Android数据库 — — —查询数据

package com.example.datebasetest;

import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button btn;    private DatabaseHelper dbHelper;    private Button addButton;    private Button updateData;    private Button deleteData;    private Button queryData;

    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);

        btn = (Button)findViewById(R.id.create_database);        dbHelper = new DatabaseHelper(this,"BookStore.db",null,2);        addButton = (Button)findViewById(R.id.add_data);        updateData = (Button)findViewById(R.id.update_data);        deleteData = (Button)findViewById(R.id.delete_data);        queryData = (Button)findViewById(R.id.query_data);

        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                dbHelper.getWritableDatabase();            }        });

        addButton.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase db = dbHelper.getWritableDatabase();                ContentValues values = new ContentValues();                values.put("name","wz");                values.put("author","xx");                values.put("price",1.0);                values.put("pages",156);                db.insert("Book",null,values);                values.clear();                values.put("name","wz2");                values.put("author","xx2");                values.put("price",2.0);                values.put("pages",122);                db.insert("Book",null,values);

            }        });

        updateData.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase db = dbHelper.getWritableDatabase();                ContentValues values = new ContentValues();                values.put("price",10.99);                db.update("Book", values, "name=?", new String[]{"wz"});            }        });

        deleteData.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase db = dbHelper.getWritableDatabase();                db.delete("Book", "pages > ?", new String[]{"120"});                Toast.makeText(MainActivity.this,"删除成功",Toast.LENGTH_SHORT).show();            }        });

        queryData.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                SQLiteDatabase db = dbHelper.getWritableDatabase();                Cursor cursor = db.query("Book",null,null,null,null,null,null);                if(cursor.moveToFirst()){                    do{                        String name = cursor.getString(cursor.getColumnIndex("name"));                        String author = cursor.getString(cursor.getColumnIndex("author"));                        int pages = cursor.getInt(cursor.getColumnIndex("pages"));                        double price = cursor.getDouble(cursor.getColumnIndex("price"));                        Log.d("Message","name"+name);                        Log.d("Message","author"+author);                        Log.d("Message","pages"+pages);                        Log.d("Message","price"+price);                    }while(cursor.moveToNext());                }                cursor.close();

            }        });    }}