主要活动
public class MainActivity extends AppCompatActivity {
public TextView kalori;
RecyclerView rv;
List<yiyecek> yiyecekList;
@SuppressLint("MissingInflatedId")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
rv=findViewById(R.id.myrecycler);
kalori=findViewById(R.id.kalori);
yiyecekList= new ArrayList<>();
yiyecekList.add(new yiyecek("Egg","50"));
yiyecekList.add(new yiyecek("Cheese","150"));
rv.setLayoutManager(new LinearLayoutManager(this));
rv.setAdapter(new MyAdapter(this,yiyecekList));
}
}
MyAdapter
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.Spinner;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
Context context;
List<yiyecek> yiyecekler;
public MyAdapter(Context context, List<yiyecek> yiyecekler ) {
this.context = context;
this.yiyecekler = yiyecekler;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new MyAdapter.MyViewHolder(LayoutInflater.from(context).inflate(R.layout.yiyecekrowitem,parent,false));
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
yiyecek ymk=yiyecekler.get(position);
String name=ymk.getAd();
String kalori=ymk.getKalori();
holder.text.setText(name);
holder.textkalori.setText(kalori);
}
@Override
public int getItemCount() {
return yiyecekler.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
public TextView text,textkalori,textadet;
public Button ekle;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
textadet=itemView.findViewById(R.id.adet);
text = itemView.findViewById(R.id.textViewad);
textkalori = itemView.findViewById(R.id.textViewKalori);
ekle=itemView.findViewById(R.id.butonekle);
itemView.findViewById(R.id.butonekle).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String ilkadet=textadet.getText().toString();
MainActivity mm=new MainActivity();
mm.kalori.setText(ilkadet);
}
});
}
}
}
RecyclerView xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="97dp"
android:layout_margin="8dp"
xmlns:app="http://schemas.android.com/apk/res-auto">
<TextView
android:id="@+id/textViewad"
android:layout_width="103dp"
android:layout_height="48dp"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="11dp"
android:layout_marginTop="11dp"
android:gravity="center"
android:text="TextView"
android:textAlignment="center"
android:textSize="20sp" />
<TextView
android:id="@+id/textViewKalori"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="22dp"
android:layout_marginTop="60dp"
android:gravity="center"
android:text="100"
android:textAlignment="center"
android:textSize="20sp" />
<Button
android:id="@+id/butonekle"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="284dp"
android:layout_marginTop="24dp"
android:text="EKLE" />
<TextView
android:id="@+id/adet"
android:layout_width="70dp"
android:layout_height="50dp"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="191dp"
android:layout_marginTop="25dp"
android:textColor="#282828"
android:text="0"
android:textSize="29sp"
android:textAlignment="center"
android:gravity="center"/>
</RelativeLayout>
例外
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.kalorirecyclerdeneme, PID: 30408
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.example.kalorirecyclerdeneme.MyAdapter$MyViewHolder$1.onClick(MyAdapter.java:91)
at android.view.View.performClick(View.java:7448)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1211)
at android.view.View.performClickInternal(View.java:7425)
at android.view.View.access$3600(View.java:810)
at android.view.View$PerformClick.run(View.java:28305)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I/Process: Sending signal. PID: 30408 SIG: 9
对不起,我的代码不好。我才刚开始我的项目是关于卡路里的计算。我在用RecyclerView分类食物。当我按下RecyclerView上的按钮时,显示数字的TextView值增加了一。我试图将其打印到MainActivity中的TextView中,但它给出了一个空错误。
我得到空错误:mm.kalori.setText(ilkadet);
我在RecyclerView中有一个按钮,我正在尝试使用此按钮更改MainActivity中TextView的值。
1条答案
按热度按时间mpbci0fu1#
您不能创建
Activity
的instance
,您可以将引用传递给视图,但更好的方法是传递一个interface
,它将在单击时从adapter
调用