Android 操作SQLite数据库初步-在程序中删除数据库

原文链接：https://my.oschina.net/qiuzhping/blog/611693

特别强调一下，Android是怎么删除数据库的，因为sqlite没有提供drop database XX的指令，所以我现在是按文件来删除数据库

刚刚学习Android关于数据库的操作，现在就将我学习的这点知识汇总一下，高手绕道哈。

关于数据库操作无非就是增删改查，下面就将这几个模块实现了。

JAVA code

package cn.qiuzhping.study;

import java.io.File;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteDatabase.CursorFactory;
import android.database.sqlite.sqliteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class sqliteStudy extends Activity {
	private Button btn_create = null;
	private Button btn_update = null;
	private Button btn_insert = null;
	private Button btn_query = null;
	private Button btn_delete = null;

	// private sqliteUtil sqliteUtil = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.sqlite_study);
		btn_create = (Button) findViewById(R.id.btn_create);
		btn_create.setonClickListener(new Btn_Create());

		btn_update = (Button) findViewById(R.id.btn_update);
		btn_update.setonClickListener(new Btn_Update());

		btn_insert = (Button) findViewById(R.id.btn_insert);
		btn_insert.setonClickListener(new Btn_Insert());

		btn_query = (Button) findViewById(R.id.btn_query);
		btn_query.setonClickListener(new Btn_Query());

		btn_delete = (Button) findViewById(R.id.btn_delete);
		btn_delete.setonClickListener(new Btn_Delete());
	}

	private class sqliteUtil extends sqliteOpenHelper {
		private static final int VERSION = 1;// 正数
		private String sql = "create table user(id int,name vachar(20))";

		public sqliteUtil(Context context, String name, CursorFactory factory,
				int version) {
			// 从左到右依次是context是Activity、name数据库表名、factory可选的数据库游标工厂类，
			// 当查询(query)被提交时，该对象会被调用来实例化一个游标。默认为null。version是数据版本号
			super(context, name, factory, version);
		}

		public sqliteUtil(Context context, String name, int version) {// 调用4个参数的构造方法
			this(context, name, null, VERSION);
		}

		public sqliteUtil(Context context, String name) {// 调用3个参数的构造方法
			this(context, name, VERSION);
		}

		@Override
		public void onCreate(sqliteDatabase arg0) {
			// 建立数据库
			Log.i("sqliteUtil onCreate", "建立数据库");
			arg0.execsql(sql);
		}

		@Override
		public void onUpgrade(sqliteDatabase arg0, int arg1, int arg2) {
			// Todo Auto-generated method stub
			Log.i("sqliteUtil onUpgrade", "更新数据库！！");
			// arg0.execsql(sql);
		}

	}

	public void deleteFile(File file) {
		if (file.exists()) { // 判断文件是否存在
			if (file.isFile()) { // 判断是否是文件
				// 设置属性:让文件可执行，可读，可写
				file.setExecutable(true, false);
				file.setReadable(true, false);
				file.setWritable(true, false);
				file.delete(); // delete()方法
			} else if (file.isDirectory()) { // 否则如果它是一个目录
				File files[] = file.listFiles(); // 声明目录下所有的文件 files[];
				for (int i = 0; i < files.length; i++) { // 遍历目录下所有的文件
					this.deleteFile(files[i]); // 把每个文件 用这个方法进行迭代
				}
			}
			file.setExecutable(true, false);
			file.setReadable(true, false);
			file.setWritable(true, false);
			file.delete();
			Log.i("deleteFile", file.getName() + "成功删除！！");
		} else {
			Log.i("deleteFile", file.getName() + "不存在！！！");
		}
	}

	class Btn_Delete implements OnClickListener {
		@Override
		public void onClick(View arg0) {
			sqliteUtil sqliteUtil = new sqliteUtil(sqliteStudy.this, "testDB1");
			sqliteDatabase db = sqliteUtil.getWritableDatabase();
			Log.i("Btn_Delete", "delete = " + db.delete("user", null, null));
			File file1 = new File("/data/data/cn.qiuzhping.study/databases/testDB1");
			deleteFile(file1);
			File file2 = new File("/data/data/cn.qiuzhping.study/databases/testDB1-journal");
			deleteFile(file2);
		}
	}

	class Btn_Create implements OnClickListener {
		@Override
		public void onClick(View arg0) {
			sqliteUtil sqliteUtil = new sqliteUtil(sqliteStudy.this, "testDB1");
			sqliteDatabase db = sqliteUtil.getReadableDatabase();

		}

	}

	class Btn_Update implements OnClickListener {

		@Override
		public void onClick(View arg0) {
			sqliteUtil sqliteUtil = new sqliteUtil(sqliteStudy.this, "testDB1");
			sqliteDatabase db = sqliteUtil.getWritableDatabase();
			ContentValues values = new ContentValues();
			values.put("name", "zhansan");
			Log.i("Btn_Update ",
					"update="
							+ db.update("user", values, "id=?",
									new String[] { "1" }));
		}

	}

	class Btn_Insert implements OnClickListener {
		@Override
		public void onClick(View arg0) {
			ContentValues values = new ContentValues();
			for (int i = 1; i <= 20;) {
				values.put("id", i);
				values.put("name", "qiuzhping" + i);
				sqliteUtil sqliteUtil = new sqliteUtil(sqliteStudy.this,
						"testDB1");
				sqliteDatabase db = sqliteUtil.getWritableDatabase();
				Log.i("Btn_Insert",
						"insert = " + db.insert("user", null, values));
				i++;
			}

		}
	}

	class Btn_Query implements OnClickListener {
		@Override
		public void onClick(View arg0) {
			ContentValues values = new ContentValues();
			values.put("name", "qiuzhping");
			sqliteUtil sqliteUtil = new sqliteUtil(sqliteStudy.this, "testDB1");
			sqliteDatabase db = sqliteUtil.getReadableDatabase();
			Cursor cursor = db.query("user", new String[] { "id", "name" },
					null, null, null, null, null);
			while (cursor.movetoNext()) {
				int id = cursor.getInt(0);// 获取ID
				String name = cursor.getString(1);// 获取name
				Log.i("Btn_Query", "id = " + id + "  name = " + name);
			}
		}
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.sqlite_study, menu);
		return true;
	}

}

xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".sqliteStudy" >

    <Button
        android:id="@+id/btn_create"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="创建数据库" />

    <Button
        android:id="@+id/btn_update"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn_create"
        android:text="更新" />

    <Button
        android:id="@+id/btn_insert"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn_update"
        android:text="插入" />

    <Button
        android:id="@+id/btn_query"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn_insert"
        android:text="查询" />
    <Button
        android:id="@+id/btn_delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn_query"
        android:text="删除数据库" />

</RelativeLayout>

转载于:https://my.oschina.net/qiuzhping/blog/611693