AndroidStudio——数据存储（一）

**Android数据存储**

数据存储：

1 . SharedPreferences（以键值对的方式保存的到.xml文件中 路径在手机Data-Data目录下 通过key来获取数据） 一般用于简单的收藏 写在这的坏处：不能同步 用于：记住密码 自动登录 创建SharedPreferences： SharedPreferences sp=getSharedPreferences(“myopt”,Context.MODE_PRIVATE); myopt文件名

2 . 读写SD卡

3 . SQLite（轻量级的数据库 文件名为.db ）

4 . ContentProvider(内容提供者 内容来自于SQLite 是一个标准的接口)

存储实例：

SharedPreferencesActivity代码：

public class SharedPreferencesActivity extends AppCompatActivity { private EditText user, pwd; private Button login; private CheckBox cb1, cb2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_shared_preferences); user = (EditText) findViewById(R.id.user); pwd = (EditText) findViewById(R.id.pwd); login = (Button) findViewById(R.id.login); cb1 = (CheckBox) findViewById(R.id.cb1); cb2 = (CheckBox) findViewById(R.id.cb2); final SharedPreferences sp = getSharedPreferences("userInfo", MODE_PRIVATE); login.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { SharedPreferences.Editor editor = sp.edit(); editor.putString("userName", user.getText().toString()); //字符串转成Int editor.putInt("userPwd", Integer.parseInt(pwd.getText().toString())); editor.putBoolean("cb1", cb1.isChecked()); editor.putBoolean("cb2", cb2.isChecked()); editor.commit(); Intent intent = new Intent(SharedPreferencesActivity.this, SettingActivity.class); startActivity(intent); } }); } @Override protected void onStart() { super.onStart(); SharedPreferences sp1 = getSharedPreferences("switch", MODE_PRIVATE); boolean switch1 = sp1.getBoolean("switch1", false); boolean switch2 = sp1.getBoolean("switch2", false); cb1.setChecked(switch1); cb2.setChecked(switch2); } }

activity_shared_preferences布局：

<?xml version="1.0" encoding="utf-8"?> <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" tools:context=".SharedPreferencesActivity"> <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/user" android:hint="请输入用户名："/> <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/user" android:id="@+id/pwd" android:hint="请输入密码："/> <CheckBox android:layout_width="match_parent" android:layout_height="wrap_content" android:text="记住密码" android:id="@+id/cb1" android:checked="false" android:layout_below="@+id/pwd" android:layout_alignParentStart="true" android:layout_marginStart="46dp" /> <CheckBox android:layout_width="match_parent" android:layout_height="wrap_content" android:text="自动登录" android:id="@+id/cb2" android:layout_marginStart="237dp" android:layout_below="@+id/pwd" android:layout_alignParentStart="true" /> <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/login" android:text="登录" android:layout_below="@+id/cb1" android:layout_alignParentStart="true" /> </RelativeLayout>

SettingActivity 代码：

public class SettingActivity extends AppCompatActivity { private Switch switch1, switch2; private Button save; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_setting); switch1 = (Switch) findViewById(R.id.switch1); switch2 = (Switch) findViewById(R.id.switch2); save = (Button) findViewById(R.id.save); save.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { SharedPreferences sp1 = getSharedPreferences("switch", MODE_PRIVATE); SharedPreferences.Editor editor = sp1.edit(); editor.putBoolean("switch1", switch1.isChecked()); editor.putBoolean("switch2", switch2.isChecked()); editor.commit(); Intent intent = new Intent(SettingActivity.this, SharedPreferencesActivity.class); startActivity(intent); } }); } @Override protected void onStart() { super.onStart(); SharedPreferences sp = getSharedPreferences("userInfo", MODE_PRIVATE); final boolean cb1 = sp.getBoolean("cb1", false); final boolean cb2 = sp.getBoolean("cb2", false); switch1.setChecked(cb1); switch2.setChecked(cb2); } }

activity_setting布局：

<?xml version="1.0" encoding="utf-8"?> <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" tools:context="com.example.dell.jreduch08.SettingsActivity"> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content"></LinearLayout> <Switch android:layout_width="match_parent" android:layout_height="wrap_content" android:text="记住密码" android:id="@+id/switch1" android:layout_alignParentTop="true" android:layout_alignParentEnd="true" android:checked="false" /> <Switch android:layout_width="match_parent" android:layout_height="wrap_content" android:text="自动登录" android:id="@+id/switch2" android:checked="false" android:layout_below="@+id/switch1" android:layout_alignParentStart="true" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="保存" android:id="@+id/save" android:layout_below="@+id/switch2" android:layout_centerHorizontal="true" /> </RelativeLayout>

实现效果：

改变选择后能与登录界面的选择框保持同步：