我希望能够检查其他活动是否检查了RecyclerView中的项目并且不知道如何操作。 我尝试使用SharedPreferences,但只获得一个空对象引用。
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at com.icedex.lolmon.testapp.firststart.FirstStartRecyclerAdapter$ViewHolder.<init>(FirstStartRecyclerAdapter.java:63)
at com.icedex.lolmon.testapp.firststart.FirstStartRecyclerAdapter.onCreateViewHolder(FirstStartRecyclerAdapter.java:35)
at com.icedex.lolmon.testapp.firststart.FirstStartRecyclerAdapter.onCreateViewHolder(FirstStartRecyclerAdapter.java:18)
at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:5116)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4416)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4326)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1955)
at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:437)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1327)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:556)
at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:171)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2713)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3011)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1626)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579)
at android.widget.FrameLayout.onLayout(FrameLayout.java:514)
at android.view.View.layout(View.java:15671)
at android.view.ViewGroup.layout(ViewGroup.java:5038)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2086)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1843)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
这是我的代码:
public class FirstStartRecyclerAdapter extends RecyclerView.Adapter<FirstStartRecyclerAdapter.ViewHolder> {
public static final String TAG = "FSRecyclerAdapter";
public ArrayList<Card> cards;
public Context context;
public SharedPreferences sharedPref;
public boolean checkMusic = false;
public FirstStartRecyclerAdapter(Context context, ArrayList<Card> cards) {
this.cards = cards;
this.context = context;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(FirstStartRecyclerAdapter.ViewHolder holder, int position) {
Card card = cards.get(position);
holder.card_tv.setText(card.cardName);
holder.card_iv.setImageResource(card.getDrawable());
holder.card_iv2.setImageResource(card.getDrawable2());
}
public int getItemCount() {
return cards.size();
}
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public ImageView card_iv;
public ImageView card_iv2;
public TextView card_tv;
public ViewHolder(View itemView) {
super(itemView);
card_tv = (TextView) itemView.findViewById(R.id.card_tv);
card_iv = (ImageView) itemView.findViewById(R.id.card_iv);
card_iv2 = (ImageView) itemView.findViewById(R.id.card_iv2);
itemView.setOnClickListener(this);
}
@Override
public void onClick(View view) {
int position = getLayoutPosition();
Log.d(TAG, "clicked position:" + position);
long postId = cards.get(position).getId();
sharedPref = context.getSharedPreferences("myPref", Context.MODE_PRIVATE);
SharedPreferences.Editor edit = sharedPref.edit();
edit.putBoolean("checkWear", false);
edit.apply();
if (postId == 1) {
if (sharedPref.getBoolean("checkWear", true)) {
card_iv2.setImageResource(R.drawable.checkbox_blank_circle_outline);
edit.putBoolean("checkWear", false);
edit.apply();
} else {
card_iv2.setImageResource(R.drawable.checkbox_marked_circle);
edit.putBoolean("checkWear", true);
edit.apply();
}
}
if (postId == 2) {
if (checkMusic) {
card_iv2.setImageResource(R.drawable.checkbox_blank_circle_outline);
checkMusic = false;
} else {
card_iv2.setImageResource(R.drawable.checkbox_marked_circle);
checkMusic = true;
}
}
}
}
}
我将不胜感激。
答案 0 :(得分:1)
Nullpointer对我来说很奇怪......无论如何,这是另一种方法:
创建一个持有状态的静态类
final class State{
static boolean somethingIsChecked = false;
static boolean isSomethingChecked(){
return somethingIsChecked;
}
static void setSomethingIsChecked(boolean isChecked){
somethingIsChecked = isChecked;
}
}
然后在ViewHolders中调用onClick
State.setSomethingIsChecked(somevalue);
其他活动现在可以致电
State.isSomethingClicked();
获取值
请注意,Sharedpreferences和静态类都不能处理指向同一变量的多个实例,因此您应该在App结构中确保这些实例始终是singleInstance。
答案 1 :(得分:0)
这就是我所做的。 (如果您不能在SharedPreferences中访问类“ context”) 1.通过“ Context mConext”创建适配器类的上下文;或“私有WeakReference mContext”; 2.在需要在SharedPrefernce内部使用上下文的任何地方,都可以使用“ this.mContext.get()”来代替“ mContext”。喜欢 SharedPreferences首选项= this.mContext.get()。getSharedPreferences(MY_PREFERENCE_NAME,Context.MODE_PRIVATE);
我尝试了许多其他解决方案,但找不到东西。