从.sqlite获取包含多个包含多个列的表的列 [英] Getting a column from .sqlite containing multiple tables with multiple columns

问题描述

！数据库由多个表和多个列组成，如图所示&我已经粘贴这个law.sqlite在assets文件夹。

数据库由多个表和多个列组成，如图所示&我已经在资源文件夹中粘贴了这个law.sqlite。

假设我想访问 AS_name 列的所有元素，如图所示。

解决方案

我试过，现在问题解决了：

面对类似问题的任何人都可以尝试我的实现：

步骤1：
$ b

创建一个GetterSetter类（在这里命名为 GS ）生成所使用的变量的 Getter-Setters 。

在我的例子中：

  public class GS {
 String AS_name; 
 
 public String getAS_name（）{
 return AS_name; 
} 
 
 public void setAS_name（String aS_name）{
 AS_name = aS_name; 
} 
} 
  

步骤2： / p>

创建一个 DBAdapter 类，扩展 SQLiteOpenHelper

剩下的只需要复制我的 DBAdapter.java code&注意实现方法 getData（），其中从数据库获取数据！

  public class DBAdapter extends SQLiteOpenHelper 
 {
 CustomAdapter adapter; 
 static String name =law.sqlite; //  - 将它替换为sqlite名称
 static String path =; 
 static ArrayList< GS> gs; 
 static SQLiteDatabase sdb; 
 
 @Override 
 public void onCreate（SQLiteDatabase db）
 {
 // TODO自动生成方法存根
} 
 
 @Override 
 public void onUpgrade（SQLiteDatabase db，int oldVersion，int newVersion）
 {
 // TODO自动生成方法存根
} 
 
 private DBAdapter（Context v）
 {
 super（v，name，null，1）; 
 path =/ data / data /+ v.getApplicationContext（）。getPackageName（）+/ databases; 
} 
 
 public boolean checkDatabase（）
 {
 SQLiteDatabase db = null; 
 try 
 {
 db = SQLiteDatabase.openDatabase（path +/+ name，null，SQLiteDatabase.OPEN_READONLY）; 
} catch（Exception e）
 {
 e.printStackTrace（）; 
} 
 if（db == null）
 {
 return false; 
} 
 else 
 {
 db.close（）; 
 return true; 
} 
} 
 
 public static synchronized DBAdapter getDBAdapter（Context v）
 {
 return（new DBAdapter（v））; 
} 
 
 public void createDatabase（Context v）
 {
 this.getReadableDatabase（）; 
 try 
 {
 InputStream myInput = v.getAssets（）。open（name）; 
 //刚刚创建的空路径db 
 String outFileName = path +/+ name; 
 //打开空数据库作为输出流
 OutputStream myOutput = new FileOutputStream（outFileName）; 
 //从输入文件传输字节到输出文件
 byte [] buffer = new byte [1024] 
 int length; 
 while（（length = myInput.read（buffer））> 0）
 {
 myOutput.write（buffer，0，length）; 
} 
 //关闭流
 myOutput.flush（）; 
 myOutput.close（）; 
 myInput.close（）; 
} catch（IOException e）
 {
 System.out.println（e）; 
} 
} 
 
 public void openDatabase（）
 {
 try 
 {
 sdb = SQLiteDatabase.openDatabase（path + /+ name，null，
 SQLiteDatabase.OPEN_READWRITE）; 
} catch（Exception e）
 {
 System.out.println（e）; 
} 
} 
 
 public ArrayList< GS> getData（）
 {
 try {
 Cursor c1 = sdb.rawQuery（SELECT DISTINCT * FROM Articles，null）; 
 gs = new ArrayList< GS>（）; 
 while（c1.moveToNext（））
 {
 GS q1 = new GS（）; 
 
 q1.setAS_name（c1.getString（3））; // ---这里3代表列号。 
 Log.v（AS_name，q1.AS_name +）; 
 gs.add（q1）; 
 
} 
} 
 catch（Exception e）{
 e.printStackTrace（）; 
} 
 return gs; 
} 
} 
  

步骤3： / p>

类 MainActivity.java ：

  public class MainActivity extends Activity {
 
 ArrayList< GS> q = new ArrayList< GS>（）; 
 CustomAdapter适配器; 
 ListView lv; 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_main）; 
 //从xml中获取ListView对象
 lv =（ListView）findViewById（R.id.listView1）; 
 
 DBAdapter db = DBAdapter.getDBAdapter（getApplicationContext（））; 
 if（！db.checkDatabase（））
 {
 db.createDatabase（getApplicationContext（））; 
} 
 db.openDatabase（）; 
 
 q = db.getData（）; 
 for（int i = 0; i< q.size（）; i ++）
 {
 Log.i（outside，+ q.get（i）.getAS_name ））; 
} 
 lv =（ListView）findViewById（R.id.listView1）; 
 lv.setAdapter（new CustomAdapter（MainActivity.this，q））; 
 //lv.setAdapter (adapter）; 
 
} 
 
 class CustomAdapter extends ArrayAdapter< GS> 
 {
 ArrayList< GS>列表; 
 LayoutInflater mInfalter; 
 public CustomAdapter（Context context，ArrayList< GS> list）
 {
 super（context，R.layout.customlayout，list）; 
 this.list = list; 
 mInfalter = LayoutInflater.from（context）; 
 for（int i = 0; i  {
 Log.i（............... 。，+ list.get（i）.getAS_name（））; 
} 
 
} 
 // public int getCount（）{
 // return list.size（）; 
 //} 
 @Override 
 public View getView（int position，View convertView，ViewGroup parent）{
 ViewHolder holder; 
 Log.i（..........，Hello in getView）; 
 if（convertView == null）
 {
 convertView = mInfalter.inflate（R.layout.customlayout，parent，false）; //  -  customlayout.xml必须有一个textView 
 holder = new ViewHolder（）; 
 holder.tv1 =（TextView）convertView.findViewById（R.id.textView1）; 
 convertView.setTag（holder）; 
} else {
 holder =（ViewHolder）convertView.getTag（）; 
} 
 
 holder.tv1.setText（list.get（position）.getAS_name（））; 
 return convertView; 
} 
 
} 
 static class ViewHolder 
 {
 TextView tv1; 
} 
} 
  

运行此代码&最后在listview中的列表将显示！ ：）

!Database consists of multiple tables and multiple columns as shown & i have pasted this law.sqlite in assets folder.

Database consists of multiple tables and multiple columns as shown & i have pasted this law.sqlite in assets folder.

Suppose i want to access all the elements of column AS_name as shown . So how should i code for it?

解决方案

I tried and now the problem is solved :

For anyone facing similar type of problem can try my implementation :

Step 1:

Make a GetterSetter class (named GS here) & generate the Getter-Setters of variables used.

Like in my case:

public class GS {
     String AS_name;

public String getAS_name() {
return AS_name;
}

public void setAS_name(String aS_name) {
AS_name = aS_name;
}
}

Step 2:

Make a DBAdapter class which extends SQLiteOpenHelper & in that assign the your name of the file with extension .sqlite !

Rest you need only to copy my DBAdapter.java code & take care to implement the method getData() in which the data from database is fetched !

public class DBAdapter extends SQLiteOpenHelper
{
CustomAdapter adapter;
static String name = "law.sqlite"; //--Replace it with ur sqlite name 
static String path = "";
static ArrayList<GS> gs;
static SQLiteDatabase sdb;

@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
} 

private DBAdapter(Context v) 
{
    super(v, name, null, 1);
    path = "/data/data/" + v.getApplicationContext().getPackageName() + "/databases";
}

public boolean checkDatabase()
{
    SQLiteDatabase db = null;
    try 
    {
        db = SQLiteDatabase.openDatabase(path + "/" + name, null, SQLiteDatabase.OPEN_READONLY);
    } catch (Exception e) 
    {
        e.printStackTrace();
    }
    if (db == null) 
    {
        return false;
    } 
    else
    {
        db.close();
        return true;
    }
}

public static synchronized DBAdapter getDBAdapter(Context v)
{
    return (new DBAdapter(v));
}

public void createDatabase(Context v) 
{
    this.getReadableDatabase();
    try
    {
        InputStream myInput = v.getAssets().open(name);
        // Path to the just created empty db
    String outFileName = path +"/"+ 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();
    } catch (IOException e) 
    {
        System.out.println(e);
    }
}

public void openDatabase() 
{
    try 
    {
        sdb = SQLiteDatabase.openDatabase(path + "/" + name, null,
                SQLiteDatabase.OPEN_READWRITE);
    } catch (Exception e) 
    {
        System.out.println(e);
    }
}

public ArrayList<GS> getData() 
{
    try{
    Cursor c1 = sdb.rawQuery("SELECT DISTINCT * FROM Articles", null);
    gs = new ArrayList<GS>();
    while (c1.moveToNext())
    {
        GS q1 = new GS();

        q1.setAS_name(c1.getString(3)); //--- here 3 represents column no.
        Log.v("AS_name",q1.AS_name+""); 
        gs.add(q1);

    }
    }
    catch (Exception e) {
        e.printStackTrace();
    }
    return gs;
}
}

Step 3:

The class MainActivity.java :

public class MainActivity extends Activity {

ArrayList<GS> q = new ArrayList<GS>();
CustomAdapter adapter;
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
       // Get ListView object from xml
     lv = (ListView) findViewById(R.id.listView1);

    DBAdapter db = DBAdapter.getDBAdapter(getApplicationContext());
    if (!db.checkDatabase()) 
    {
        db.createDatabase(getApplicationContext());
    }
    db.openDatabase();

    q = db.getData();
    for(int i=0;i<q.size();i++)
    {
        Log.i("outside",""+q.get(i).getAS_name());
    }
    lv = (ListView) findViewById(R.id.listView1);
    lv.setAdapter(new CustomAdapter(MainActivity.this,q));
    //lv.setAdapter(adapter);

}

class CustomAdapter extends ArrayAdapter<GS>
  {
       ArrayList<GS> list;
       LayoutInflater mInfalter;    
       public CustomAdapter(Context context, ArrayList<GS> list)
       {
           super(context,R.layout.customlayout,list);
          this.list= list;  
          mInfalter = LayoutInflater.from(context);
          for(int i=0;i<list.size();i++)
         {
             Log.i("................",""+list.get(i).getAS_name());
         }

       }
//         public int getCount(){
//              return list.size();
//          }
       @Override
        public View getView(int position, View convertView, ViewGroup parent) {
          ViewHolder holder;
          Log.i("..........","Hello in getView");
          if(convertView==null)
          {
               convertView = mInfalter.inflate(R.layout.customlayout,parent,false);//--customlayout.xml must have a textView 
               holder = new ViewHolder();
               holder.tv1 = (TextView)convertView.findViewById(R.id.textView1); 
               convertView.setTag(holder); 
          }else{
                holder = (ViewHolder)convertView.getTag();
          } 

                holder.tv1.setText(list.get(position).getAS_name());
          return convertView;
    }

  }
 static class ViewHolder
    {
        TextView tv1;
    }  
}

Run this code & finally the list in the listview will be displayed ! :)

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