Toast消息不可见\\在Android中弹出

Question

I'm creating an android application in Java where IDE is Android Studio. This application gets two numeric input from the EditText and summation of those numbers will be shown in Toast Message on button click event.

Following is the XML code for reference (activity_main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <EditText
            android:id="@+id/editText"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"/>

        <EditText
            android:id="@+id/editText2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="number"/>

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Sum" />
</LinearLayout>

Following is the Java code for the reference (MainActivity.java)

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Button;
import android.widget.Toast;
import android.content.Context;

public class MainActivity extends Activity {
private EditText ed1, ed2;
private Button b1;

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

    }

    public void addButtonListener(){
        ed1 = (EditText)findViewById(R.id.editText);
        ed2 = (EditText)findViewById(R.id.editText2);
        b1 = (Button)findViewById(R.id.button);

        b1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String value1 = ed1.getText().toString();
                String value2 = ed2.getText().toString();
                int a = Integer.parseInt(value1);
                int b = Integer.parseInt(value2);
                int sum = a + b;
                Context context = getApplicationContext();
                System.out.println(String.valueOf(sum));
                Toast toast = Toast.makeText(context,String.valueOf(sum),Toast.LENGTH_LONG);
                toast.show();
            }
        });
    }
}

I install this application on my Android Device for testing purpose.

My issue is that I don't get any Toast Message or Notification whenever I click on the Sum button while adding two values.

I have also enabled the Notification in my Settings.

Answer 1

在oncreate方法addButtonListener（）中调用此方法；

Answer 2

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Button;
import android.widget.Toast;
import android.content.Context;

public class MainActivity extends Activity {
private EditText ed1, ed2;
private Button b1;

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

}

public void addButtonListener(){
    ed1 = (EditText)findViewById(R.id.editText);
    ed2 = (EditText)findViewById(R.id.editText2);
    b1 = (Button)findViewById(R.id.button);

    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String value1 = ed1.getText().toString();
            String value2 = ed2.getText().toString();
            int a = Integer.parseInt(value1);
            int b = Integer.parseInt(value2);
            int sum = a + b;
            Context context = getApplicationContext();
            System.out.println(String.valueOf(sum));
            Toast toast = Toast.makeText(context,String.valueOf(sum),Toast.LENGTH_LONG);
            toast.show();
            }
        });
    }
}

Answer 3

The reason that you are not seeing any Toast Message or Notification is that the click listener is inside addButtonListener() method.

All good so far but you forgot to call this method, so it will remain not used and the clickListener for your button will not be a created, so when you will press the button you will not see ant Toast Message or Notification.

If you want to fix this just call this method inside onCreate / onStart() , for example:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    addButtonListener(); // now you will see your Toast
}