CODEWITHSUNDEEP
androidandroid-layoutlayoutbackground
salihgueler
salihgueler

Reputation: 3622

changing layout color android app

i am trying to write a program that changes the background color of the screen to the color that i decided. i wrote something like that but when it runs it crashes what is sthe problem,please help me.here is the xml code

  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <LinearLayout 

        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_gravity="bottom"
        android:background="#FFFFFF"


        >

        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Red"
            />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Green" />

        <Button
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Blue" />
         <Button
            android:id="@+id/button4"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="White" />

    </LinearLayout>

</LinearLayout>

and here is the .java code

package com.example.flashlight;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Color;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;

public class FlashLight extends Activity {

Button red,green,blue,white;
LinearLayout view;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_flash_light);
    red=(Button) findViewById(R.id.button1);
    green=(Button) findViewById(R.id.button2);
    blue=(Button) findViewById(R.id.button3);
    white=(Button) findViewById(R.id.button4);

    red.setOnClickListener(new View.OnClickListener() {

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

            view.setBackgroundColor(Color.RED);

        }
    });

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_flash_light, menu);
    return true;
}
}

Upvotes: 1

Views: 10673

Answers (4)

Master_GoGo
Master_GoGo

Reputation: 1690

After onClick use this below code:

view.setBackgroundColor(Color.DKGRAY);

Example:

public void onClick(View v) {
        view.setBackgroundColor(Color.DKGRAY); //Add any color you want
    }

Upvotes: 0

Arvind Kanjariya
Arvind Kanjariya

Reputation: 2097

Try this code

This will work for me... In youyr xml file set id for your Linear Layout as a view.

<LinearLayout 

    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_gravity="bottom"
    android:id="@+id/view"
    android:background="#FFFFFF"


    >

In Your java file your linear layout view is null because of id.

so put below line in your java file 

 view  = (LinearLayout) findViewById(R.id.view);

This will work for me....

Happy coding..

Upvotes: 0

A. AMAIDI
A. AMAIDI

Reputation: 6849

you need to assign an id to your LinearLayout

 <LinearLayout 
    android:id="@+id/view"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_gravity="bottom"
    android:background="#FFFFFF"

then initialize your view

view = (LinearLayout) findViewById(R.id.view)
red.setOnClickListener(new View.OnClickListener() {

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

        view.setBackgroundColor(Color.RED);

    }
});

Upvotes: 1

thepoosh
thepoosh

Reputation: 12587

you are not assigning the view variable to anything, that is probably causing a NullPointerException in your code

try adding in your XML file this line under the LinearLayout:

android:id="@+id/view"

and adding this line to your onCreate:

view = (LinearLayout)findViewBiId(R.id.view);

Upvotes: 0

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