Android - 持久化方案
Android Studio文件夹：View -> Tool Windows -> Device Explorer
-
三种持久化方案
- 文件存储
- 文件写入模式
- MODE_APPEND：存在文件则追加内容
- MODE_PRIVATE：存在文件则覆盖内容
- 文件写入模式
- SharedPreferences
- 数据库
- 文件存储
-
实践
2.1 SharedPreferences存储、恢复数据
- 编写UI页面（包含存储、清空、恢复数据按钮）
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="50dp"
android:gravity="center"
android:layout_marginLeft="30dp"
android:layout_marginTop="17dp"
android:textSize="20dp"
android:text="用户名：" />
<EditText
android:id="@+id/username"
android:layout_marginLeft="130dp"
android:layout_marginTop="20dp"
android:gravity="center"
android:background="@color/purple_200"
android:textSize="20dp"
android:textColor="@color/black"
android:layout_width="200dp"
android:layout_height="40dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="30dp"
android:gravity="center"
android:layout_marginLeft="30dp"
android:layout_marginTop="80dp"
android:textSize="20dp"
android:text=" 密 码 ：" />
<EditText
android:id="@+id/password"
android:layout_marginLeft="130dp"
android:layout_marginTop="80dp"
android:gravity="center"
android:background="@color/cardview_shadow_start_color"
android:textSize="20dp"
android:textColor="@color/black"
android:layout_width="200dp"
android:layout_height="40dp" />
<Button
android:id="@+id/login"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="150dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="登录" />
<Button
android:id="@+id/remove"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="200dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清空" />
<Button
android:id="@+id/recover"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="250dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="恢复" />
RelativeLayout>
- 核心处理逻辑
public class SharedPreferencesStore extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
findViewById(R.id.login).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
String username = usernameTextView.getText().toString();
TextView passwordTextView = findViewById(R.id.password);
String password = passwordTextView.getText().toString();
SharedPreferences loginMsg = getSharedPreferences("loginMsg", MODE_PRIVATE);
SharedPreferences.Editor edit = loginMsg.edit();
edit.putString("username", username);
edit.putString("password", password);
edit.apply();
}
});
findViewById(R.id.remove).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
usernameTextView.setText(null);
TextView passwordTextView = findViewById(R.id.password);
passwordTextView.setText(null);
}
});
findViewById(R.id.recover).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences loginMsg = getSharedPreferences("loginMsg", MODE_PRIVATE);
String username = loginMsg.getString("username", "");
String password = loginMsg.getString("password", "");
TextView usernameTextView = findViewById(R.id.username);
usernameTextView.setText(username);
TextView passwordTextView = findViewById(R.id.password);
passwordTextView.setText(password);
}
});
}
}
- 数据存储地方：data/data/packageName/shared_prefs/fileName
2.2 Sqlite
- 实现SqliteOpenHelper继承类
public class UserSql extends SQLiteOpenHelper {
private Context context;
public UserSql(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
this.context = context;
}
// 创建DB
@Override
public void onCreate(SQLiteDatabase db) {
String sql = "create table user( " +
"id integer primary key autoincrement, " +
"username text, " +
"password text )";
db.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
- 编写CRUD
public class SqliteStore extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login_sqlite);
UserSql userSql = new UserSql(this, "user.db", null, 1);
// 增加
findViewById(R.id.login).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
TextView passwordTextView = findViewById(R.id.password);
String username = usernameTextView.getText().toString();
String password = passwordTextView.getText().toString();
SQLiteDatabase writableDatabase = userSql.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("username", username);
contentValues.put("password", password);
contentValues.put("id", new Random().nextInt(100));
writableDatabase.insert("user", null, contentValues);
Toast.makeText(SqliteStore.this, "登录成功！", Toast.LENGTH_SHORT).show();
}
});
// 删除
findViewById(R.id.delete).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
String username = usernameTextView.getText().toString();
SQLiteDatabase writableDatabase = userSql.getWritableDatabase();
writableDatabase.delete("user", "username = ?", new String[]{username});
}
});
// 修改
findViewById(R.id.update).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
String username = usernameTextView.getText().toString();
String updatePassword = "updateupdate";
SQLiteDatabase writableDatabase = userSql.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("password", updatePassword);
writableDatabase.update("user", contentValues, "username = ?", new String[]{username});
}
});
// 查询
findViewById(R.id.search).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SQLiteDatabase readableDatabase = userSql.getWritableDatabase();
Cursor cursor = readableDatabase.query("user", null, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
String id = cursor.getString(cursor.getColumnIndexOrThrow("id"));
String username = cursor.getString(cursor.getColumnIndexOrThrow("username"));
String password = cursor.getString(cursor.getColumnIndexOrThrow("password"));
Toast.makeText(SqliteStore.this, id + username + password, Toast.LENGTH_LONG).show();
} while (cursor.moveToNext());
}
}
});
// 这个不用理，清楚输入框的
findViewById(R.id.remove).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView usernameTextView = findViewById(R.id.username);
TextView passwordTextView = findViewById(R.id.password);
usernameTextView.setText(null);
passwordTextView.setText(null);
}
});
}
}
- UI界面
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="50dp"
android:gravity="center"
android:layout_marginLeft="30dp"
android:layout_marginTop="17dp"
android:textSize="20dp"
android:text="用户名：" />
<EditText
android:id="@+id/username"
android:layout_marginLeft="130dp"
android:layout_marginTop="20dp"
android:gravity="center"
android:background="@color/purple_200"
android:textSize="20dp"
android:textColor="@color/black"
android:layout_width="200dp"
android:layout_height="40dp" />
<TextView
android:layout_width="wrap_content"
android:layout_height="30dp"
android:gravity="center"
android:layout_marginLeft="30dp"
android:layout_marginTop="80dp"
android:textSize="20dp"
android:text=" 密 码 ：" />
<EditText
android:id="@+id/password"
android:layout_marginLeft="130dp"
android:layout_marginTop="80dp"
android:gravity="center"
android:background="@color/cardview_shadow_start_color"
android:textSize="20dp"
android:textColor="@color/black"
android:layout_width="200dp"
android:layout_height="40dp" />
<Button
android:id="@+id/login"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="150dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="登录" />
<Button
android:id="@+id/delete"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="200dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除" />
<Button
android:id="@+id/search"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="250dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查找" />
<Button
android:id="@+id/update"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="300dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="修改" />
<Button
android:id="@+id/remove"
android:gravity="center"
android:layout_marginLeft="180dp"
android:layout_marginTop="350dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="清空" />
RelativeLayout>
- LitePal操作Sqlite
- 下载第三方LitePal的jar包，链接：https://github.com/guolindev/LitePal/tree/master/downloads
- Android Studio导入，放到app/libs目录下，右键jar包 -> Add as library…
- AndroidManifest.xml添加name，android:name=“org.litepal.LitePalApplication”
- app/src/main目录下创建assets，再创建litepal.xml
<litepal>
// 操作的数据库名称
<dbname value="student">dbname>
// 迭代的版本号
<version value="1">version>
<list>
// 关联的实体类
<mapping class="com.example.myapplication.entity.Student">mapping>
list>
litepal>
- 创建实体类继承于DataSupport
public class Student extends DataSupport {
private Integer id;
private String username;
private String password;
public Student() {}
public Student(Integer id, String username, String password) {
this.id = id;
this.username = username;
this.password = password;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
- CRUD
public class LitepalStore extends AppCompatActivity {
// 创建数据库
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login_litepal);
findViewById(R.id.create_db).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
LitePal.getDatabase();
}
});
// 新增
findViewById(R.id.login).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int id = new Random().nextInt(100);
String username = ((TextView) findViewById(R.id.username)).getText().toString();
String password = ((TextView) findViewById(R.id.password)).getText().toString();
Student student = new Student(id, username, password);
student.save();
}
});
// 删除
findViewById(R.id.delete).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username = ((TextView) findViewById(R.id.username)).getText().toString();
Toast.makeText(LitepalStore.this, username, Toast.LENGTH_LONG).show();
DataSupport.deleteAll(Student.class, "username = ?", username);
}
});
// 修改
findViewById(R.id.update).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String username = ((TextView) findViewById(R.id.username)).getText().toString();
List<Student> studentList = LitePal.findAll(Student.class);
Integer id = null;
for (Student student : studentList) {
if (username.equals(student.getUsername())) {
id = student.getId();
}
}
Student student = new Student();
student.setUsername(username);
student.setPassword("updatePassword");
student.update(id);
}
});
// 查询
findViewById(R.id.search).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
List<Student> studentList = LitePal.findAll(Student.class);
for (Student student : studentList) {
Toast.makeText(LitepalStore.this, student.toString(), Toast.LENGTH_SHORT).show();
}
}
});
}
}
- UI代码