CoderzHeaven

Here is a simple example showing how to load a database values in a spinner in android.

OK we will start.

This is the layout for the spinner row.
spinner_row.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView 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/tv"
    android:layout_margin="10dp">   
</TextView>

This is the layout for the interface.

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:textStyle="bold"
        android:text="Load DB values into Spinner"
         >
    </TextView>

    <Spinner
        android:id="@+id/spinner1"
        android:layout_below="@+id/tv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true" />

</LinearLayout>

Now this is the MainActivity.java file that uses the spinner and the database.

package com.coderzheaven.loadspinnerfromdb;

import   java  .util  .ArrayList;

import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;

public class MainActivity extends Activity {

	SQLiteDatabase mydb;
	private   static String DBNAME = "PERSONS.db";
	private static String TABLE = "MY_TABLE";

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		createTable();
		insertIntoTable();

		ArrayList<String> my_array = new ArrayList<String>();
		my_array = getTableValues();

		Spinner My_spinner = (Spinner) findViewById(R.id.spinner1);
		ArrayAdapter my_Adapter = new ArrayAdapter(this, R.layout.spinner_row,
				my_array);
		My_spinner.setAdapter(my_Adapter);
	}

	// CREATE TABLE IF NOT EXISTS
	public void createTable() {
		try {
			mydb = openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE, null);
			mydb.execSQL("CREATE TABLE IF  NOT EXISTS " + TABLE
					+ " (ID INTEGER PRIMARY KEY, NAME TEXT, PLACE TEXT);");
			mydb.close();
		} catch (Exception e) {
			Toast.makeText(getApplicationContext(), "Error in creating table",
					Toast.LENGTH_LONG);
		}
	}

	// THIS FUNCTION INSERTS DATA TO THE DATABASE
	public void insertIntoTable() {
		try {
			mydb = openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE, null);
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('CODERZHEAVEN','GREAT INDIA')");
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('ANTHONY','USA')");
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('SHUING','JAPAN')");
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('JAMES','INDIA')");
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('SOORYA','INDIA')");
			mydb.execSQL("INSERT INTO " + TABLE
					+ "(NAME, PLACE) VALUES('MALIK','INDIA')");
			mydb.close();
		} catch (Exception e) {
			Toast.makeText(getApplicationContext(),
					"Error in inserting into table", Toast.LENGTH_LONG);
		}
	}

	// THIS FUNCTION SHOWS DATA FROM THE DATABASE
	public ArrayList<String> getTableValues() {

		ArrayList<String> my_array = new ArrayList<String>();
		try {
			mydb = openOrCreateDatabase(DBNAME, Context.MODE_PRIVATE, null);
			Cursor allrows = mydb.rawQuery("SELECT * FROM " + TABLE, null);
			System.out.println("COUNT : " + allrows.getCount());

			if (allrows.moveToFirst()) {
				do {

					String ID = allrows.getString(0);
					String NAME = allrows.getString(1);
					String PLACE = allrows.getString(2);
					my_array.add(NAME);

				} while (allrows.moveToNext());
			}
			allrows.close();
			mydb.close();
		} catch (Exception e) {
			Toast.makeText(getApplicationContext(), "Error encountered.",
					Toast.LENGTH_LONG);
		}
		return my_array;
	}

}

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Download the complete source code for this example from here.

I ran into problem when I had multiple C files in my project. Single C file was OK for me.
I was getting undefined reference error while doing this.
Then I found out the solution after a lot of search in google.

You can check this post before going through this post.
This is about setting up NDK in MAC.
Starting with NDK for Android – A Simple example. OR How to run a C code in android?

I have to make the change in the Android.mk file to include other files to compile.

This is the content of my Android.mk file

LOCAL_PATH := $(call my-dir)
 
include $(CLEAR_VARS)
 
LOCAL_LDLIBS := -llog
 
LOCAL_MODULE    := ndksetup
LOCAL_SRC_FILES := native.c test.c test_2.c
 
include $(BUILD_SHARED_LIBRARY)

Here is my native.c code in which I am including those two files test.c and test2.c

#include <jni.h>
#include <string.h>
#include <android/log.h>

// my test file 
#include "test.h"
#include "test_2.h"

#define DEBUG_TAG "NDKSetupActivity"
 
void Java_com_ndksetup_NDKSetupActivity_printLog(JNIEnv * env, jobject this, jstring logString)
{
    jboolean isCopy;
    const char * szLogString = (*env)->GetStringUTFChars(env, logString, &isCopy);
 
    __android_log_print(ANDROID_LOG_DEBUG, "TAGGGGG", "NDK: %s", szLogString);
 
    (*env)->ReleaseStringUTFChars(env, logString, szLogString);
}
int Java_com_ndksetup_NDKSetupActivity_fibonacci(int value)
{
	int p = 8;
	printMe();
	printMe2();
	return p;
}

If you are writing memory consuming applications there is a bigger chance that your application may be running out of memory after sometime. So there are some methods in android that invokes the garbage collector explicitly.

See the following function which invokes the garbage collector to free a lot of memory.

public void freeMemory(){		
    System.runFinalization();
    Runtime.getRuntime().gc();
    System.gc();
}

A little explanation about the methods.

Java.Lang.Runtime.RunFinalization Method
Provides a hint to the VM that it would be useful to attempt to perform any outstanding object finalization.

Both System.gc() is effectively equivalent to Runtime.gc(). System.gc() internally calls Runtime.gc().
The only diff is System.gc() is a class method where as Runtime.gc() is an instance method. So, System.gc() is more convenient.

Hello all………..

Android has been absoultely wonderful for customizing widgets. I have shown a lot of example to customize ListViews, spinners etc.
Today I will show you how to customize gridviews.
Using this method you can actually place anything inside a gridview even a webview also.

So here we start.
We customize a gridview by creating an adapter that extends “BaseAdapter”.
This is the class that extends “BaseAdapter” and create a customAdapter.

 public class MyAdapter extends BaseAdapter {

    	private Context mContext;

		public MyAdapter(Context c) {
			mContext = c;
		}

		@Override
		public int getCount() {
			return mThumbIds.length;
		}

		@Override
		public Object getItem(int arg0) {
			return mThumbIds[arg0];
		}

		@Override
		public long getItemId(int arg0) {
			return arg0;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {

			View grid;

			if(convertView==null){
				grid = new View(mContext);
				LayoutInflater inflater=getLayoutInflater();
				grid=inflater.inflate(R.layout.mygrid_layout, parent, false);
			}else{
				grid = (View)convertView;
			}

			ImageView imageView = (ImageView)grid.findViewById(R.id.image);
			imageView.setImageResource(mThumbIds[position]);

			return grid;
		}

	}

Acually we can provide any custom layout for the view inside the gridview that is for each cell.

The xml I am using here is “mygrid_layout.xml” which looks like this.

<?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="@drawable/customshape_header"
	android:orientation="vertical">
	<ImageView
		android:id="@+id/image"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"/>
</LinearLayout>

This is the custom shape header class which is used for styling which is saved in res/drawable folder.

<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <corners android:radius="5dp" />
    <solid android:color="#660033"/>
    <stroke
        android:width="1dip"
        android:color="#C0C0C0" />
</shape>

Now the full source code for implementing this class.

package com.coderzheaven.pack;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class CustomGridViewExample extends Activity {

	private Integer[] mThumbIds = {
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			R.drawable.android_2,
			};


	/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new MyAdapter(this));
        gridview.setNumColumns(4);
    }

  public class MyAdapter extends BaseAdapter {

    	private Context mContext;

		public MyAdapter(Context c) {
			mContext = c;
		}

		@Override
		public int getCount() {
			return mThumbIds.length;
		}

		@Override
		public Object getItem(int arg0) {
			return mThumbIds[arg0];
		}

		@Override
		public long getItemId(int arg0) {
			return arg0;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {

			View grid;

			if(convertView==null){
				grid = new View(mContext);
				LayoutInflater inflater=getLayoutInflater();
				grid=inflater.inflate(R.layout.mygrid_layout, parent, false);
			}else{
				grid = (View)convertView;
			}

			ImageView imageView = (ImageView)grid.findViewById(R.id.image);
			imageView.setImageResource(mThumbIds[position]);

			return grid;
		}
	}
}

Here is the main.xml file

<?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"
    >
<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    android:padding="10dp"
    android:gravity="center"
    android:textStyle="bold"
    />

<GridView
	android:id="@+id/gridview"
	android:layout_width="fill_parent"
	android:layout_height="fill_parent"
	android:numColumns="auto_fit"
	android:verticalSpacing="10dp"
	android:horizontalSpacing="10dp"
	android:stretchMode="columnWidth"
	android:gravity="center"
	android:scrollbars="none" />
</LinearLayout>

Custom GridView in Android

You can download the complete source code from here.