自定义列表视图和自定义ArrayAdapter

Question

我没有在这里得到任何错误，但我没有在屏幕上显示任何东西 我有2个XML文件main.xml有一个列表视图与id @ id/android：list和另一个xml有一个有3个文本视图的相对布局我试图显示数据库中的数据，但似乎没有出现。我尝试了简单的列表布局，然后我能够显示数据库中某列的内容。但是，当我尝试这个自定义布局没有显示除空行。

这是启动应用程序时启动的主要活动。

public class Db extends ListActivity { 
private SQLiteDatabase newDb; 
DataBaseHelper myDbHelper = new DataBaseHelper(this); 
public ListAdapter adapter; 
private ArrayList<String> results = new ArrayList<String>(); 


public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

setContentView(R.layout.main); 
    openDatabase(); 
    newDb = myDbHelper.getReadableDatabase(); 
    Cursor c = newDb.rawQuery("SELECT _id, organisation, address, postcode FROM shoplist", null); 
    int i_organisation = c.getColumnIndex("organisation"); 
    int i_id = c.getColumnIndex("_id"); 
    int i_address = c.getColumnIndex("address"); 
    int i_postcode = c.getColumnIndex("postcode"); 

    //int count = c.getCount(); 
    //String data[] = new String[count]; 
    //int i= 0; 
    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) 
    { 
     String i1 = c.getString(c.getColumnIndex("_id")); 
     String i2 = c.getString(c.getColumnIndex("organisation")); 
     String i3 = c.getString(c.getColumnIndex("address")); 
     results.add(i1); 

     //i++; 
    } 
    customAdapter adapter = new customAdapter(getApplicationContext(), 
      R.layout.main, results, results, results); 
    setListAdapter(adapter); 





} 

private long inserttodata() { 
    // TODO Auto-generated method stub 
    ContentValues cv = new ContentValues(); 
    cv.put("id", "112"); 
    cv.put("organisation","test"); 
    return newDb.insert("shoplist", null, cv); 
} 

private void openDatabase() { 

    try { 

     myDbHelper.createDataBase(); 

    } catch (IOException ioe) { 

     throw new Error("Unable to create database"); 

    } 

    try { 

     myDbHelper.openDataBase(); 


    } catch (SQLException sqle) { 
System.out.println("failed to open"); 
     throw sqle; 

    } 
    //String[] columns= new String[]{"_id", "Organisation"}; 
    //cursor = newDb.query("Shop", columns, null, null, null, null, null); 

} 

} 

我的数据库辅助类

public class DataBaseHelper extends SQLiteOpenHelper{ 

//The Android's default system path of your application database. 
private static String DB_PATH = "/data/data/calc.three/databases/"; 

private static String DB_NAME = "charity.db"; 

private SQLiteDatabase myDataBase; 

private final Context myContext; 


public DataBaseHelper(Context context) { 

    super(context, DB_NAME, null, 1); 
    this.myContext = context; 
} 


public void createDataBase() throws IOException{ 

    boolean dbExist = checkDataBase(); 

    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(){ 

    SQLiteDatabase checkDB = null; 

    try{ 
     String myPath = DB_PATH + DB_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{ 

    //Open your local db as the input stream 
    InputStream myInput = myContext.getAssets().open(DB_NAME); 

    // Path to the just created empty db 
    String outFileName = DB_PATH + DB_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[2048]; 
    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{ 

    //Open the database 
    String myPath = DB_PATH + DB_NAME; 
    SQLiteDatabase.CursorFactory c = null; 
    myDataBase = SQLiteDatabase.openDatabase(myPath, c , SQLiteDatabase.OPEN_READWRITE); 

} 

@Override 
public synchronized void close() { 

     if(myDataBase != null) 
      myDataBase.close(); 

     super.close(); 

} 

@Override 
public void onCreate(SQLiteDatabase db) { 

} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

}} 

我的自定义适配器类

public class customAdapter extends ArrayAdapter<String> { 
static List<String> serialNo = new ArrayList<String>(); 
static List<String> name = new ArrayList<String>(); 
static List<String> address = new ArrayList<String>(); 

Context myContext; 

public customAdapter(Context context, int resource, List<String> c_serialNo, 
    List<String> c_name, List<String> c_address) { 

super(context, resource, c_serialNo); 

myContext = context; 
serialNo = c_serialNo; 
name = c_name; 
address = c_address; 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
View v = convertView; 
if (v == null) { 
    LayoutInflater vi = (LayoutInflater) myContext 
      .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    v = vi.inflate(R.layout.main, null); 
} 

TextView tv_serialNo = (TextView) v.findViewById(R.id.serialNo); 
TextView tv_name = (TextView) v.findViewById(R.id.name); 
TextView tv_address = (TextView) v.findViewById(R.id.address); 

if (tv_serialNo != null) { 
    tv_serialNo.setText(serialNo.get(position)); 
} 
if (tv_name != null) { 
    tv_name.setText(name.get(position)); 
} 
if (tv_address!= null) { 
    tv_address.setText(address.get(position)); 
} 

return v; }} 

main.xml中的文件

<?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"> 

    <ListView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@id/android:list"></ListView> 


</LinearLayout> 

的custom_list.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"> 



     <RelativeLayout android:layout_width="fill_parent" android:layout_height="80dp" > 
      <TextView android:id="@+id/serialNo" 
       android:layout_height="38dp" 
       android:layout_width="40dp" 
       android:padding="1dip" 
       android:gravity="top"      
       android:text="sn" 
            /> 
      <TextView android:id="@+id/name" 
       android:layout_height="38dp" 
       android:layout_width="240dp" 
       android:padding="1dip" 
       android:gravity="top"      
       android:text="name" 
       android:layout_toRightOf="@id/serialNo" 
            /> 

      <ImageButton 
       android:id="@+id/fav" 
       android:layout_width="38dp" 
       android:layout_height="38dp" 
       android:layout_alignParentTop="true" 
       android:layout_toRightOf="@+id/name" 
       android:src="@drawable/ic_launcher" /> 
      <TextView android:id="@+id/address" 
       android:layout_height="40dp" 
       android:layout_width="300dp" 
       android:padding="1dip" 

       android:text="name" 
       android:layout_below="@id/serialNo" 
            /> 

      <ImageView 
       android:id="@+id/source" 
       android:layout_width="40dp" 
       android:layout_height="40dp" 
       android:layout_alignBottom="@+id/address" 
       android:layout_toRightOf="@+id/address" 
       android:src="@drawable/pg" /> 

     </RelativeLayout> 


</LinearLayout> 

Answer 1

解决：我膨胀了错误的XML文件。充气custom_list.xml并开始显示。

Answer 2

我看到的几件事... R.layout main是你的主要布局，你试图将它设置为适配器的行布局。这两个应该是不同的。

其次，除非你有某种原因，这不是很明显，你做了很多额外的工作，创建阵列......

第三，它看起来像你正试图列出不是从你的光标拉东西或者你显示的任何其他数组（serialNo）。

这将是更简单的使用SimpleCursorAdapter像这样：

openDatabase(); 
newDb = myDbHelper.getReadableDatabase();  
Cursor c = newDb.rawQuery("SELECT _id, organisation, address, postcode FROM shoplist", null); 

// let the system manage your cursor 
getActivity().startManagingCursor(c);  

// tell the adapter what columns to pull data from 
String[] from = new String[] { "_id", "organisation", "address" };  

// tell the adapter what resource ids in your row layout to map the data to  
int[] to = new int[] { R.id.serialNo, R.id.name, R.id.address };  

// create the adapter, specifying the context, the xml file to use for the row layout, the cursor to pull the data from, and the map of where to put the data in the form of from and to arrays 
SimpleCursorAdapter mAdapter = new SimpleCursorAdapter(this, R.layout.your_row_xml, c, from, to); 

// set the adapter to your list 
setListAdapter(mAdapter);