Android: Have toast appear on button click

问题:

I'm fairly new to Android and just getting familiarized with the common stuff, but I can't get the hang of the onClickListner(); I basically have two checkboxes and a button and on button click a toast should show up and say which checkboxes are checked and which aren't.

public class ExActivity extends Activity implements View.OnClickListener {
    CheckBox cb;
    CheckBox cb2;
    Button buton;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        cb=(CheckBox) findViewById(R.id.cb);
        cb2=(CheckBox) findViewById(R.id.checkbox);
        buton = (Button)findViewById(R.id.buton);
        buton.setOnClickListener(this);
    }

    public void onClick(View arg0) {
        Toast toast;
        if(cb.isChecked()&&cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Amandoua sunt bifate", Toast.LENGTH_SHORT);
        else if(cb.isChecked()&&!cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Doar prima e bifata", Toast.LENGTH_SHORT);
        else if(!cb.isChecked()&&cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Doar a doua e bifata", Toast.LENGTH_SHORT);
        else if(!cb.isChecked()&&!cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Nici una nu e bifata", Toast.LENGTH_SHORT);
    }
}

Disregard the romanian variable names and texts and the XML is all right. I also tried to add the onClick() like this:

buton.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        // my code;
    }
});

but this one is even worse. Help?

回答1:

Both ways are correct. It seems to me that you just didn't show the toast in the end. Which can look like the onClick wasn't executed.

Adding

if(toast != null) {
    toast.show();
}

to the end of your onClick() method should do the trick.
(The null check just in case you didn't create a toast instance because no condition was matched before).

回答2:

You need to call show() for the toast to appear :

Toast.makeText(getApplicationContext(), "text", Toast.LENGTH_SHORT).show();

回答3:

you just forgot to add .show() after your .makeText(context,text,duration)

so your code should like this:

[...]
if(cb.isChecked()&&cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Amandoua sunt bifate", Toast.LENGTH_SHORT).show();
    else if(cb.isChecked()&&!cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Doar prima e bifata", Toast.LENGTH_SHORT).show();
    else if(!cb.isChecked()&&cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Doar a doua e bifata", Toast.LENGTH_SHORT).show();
    else if(!cb.isChecked()&&!cb2.isChecked()) toast = Toast.makeText(getApplicationContext(), "Nici una nu e bifata", Toast.LENGTH_SHORT).show();
[...]

回答4:

Previous answers are correct, telling you don't call the show() method of the Toast. You can also take a look at this tutorial to see how you can define a handler method to your button in the XML. This way the code will look clearer, because you don't have to explicitly implement onClickListener interface, or set new onClickListener to a button (it's done behind the scenes). Here's a simple example (you can easily supplement the System prints with "showToast" methods):

button definition in xml:

      <Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="10dp"
    android:text="Click Me"
    android:onClick="buttonHandler" />

Activity class

public class TwoCheckboxesActivity extends Activity {

    private CheckBox check1;
    private CheckBox check2;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        check1 = (CheckBox)findViewById(R.id.checkbox1);
        check2 = (CheckBox)findViewById(R.id.checkbox2);

    }

    public void buttonHandler(View view) { 
        System.out.println("Button Clicked"); 

        System.out.println(check1.isChecked());
        System.out.println(check2.isChecked()); 
    }
}

回答5:

Add this in your java resource

  public void toast(View v) {
  Toast.makeText(MainActivity.this, "Hey I'm a toast messsage",         
          Toast.LENGTH_LONG).show();

}

Then this code for adding a button and implementing it to display the toast message in your XML resource.

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Toast Button"
    android:id="@+id/button"
    android:layout_centerVertical="true"
    android:layout_centerHorizontal="true"
    android:onClick="toast" />

Hope this helped. Happy Coding