Android存储技术简介

SharePreferences

实现SharedPreferences存储的步骤如下：

一、根据Context获取SharedPreferences对象。

二、利用edit()方法获取Editor对象。

三、通过Editor对象存储key-value键值对数据。

四、通过commit()方法提交数据。

下面介个例子都是保存用户用户名，及登陆密码的例子。

SharedPreferences实例：

/* 保存数据 */
private void toSave() {
String name = mEditText1.getText().toString().trim();
String pswd = mEditText2.getText().toString().trim();
/* 获得活动的Preferences对象 */
SharedPreferences setting = getPreferences(Activity.MODE_PRIVATE);
/* 保存时要取得编辑对象 */
SharedPreferences.Editor editor = setting.edit();
/* 赋予键-值 */
editor.putString("name", name);
editor.putString("pswd", pswd);
/* 别忘记提交保存 */
editor.commit();
}

/* 页面显示 */
private void toShow() {
Map<String, String> map = getDate();
mEditText1.setText(map.get("name"));
mEditText2.setText(map.get("pswd"));
String text = "用户名：" + map.get("name") + "\n";
text += "密码：" + map.get("pswd") + "\n";
mTextView.setText(text);
}

/* 获取数据 */

private Map<String, String> getDate() {

Map<String, String> map = new HashMap<String, String>();

SharedPreferences setting = getPreferences(Activity.MODE_PRIVATE);

map.put("name", setting.getString("name", ""));

map.put("pswd", setting.getString("pswd", ""));

return map;

}

File存储

openFileOutput()方法的第一参数用于指定文件名称，不能包含路径分隔符“/” ，如果文件不存在，Android 会自动创建它。创建的文件保存在/data/data/<package name>/files目录，如： /data/data/cn.itcast.action/files/itcast.txt ，通过点击Eclipse菜单“Window”-“Show View”-“Other”，在对话窗口中展开android文件夹，选择下面的File Explorer视图，然后在File Explorer视图中展开/data/data/<package name>/files目录就可以看到该文件。

/* 保存数据 */
private void toSave() {
String name = mEditText1.getText().toString().trim();
String pswd = mEditText2.getText().toString().trim();
Properties properties = new Properties();
properties.put("name", name);
properties.put("pswd", pswd);
try {
/* 写入文件 */
FileOutputStream stream = this.openFileOutput("info.cfg",
Context.MODE_PRIVATE);
properties.store(stream, "");
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
/* 页面显示 */
private void toShow() {
Map<String, String> map = getDate();
mEditText1.setText(map.get("name"));
mEditText2.setText(map.get("pswd"));
String text = "用户名：" + map.get("name") + "\n";
text += "密码：" + map.get("pswd") + "\n";
mTextView.setText(text);
}
/* 获取数据 */
private Map<String, String> getDate() {
Map<String, String> map = new HashMap<String, String>();
String name = "";
String pswd = "";
Properties properties = new Properties();
try {
/* 打开文件 */
FileInputStream stream = this.openFileInput("info.cfg");
/* 读取文件内容 */
properties.load(stream);
name = properties.get("name").toString();
pswd = properties.get("pswd").toString();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
map.put("name", name);
map.put("pswd", pswd);
return map;
}

NetWork存储数据：包含对json的解析

public class NetworkActivity extends Activity implements OnClickListener {
private EditText mEditText1, mEditText2;
private Button returnhome, submit;
private TextView mTextView, explain;
private String mResult = "";
private JSONArray info = new JSONArray();
private Handler handler = null;
/* 定义需要获取的内容来源地址 */
private static final String SERVER_URL = "http://115.29.188.74:83/temp_dir/chongqtest.txt";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.share_preferences);
initControl();
// 创建属于主线程的handler
handler = new Handler();
// 启动线程执行下载任务
new Thread(downloadRun).start();
}
/* 初始化 */
private void initControl() {
returnhome = (Button) this.findViewById(R.id.returnhome);
returnhome.setOnClickListener(this);
mEditText1 = (EditText) this.findViewById(R.id.username);
mEditText1.setVisibility(View.GONE);
mEditText2 = (EditText) this.findViewById(R.id.password);
mEditText2.setVisibility(View.GONE);
mTextView = (TextView) this.findViewById(R.id.toshow);
mTextView.setVisibility(View.GONE);
explain = (TextView) this.findViewById(R.id.explain);
submit = (Button) this.findViewById(R.id.submit);
submit.setOnClickListener(this);
submit.setVisibility(View.GONE);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.returnhome:
super.finish();
break;
case R.id.submit:
break;
}
}
Runnable downloadRun = new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
/* 根据内容来源地址创建一个HTTP请求 */
HttpPost request = new HttpPost(SERVER_URL);
/* 添加一个变量 */
List<NameValuePair> params = new ArrayList<NameValuePair>();
/* 设置一个地区名称，添加必须的参数 */
params.add(new BasicNameValuePair("PlaceName", "NewYork"));
try {
// 设置参数的编码
request.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
// 发送请求并获取反馈
HttpResponse httpResponse = new DefaultHttpClient()
.execute(request);
// 解析返回的内容
if (httpResponse.getStatusLine().getStatusCode() != 404) {
String result = EntityUtils.toString(httpResponse
.getEntity());
JSONObject jsonObja = new JSONObject(result)
.getJSONObject("response");
JSONArray jsonObjb = jsonObja.getJSONArray("list");
for (int k = 0; k < jsonObjb.length(); k++) {
JSONObject jsonObj = (JSONObject) jsonObjb.opt(k);
JSONArray jsonArr = jsonObj.getJSONArray("items");
for (int i = 0; i < jsonArr.length(); i++) {
JSONObject jsonO = ((JSONObject) jsonArr.opt(i));
mResult += "ID：" + jsonO.getString("id").toString()
+ "\n";
mResult += "name：" + jsonO.getString("name") + "\n";
mResult += "title：" + jsonO.getString("title")
+ "\n";
mResult += "short_content："
+ jsonO.getString("short_content") + "\n";
handler.post(runnableUi);
// Thread.sleep(1000);   模拟了界面一点点的更新
}
}
Log.d("TAG", result);
Log.d("TAG", info.toString());
}
} catch (Exception e) {
e.printStackTrace();
}
}
};
// 构建Runnable对象，在runnable中更新界面
Runnable runnableUi = new Runnable() {
@Override
public void run() {
// 更新界面
explain.setText("the Content is:" + mResult);
}
};
}

Sqlite实例

cur.getCount() 得到的是查询到的记录的条数，指行数

cur.getColumnCount() 得到的是列数，指的是表机构的列数，与记录无关。

/* 查询数据 */

private List<HashMap<String, Object>> getData(String where) {
HashMap<String, Object> hashMap;
Cursor cur = mSQLiteDataBase.rawQuery(where, null);
if (cur != null) {
if (cur.moveToFirst()) {
do {
int id = cur.getInt(cur.getColumnIndex("_id"));
String name = cur.getString(cur.getColumnIndex("name"));
String pswd = cur.getString(cur.getColumnIndex("pswd"));
hashMap = new HashMap<String, Object>();
hashMap.put("recordid", String.valueOf(id));
hashMap.put("name", name);
hashMap.put("pswd", pswd);
mList.add(hashMap);
} while (cur.moveToNext());
}
}
return mList;
}

/* 打开数据库，创建表 */

private void openDataBase() {
mSQLiteDataBase = this.openOrCreateDatabase("examples.db",
MODE_PRIVATE, null);
String CREATE_TABLE = "create table if not exists table1 (_id INTEGER PRIMARY KEY,name TEXT,pswd TEXT);";
mSQLiteDataBase.execSQL(CREATE_TABLE);
}

/* 添加一条数据 */

private void addData() {
String name = mEditText1.getText().toString().trim();
String pswd = mEditText2.getText().toString().trim();
/* 添加方式一 */
ContentValues cv = new ContentValues();
cv.put("name", name);
cv.put("pswd", pswd);
mSQLiteDataBase.insert("table1", null, cv);
/* 添加方式二 */
String INSERT_DATA = "INSERT INTO table1 (name,pswd) values ('" + name
+ "2','" + pswd + "2')";
mSQLiteDataBase.execSQL(INSERT_DATA);
/* 动态更新页面显示 */
// mList = getData("SELECT * FROM table1 where name='" + name
// + "' or name ='" + name + "2'");

/* 第二种方式 */
mList.clear();
mList = getData("SELECT * FROM table1");
adapter.notifyDataSetChanged();
}

/* 删除一条数据 */

private void delData(int recordid) {

String DELETE_DATA = "DELETE FROM table1 WHERE _id=" + recordid + ";";

mSQLiteDataBase.execSQL(DELETE_DATA);

}

/* 动态删除页面记录 */

mList.remove(position);

adapter.notifyDataSetChanged();