Java android studio 从Sqlite数据库中检索数据并将其显示到textview中
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原文地址: http://stackoverflow.com/questions/44876568/
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android studio retrieve data from Sqlite database and display it into textview
提问by Ra Isse
Hi guys please I need your help. I create SQLite Database in my app and I insert the data into it. And now I want to retrieve data from it but I want just insert one data and retrieve it then display it into a TextView.
嗨，伙计们，我需要你们的帮助。我在我的应用程序中创建了 SQLite 数据库并将数据插入其中。现在我想从中检索数据，但我只想插入一个数据并检索它，然后将其显示到 TextView 中。
please help me guys this is my first time I use SQLite Database.
请帮助我这是我第一次使用 SQLite 数据库。
public class Db_sqlit extends SQLiteOpenHelper{
String TABLE_NAME = "BallsTable";
public final static String name = "db_data";
public Db_sqlit(Context context) {
super(context, name, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table "+TABLE_NAME+" (id INTEGER PRIMARY KEY AUTOINCREMENT, ball TEXT)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
public boolean insertData(String balls){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("ball",balls);
long result = db.insert(TABLE_NAME,null,contentValues);
if(result == -1){
return false;
}
else
return true;
}
public void list_balls(TextView textView) {
Cursor res = this.getReadableDatabase().rawQuery("select ball from "+TABLE_NAME+"",null);
textView.setText("");
while (res.moveToNext()){
textView.append(res.getString(1));
}
}
}
采纳答案by HB.
Here is an example of how I achieved this.
这是我如何实现这一目标的示例。
In this example I will store, retrieve, updateand deletea students name and age.
在这个例子中，我将store、retrieve、update和delete一个学生的名字和年龄。
First create a class, I called mine
首先创建一个类，我叫我的
DBManager.java
数据库管理器
public class DBManager {
private Context context;
private SQLiteDatabase database;
private SQLiteHelper dbHelper;
public DBManager(Context c) {
this.context = c;
}
public DBManager open() throws SQLException {
this.dbHelper = new SQLiteHelper(this.context);
this.database = this.dbHelper.getWritableDatabase();
return this;
}
public void close() {
this.dbHelper.close();
}
public void insert(String name, String desc) {
ContentValues contentValue = new ContentValues();
contentValue.put(SQLiteHelper.NAME, name);
contentValue.put(SQLiteHelper.AGE, desc);
this.database.insert(SQLiteHelper.TABLE_NAME_STUDENT, null, contentValue);
}
public Cursor fetch() {
Cursor cursor = this.database.query(SQLiteHelper.TABLE_NAME_STUDENT, new String[]{SQLiteHelper._ID, SQLiteHelper.NAME, SQLiteHelper.AGE}, null, null, null, null, null);
if (cursor != null) {
cursor.moveToFirst();
}
return cursor;
}
public int update(long _id, String name, String desc) {
ContentValues contentValues = new ContentValues();
contentValues.put(SQLiteHelper.NAME, name);
contentValues.put(SQLiteHelper.AGE, desc);
return this.database.update(SQLiteHelper.TABLE_NAME_STUDENT, contentValues, "_id = " + _id, null);
}
public void delete(long _id) {
this.database.delete(SQLiteHelper.TABLE_NAME_STUDENT, "_id=" + _id, null);
}
}
Then create a SQLiteOpenHelperI called mine
然后创建一个SQLiteOpenHelper我称之为我的
SQLiteHelper.java
SQLiteHelper.java
public class SQLiteHelper extends SQLiteOpenHelper {
public static final String AGE = "age";
private static final String CREATE_TABLE_STUDENT = " create table STUDENTS ( _id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NOT NULL , age TEXT );";
private static final String DB_NAME = "STUDENTS.DB";
private static final int DB_VERSION = 1;
public static final String NAME = "name";
public static final String TABLE_NAME_STUDENT = "STUDENTS";
public static final String _ID = "_id";
public SQLiteHelper(Context context) {
super(context, DB_NAME, null, 1);
}
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_STUDENT);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS STUDENTS");
onCreate(db);
}
}
TO ADD:
加上：
In this example I take the text from EditTextand when the button is clicked I check if the EditTextis empty or not. If it is not empty and the student doesn't already exist I insert the students name and age into the database. I display a Toast, letting the user know of the status:
在这个例子中，我从中获取文本EditText，当单击按钮时，我检查它是否EditText为空。如果它不为空并且学生不存在，我会将学生的姓名和年龄插入数据库。我显示一个Toast，让用户知道状态：
btnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (edtName.getText().toString().trim().length() == 0) {
Toast.makeText(getApplicationContext(), "Please provide your students name", Toast.LENGTH_SHORT).show();
} else{
try {
if (edtAge.getText().toString().trim().length() != 0) {
String name = edtName.getText().toString().trim();
String age = edtAge.getText().toString().trim();
String query = "Select * From STUDENTS where name = '"+name+"'";
if(dbManager.fetch().getCount()>0){
Toast.makeText(getApplicationContext(), "Already Exist!", Toast.LENGTH_SHORT).show();
}else{
dbManager.insert(name, age);
Toast.makeText(getApplicationContext(), "Added successfully!", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(getApplicationContext(), "please provide student age!", Toast.LENGTH_SHORT).show();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
});
TO UPDATE:
Here I take the Text in EditTextand update the student when the button is clicked. You can also place the following in a try/catchto make sure it is updated successfully.
更新：
在这里，我将文本输入EditText并在单击按钮时更新学生。您还可以将以下内容放在 a 中try/catch以确保它已成功更新。
btnupdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String name = nameText.getText().toString();
String age = ageText.getText().toString();
dbManager.update(_id, name, age);
Toast.makeText(getApplicationContext(), "Updated successfully!", Toast.LENGTH_SHORT).show();
}
});
TO DELETE:
删除：
dbManager.delete(_id);
Toast.makeText(getApplicationContext(), "Deleted successfully!", Toast.LENGTH_SHORT).show();
TO GET:
要得到：
Here I get the name of the student and display it in a TextView
在这里，我获取学生的姓名并将其显示在 TextView
DBManager dbManager = new DBManager(getActivity());
dbManager.open();
Cursor cursor = dbManager.fetch();
cursor.moveToFirst();
final TextView studentName = (TextView) getActivity().findViewById(R.id.nameOfStudent);
studentName.settext(cursor.getString(0));
