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Android

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,253 Points
Posted by Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

Change default text of a TextView Android

So for practice, I thought I'd make a little app. Click a button change the default text of a TextView component. Nice and straight forward but I can't do it!

I've been able to set up an Activity, with the components I need and the code is free of errors.

Any ideas what I'm missing? I suspect it's a little trickier than I'm trying!

activity_test.xml 
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:id="@+id/RelativeLayout"
    tools:context="uk.co.jonniegrieve.newtestapp.TestActivity"
    android:textAlignment="center">

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:layout_alignParentTop="true"
        android:layout_marginTop="99dp"
        android:textSize="18pt"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:id="@+id/singleText"
        android:textAlignment="center"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Click Me!"
        android:id="@+id/button"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:background="#fef994"/>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Jonnie Grieve Digital Media"
        android:id="@+id/textView"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:background="#2d2291"
        android:textColor="#fff155"
        android:textAlignment="center"/>

</RelativeLayout>
testactivity.java 
package uk.co.jonniegrieve.newtestapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

public class TestActivity extends AppCompatActivity {

    private TextView mText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {


        mText = (TextView) findViewById(R.id.singleText);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
    }

    View.OnClickListener listener = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mText.setText("New Text");
            Log.i("Message","Logging click of button");
        }


    };
}

1 Answer

Seth Kroger
Seth Kroger
56,413 Points
Seth Kroger
Seth Kroger
56,413 Points

You're forgetting to attach the listener to the button. Right now the listener isn't set to any view, so there is no way to trigger it.

Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

Thanks Seth,

It took me a while but with your guidance, I just finished my first Android app (outside the Simple App course).

It took so much trial and error and it worked before I even realise. (My emulator runs very slowly)

I added the code for the button and after a couple of runtime errors itseemed to work after I switched the default ClickListener code so the variables went below it.

 protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);

        /*below super.OnCreate not above*/.
        mText = (TextView) findViewById(R.id.singleText);
        mButton = (Button) findViewById(R.id.button);

         //code goes here


}

I know it's early on in my learning journey but where to do propose I go from here? I'm a little overwhelmed with how much I feel I still have to learn :-)