【发布时间】：2020-12-29 00:09:55
【问题描述】：
我是 Android 新手，我为我的学习目的创建了一个简单的应用程序，应用程序的想法是我显示学生信息，如 Parent Table 是 College Name（列表视图中的大学名称列表）-> Child Table是Student Names（显示该学院的学生姓名）
1.AnnaUniversity 2.MGRUniversity---->Parent Table
-------------- --------------
1.arun 1.Raja
2.visnu 2.Bharathi
3.vihal ---->Child Table
为此，我在名为“Details.db”的单个数据库中的 SQlite 中创建了两个表（学院名称和学生名称）
在First Activity我得到了大学名称的用户输入并存储在SQlite中并在Listview中显示
当 First Activity ListViewitem is Clciked 调用自定义对话框时，用户将存储在第二个表中的该学院的学生姓名输入到第二个表中，并在 Second Activityof Listview 和 CheckBox 中显示该名称
问题是学生姓名存储在第二个表中，它不会根据学院名称显示也没有显示在第二个活动的列表视图中例如：在 AnnaUniversity 父表中我添加了一些名称（子表）它存储到数据库中，但它不根据父名称显示
数据库助手
// Database Name
public static final String DATABASE_NAME = "details.db";
// Table 1
public static final String TABLE_NAME = "CollegeName";
public static final String COLUMN_ID = "ID";
public static final String COLUMN_TITLE = "college_NAME";
private static final String COLUMN_IMAGE = "image_bitmap";
// Table 2
private static final String TABLE2_NAME = "studentsName";
public static final String COLUMN1_ID = "ID";
public static final String COLUMN2_TITLE = "students_NAME";
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String query =
"CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY ,"
+ COLUMN_TITLE + " TEXT, "
+ COLUMN_IMAGE + " BLOB )";
sqLiteDatabase.execSQL(query);
String query1 =
"CREATE TABLE IF NOT EXISTS " + TABLE2_NAME + "("
+ COLUMN1_ID + " INTEGER PRIMARY KEY ,"
+ COLUMN2_TITLE + " TEXT )";
sqLiteDatabase.execSQL(query1);
}
/**
* All CRUD(Create, Read, Update, Delete) Operations
*/
// Creating a College Name ( College Name was Saved in College table )
void createlist(String title, byte[] image) {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COLUMN_TITLE, title);
cv.put(COLUMN_IMAGE, image);
Long result = sqLiteDatabase.insert(TABLE_NAME, null, cv);
if (result == -1) {
Toast.makeText(context, "Failed to create", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(context, "College Name Created Sucessfully", Toast.LENGTH_SHORT).show();
}
}
// Read ( Displaying the saved College Names)
Cursor readAllData() {
String query = "SELECT * FROM " + TABLE_NAME;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = null;
if (db != null) {
cursor = db.rawQuery(query, null);
}
return cursor;
}
// Creating a second table Students Name ( Students Name was Saved in student table )
void itemlist(String items) {
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(COLUMN2_TITLE, items);
Long result = sqLiteDatabase.insert(TABLE2_NAME, null, cv);
if (result == -1) {
Toast.makeText(context, "Failed to create", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(context, "Students name Added Sucessfully", Toast.LENGTH_SHORT).show();
}
}
// Read ( Displaying the saved students Names)
Cursor readlistAllData() {
String query = "SELECT * FROM " + TABLE2_NAME;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = null;
if (db != null) {
cursor = db.rawQuery(query, null);
}
return cursor;
}
添加学生：
public class AddStudents extends AppCompatActivity {
private LinearLayout linearLayout;
DatabaseHelper myDB;
ArrayList<String> listitems;
StudentsCustomAdapter sca;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_items);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab_button);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Custom Dialog is Called when Plus Button is Clicked to add Students Name inside the Selected College Name
ShowPopup();
}
});
myDB = new DatabaseHelper(AddStudents.this);
listitems = new ArrayList<>();
DisplayList();
sca = new StudentsCustomAdapter(AddStudents.this,listitems);
}
// Displaying the Students Name
private void DisplayList(){
Cursor cursor = myDB.readlistAllData();
if (cursor.getCount() == 0) {
Toast.makeText(this, "No Data.", Toast.LENGTH_SHORT).show();
} else {
while (cursor.moveToNext()) {
listitems.add(cursor.getString(1));
}
}
}
//adding a Students name in custom dialog
private void ShowPopup() {
final Dialog dialog = new Dialog(this);
dialog.setContentView(R.layout.custom_dialog);
dialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
dialog.show();
final EditText lname = dialog.findViewById(R.id.list_Edit_txt);
Button add = dialog.findViewById(R.id.add);
Button cancel = dialog.findViewById(R.id.cancel);
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
dialog.dismiss();
}
});
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String name = lname.getText().toString();
if (!TextUtils.isEmpty(lname.getText().toString())) {
DatabaseHelper db = new DatabaseHelper(getApplicationContext());
db.itemlist(name);
Toast.makeText(AddItems.this, "Students Added Sucessfully !", Toast.LENGTH_SHORT).show();
} else
Toast.makeText(AddItems.this, "The name cannot be empty!", Toast.LENGTH_LONG).show();
}
});
}
学生自定义适配器
public class StudentsCustomAdapter extends BaseAdapter {
private LayoutInflater mInflater;
private Context context;
private ArrayList<String> listitem_name;
public StudentsCustomAdapter(Context c, ArrayList<String> listnames)
{
this.context=c;
this.listitem_name=listnames;
this.mInflater= (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return listitem_name.size();
}
@Override
public Object getItem(int i) {
return null;
}
@Override
public long getItemId(int i) {
return 0;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
if (view == null) {
view = mInflater.inflate(R.layout.custom_list_items, viewGroup, false);
}
CheckBox checkBox = view.findViewById(R.id.cheeckbox);
TextView listitemnames = view.findViewById(R.id.listitem_name);
listitemnames.setText((CharSequence) listitem_name);
return null;
}
【问题讨论】：
标签： android android-listview android-sqlite