Develop Reference

Android Studio change background color multiple times with 1 button click

I am brand new to Android Studio and am trying to figure out how to change the background color of my start up app.
The moment the app loads, I see a button on the screen, and when I click, it goes to the color red.
What I want is when you click the button, it goes from red to green to blue than back to red.
However, I keep getting these errors:
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
Compilation failed; see the compiler error output for details.
Error:(72, 9) error: class, interface, or enum expected
Main Activity XML File:
<?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"
android:id="#+id/layout">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change Color"
android:onClick="onChangeColor"/>
</LinearLayout>
Test Activity Java Code:
private int colorIndex = 1;
public void onChangeColor(View view) {
int color;
if(colorIndex==0) {
color = Color.RED;
colorIndex = 1;
}else if(colorIndex==1) {
color = Color.GREEN;
colorIndex = 2;
}else {
//colorIndex = 2
color = Color.BLUE;
colorIndex = 0;
}
View layout = findViewById(R.id.layout);
layout.setBackgroundColor(color);
}
public class TestActivity extends AppCompatActivity {
View view;
//declare a string variable in java a class
//private var colour = "green";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View layout = findViewById(R.id.layout);
layout.setBackgroundColor(Color.RED);
view= this.getWindow().getDecorView();
view.setBackgroundResource(R.color.gray);
}
public void goRed(View v)
{
//if (colour == "green"){
view.setBackgroundResource(R.color.red);
//colour = "red";
//}
}
}

To give you a excellent help, it will be necessary to see you code.
Any way if i andersted you right maybe this will help you :
On your xml layout:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:id="#+id/layout">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change Color"
android:onClick="onChangeColor"/>
</LinearLayout>
On your activity :
private int colorIndex = 1;
public void onChangeColor(View view) {
int color;
if(colorIndex==0) {
color = Color.RED;
colorIndex = 1;
}else if(colorIndex==1) {
color = Color.GREEN;
colorIndex = 2;
}else {
//colorIndex = 2
color = Color.BLUE;
colorIndex = 0;
}
View layout = findViewById(R.id.layout);
layout.setBackgroundColor(color);
}
On you onCreate in the activity
View layout = findViewById(R.id.layout);
layout.setBackgroundColor(Color.RED);

If I understood correctly what you want is, to transition over a series of colours over time, and each colour lasting for some 1-2 seconds. You can use Android's default CountDownTimer.
Keep Your xml layout same.
In your Activity:
public class TestActivity extends AppCompatActivity {
LinearLayout layout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
layout = (LinearLayout)findViewById(R.id.layout);
layout.setBackgroundColor(Color.RED);
}
public void onChangeColor(View view) {
// start your timer on button click
new CountDownTimer(3000, 1000) {
public void onTick(long millisUntilFinished) {
changeBackground(3-millisUntilFinished/1000);
}
}.start();
}
private void changeBackground(int colorIndex){
int color;
if(colorIndex==1) {
color = Color.GREEN;
}else if(colorIndex==2) {
color = Color.BLUE;
}else {
color = Color.RED;
}
layout.setBackgroundColor(color);
}
}
Hope this might help. If I misunderstood something please comment.
Edit: I typecasted View to LinearLayout

Hide Android-PullToRefresh along with Action Bar

I have three tabs and hiding the Action Bar on the middle tab. The third tab had pull to refresh. Android does a great job of animating the sliding in and out of the Action Bar but when I pull to refresh on the third tab and switch to the middle tab (where the Action Bar is hidden) I see the following:
The action bar is hidden from the PageAdapter and hidden as follows:
#Override
public void onPageSelected(int position) {
if (position == 1) {
mActionBar.hide();
} else {
mActionBar.show();
}
}
Pull to Refresh is implemented in a fragment (third tab) with the layout as:
<?xml version="1.0" encoding="utf-8"?>
<uk.co.senab.actionbarpulltorefresh.extras.actionbarsherlock.PullToRefreshLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/ptr_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/grey_canvas_bg"
android:orientation="vertical"
>
<se.emilsjolander.stickylistheaders.StickyListHeadersListView
android:id="#+id/list_feed"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</uk.co.senab.actionbarpulltorefresh.extras.actionbarsherlock.PullToRefreshLayout>
and initialised in the OnCreateView as follows:
mPullToRefreshLayout = (PullToRefreshLayout) view.findViewById(R.id.ptr_layout);
ActionBarPullToRefresh.from(getActivity())
.allChildrenArePullable()
.useViewDelegate(StickyListHeadersListView.class, new ViewDelegate() {
#Override
public boolean isReadyForPull(View view, float v, float v2) {
View childView = updatesListView.getChildAt(0);
int top = (childView == null) ? 0 : childView.getTop();
return top >= 0;
}
})
.listener(this)
.setup(mPullToRefreshLayout);
Thanks for any help!

How to create an expandable list?

I need to create Collapse / Expand forms in Android. I am thinking about using either RelativeLayout or TableLayout for this purpose. But, what XML element make these forms expand and hide in android?
If you are not sure what I am not talking about, take an application like Sales Force for an example. There you have these expandable menus in all the forms. How can I do this?
Following is an example (taken from Sales Force)
When you expand these, it looks like below

You could do the following. create a layout that has the following:
1. A Heading or a textview with the label contacts
2. Below it a layout that has forms related to it
3. Add another textview below #2 and name it address
4. Add a lyout below #3 .
The layout 2 and 4 will have visibility gone in the first case
When the user taps on layout 1, or the first textview, make layout 2 visible and vice versa. Do the same with the second textview.
Hope that helps.!

I have had a similar problem, i want parts of my form to be hidden in sektions and created a class for this issue.
public class section extends LinearLayout{
public LinearLayout container;
public Button toggler;
public section(Context context, String section_name, String section_state) {
super(context);
LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate(R.layout.flxsection, this);
container = (LinearLayout) this.findViewById(R.id.container);
container.setVisibility(section_state.equals("0") ? View.GONE:View.VISIBLE);
toggler = ((Button)this.findViewById(R.id.section_toggle));
toggler.setTag(section_state);
toggler.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
String tag = (String) v.getTag();
v.setTag(tag.equals("0") ? "1":"0");
if(tag.equals("0")){expand(container,false);}else{collapse(container,false);}
setImage(tag.equals("0"));
}
});
toggler.setText(" " + section_name);
setImage(section_state.equals("1"));
setTextSize();
}
public void setTextSize(){
toggler.setTextSize(GV.Style.TextSize);
}
public void setImage(boolean open){
int a = open ? R.drawable.minus_48_white: R.drawable.plus_48_white;
Drawable img = main.res.getDrawable(a);
final float scale = main.res.getDisplayMetrics().density;
int size = (int) (12 * scale + 0.5f);
img.setBounds(0,0,size,size);
toggler.setCompoundDrawables(img,null,null,null);
}
}
the xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:focusable="false"
android:layout_marginLeft="4dip"
android:layout_marginRight="4dip"
android:orientation="vertical" >
<Button
android:id="#+id/section_toggle"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="4dip"
android:layout_marginTop="4dip"
android:background="#drawable/section"
android:drawableLeft="#drawable/plus_48"
android:focusable="false"
android:gravity="left|center_vertical"
android:padding="6dip"
android:textAppearance="?android:attr/textAppearanceLargeInverse"
android:textSize="22dip" />
<LinearLayout
android:id="#+id/container"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:focusable="false"
android:background="#android:color/transparent"
android:orientation="vertical" >
</LinearLayout>
Expand and collapse:
public static void expand(final View v,boolean quick) {
v.requestLayout();
v.measure(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT);
final int targtetHeight = v.getMeasuredHeight();
v.getLayoutParams().height = 0;
v.getLayoutParams().width = LayoutParams.FILL_PARENT;
v.setVisibility(View.VISIBLE);
if(quick){
v.getLayoutParams().height = LayoutParams.WRAP_CONTENT;
v.requestLayout();
}else{
android.view.animation.Animation a = new android.view.animation.Animation()
{
#Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
v.getLayoutParams().height = interpolatedTime == 1
? LayoutParams.WRAP_CONTENT
: (int)(targtetHeight * interpolatedTime);
v.requestLayout();
}
#Override
public boolean willChangeBounds() {
return true;
}
};
// 1dp/ms
int duration = (int)(targtetHeight / v.getContext().getResources().getDisplayMetrics().density);
if(duration> 500)duration=500;
a.setDuration(duration);
//(int)(targtetHeight / v.getContext().getResources().getDisplayMetrics().density)
v.startAnimation(a);
}
}
public static void collapse(final View v,boolean quick) {
v.requestLayout();
final int initialHeight = v.getMeasuredHeight();
if(quick){
v.setVisibility(View.GONE);
v.requestLayout();
}else{
android.view.animation.Animation a = new android.view.animation.Animation()
{
#Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
if(interpolatedTime == 1){
v.setVisibility(View.GONE);
}else{
v.getLayoutParams().height = initialHeight - (int)(initialHeight * interpolatedTime);
v.requestLayout();
}
}
#Override
public boolean willChangeBounds() {
return true;
}
};
// 1dp/ms
int duration = (int)( initialHeight/ v.getContext().getResources().getDisplayMetrics().density);
if(duration> 500)duration=500;
a.setDuration(duration);
v.startAnimation(a);
}
}
If if create a form and need a section, i create a instance of this class and add the controls.
You might need to turn the hardware acceleration on in order to get the best performance
edit:
Usage is like:
section s = new section(context, section_name, section_state);
s.container.addView([your view 1]);
s.container.addView([your view 2]);
s.container.addView([your view 3]);
//...
form.addView(s);

How to change textView (digitalClock) color on touch(screen)

I'm making an app that just displays a clock, but I want is so that everytime a user touches the screen it changes the color of the text (from a list of preselected colors in a colors.xml file) but I haven't got a clue where to start. Can someone point me in the right direction?
Here's the main activity:
public class MainActivity extends Activity {
private static final Random RANDOM = new Random();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
setContentView(R.layout.activity_main);
Handler handler = new RandomMoveHandler((TextView) findViewById(R.id.digitalClock1));
handler.sendEmptyMessage(0);
}
// Make the handler subclass static because of this: http://stackoverflow.com/a/11408340/111777
private static class RandomMoveHandler extends Handler {
private final WeakReference<TextView> textViewWeakReference;
private RandomMoveHandler(TextView textView) {
this.textViewWeakReference = new WeakReference<TextView>(textView);
}
#Override
public void handleMessage(Message msg) {
TextView textView = textViewWeakReference.get();
if (textView == null) {
Log.i(TAG, "WeakReference is gone so giving up.");
return;
}
int x = RANDOM.nextInt(350 - 100);
int y = RANDOM.nextInt(800 - 100);
Log.i(TAG, String.format("Moving text view to (%d, %d)", x, y));
textView.setX(x);
textView.setY(y);
//change the text position here
this.sendEmptyMessageDelayed(0, 30000);
}
}
private static final String TAG = MainActivity.class.getSimpleName();
}
and here's the layout xml:
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity"
android:background="#color/black" >
<DigitalClock
android:id="#+id/digitalClock1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="DigitalClock"
android:textColor="#color/ics_blue"
android:textSize="28sp" />

I haven't making deal with DigitalClock but I think, at first, you should reference DigitalClock variable, not TextView. And second, to intercept touch event you need to override onTouckEvent method of your activity, it will callback everytime user touches the screen.

You should follow these steps
Use a TimerTask to.continusly show the time
Implement a touchlistener on that clock view
like this
view.setOnTouchListener
Make an array Colors like this
int[] colr={Color.BLACK,Color.BLUE};
and use random index in your touch event andset it as your color of the view

Scrolling ListViews Together

I've got two ListView objects that I would like to scroll together. They are side-by-side, so if one scrolls a certain amount, the other scrolls that same amount. I've found some examples on how to do this, but I believe that they rely on the items in the ListView being the same height (correct me if I am wrong). The items in one of my ListView objects are taller than the ones in the other, spanning 2-3 items.
How do I "lock" these 2 ListView objects together?
EDIT: Here's a screenshot of what I have, maybe it will better explain what I'm going for. The left side (red) is a list of items and the right side is a separate list. You can see how the lists don't align perfectly, so it isn't exactly a grid. What I would like to do is have this act like one big list, where scrolling either list will also scroll the other.

I created a rough class that does basically what I wanted to do. It's not smart enough to handle if the 2nd list is longer than the 1st or if the orientation changes, but it's good enough to get the concept down.
To set it up:
list1.setOnScrollListener(new SyncedScrollListener(list2));
list2.setOnScrollListener(new SyncedScrollListener(list1));
SyncedScrollListener.java
package com.xorbix.util;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
public class SyncedScrollListener implements OnScrollListener{
int offset;
int oldVisibleItem = -1;
int currentHeight;
int prevHeight;
private View mSyncedView;
public SyncedScrollListener(View syncedView){
if(syncedView == null){
throw new IllegalArgumentException("syncedView is null");
}
mSyncedView = syncedView;
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
int[] location = new int[2];
if(visibleItemCount == 0){
return;
}
if(oldVisibleItem != firstVisibleItem){
if(oldVisibleItem < firstVisibleItem){
prevHeight = currentHeight;
currentHeight = view.getChildAt(0).getHeight();
offset += prevHeight;
}else{
currentHeight = view.getChildAt(0).getHeight();
View prevView;
if((prevView = view.getChildAt(firstVisibleItem - 1)) != null){
prevHeight = prevView.getHeight();
}else{
prevHeight = 0;
}
offset -= currentHeight;
}
oldVisibleItem = firstVisibleItem;
}
view.getLocationOnScreen(location);
int listContainerPosition = location[1];
view.getChildAt(0).getLocationOnScreen(location);
int currentLocation = location[1];
int blah = listContainerPosition - currentLocation + offset;
mSyncedView.scrollTo(0, blah);
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
}

I think it is more appropriate to use a GridView with 2 columns, something like this:
<GridView
android:id="#+id/grid_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:numColumns="2"
/>

What I would like to do is to listen to the scrolling event for the left listview and then scroll the right listview by an proper offset. Below is my code, I tested it(very simple, just show you my thought) and you may add your code based on it.
package viewTest.example.hy;
import android.app.Activity;
import android.os.Bundle;
import android.widget.AbsListView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.AbsListView.OnScrollListener;
public class ViewTestActivity extends Activity {
private ArrayAdapter<String> adapter0;
private ArrayAdapter<String> adapter1;
private String[] array0;
private String[] array1;
private ListView lv0;
private ListView lv1;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
array0 = getResources().getStringArray(R.array.LV0);//letters from A to O
array1 = getResources().getStringArray(R.array.LV1);//numbers from 1 to 14
adapter0 = new ArrayAdapter<String>(this, R.layout.item, array0);
adapter1 = new ArrayAdapter<String>(this, R.layout.item, array1);
lv0 = (ListView) findViewById(R.id.listView1);
lv1 = (ListView) findViewById(R.id.listView2);
lv0.setAdapter(adapter0);
lv1.setAdapter(adapter1);
lv0.setOnScrollListener(new OnScrollListener() {
#Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
#Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
lv1.setSelection(firstVisibleItem);//force the right listview to scrollyou may have to do some calculation to sync the scrolling status of the two listview.
}
});
}
}
And this is the main.xml layout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/layout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<ListView
android:id="#+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:scrollbars="none">
</ListView>
<ListView
android:id="#+id/listView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:scrollbars="none" >
</ListView>
</LinearLayout>
Here is my screenshot:

I ended up using the top s/o answer here: Android. Scrolling 2 listviews together
Intercepting and redirecting events seems to be a lot more elegant and consistent than trying to do my own math on the dimensions and state of the listviews.