No resource identifier found for attribute 'indicator_gravity' in package ….

I was trying to porting the Tree-View-List-Android into my project recently. I have created a project called com.dotnetideas.treeview and added everything in. I can run the demo without any issue. But when I use it in another project, I kept getting “No resource identifier found for attribute 'indicator_gravity' in package com.dotnetideas.treeview” in main_demo.xml.
Here is the xml looks like.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:treeView="http://schemas.android.com/apk/res/com.dotnetideas.treeview"
  android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent">
  <ListView android:layout_width="0dip" android:layout_height="0dip" android:scrollbars="vertical"
    android:visibility="gone"> <!-- Just to test some attributes in IDE -->
  </ListView>
  <pl.polidea.treeview.TreeViewList android:id="@+id/mainTreeView" android:layout_width="fill_parent"
    android:layout_height="fill_parent" treeView:indicator_gravity="right|center_vertical"
    android:scrollbars="vertical" android:smoothScrollbar="true"/>
</LinearLayout>

Although I followed the old code to changed the xml namespace from xmlns:treeView=http://schemas.android.com/apk/res/pl.polidea.treeview to xmlns:treeView=http://schemas.android.com/apk/res/com.dotnetideas.treeview. It doesn’t seem like valid xml namespace. It turned out that the namespace needs to be xmlns:treeView="http://schemas.android.com/apk/res-auto" if we reference as a library project.

AlarmManager and NotificationManager sample code

This is not a complete tutorial on how to use AlarmManager and NotificationManager, but a simple sample.

The scenario is I want to have an alarm set to certain time. When it goes off, it show notification icon on status bar. When click on the notification, it will start an activity.

1. Create the BroadcastReceiver

public class AlarmReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        NotificationManager mNM;
        mNM = (NotificationManager)context.getSystemService(context.NOTIFICATION_SERVICE);
        // Set the icon, scrolling text and timestamp
        Notification notification = new Notification(R.drawable.icon, "Test Alarm",
        System.currentTimeMillis());
        // The PendingIntent to launch our activity if the user selects this notification
        PendingIntent contentIntent = PendingIntent.getActivity(context, 0, new Intent(context, TestActivity.class), 0);
        // Set the info for the views that show in the notification panel.
        notification.setLatestEventInfo(context, context.getText(R.string.alarm_service_label), "This is a Test Alarm", contentIntent);
        // Send the notification.
        // We use a layout id because it is a unique number. We use it later to cancel.
        mNM.notify(R.string.alarm_service_label, notification);
    }
}

2. Add Receiver to Manifest.xml

<receiver android:process=":remote" android:name="AlarmReceiver"></receiver>

3. Set the alarm

public class AlarmService {
    private Context context;
    private PendingIntent mAlarmSender;
    public AlarmService(Context context) {
        this.context = context;
        mAlarmSender = PendingIntent.getBroadcast(context, 0, new Intent(context, AlarmReceiver.class), 0);
    }

    public void startAlarm(){
        //Set the alarm to 10 seconds from now
        Calendar c = Calendar.getInstance();
        c.add(Calendar.SECOND, 10);
        long firstTime = c.getTimeInMillis();
        // Schedule the alarm!
        AlarmManager am = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
        am.set(AlarmManager.RTC_WAKEUP, firstTime, mAlarmSender);
    }
}

How to use and customize tab(image, font)?

1. Create tabs

TabHost tabHost = getTabHost(); // The activity TabHost
TabHost.TabSpec spec; // Resusable TabSpec for each tab
Intent intent; // Reusable Intent for each tab
// Create an Intent to launch an Activity for the tab (to be reused)
intent = new Intent().setClass(this, TaskActivity.class);
// Initialize a TabSpec for each tab and add it to the TabHost
spec = tabHost.newTabSpec("task").setIndicator("Task", null).setContent(intent);
tabHost.addTab(spec); // Do the same for the other tabs
intent = new Intent().setClass(this, CalendarActivity.class);
spec = tabHost.newTabSpec("calendar").setIndicator("Calendar", null).setContent(intent);
tabHost.addTab(spec); 

2. Customize tabs

TabHost tabHost = getTabHost();
LinearLayout linearLayout = (LinearLayout) tabHost.getChildAt(0); 
TabWidget tw = (TabWidget) linearLayout .getChildAt(0);
RelativeLayoutfirstTabLayout = (RelativeLayout) tw.getChildAt(0); 
//First tab
TextViewtabHeader = (TextView) firstTabLayout .getChildAt(1); 
tabHeader .setTextSize(18); //Change text size
tabHost.getTabWidget().getChildAt(0).getLayoutParams().height = 36; 
//Change first tab header height
firstTabLayout.setBackgroundResource(R.drawable.group_background_overdue);
tabHeader.setText("Tab page 1");

How to sort array list?

Sort by simple type property

1. Implement the Comparable interface

public class Item implements Comparable<Item> {
…
}

2. Implement the compareTo method.

@Override
public int compareTo(Item another) {
    //Compare the name
    return this.name.compareTo(another.name);
}

3. Call sort

List<Item> items = ..
items.sort();

Sort by user defined property

1. Create a new class

import java.util.Comparator;
public class ItemCompareByLocation implements Comparator<Item>{
    @Override
    public int compare(Item arg0, Item arg1) {
        return arg0.getLocation().compareTo(arg1.getLocation());
    }
}

2. Call sort

Collections.sort(items, new ItemCompareByLocation());

How to use Style

Create style.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="DetailTextView" parent="@android:style/TextAppearance">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:textSize">14sp</item>
        <item name="android:textStyle">bold</item>
    </style>
    <style name="DateTimeButton" parent="@android:style/Widget.Button">
        <item name="android:layout_width">fill_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:gravity">left|center_vertical</item>
        <item name="android:textSize">19sp</item>
    </style>
</resources>

Use it in layout

<TextView android:id="@+id/TextView01" android:text="What" style="@style/DetailTextView" />

How to show toast?

Simple toast:

Context context = getApplicationContext();
CharSequence text = "Hello toast!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();

Customized toast:

LayoutInflater inflater;
inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.detail_toast, 
(ViewGroup)arg0.findViewById(R.id.toast_layout_root));
TextView taskTextView = (TextView) 
layout.findViewById(R.id.taskTextView);
taskTextView.setText(task.getName());
TextView detailTextView = (TextView) 
layout.findViewById(R.id.detailTextView);
detailTextView.setText(sb.toString());
Toast toast = new Toast(context.getApplicationContext());
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();

How to customize control

There are some icons and xmls under C:\Android\android-sdk-windows-1.6_r1\platforms\android-1.5(or other version)\data\res\drawable

To use different icons for standard control, we can copy the xml file and icons used in the xml to our own \drawable folder and set it in the layout xml

1) Grab the checkbox_background.xml and checkbox.xml from above folder and copy to the drawable folder in my project

2) Copy all the PNG files for the checkbox to the drawable folder in my project

3) Change the layout to use the checkbox (In my case, it is a CheckedTextView)

android:checkMark="@drawable/checkbox"