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Android：如何更改RecyclerView列表项的语言？

javaandroidandroid-recyclerview
3
我是一名新手安卓开发者。我想要改变我的RecyclerView列表项的语言。我的列表项存储在values文件夹下的字符串数组中。我该如何在单击列表项时更改其语言？以下是我尝试过的代码，但出现了错误。请问有人能够纠正我的错误或向我展示实现所需结果的正确方法吗？
错误信息：
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
                  at com.example.chaitanya.kundli.MainActivity.setLocale(MainActivity.java:60)
                  at com.example.chaitanya.kundli.RecyclerViewAdapter$1.onClick(RecyclerViewAdapter.java:66)
                  at android.view.View.performClick(View.java:4759)
                  at android.view.View$PerformClick.run(View.java:19770)
                  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:5237)
                  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:912)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:707)

MainActivity.java

 public class MainActivity extends AppCompatActivity {
android.content.res.Resources res;

RecyclerView recyclerView;

Context context;
String[] numbers;

RecyclerView.Adapter recyclerView_Adapter;

RecyclerView.LayoutManager recyclerViewLayoutManager;


@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);
    res = getResources();

    numbers = res.getStringArray(R.array.abc);
    getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
    getSupportActionBar().setCustomView(R.layout.action_bar);

    context = getApplicationContext();

    recyclerView = (RecyclerView) findViewById(R.id.recycler_view1);

    //Change 2 to your choice because here 2 is the number of Grid layout Columns in each row.
    recyclerViewLayoutManager = new GridLayoutManager(context, 2);

    recyclerView.setLayoutManager(recyclerViewLayoutManager);

    recyclerView_Adapter = new RecyclerViewAdapter(context,numbers);

    recyclerView.setAdapter(recyclerView_Adapter);

}
public void setLocale(String lang) {
    Locale myLocale = new Locale(lang);
    Resources res = context.getResources();
    DisplayMetrics dm = res.getDisplayMetrics();
    Configuration conf = res.getConfiguration();
    conf.locale = myLocale;
    res.updateConfiguration(conf, dm);
    Intent refresh = new Intent(this, MainActivity.class);
    startActivity(refresh);
    finish();
}
}

RecyclerViewAdapter.java

    public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>{

String[] values;
Context context1;

public RecyclerViewAdapter(Context context2,String[] values2){

    values = values2;

    context1 = context2;
}

public static class ViewHolder extends RecyclerView.ViewHolder{

    public TextView textView;

    public ViewHolder(View v){

        super(v);

        textView = (TextView) v.findViewById(R.id.textview1);

    }
}

@Override
public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType){

    View view1 = LayoutInflater.from(context1).inflate(R.layout.recycler_view_items,parent,false);

    ViewHolder viewHolder1 = new ViewHolder(view1);

    return viewHolder1;
}

@Override
public void onBindViewHolder(ViewHolder Vholder,final int position){

    Vholder.textView.setText(values[position]);

    Vholder.textView.setBackgroundColor(Color.parseColor("#ffc947"));

    Vholder.textView.setTextColor(Color.BLACK);
    Vholder.textView.setBackgroundResource(R.drawable.rounded_corner);

    Vholder.itemView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            MainActivity aa = new MainActivity();
            if(position == 4){
                aa.setLocale("hi");//calling function
            }
        }
    });

}

@Override
public int getItemCount(){

    return values.length;
}
}

string.xml

   <?xml version="1.0" encoding="utf-8"?>
 <resources>
<string name="app_name">nnn</string>
<string-array name="abc">
    <item>Query</item>
    <item>Answers</item>
    <item>Rate Us</item>
    <item>Change Language</item>
    <item>Logout</item>
</string-array>
</resources>

string.xml(hi)

  <?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">nnn</string>
<string-array name="abc">
    <item>सवाल पूछें </item>
    <item>उत्तर देखें</item>
    <item>रेटिंग दीजिये</item>
    <item>भाषा बदलें</item>
    <item>बाहर निकलें</item>
</string-array>
</resources>
哪一行导致了 NPE？ - Code-Apprentice
3个回答
3

系统会处理活动的创建，您不应该调用new WhateverActivity()。

相反，您可以使用接口作为监听器，例如：

LocaleListener.java

public interface LocaleListener {
    void setLocale(String values)
}

在你的适配器中创建一个LocaleListener变量和一个setter函数:

    public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>{

       String[] values;
       Context context1;
       private LocaleListener mListener;  //some change here

       public RecyclerViewAdapter(Context context2,String[] values2){

           values = values2;

           context1 = context2;
       }

       public static class ViewHolder extends RecyclerView.ViewHolder{

           public TextView textView;

           public ViewHolder(View v){

               super(v);

               textView = (TextView) v.findViewById(R.id.textview1);

           }
      }

     @Override
     public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType){

         View view1 = LayoutInflater.from(context1).inflate(R.layout.recycler_view_items,parent,false);

         ViewHolder viewHolder1 = new ViewHolder(view1);

         return viewHolder1;
    }

    @Override
    public void onBindViewHolder(ViewHolder Vholder,final int position){

        Vholder.textView.setText(values[position]);

        Vholder.textView.setBackgroundColor(Color.parseColor("#ffc947"));

       Vholder.textView.setTextColor(Color.BLACK);
       Vholder.textView.setBackgroundResource(R.drawable.rounded_corner);

       Vholder.itemView.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View view) {
               if(position == 4 && mListener != null){ // some change here
                   mListener.setLocale("hi");//calling function
               }
           }
       });

      }

    @Override
    public int getItemCount(){

        return values.length;
    }

    //some change here
    public void setLocaleListener(LocaleListener listener) {
        mListener = listener
    }
}

最后将您的Activity设置为LocaleListener：

public class MainActivity extends AppCompatActivity implements LocaleListener{
   android.content.res.Resources res;

   RecyclerView recyclerView;

   Context context;
   String[] numbers;

   RecyclerView.Adapter recyclerView_Adapter;

   RecyclerView.LayoutManager recyclerViewLayoutManager;


   @Override
   protected void onCreate(Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      setContentView(R.layout.activity_main);
      res = getResources();

      numbers = res.getStringArray(R.array.abc);

      getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
      getSupportActionBar().setCustomView(R.layout.action_bar);

      context = getApplicationContext();

      recyclerView = (RecyclerView) findViewById(R.id.recycler_view1);

    //Change 2 to your choice because here 2 is the number of Grid layout Columns in each row.
       recyclerViewLayoutManager = new GridLayoutManager(context, 2);

       recyclerView.setLayoutManager(recyclerViewLayoutManager);

       recyclerView_Adapter = new RecyclerViewAdapter(context,numbers);

       recyclerView_Adapter.setLocaleListener(this); // some change here

       recyclerView.setAdapter(recyclerView_Adapter);

   }

   @Override
   public void setLocale(String lang) {
       Locale myLocale = new Locale(lang);
       Resources res = context.getResources();
       DisplayMetrics dm = res.getDisplayMetrics();
       Configuration conf = res.getConfiguration();
       conf.locale = myLocale;
       res.updateConfiguration(conf, dm);
       Intent refresh = new Intent(this, MainActivity.class);
       startActivity(refresh);
       finish();
    }
}

希望这能帮到您。
你是否像上面那样在你的活动定义中添加了 implements LocaleListener？ - Cochi
我明白了，你应该使用 RecyclerViewAdapter recyclerView_Adapter 而不是 RecyclerView.Adapter recyclerView_Adapter :) - Cochi
1
请勿重新创建MainActivity，而是创建一个Interface来更新语言。 接口 
public interface RecyclerViewOnClickListenerHack {

    void onLanguage(String language);
}

MainActivity

public class MainActivity extends AppCompatActivity implements RecyclerViewOnClickListenerHack {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...

        recyclerView_Adapter = new RecyclerViewAdapter(context,numbers);
        recyclerView_Adapter.setmRecyclerViewOnClickListenerHack(this)
        recyclerView.setAdapter(recyclerView_Adapter);
    }

    @Override
        public void onLanguage(String language) {
           setLocale(String language)
        }

}

RecyclerViewAdapter（适用于RecyclerView的适配器）
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>{

    private RecyclerViewOnClickListenerHack mRecyclerViewOnClickListenerHack;

    public void setmRecyclerViewOnClickListenerHack(RecyclerViewOnClickListenerHack r) {
        this.mRecyclerViewOnClickListenerHack = r;
    }


    @Override
    public void onBindViewHolder(ViewHolder Vholder,final int position){
        ...
        Vholder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
              if(position == 4){
                RecyclerViewOnClickListenerHack.onLanguage("hi");//calling function
              }
            }
        });
    }

}
-1

我不确定错误是什么，如果可能的话，请分享GITHUB链接。但我认为我可以帮忙，我尝试了以下两种方法来解决这个问题。

1）您需要将手机语言更改为印地语，然后尝试加载应用程序，它将加载印地语内容。

2）您只想在应用程序中更改语言（这是不可取的）

请查找我的GitHUB链接，我在其中更新了两个项目。 您可以参考第15个项目以获取本地语言。 第16个项目用于在应用程序中更改语言。 Android Mini Apps

谢谢 Ashish

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