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效果图

SQLite的简单操作，没有用ListView,直接用的TextView显示，效果图

代码

• activity_layout.xml

• MianActivity.java

package henu.soft.saveindatabasedemo;import androidx.appcompat.app.AppCompatActivity;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.View;import android.widget.EditText;import android.widget.LinearLayout;import android.widget.TextView;import android.widget.Toast;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity implements View.OnClickListener {       private String name = "";    private String age = "";    private List
   
     users = new ArrayList<>();    private MyDBHelper myDBHelper;    @Override    protected void onCreate(Bundle savedInstanceState) {           super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // 创建数据库        myDBHelper = new MyDBHelper(MainActivity.this, "db", null, 2);        // 查询数据        findAll();        findViewById(R.id.btn_save).setOnClickListener(this);        findViewById(R.id.btn_clear).setOnClickListener(this);    }    @Override    public void onClick(View v) {           switch (v.getId()) {               case R.id.btn_save:                EditText et_name = (EditText) findViewById(R.id.et_name);                EditText et_age = (EditText) findViewById(R.id.et_age);                name = et_name.getText().toString();                age = et_age.getText().toString();                if ("".equals(name) && "".equals(age)) {                       Toast.makeText(this, "名字和年龄都为空，请重新填写！xs", Toast.LENGTH_SHORT).show();                } else {                       insert(name, age);                }                break;            case R.id.btn_clear:                clear();                break;        }    }    // 1. 增加一条数据    public void insert(String name, String age) {           SQLiteDatabase db = myDBHelper.getWritableDatabase();        ContentValues values = new ContentValues();        values.put("name", name);        values.put("age", age);        long result = db.insert("user_info", null, values);        Toast.makeText(MainActivity.this, "插入一条数据成功！xs", Toast.LENGTH_SHORT).show();        findAll();        db.close();    }    // 2. 查询所有数据    public void findAll() {           LinearLayout linearLayout = (LinearLayout) findViewById(R.id.ll_show);        linearLayout.removeAllViewsInLayout();        SQLiteDatabase db = myDBHelper.getWritableDatabase();        Cursor cursor = db.query("user_info", null, null, null, null, null, null);        while (cursor.moveToNext()) {               // 移动游标，获取所有记录//            String _id = cursor.getString(cursor.getColumnIndex("_id"));//            String name = cursor.getString(cursor.getColumnIndex("name"));//            String age = cursor.getString(cursor.getColumnIndex("age"));            String _id = cursor.getString(0);            String name = cursor.getString(1);            String age = cursor.getString(2);//            String _id = cursor.getColumnName(0);//            String name = cursor.getColumnName(1);//            String age = cursor.getColumnName(2);            // 放入list中            users.add(new User(_id, name, age));        }        for (User user : users) {               //1.集合中每有一条数据，就new一个TextView            TextView tv = new TextView(MainActivity.this);            //2.把人物的信息设置为文本的内容            tv.setText(user.toString());            tv.setTextSize(18);            //3.把TextView设置成线性布局的子节点            linearLayout.addView(tv);        }        db.close();    }    // 3. 删除表，清空数据    public void clear() {           SQLiteDatabase db = myDBHelper.getWritableDatabase();        db.delete("user_info", null, null);        //db.execSQL("drop table user_info");        db.close();        Toast.makeText(MainActivity.this, "表删除成功！", Toast.LENGTH_SHORT).show();        LinearLayout linearLayout = (LinearLayout) findViewById(R.id.ll_show);        linearLayout.removeAllViewsInLayout();    }}
   

• User.java

package henu.soft.saveindatabasedemo;public class User {       private String id;    private String name;    private String age;    public User(String id, String name, String age) {           this.id = id;        this.name = name;        this.age = age;    }    public String getId() {           return id;    }    public String getName() {           return name;    }    public String getAge() {           return age;    }    public void setId(String id) {           this.id = id;    }    public void setName(String name) {           this.name = name;    }    public void setAge(String age) {           this.age = age;    }    @Override    public String toString() {           return "User{" +                "id='" + id + '\'' +                ", name='" + name + '\'' +                ", age='" + age + '\'' +                '}';    }}

• MyDBHelper.java

package henu.soft.saveindatabasedemo;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import androidx.annotation.Nullable;public class MyDBHelper extends SQLiteOpenHelper {       // 构造器    public MyDBHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {           super(context, "db", null, 2);    }    // 启动创建数据库    @Override    public void onCreate(SQLiteDatabase db) {           db.execSQL("create table user_info (_id integer primary key autoincrement, name varchar(20),age varchar(20)) ");    }    // 更新数据库调用    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {       }    // 删除数据库}

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