读取SDcard Database并在Android ListView显示的处理流程

虽然整个功能比较简单，但要掌握的东西还是很多的

完成整个功能主要需要以下几点内容：

一. 申请SDcard权限，让程序可以在SDcard创建文件夹和数据库文件

二. 创建一个ListView Activity 和 Activity对应的list.xml layout

三. 使用 SQLiteDatabase 来管理 SQL , execute SQL commands, and perform other common database management tasks

四. 使用 Adapter 把数据映射到ListView ，且把数据传到TextView等控件中显示出来（这位同学有关于Adapter相关资料：Android开发——说说Adapter那点事）

首先来设置SDcard的权限,加上uses-permission

AndroidManifest.xml

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

创建listview元素文件:

布局layout中, android:descendantFocusability="blocksDescendants"  这个属性尤其关键， 如果你需要在listview里添加按钮什么的，就需要添加这个元素，使listview不把按钮的焦点覆盖

list.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:descendantFocusability="blocksDescendants">

    <ImageView android:id="@+id/img" 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" 
        android:layout_margin="2px"
        android:layout_alignParentLeft="true"/>
    <TextView android:id="@+id/text" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:textColor="#FFFFFFFF"
        android:textSize="13px" 
        android:paddingTop="8px"
        android:paddingLeft="35px"
        />
</RelativeLayout>

创建MyListViewActivity 继承 ListActivity , 它和Activity差不多，只是多了对ListView的一些优化
MyListViewActivity.java

 

public class MyListViewActivity extends ListActivity {
    /** Called when the activity is first created. */
    //定义SQLiteDatabase对象,用于处理数据库的操作
    private SQLiteDatabase  db = null;
    //定义Cursor游标,用于管理数据，比如获得数据库的每一行数据
    private Cursor cursor = null; 
    //定义一个列表储存 mData 
    private List<Map<String, Object>> mData;
    
    //获取自定义的function
    function function = new function();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        //初始化数据库，创建文件夹和数据库文件
        function.initDatabase();
        
        mData = getData();

        MyAdapter adapter = new MyAdapter(this);
        setListAdapter(adapter);
    }


    private List<Map<String, Object>> getData() {
        List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
        
        //使用SQLiteDatabase的openOrCreateDatabase获取SDcard的数据库
        //config.f 是在config.java里定义的文件路径变量
        db = SQLiteDatabase.openOrCreateDatabase(config.f, null); 
        Map<String, Object> map = new HashMap<String, Object>();
        try {
            //查询test_listview数据
            cursor = db.query("test_listview", new String[]{}, null, null, null, null, null);
            //通过强大的cursor把数据库的资料一行一行地读取出来
            while(cursor.moveToNext()){
                String text = cursor.getString(cursor.getColumnIndex("text"));
                map = new HashMap<String, Object>();
                map.put("text", text);
                map.put("img", R.drawable.info);
                list.add(map);
            }
        } catch (Exception e) {
            // TODO: handle exception
            Log.i("opendatabase", e.toString());
        }
        
        return list;
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        
        super.onListItemClick(l, v, position, id);
        function.showDialog((String)mData.get(position).get("text"), MyListViewActivity.this);
        //Toast.makeText(MyListViewActivity.this, (String)mData.get(position).get("text"), Toast.LENGTH_LONG).show(); 
    }

    public final class ViewHolder{
        public ImageView img;
        public TextView text;    
    }

    public class MyAdapter extends BaseAdapter{

        private LayoutInflater mInflater;
        ViewHolder holder = null;
        public MyAdapter(Context context){
            this.mInflater = LayoutInflater.from(context);
        }
        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return mData.size();
        }
    
        @Override
        public Object getItem(int arg0) {
            // TODO Auto-generated method stub
            return null;
        }
    
        @Override
        public long getItemId(int arg0) {
            // TODO Auto-generated method stub
            return 0;
        }
    
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                holder=new ViewHolder();  
                
                convertView = mInflater.inflate(R.layout.list, null);
                holder.img = (ImageView)convertView.findViewById(R.id.img);
                holder.text = (TextView)convertView.findViewById(R.id.text);
                convertView.setTag(holder);
                
            }else {
                
                holder = (ViewHolder)convertView.getTag();
            }
    
            holder.img.setBackgroundResource((Integer)mData.get(position).get("img"));
            //把字符串设置在TextView上显示
            holder.text.setText((String)mData.get(position).get("text"));
            
            return convertView;
        }
    }
}

配置文件，定义各种常量和变量，方便重复使用
config.java

public class config {
    //获取SDcard路径
    public static String CR_SDCARD = android.os.Environment.getExternalStorageDirectory().getAbsolutePath();
    
    //定义SDcard存放数据库的文件夹
    public static final String CR_URL_DBFILE = "/listview";
    public static final String CR_PATH = CR_SDCARD+CR_URL_DBFILE;
    public static final String CR_DBNAME = "database.db";
    public static final String CR_URL_DBTABLE = CR_PATH+"/"+CR_DBNAME;//database file
    public static File path = new File(CR_PATH); 
    public static File f = new File(CR_URL_DBTABLE);
}

自定义函数文件

function.java

public class function{
    private SQLiteDatabase db;
    private int i;
    /**
     * create database folder and database 
     * and check the table is already exist to create new 
     */
    public void initDatabase(){
         
        if(!config.path.exists()){  
            config.path.mkdirs();    
            Log.i("init", "create a database folder");  
        }   
        if(!config.f.exists()){      
            try{   
                config.f.createNewFile();  
                Log.i("init", "create a new database file");
            }catch(IOException e){   
                Log.i("init", e.toString());  
            }   
        } 
          
        try {
            if(tabIsExist("test_listview")==false){
                db.execSQL("create table test_listview(id integer primary key autoincrement," +
                        "text varchar(128))");
                for(i=0;i<10;i++){
                    db.execSQL("insert into test_listview(text)values('Auto insert value "+i+"')");
                }
                Log.i("init", "create a table test_listview");
            }
        } catch (Exception e) {
            // TODO: handle exception
            Log.i("init", e.toString());  
        }
    }
    /**
     * check the database is already exist
     * @param tabName
     * @return
     */
    public boolean tabIsExist(String tabName){
        boolean result = false;
        if(tabName == null){
                return false;
        }
        Cursor cursor = null;
        db = SQLiteDatabase.openOrCreateDatabase(config.f, null); 
        try {
            String sql = "select count(*) as c from sqlite_master where type ='table' " +
                        "and name ='"+tabName.trim()+"' ";
            cursor = db.rawQuery(sql, null);
            if(cursor.moveToNext()){
                int count = cursor.getInt(0);
                if(count>0){
                    result = true;
                }
            }
                
        } catch (Exception e) {
                // TODO: handle exception
        }                
        return result;
    }
    /**
     * define a dialog for show the message
     * @param mess
     * @param activity
     */
    public void showDialog(String mess,Activity activity){
      new AlertDialog.Builder(activity).setTitle("Message").setMessage(mess)
       .setNegativeButton("Confirm",new DialogInterface.OnClickListener()
       {
         public void onClick(DialogInterface dialog, int which)
         {          
         }
       })
       .show();
    }
}

adb查看数据sdcard数据库

补充一下，如果你需要把现有的数据库放到SDcard的话，（既是用户安装使用该软件的时候，把已经装好数据的Database放到SDcard）

先把处理好的数据库放在assets文件夹中，然后当程序第一次运行的时候，就把数据库复制到SDcard

第一步，复制已经处理好的database.db放在assets文件夹

第二步，在程序的第一个Activity判断用户的SDcard中是否已经存在这个数据库文件

第三步，若不存在，则进行复制

 

    public void createDataBase() throws IOException{          
        File dbdir = config.path;
        if(!dbdir.exists()){ 
            dbdir.mkdirs(); 
        } 
        if(!config.f.exists()){
            config.f.createNewFile();  
            SQLiteDatabase.openOrCreateDatabase(config.f, null);
            copyDataBase();
        }
    }
    
    private void copyDataBase() throws IOException {
        InputStream myInput;
        //复制到的目标路径
        String outFileName = config.CR_URL_DBTABLE; 
        OutputStream myOutput = new FileOutputStream(outFileName);
        //获取Assets文件夹中的databae.db
        myInput = this.getAssets().open(config.CR_DBNAME);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }
        myOutput.flush();
        myInput.close();
        myOutput.close();
    }