Android Stuff

GridView layout is used to display data in two dimensional grid. It is a subclass of AdapterView. You can bind data from an external source to the GridView only by using an Adapter. Adapter acts as a bridge between the UI components and data source. It simply retrieves and fills the data to the UI components like gridview, listview or spinner.

Attributes:

1) numColumns: defines the number of columns to be displayed in a grid. You can assign a value "auto_fit" which displays as many columns as possible to fill the available space.

2) columnWidth:  It specifies the fixed width for each column.

3) gravity: It specifies the gravity/ alignment within each cell.

4) stretchMode: You can specify certain values for this attribute as shown below

none: stretching is disabled

spacingWidth: The spacing between each column is stretched.

columnWidth: Each column is stretched equally.

spacingWidthUniform: The spacing between each column is uniformly stretched.

5) padding: It adds space between content and border i.e. padding top, bottom, right and left.

6) margin: It adds space between border and its parent layout. Like padding, adds space on top, bottom, left and right.

7) horizontalSpacing: It adds space between cells in each row or say spacing between each column (horizontally). This could be in px, dp, sp, in or mm.

8) verticalSpacing: It adds space between cells in each column or say spacing between each row (vertically). This could be in px, dp, sp, in or mm.

9) scrollbars: It defines which scrollbar should be displayed on scrolling or not. i.e. horizontal or vertical or none.

10) background: It sets a drawable background or specific background color for the view.

 You can get or set the values of each attribute at runtime. Some of the get and set methods have been defined as follows:

 Get  Methods

public  int getNumColumns()

public  int getColumnWidth()

public  int getGravity()

public  int getHorizontalSapcing()

public  int getVerticalSpacing()

public  int getStretchMode()

public  ListAdapter getAdapter()

Set  Methods

public  void setNumColumns(int numColumns)

public  void setColumnWidth(int columnWidth)

public  int getGravity(int Gravity)

public  int getHorizontalSapcing(int horizontalSpacing)

public  int getVerticalSpacing(int verticalSpacing)

public  int getStretchMode(int stretchMode)

public  ListAdapter getAdapter(ListAdapter adapter)

 To load String array using ArrayAdapter:

· ArrayAdapter fits in between an ArrayList (data source) and the GridView (visual representation) and configures two aspects: (i) Which array to use as the data source for the grid; (ii) How to convert any given item in the array into a corresponding View object.

·ArrayAdapter arr = new ArrayAdapter(Context c, int Resource, String[] objects);

where,

Context  defines the activity instance.

Resource  defines the XML layout to be used.

objects  defines the array of data.

 Example:

gridview_layout.xml

<?xml version="1.0" encoding="utf-8"?> <GridView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:id="@+id/lGridSimple"    android:numColumns="auto_fit"    android:columnWidth="100dp"    android:gravity="center"    android:stretchMode="columnWidth"> </GridView>

Gridview_code.java

public class GridView_code extends Activity {

   GridView grid_alpha;    static final String[] numbers = new String[]{            "A", "B", "C", "D","E",            "F", "G", "H", "I", "J", "K",            "L","M","N","O", "P",            "Q", "R", "S", "T", "U",            "V", "W", "X", "Y", "Z"    };      @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.gridview_layout);        grid_alpha = (GridView) findViewById(R.id.lGridSimple);        ArrayAdapter<String> adapter = new ArrayAdapter<String> (this,   android .R.layout.simple_list_item_1, numbers);        grid_alpha.setAdapter(adapter);

    grid_alpha.setOnItemClickListener(new AdapterView.OnItemClickListener () {     @Override

   public void onItemClick(AdapterView<?> parent, View view, int position, long id) {    Toast.makeText(getApplicationContext(),"You have pressed " + ((TextView) view).getText(), Toast.LENGTH_SHORT).show();      }   }); } }

 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    package="com.example.admin.androidstuff" >    <application        android:allowBackup="true"        android:label="@string/app_name"

It is an extension of a View class. A view which is used to make your android app a 'web application' is WebView. Although, a user can use browser to access web pages; but WebView will open a web page as a part of your activity layout. The only difference is, WebView does not include any features of a fully developed web browser, such as address bar, navigation control, does not enable JavaScript or web page errors are ignored. You can also display HTML / text contents in it.

Constructors:

1) public WebView (Context c)

2) public WebView (Context c, AttributeSet attrs)

3) public WebView (Context c, AttributeSet attrs, int defStyleAttr)

4) public WebView (Context c, AttributeSet attrs, int defStyleAttr, int defStyleRes)

where,

context is used to access application assets.

AttributeSet is layout parameter

defStyleAttr is an attribute in the current theme that contains a reference to a style resource that supplies default values for the view. It can be zero to not look for defaults.

defStyleRes is a resource identifier of a style resource that supplies default values for the view, used only if defStyleAttr is zero or cannot be found in the theme. It can be zero to not look for defaults.

Methods:

1) Public void loadUrl  (String url)

Specifies the required  URL to open in a WebView

2) Public String getUrl()

Returns the URL of the  current page

3) Public String getTitle()

Returns the title of the  current page

4) Public boolean  canGoBack()

To check the back history  of a webview

5) Public boolean  canGoForward()

To check the forward  history of a webview

6) Public boolean  canGoBackOrForward (int step)

To check whether the page  can go back or forward the given number of steps

7) Public void goBack()

To navigate to the  previous page in a webview

8) Public void goForward()

To navigate to the next  page in a webview

9) Public void  goBackOrForward (int steps)

To navigate to the  previous or to the next page for the defined number of steps in the history  of WebView. Value of Steps is negative to move back and positive to move  forward

10) Public void  clearHistory()

To clear the back and  forward history of a webview

11) Public void reload()

To refresh the contents  of the current page

12) Public boolean  canZoomIn()

To check whether zooming  in the view of a current page is possible. This method was deprecated in API  level 17

13) Public boolean  canZoomOut()

To check whether zooming  out the view of a current page is possible. This method was deprecated in API  level 17

14) Public void  setInitialScale (int percentage)

To set initial scale for  the webview when trying to zoom in or out the content of a web page. default  value is '0'. You can define 100% to fit the content into the webview control  by its width

15) public void  loadData(String data, String mimeType, String encoding)

Loads the given data into  this webview using 'data' scheme URL

16) Public void findAllAsync (string  text)

Finds all instances of  string and highlight them

To add WebView in your application:

     <?xml version="1.0" encoding="utf-8"?>       <WebView xmlns:android="http://schemas.android.com/apk/res/android"                  android:id="@+id/wv"                  android:layout_width="fill_parent"                  android:layout_height="fill_parent">

To Load WebView in a web page:

WebView wv = (WebView) findViewById(R.id.wv);

wv.loadUrl("http://www.google.com");

To load data from an HTML string:

String summary = "<html> <body> I love <b> Android </b> Programming </body> </html>";

wv.loadData(summary, "text/ html", null);

Request INTERNET access in manifest file:

An application must have an Internet access to support WebView. You must add the INTERNET permissions in Android Manifest file. This must be a child of the element.

<uses-permission android:name = "android.permission.INTERNET" />

Example:

webview_layout.xml

<?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">    <LinearLayout        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <EditText            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/letBrowserText"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbGo"            android:text="GO"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbBack"            android:text="Back"/>    </LinearLayout>    <LinearLayout        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbForward"            android:text="Forward"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbRefresh"            android:text="Page Refresh"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbHistory"            android:text="Clear History"/>    </LinearLayout>    <LinearLayout        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbZoomIn"            android:text="Zoom In"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbZoomOut"            android:text="Zoom Out"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbGetTitle"            android:text="Get Title"/>        <Button            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/lbHighlight"            android:text="Highlight"/>    </LinearLayout>        <WebView            android:layout_width="fill_parent"            android:layout_height="fill_parent"            android:id="@+id/lWebView1"></WebView> </LinearLayout>

Webview_code.java

public  class Webview_code extends Activity implements View.OnClickListener{ WebView wv; Button bGo, bGoBack, bGoForward,  bRefresh, bHistory, bZoomIn, bZoomOut,  bGetTitle, bHighlight; EditText etBrowseText; @Override protected void onCreate(Bundle  savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.webview_browser); wv = (WebView)  findViewById(R.id.lWebView1);

//setWebViewClient  method is used to open link in WebView only, instead of in a new browser wv.setWebViewClient(new WebViewClient() { public boolean  shouldOverrideUrlLoading(WebView v, String url) { wv.loadUrl(url); return true; } });

       initialize();            bGo.setOnClickListener(this);        bGoBack.setOnClickListener(this);        bGoForward.setOnClickListener(this);        bRefresh.setOnClickListener(this);        bHistory.setOnClickListener(this);        bZoomIn.setOnClickListener(this);        bZoomOut.setOnClickListener(this);        bGetTitle.setOnClickListener(this);        bHighlight.setOnClickListener(this);    }    private void initialize(){        bGo = (Button) findViewById(R.id.lbGo);        bGoBack = (Button) findViewById(R.id.lbBack);        bGoForward = (Button) findViewById(R.id.lbForward);        bRefresh = (Button) findViewById(R.id.lbRefresh);        bHistory = (Button) findViewById(R.id.lbHistory);        bZoomIn = (Button) findViewById(R.id.lbZoomIn);        bZoomOut = (Button) findViewById(R.id.lbZoomOut);        bGetTitle = (Button) findViewById(R.id.lbGetTitle);        bHighlight = (Button) findViewById(R.id.lbHighlight);        etBrowseText = (EditText) findViewById(R.id.letBrowserText);    }      public void onClick(View v){        switch (v.getId()){            case R.id.lbGo:                String website = etBrowseText.getText().toString();                wv.loadUrl(website);                break;            case R.id.lbBack:                if(wv.canGoBack())                wv.goBack();                break;            case R.id.lbForward:                if(wv.canGoForward())                    wv.goForward();                break;            case R.id.lbRefresh:                wv.reload();                break;            case R.id.lbHistory:                wv.clearHistory();                break;            case R.id.lbZoomIn:                if(wv.canZoomIn())                    wv.setInitialScale(-10);                break;            case R.id.lbZoomOut:                if(wv.canZoomOut())                    wv.setInitialScale(0);                break;            case R.id.lbGetTitle:                String pagetitle = wv.getTitle().toString();                etBrowseText.setText(pagetitle);                break;            case R.id.lbHighlight:                wv.findAllAsync("android");                break;        }    } }

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    package="com.example.admin.androidstuff" >    <uses-permission android:name="android.permission.INTERNET" />    <application        android:allowBackup="true"        android:label="@string/app_name"

tools:ignore="NewApi">

<activity android:name=".Webview_code" android:label="@string/app_name">

           <intent-filter>                <action android:name="android.intent.action.MAIN"/>                <category android:name="android.intent.category.LAUNCHER"/>            </intent-filter>        </activity>    </application> </manifest>