Simple Drag n Drop on Android

Till now, there is no Drag and Drop like control on the Android. This feature might come in handy in a few situations to improve the usability of your apps. Here is a simple Drag and Drop app which allows you to drag a button and drop it anywhere on the screen.
Theory: Go for a FrameLayout.
FrameLayout is designed to block out an area on the screen to display a single item. You can add multiple children to a FrameLayout, but all children are pegged to the top left of the screen. Children are drawn in a stack, with the most recently added child on top.
In our main layout, we have a single button. We write a touch listener which will track the touch events and also help us to move the button around the screen. In this example, we will not be moving the button, but it’s image which we set to a ImageView. Also, instead of actually moving the ImageView, we will change the padding of the ImageView as the mouse moves, which will give an impression of the ImageView being moved.

The source code for this can be found on this link.
Drag and Drop example

Custom ProgressBar for Android

We will try to make a new progress bar with our own progress animation. It's pretty simple and can be easily set up to run in few minutes. Here we go.

1. MyProgressBar.java
This class extends the ProgressBar class and has two methods that we would need to call to start and stop the animation.

       To start the animation: call startAnimation()
       To stop the animation: call dismiss()

Basically, we run a thread which keeps on switching the images. That's it.

2. myprogressbar.xml

This is the layout that the MyProgressBar would be using. This animation would be using 9 images which are in the drawable folder.

You can check out the whole project from the SVN. Here is the link.

https://myandroidwidgets.googlecode.com/svn/trunk/Custom_Progress_Bar

Custom AutoComplete for Android

The default custom AutoCompleteTextView is quite a nice widget. But if you want to extend it's functionality, you will need to write your own custom widget. As an example, if you wish to have a EditText for a "To" address field as any email application has, where you want to collect multiple selections from the list that pops up, you will need to extend the AutoCompleteTextView class and write your own small little widget. It's very simple to create one that will suit your need.
So here we go.
1. Class CustomAutoComplete.java

   1: package com.beanie.example.widgets;

   2: import android.content.Context;

   3: import android.text.TextUtils;

   4: import android.util.AttributeSet;

   5: import android.widget.AutoCompleteTextView;

   6:  

   7: public class CustomAutoComplete extends AutoCompleteTextView {

   8:     private String previous = "";

   9:     private String seperator = ";";

  10:     public CustomAutoComplete(final Context context, final AttributeSet attrs, final int defStyle) {

  11:         super(context, attrs, defStyle);

  12:         this.setThreshold(0);

  13:     }

  14:     public CustomAutoComplete(final Context context, final AttributeSet attrs) {

  15:         super(context, attrs);

  16:         this.setThreshold(0);

  17:     }

  18:     public CustomAutoComplete(final Context context) {

  19:         super(context);

  20:         this.setThreshold(0);

  21:     }

  22:     /**

  23:      * This method filters out the existing text till the separator

  24:      * and launched the filtering process again

  25:      */

  26:     @Override

  27:     protected void performFiltering(final CharSequence text, final int keyCode) {

  28:         String filterText = text.toString().trim();

  29:         previous = filterText.substring(0,filterText.lastIndexOf(getSeperator())+1);

  30:         filterText = filterText.substring(filterText.lastIndexOf(getSeperator()) + 1);

  31:         if(!TextUtils.isEmpty(filterText)){

  32:             super.performFiltering(filterText, keyCode);

  33:         }

  34:     }

  35:     /**

  36:      * After a selection, capture the new value and append to the existing

  37:      * text

  38:      */

  39:     @Override

  40:     protected void replaceText(final CharSequence text) {

  41:         super.replaceText(previous+text+getSeperator());

  42:     }

  43:     public String getSeperator() {

  44:         return seperator;

  45:     }

  46:     public void setSeperator(final String seperator) {

  47:         this.seperator = seperator;

  48:     }

  49: }

This class is the main widget class that extends thet AutoCompleteTextView. You have to override 2 methods,

protected void replaceText(final CharSequence text)

protected void performFiltering(final CharSequence text, final int keyCode)

2. You main layout file (main.xml)

   1: <?xml version="1.0" encoding="utf-8"?>

   2: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

   3:     android:orientation="vertical" android:layout_width="fill_parent"

   4:     android:layout_height="fill_parent">

   5:     <com.beanie.example.widgets.CustomAutoComplete android:layout_width="fill_parent"

   6:         android:layout_height="wrap_content" android:id="@+id/autocomplete"/>

   7: </LinearLayout>

3. Now we test it. This is your activity class.

   1: package com.beanie.example;

   2: import android.app.Activity;

   3: import android.os.Bundle;

   4: import android.widget.ArrayAdapter;

   5: import com.beanie.example.widgets.CustomAutoComplete;

   6:  

   7: public class TestAutoComplete extends Activity {

   8:     /** Called when the activity is first created. */

   9:     @Override

  10:     public void onCreate(Bundle savedInstanceState) {

  11:         super.onCreate(savedInstanceState);

  12:         setContentView(R.layout.main);

  13:         CustomAutoComplete myAutoComplete = (CustomAutoComplete)findViewById(R.id.autocomplete);

  14:         ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line);

  15:  

  16:         adapter.add("aaaa");

  17:         adapter.add("abaa");

  18:         adapter.add("acaa");

  19:         adapter.add("adaa");

  20:         adapter.add("aaba");

  21:         adapter.add("aaca");

  22:         adapter.add("aaba");

  23:         adapter.add("aaae");

  24:         

  25:         myAutoComplete.setAdapter(adapter);

  26:     }

  27: }

Voila, you are done. Here’s a screenshot of our Custom Auto-Complete Text view at work.

You can also change the separator from the default “;” to any other character like a “,” or anything else.
On the adapter, you call the method setSeparator(String any);
Now you have your own custom auto-complete widget for Android.

For this particular example, however, Android provides you a widget by default. MultiAutoCompleteTextView is specifically designed to handle such kind of input.

Custom Buttons on Android

The default buttons are a kind of ugly when you change the background of an activity. In some scenarios, you will be forced to change the way your Buttons look. To achieve this, you need not create your own custom Button class. The Android framework provides ways to achieve this with minimum effort.


Let's say we have a Button in a simple layout for which we need to do this. Here is a simple layout with just a button.

<?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"
    >
<Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/click"
    android:background="@drawable/custom_button"
    />
</LinearLayout>

Note the android:background attribute on the Button. This refers to a drawable which is an xml in your drawable folder which will determine the different states of your button, namely,
1. default
2. pressed
3. focussed

This is the code for custom_button.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_focused="true" android:state_pressed="false" android:drawable="@drawable/focussed" />
    <item android:state_focused="true" android:state_pressed="true" android:drawable="@drawable/focussedandpressed" />
    <item android:state_focused="false" android:state_pressed="true" android:drawable="@drawable/pressed" />
    <item android:drawable="@drawable/default" />
</selector>

For this selector tag, note all the drawable attributes. You will have different png images for each of the states which you would put in your drawable folder.

Now you have your own custom button with customized look and feel.

Youtube/Market Intent for Search in Android

Here is a trick that would help other applications that need to open search results for videos based on a particular keyword.

You need to create an implicit Intent and trigger it. Here is a snippet of code that works.

For Youtube
Intent intent = new Intent(Intent.ACTION_SEARCH);
intent.setPackage("com.google.android.youtube");
intent.putExtra("query", "Android");
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

Here, "Android" is the keyword. Now, the Youtube app will show you videos with the keyword "Android"

For Market
Similarly, by changing only the package name, you can bring up search results with the Android Market app as well.

Intent intent = new Intent(Intent.ACTION_SEARCH);
intent.setPackage("com.android.vending");
intent.putExtra("query", "Android");
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

For Contacts
The package name for the Contacts app is "com.google.contacts".

You just need the package name of the target app if you don't want the Resolver activity to show up. This might work for other google apps as well. I haven't checked though.