Android第十九期 - Sqlite离线存储教你写小米记事本
这期说sqlite离线存储，最近app要加上离线文件下载的功能，自己也是弄了一天，总算是小有成果，要好好感谢老婆的大力支持，帮我测试什么的，都任劳任怨，现在能这样对我这样的好的人只有老婆了。分享代码给大家，看着一些记事本都很实用，所以也就估摸着弄了一个，UI自己设计吧，功能实现了一切都好说。下面开始：
首先，sqlite可以去官网http://www.sqlite.org/lang.html，去查询所有进行的操作，创建表，增删改查等等。
然后就是建一个sqlite的类继承至SQLiteOpenHelper：
package com.liangxiao.usingsqlite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class Db extends SQLiteOpenHelper {
public Db(Context context, String name, CursorFactory factory, int version) {
super(context, "db", null, 1);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
// db.execSQL("CREATE TABLE USER(" + "name TEXT DEFAULT \"\","
// + "sex TEXT DEFAULT \"\")");
db.execSQL("CREATE TABLE USER("
+"_id INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "name TEXT DEFAULT \"\"," + "sex TEXT DEFAULT \"\")");
// db.execSQL("CREATE TABLE USER(" + "name TEXT DEFAULT \"\"");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
}
注意：这里面的adapter我用了官方自带的方便操作了，所以需求引用表的_id ,就加了一个字段。
然后是我给大家写了两种读取操作界面，一种是textview的读取，一种是listview的读取方式。
先说textview，大家可以发挥想象去构造UI，什么下拉悬停，ScrollView等等。
代码我都注释过PS：跳转窗体到MainActivity_dbRead：
package com.liangxiao.usingsqlite;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity_dbRead extends Activity {
private TextView xianshi;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_dbread);
xianshi = (TextView) findViewById(R.id.xianshi);
read_db();
}
/**
* 读取db部分
*/
private void read_db() {
Db db = new Db(this, "db", null, 1);
SQLiteDatabase dbRead = db.getReadableDatabase();
Cursor c = dbRead.query("user", null, null, null, null, null, null);
while (c.moveToNext()) {
String name = c.getString(c.getColumnIndex("name"));
String sex = c.getString(c.getColumnIndex("sex"));
db_lastindex_content += "心情：" + name + " " + "当事人：" + sex + "\n";
}
xianshi.setText(db_lastindex_content.toString());
}
private String db_lastindex_content = "";
}
注意：这个textview你可以在当前的页面显示你的操作，也可以跳转操作，都会直接显示在主UI上，没有卡顿的现象，很流畅的。
主窗体MainActivity：
package com.liangxiao.usingsqlite;
import android.app.Activity;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity implements OnClickListener {
private Button btn_fly;
private TextView xianshi1;
private EditText add_db_text;
private EditText add_db_text2;
private Db db;
private SQLiteDatabase dbRead, dbWrite;
private Cursor c;
// private String add_db_text_string;
// private String add_db_text_string2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
read_db();
}
/**
* 初始化部分
*/
private void init() {
xianshi1 = (TextView) findViewById(R.id.xianshi1);
btn_fly = (Button) findViewById(R.id.btn_fly);
add_db_text = (EditText) findViewById(R.id.add_db_text);
add_db_text2 = (EditText) findViewById(R.id.add_db_text2);
btn_fly.setOnClickListener(this);
}
/**
* 添加操作部分
*/
private void add_db() {
String add_db_text_string = add_db_text.getText().toString();
String add_db_text_string2 = add_db_text2.getText().toString();
Toast.makeText(this, add_db_text_string + "," + add_db_text_string2, 2)
.show();
db = new Db(this, "db", null, 1);
dbWrite = db.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put("name", add_db_text_string);
cv.put("sex", add_db_text_string2);
dbWrite.insert("user", null, cv);
dbWrite.close();
}
/**
* 读取db部分
*/
private void read_db() {
db = new Db(this, "db", null, 1);
dbRead = db.getReadableDatabase();
c = dbRead.query("user", null, null, null, null, null, null);
while (c.moveToNext()) {
String name = c.getString(c.getColumnIndex("name"));
String sex = c.getString(c.getColumnIndex("sex"));
System.out.println(String.format("name%s,sex%s", name, sex));
// xianshi1.setText("心情：" + name + " " + "当事人：" + sex + "\n");
db_dateBase += "心情：" + name + " " + "当事人：" + sex + "\n";
}
xianshi1.setText(db_dateBase.toString());
}
private String db_dateBase = "";
private void refresh() {
db = new Db(this, "db", null, 1);
dbRead = db.getReadableDatabase();
c = dbRead.query("user", null, null, null, null, null, null);
while (c.moveToNext()) {
String name = c.getString(c.getColumnIndex("name"));
String sex = c.getString(c.getColumnIndex("sex"));
System.out.println(String.format("name%s,sex%s", name, sex));
// xianshi1.setText("心情：" + name + " " + "当事人：" + sex + "\n");
db_dateBase = "心情：" + name + " " + "当事人：" + sex + "\n";
}
String xinshi_text_lastindex = xianshi1.getText().toString();
xianshi1.setText(xinshi_text_lastindex+db_dateBase.toString());
}
/**
* click部分
*/
@Override
public void onClick(View v) {
add_db();
refresh();
// Intent intent = new Intent();
// intent.setClass(MainActivity.this, MainActivity_dbRead.class);
// MainActivity.this.startActivity(intent);
// MainActivity.this.finish();
}
}
注意在onClick中，我注释的部分是跳转的操作，当前的是主窗体的UI显示操作。
两种效果如下：
然后是对于listview的操作，大家一般都是对于这个操作多些，首先是主窗体MainActivity_ListView_db：
package com.liangxiao.usingsqlite;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.content.ContentValues;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity_ListView_db extends ListActivity implements
OnClickListener {
private ListView list;
private EditText edit_name, edit_sex;
private TextView tvname, tvsex;
private Button btn;
private SimpleCursorAdapter adapter;
private Db db;
private SQLiteDatabase dbRead, dbWrite;
private Cursor c;
private long firstime = 0;
private RelativeLayout mainLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_listview);
init();
db_add_read();
refreshListView();
}
private void init() {
btn = (Button) findViewById(R.id.btn);
// list = (ListView) findViewById(R.id.list);
edit_name = (EditText) findViewById(R.id.edit_name);
edit_sex = (EditText) findViewById(R.id.edit_sex);
btn.setOnClickListener(this);
}
private void db_add_read() {
db = new Db(this, "db", null, 1);
dbRead = db.getReadableDatabase();
// c = dbRead.query("user", null, null, null, null, null, null);
dbWrite = db.getWritableDatabase();
adapter = new SimpleCursorAdapter(this,
R.layout.activity_main_listview_item, null, new String[] {
"name", "sex" }, new int[] { R.id.tvname, R.id.tvsex });
// list.setAdapter(adapter);
setListAdapter(adapter);
// 删除操作部分
getListView().setOnItemLongClickListener(new OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view,
final int position, long id) {
new AlertDialog.Builder(MainActivity_ListView_db.this)
.setTitle("你妹妹")
.setMessage("Are you sure?")
.setNegativeButton("No", null)
.setPositiveButton("delete",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface arg0,
int arg1) {
// TODO Auto-generated method stub
Cursor c = adapter.getCursor();
c.moveToPosition(position);
int itemId = c.getInt(c
.getColumnIndex("_id"));
dbWrite.delete("user", "_id=?",
new String[] { itemId + "" });
refreshListView();
}
}).show();
return true;
}
});
// 修改部分
getListView().setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Cursor c = adapter.getCursor();
c.moveToPosition(position);
int itemId = c.getInt(c.getColumnIndex("_id"));
Intent intent = new Intent();
intent.putExtra("itemId", itemId + "");
intent.setClass(MainActivity_ListView_db.this,
MainActivity_ListView_db_detail.class);
MainActivity_ListView_db.this.startActivity(intent);
MainActivity_ListView_db.this.finish();
}
});
}
private void refreshListView() {
c = dbRead.query("user", null, null, null, null, null, null);
adapter.changeCursor(c);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (v == btn) {
ContentValues cv = new ContentValues();
cv.put("name", edit_name.getText().toString());
cv.put("sex", edit_sex.getText().toString());
dbWrite.insert("user", null, cv);
refreshListView();
edit_name.getText().clear();
edit_sex.getText().clear();
}
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
// RelativeLayout.LayoutParams lp = (LayoutParams) mainLayout
// .getLayoutParams();
long secondtime = System.currentTimeMillis();
if (secondtime - firstime > 3000) {
Toast.makeText(MainActivity_ListView_db.this, "再按一次返回键退出",
Toast.LENGTH_SHORT).show();
firstime = System.currentTimeMillis();
return true;
} else {
MainActivity_ListView_db.this.finish();
System.exit(0);
android.os.Process.killProcess(android.os.Process.myPid());
}
}
return super.onKeyDown(keyCode, event);
}
}
然后是编辑MainActivity_ListView_db_detail：
package com.liangxiao.usingsqlite;
import android.app.Activity;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity_ListView_db_detail extends Activity {
private EditText name, sex;
private Button btn_update;
private SQLiteDatabase dbRead, dbWrite;
private String itemId;
private Cursor c;
private Db db;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_listview_detail);
init();
Intent intent = getIntent();
itemId = intent.getStringExtra("itemId");
c = dbRead.query("user", null, "_id=?", new String[] { itemId }, null,
null, null);
// String name1 = c.getString(c.getColumnName(1));
if (c.moveToFirst()) {
String name1 = c.getString(c.getColumnIndex("name"));
String sex1 = c.getString(c.getColumnIndex("sex"));
name.setText(name1);
sex.setText(sex1);
}
c.close();
}
private void init() {
db = new Db(this, "db", null, 1);
dbRead = db.getReadableDatabase();
dbWrite = db.getWritableDatabase();
name = (EditText) findViewById(R.id.name);
sex = (EditText) findViewById(R.id.sex);
btn_update = (Button) findViewById(R.id.btn_update);
btn_update.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
ContentValues cv = new ContentValues();
cv.put("name", name.getText().toString());
cv.put("sex", sex.getText().toString());
// dbWrite.insert("user", null, cv);
dbWrite.update("user", cv, "_id=?", new String[] { itemId });
Intent intent = new Intent(
MainActivity_ListView_db_detail.this,
MainActivity_ListView_db.class);
MainActivity_ListView_db_detail.this.startActivity(intent);
MainActivity_ListView_db_detail.this.finish();
}
});
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
Intent intent = new Intent(MainActivity_ListView_db_detail.this,
MainActivity_ListView_db.class);
MainActivity_ListView_db_detail.this.startActivity(intent);
MainActivity_ListView_db_detail.this.finish();
}
return super.onKeyDown(keyCode, event);
}
}
注意：编辑详情的有两个操作，一个是查询所在listview的id的一行记录，还有更新操作。而主窗体是读取和添加的操作。代码里面都写的比较详细，自己看吧，PS：这个里面有2个小操作，一个是listeview item点击，一个是长按，自己试试吧，效果如下图：
爱老婆，爱生活，爱IT...
