我在这里没有收到任何错误，但我无法在屏幕上显示任何内容我有 2 个 XML 文件 main.xml 有一个带有 id @id/android:list 的列表视图，另一个 xml 有一个带有 3 个文本视图的相对布局我是试图显示数据库中的数据，但似乎什么也没有。我尝试了简单的列表布局，然后我能够显示数据库中一列的内容。但是当我为自定义布局尝试这个时，除了空白行之外什么都没有显示。
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);
}
}
我的数据库助手类
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 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>
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>