如何從適配器調用外部活動方法？

Question

我想打電話從適配器外類方法，如

new MainActivity().openPainRecordDialog(context,dbHelper); 

它工作正常。

但是當我做這樣的

Boolean status=new MainActivity().openPainRecordDialog(context,dbHelper); 

if(status) 
    check(); 

檢查（）是適配器類的方法。

和

openPainRecordDialog(final Context context, final DbHelper dbHelper) 
{ 

    //some unrelated data. 
    if (logged_in && isNetworkConnected()){ 

    } 
} 

public boolean isNetworkConnected() { 
     ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 
     return cm.getActiveNetworkInfo() != null; 
    } 

錯誤我越來越 不適用於活動系統服務的onCreate（） 之前在這行代碼ConnectivityManager釐米=（ConnectivityManager）getSystemService（Context.CONNECTIVITY_SERVICE）;

問題

1. 這是調用活動方法的正確途徑。 2.爲什麼我得到這個錯誤。

編輯

我試圖通過接口來做到這一點。 但最終得到錯誤。

'INT self.anotherclassfunction.SimpleAdapter $ AdapterCallback.onMethodCallback（）' 上的空對象引用

適配器類

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

    String[] goals; 
    Context context; 
    private AdapterCallback mAdapterCallback; 


    public SimpleAdapter(Context context, String[] goals) 
    { 
     super(); 
     this.context=context; 
     this.goals=goals; 

    } 

    public SimpleAdapter(Context context) { 

     try { 
      this.mAdapterCallback = ((AdapterCallback) context); 
     } catch (ClassCastException e) { 
      throw new ClassCastException("Activity must implement AdapterCallback."); 
     } 

    } 

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

     View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.simple_item,parent,false); 
     return new ViewHolder(view); 
    } 

    @Override 
    public void onBindViewHolder(final SimpleAdapter.ViewHolder holder, int position) { 

     holder.textView.setText(goals[position]); 

     holder.textView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 

       try { 
        **int result=mAdapterCallback.onMethodCallback();** //this is the line where I am getting error 

        Toast.makeText(context,Integer.toString(result), Toast.LENGTH_SHORT).show(); 
       } catch (ClassCastException exception) { 
        // do something 
        Log.i("In the catch","Yes"); 
       } 




      } 
     }); 

    } 

    @Override 
    public int getItemCount() { 
     return goals.length; 
    } 


    public class ViewHolder extends RecyclerView.ViewHolder { 

     Button textView; 

     public ViewHolder(View itemView) { 
      super(itemView); 

      textView=(Button) itemView.findViewById(R.id.text); 
     } 
    } 

    public static interface AdapterCallback { 
     int onMethodCallback(); 
    } 


} 

適配器調用類

public class OtherClass extends AppCompatActivity { 

    RecyclerView recyclerView; 
    SimpleAdapter simpleAdapter; 
    String[] action_name={"Swimming","Yoga","SWD","IFT","Follow Diet Plan", "Diagnostic Tests","Record Temperature","Record Blood Pressure"," Record Sugar Level","Record Weight"}; 

    @Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.xtra); 

     recyclerView=(RecyclerView) findViewById(R.id.recylerview); 
     recyclerView.setHasFixedSize(true); 
     recyclerView.setLayoutManager(new LinearLayoutManager(this)); 


     simpleAdapter=new SimpleAdapter(this, action_name); 

     recyclerView.setAdapter(simpleAdapter); 

    } 
} 

我試圖調用的方法的活動：

public class MainActivity extends AppCompatActivity implements SimpleAdapter.AdapterCallback { 

    private SimpleAdapter mAdapterCallback; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     this.mAdapterCallback=new SimpleAdapter(MainActivity.this); 


     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 
    } 

    @Override 
    public int onMethodCallback() { 
     // do something 
     return 2; 
    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.menu_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 


    public void test(View v) 
    { 
     startActivity(new Intent(MainActivity.this,OtherClass.class)); 
     finish(); 
    } 

    public int sampleFunction() 
    { 
     return 2; 
    } 
} 

Answer 1

爲什麼不在Utils這樣的類中創建isNetworkConnected並根據需要隨時調用。

private boolean isNetworkConnected(Context context) { 
    ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 
     if (connectivity != null) { 
      NetworkInfo[] info = connectivity.getAllNetworkInfo(); 
      if (info != null) { 
       for (int i = 0; i < info.length; i++) { 
        if (info[i].getState() == NetworkInfo.State.CONNECTED) { 
         return true; 
       } 
      } 
     } 
    } 
    return false; 
} 

Answer 2

您需要通過上下文isNetworkConnected方法，

openPainRecordDialog(final Context context, final DbHelper dbHelper) 
{ 
    if (logged_in && isNetworkConnected(context)) 
{ 
    } 
} 
public boolean isNetworkConnected(Conext context) { 
     ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); 
     return cm.getActiveNetworkInfo() != null; 
    }