Android加载asset的db

extends:http://blog.csdn.net/lihenair/article/details/21232887

项目需要将预先处理的db文件加载到数据库中，然后读取其中的信息并显示

加载数据库的代码参考了http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

效果如下：

1. 将asset中的db文件复制到database数据库中

public class DBHelper extends SQLiteOpenHelper {  

    private static final String LOG_TAG = "DataHelper";  

    private SQLiteDatabase mDataBase;
    private final Context mContext;  

    private static final String DATABASE_PATH = "/data/data/PACKAGE_NAME/databases/";
    private static final String DATABASE_NAME = "xx.db";
    private static final int DATABASE_VERSION = 1;  

    public DBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        this.mContext = context;
    }  

    public DBHelper(Context context, String name, CursorFactory factory,
            int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
        this.mContext = context;
    }  

    /**
     * Creates a empty database on the system and rewrites it with your own
     * database.
     * */
    public void createDataBase() throws IOException {  

        boolean dbExist = checkDataBase();  

        Log.d(LOG_TAG, "dbExist: " + dbExist);  

        if (dbExist) {
            // do nothing - database already exist
        } else {
            // By calling this method and empty database will be created into
            // the default system path
            // of your application so we are gonna be able to overwrite that
            // database with our database.
            this.getReadableDatabase();  

            try {
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }  

    }  

    /**
     * Check if the database already exist to avoid re-copying the file each
     * time you open the application.
     *
     * @return true if it exists, false if it doesn't
     */
    private boolean checkDataBase() {
        Log.d(LOG_TAG, "checkDataBase");
        SQLiteDatabase checkDB = null;  

        try {
            String myPath = DATABASE_PATH + DATABASE_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
            // database does't exist yet.
        }  

        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }  

    /**
     * Copies your database from your local assets-folder to the just created
     * empty database in the system folder, from where it can be accessed and
     * handled. This is done by transfering bytestream.
     * */
    private void copyDataBase() throws IOException {
        Log.d(LOG_TAG, "copyDataBase");
        // Open your local db as the input stream
        InputStream myInput = mContext.getAssets().open(DATABASE_NAME);  

        // Path to the just created empty db
        String outFileName = DATABASE_PATH + DATABASE_NAME;  

        // Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(outFileName);  

        // transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }  

        // Close the streams
        myOutput.flush();
        myOutput.close();
        myInput.close();  

    }  

    public void openDataBase() throws SQLException {
        Log.d(LOG_TAG, "openDataBase");
        // Open the database
        String myPath = DATABASE_PATH + DATABASE_NAME;
        mDataBase = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);  

    }  

    @Override
    public synchronized void close() {
        if (mDataBase != null)
            mDataBase.close();
        super.close();  

    }  

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
    }  

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
    }  

}  

 

调用的代码如下：

DataBaseHelper myDbHelper = new DataBaseHelper();
        myDbHelper = new DataBaseHelper(this);  

        try {
            myDbHelper.createDataBase();
    } catch (IOException ioe) {
        throw new Error("Unable to create database");
    }
    try {
        myDbHelper.openDataBase();
    }catch(SQLException sqle){
        throw sqle;
    }  

 

2. 显示数据库中的内容

 

public class CityGPS extends Activity {  

private static final String TAG = CityGPS.class.getSimpleName();  

private EditText mCityEdit;
private TextView mNameText;
private TextView mLattText;
private TextView mLongText;
private Button mButton;
private ListView mList;
private SimpleCursorAdapter mAdapter;
private Cursor cursor = null;  

@Override
protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);  

   DBHelper mDbHelper = new DBHelper(this);  

   try {
       mDbHelper.createDataBase();
   } catch (IOException ioe) {
       throw new Error("Unable to create database");
   }  

   try {
       mDbHelper.openDataBase();
   } catch (SQLException sqle) {
       throw sqle;
   }  

   mCityEdit = (EditText) findViewById(R.id.city);
   mNameText = (TextView) findViewById(R.id.name);
   mLattText = (TextView) findViewById(R.id.lat);
   mLongText = (TextView) findViewById(R.id.lon);  

   String sql = "SELECT * FROM citygps";
   cursor = mDbHelper.getReadableDatabase().rawQuery(sql, null);  

   String[] strings = { "city", "lat", "lon" };
   int[] ids = { R.id.name, R.id.lat, R.id.lon };
   mAdapter = new SimpleCursorAdapter(this, R.layout.item, cursor,
           strings, ids, 0);
   mList = (ListView) findViewById(R.id.list);
   mList.setAdapter(mAdapter);
   mButton = (Button) findViewById(R.id.btn);
   mButton.setOnClickListener(new OnClickListener() {  

       @Override
       public void onClick(View v) {
           // TODO Auto-generated method stub
           String city = mCityEdit.getText().toString();  

           if (TextUtils.isEmpty(city) == true) {
               Toast.makeText(CityGPS.this, "plz input city",
                       Toast.LENGTH_SHORT).show();
               return;
           }  

           String[] projection = { CityGPSTable.CITY,
                   CityGPSTable.LATITUDE, CityGPSTable.LONGITUDE };
           String selection = CityGPSTable.CITY + " = " + "\"" + city + "\"";
           Cursor cursor = getContentResolver().query(
                   CityGPSContentProvider.CONTENT_URI, projection, selection,
                   null, null);  

           if (cursor != null) {
               cursor.moveToFirst();
               Float lat = cursor.getFloat(cursor.getColumnIndex(CityGPSTable.LATITUDE));
               Float lon = cursor.getFloat(cursor.getColumnIndex(CityGPSTable.LONGITUDE));  

               Log.d(TAG, "lat: " + lat + " lon: " + lon);  

               mNameText.setText(city);
               mLattText.setText(lat.toString());
               mLongText.setText(lon.toString());
           }
       }
   });
}
}  

 

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"
    tools:context=".CityGPS" >  

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >  

        <EditText
            android:id="@+id/city"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:ems="10"
            android:inputType="text" />  

        <Button
            android:id="@+id/btn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/search" />
    </LinearLayout>  

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >  

        <TextView
            android:id="@+id/name"
            style="@android:style/TextAppearance.Holo.Medium"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/city" />  

        <TextView
            android:id="@+id/lat"
            style="@android:style/TextAppearance.Holo.Medium"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/lat" />  

        <TextView
            android:id="@+id/lon"
            style="@android:style/TextAppearance.Holo.Medium"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="@string/lon" />
    </LinearLayout>  

    <View
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:background="@android:color/holo_red_dark"
        android:visibility="visible" />  

    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="0dip"
        android:layout_weight="1" />  

</LinearLayout>  

 

item.xml，每行都带分割线

<?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="horizontal" >  

    <TextView
        style="@android:style/TextAppearance.Holo.Medium"
        android:id="@+id/name"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="@string/city" />  

    <View
        android:layout_width="1px"
        android:layout_height="match_parent"
        android:background="#B8B8B8"
        android:visibility="visible" />  

    <TextView
        style="@android:style/TextAppearance.Holo.Medium"
        android:id="@+id/lat"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="@string/lat" />  

    <View
        android:layout_width="1px"
        android:layout_height="match_parent"
        android:background="#B8B8B8"
        android:visibility="visible" />  

    <TextView
        style="@android:style/TextAppearance.Holo.Medium"
        android:id="@+id/lon"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:hint="@string/lon" />  

</LinearLayout>