java - Toast 不会在 Android 应用程序上显示，使用 android studio

Question

早上好，我尝试让 toast 来显示学生人数是否小于 0 或大于 100。该应用程序似乎工作正常，除了显示 toast 之外。这项作业将于明天晚上截止。

这是我的代码:

package co.tekitall.classroommanager;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.View;
  import android.view.View.OnClickListener;
  import android.widget.Button;
  import android.widget.EditText;
  import android.widget.Toast;

  import java.util.ArrayList;

  import static co.tekitall.classroommanager.R.id.NumOfStudents;

  public class Classroom extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_classroom);
      Button button = (Button) findViewById(R.id.SubmitClassRoomInfoButton);

    }

    void ClassroomElements() {
      //ArrayList
      ArrayList<EditText> arrayList = new ArrayList<>();
      arrayList.add((EditText) findViewById(R.id.Teacher_Name));
      arrayList.add((EditText) findViewById(R.id.Room_Number));
      arrayList.add((EditText) findViewById(R.id.ClassroomHelper));
      arrayList.add((EditText) findViewById(R.id.NumOfStudents));
    }

    OnClickListener listener = new OnClickListener() {
      @Override
      public void onClick(View v) {
        EditText numofstudents = (EditText) findViewById(R.id.NumOfStudents);
        String getstucount = numofstudents.getText().toString();

        int setstucount = Integer.parseInt(getstucount);

        if(setstucount < 0) {

          numofstudents.setText("");
          Toast toast = Toast.makeText(Classroom.this, "Please try Again! Number must be greater then 0 and less than 100...", Toast.LENGTH_LONG);
          toast.show();

        }

        if(setstucount > 100) {

          numofstudents.setText("");
          Toast toast = Toast.makeText(Classroom.this, "Please try Again! Number must be greater then 0 and less than 100...", Toast.LENGTH_LONG);
          toast.show();

        } else
          numofstudents.setText("");
          Toast toast = Toast.makeText(Classroom.this, "Good Job", 
          Toast.LENGTH_LONG);
          toast.show();
        }
    };
  }

Answer 1

您需要使用绑定(bind)按钮和监听器

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_classroom);
    Button button = (Button) findViewById(R.id.SubmitClassRoomInfoButton);
    button.setOnClickListener(listener);
    // ^^^^^^^^^^^^^^^^^^^^^^^^^^^
}

另外使用 if 和 else-if 而不是多个 if，因为数字只能小于 0 否则大于 100 或介于 |等于 0 或 100

if(setstucount < 0){//...code}
else if(setstucount > 100){//...code}
else  {//...code}