Question

我的应用程序可以完美地加载所有活动和活动。但是，当我尝试加载包含RecyclerView的Activity来显示一些存储的字符串时。它崩溃了finish。我不知道语法是错误的还是代码本身的逻辑。

我从听众那里调用活动

可分配给新活动的对象：

final public FrasesProvisional frases = new FrasesProvisional();

开始活动的方法：

 @Override
 public boolean onOptionsItemSelected(MenuItem item) {
     switch (item.getItemId()) {
         case R.id.config:
             lanzarConfiguracion(null);
             break;

         case R.id.about:
             lanzarAbout(null);
             break;
         case R.id.mismotivaciones:
             abrirMotivaciones(null);
             break;
     }
     return true;
 }

 private void abrirMotivaciones(View view) {
     Intent i = new Intent(this, MotivacionesUser.class);
     startActivity(i);
 }

活动内容：

   import android.os.Bundle;
   import android.os.PersistableBundle;
   import android.support.v7.app.AppCompatActivity;
   import android.support.v7.widget.LinearLayoutManager;
   import android.support.v7.widget.RecyclerView;

   /**
    * Created by Pablo on 14/01/2017.
    */
   public class MotivacionesUser extends AppCompatActivity {
       private RecyclerView mRecyclerView;
       private RecyclerView.Adapter mAdapter;
       private RecyclerView.LayoutManager mLayoutMmanager;

       @Override
       public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.motivacionesrecycler);

           FrasesProvisional frases = getIntent().getParcelableExtra("frases");

           mRecyclerView = (RecyclerView) findViewById(R.id.motivaciones_recycler);
           // use this setting to improve performance if you know that changes
           // in content do not change the layout size of the RecyclerView
           mRecyclerView.setHasFixedSize(true);
           //Init LayoutManager

           mLayoutMmanager = new LinearLayoutManager(this); //Podemos elegir entre LinearM, GridM o ScrappableM en relación al estilo que queramos
           mRecyclerView.setLayoutManager(mLayoutMmanager); //Set the Layout to the RrecyclerView

           mAdapter = new RecyclerAdaptador(frases.getArrayList()); //Especificamos el adaptador a usar y lo agenciamos al Recycler
           mRecyclerView.setAdapter(mAdapter);
       }
   }

RecyclerView代码：

  import android.support.v7.widget.RecyclerView;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.TextView;
  import java.util.ArrayList;

  /**
   * Created by Pablo on 14/01/2017.
   */
  public class RecyclerAdaptador extends RecyclerView.Adapter < RecyclerAdaptador.ViewHolder > {

      private ArrayList < String > frases;

      public static class ViewHolder extends RecyclerView.ViewHolder {
          // each data item is just a string in this case
          public TextView mTextView;
          public ViewHolder(View v) {
              super(v); //Inicializa el textview
              mTextView = (TextView) v.findViewById(R.id.text_recycler);
          }
      }

      public RecyclerAdaptador(ArrayList < String > frases) {
          this.frases = frases;
      }

      @Override
      public RecyclerAdaptador.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
          //Create a new view
          View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.frase_recycler, parent, false);
         ViewHolder vh = new ViewHolder(view);

          return vh;
      }


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

          //Get element of the data set at the position x and replace the content of the rextView with it

          holder.mTextView.setText(frases.get(position));

      }

      @Override
      public int getItemCount() {
          return frases.size();
      }
  }

提前致谢！

Answer 1

查看代码，您可以通过以下代码段创建活动：

Intent i = new Intent(this, MotivacionesUser.class);
startActivity(i);

但是，在活动中，您尝试在FrasesProvisional frases = getIntent().getParcelableExtra("frases");中读取额外数据。

由于您从未将该数据附加到将返回null的意图。然后使用它而不检查它是否在new RecyclerAdaptador(frases.getArrayList());处为空，从而导致NullPointerException并使您的类崩溃。

Answer 2

添加一个类变量

Context context;


public RecyclerAdaptador(Context context,ArrayList<String> frases) {
this.context=context
   this.frases = frases;
}

来自活动

mAdapter = new RecyclerAdaptador(this,frases.getArrayList());

应用程序崩溃在RecyclerView上

2 个答案: