Setting up buttons for Android

Here is my problem. I setup the buttons exactly the way they are setup in the Android documentation, but I am getting a warning, and the button will not do anything.

Here is my Java code:

package com.variDice;

import android.app.Activity;
import android.os.Bundle;
import android.widget.*;

public class VariDiceActivity extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
      开发者_高级运维  setContentView(R.layout.main);

        //die1Clicked();
    }

    private void die1Clicked() {
        ImageButton die1button = (ImageButton)findViewById(R.id.die1button);
        die1button.setImageResource(R.drawable.icon);
    }
}

...and the XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:weightSum="1" android:layout_gravity="center_horizontal">

    <ImageView 
        android:id="@+id/varidice_icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:src="@drawable/icon"></ImageView>
    <ImageButton
        android:id="@+id/die1button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:background="@null"></ImageButton>

</LinearLayout>

...and the warning:

The method die1Clicked from the type VariDiceActivity is never used locally.

I must say that I am completely new to Android development. I made my app for the iPhone, and I am now trying to make a version for the android. The iPhone version was sooo much easier, because of the better interface builder (so I can just make an action and connect it to the button that way), so this is almost impossibly hard for me to understand. In other words, I do not understand how you connect an action to the button. Could somebody please tell me what I am doing wrong?

Try this in your xml:

<ImageButton
    android:id="@+id/die1button"
    android:onClick="die1Clicked"
    ...></ImageButton>

And in your code, change the method signature to:

public void die1Clicked(android.view.View v) {
    ImageButton die1button = (ImageButton)findViewById(R.id.die1button);
    die1button.setImageResource(R.drawable.icon);
}

Here is the Android Button tutorial.

To bind some behavior to an UI button, you need to register a listener that receives notifications of a certain event type. In your case, you register a OnClickListener (for the click event); just like in the following snippet:

// create the implementation of OnClickListener
private OnClickListener mDie1Listener = new OnClickListener() {
    public void onClick(View v) {
      // do something when the button is clicked
    }
};

protected void onCreate(Bundle savedValues) {
    ...
    // get the button from layout
    Button button = (Button)findViewById(R.id.die1button);
    // register the onClick listener with the implementation above
    button.setOnClickListener(mDie1Listener);
    ...
}

You need to add a click listener to your button. Put this in your onCreate():

ImageButton die1button = (ImageButton)findViewById(R.id.die1button);
die1button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
    // What to do when the button is clicked    
});

Most answers on SO tend to use 'setOnClickListener' instead of using xml properties. I personally prefer using xml for making items clickable in android.

The mistake you have made is setting your function as private. The function which gets called after clicking the item should be public.

There are 3 things you should keep in mind:

1. Define the 2 properties in xml.

   android:clickable="true" android:onClick="functionName"

2. Define that function in the Activity file. Make sure to keep the function public.

   public void functionName(View v) { // TODO Auto-generated method stub
   }

3. Make sure to pass 'View v' as an argument for that function.