages;
}
}
如果您希望此代码有效，您应该为这些代码实现ProfileImageAdapter mAdapter，ProfileImage对象和所有xml布局。