第一行代码Android学习（七）

第一行代码Android学习：第七部分主要涉及到文件存储、SharedPreferences存储、SQLite数据库存储

文件存储：DYHDM_06_00FilePersistenceTest

1.activity_main.xml <LinearLayout 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=".MainActivity" > <EditText android:id="@+id/et" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="Type something here" /> </LinearLayout> 2.MainActivity.java package com.example.dyhdm_06_00filepersistencetest; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStreamReader; import java.io.OutputStreamWriter; import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.text.TextUtils; import android.widget.EditText; import android.widget.Toast; public class MainActivity extends Activity { private EditText et; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); et = (EditText) findViewById(R.id.et); String inputText = load(); // 一次可以判断两种空值null或"" if (!TextUtils.isEmpty(inputText)) { et.setText(inputText); // 光标移动到文本的末尾 et.setSelection(inputText.length()); Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT) .show(); } } /** * 在页面关闭的时候保存输入的数据 重载方法 */ @Override protected void onDestroy() { super.onDestroy(); String inputText = et.getText().toString(); save(inputText); } /** * TODO 保存数据到文件 * * @throw * @return void * @param inputText */ private void save(String inputText) { FileOutputStream out = null; BufferedWriter writer = null; try { out = openFileOutput("data", Context.MODE_PRIVATE); writer = new BufferedWriter(new OutputStreamWriter(out)); writer.write(inputText); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { try { if (writer != null) { writer.close(); } } catch (IOException e) { e.printStackTrace(); } } } /** * TODO 从文件中读取数据 * * @throw * @return String */ private String load() { FileInputStream in = null; BufferedReader reader = null; StringBuilder content = new StringBuilder(); try { in = openFileInput("data"); reader = new BufferedReader(new InputStreamReader(in)); String line = ""; while ((line = reader.readLine()) != null) { content.append(line); } } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (Exception e) { e.printStackTrace(); } } } return content.toString(); } }

SharedPreferences存储：DYHDM_06_01SharedPreferencesTest

1.activity_main.xml <LinearLayout 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:orientation="vertical" tools:context=".MainActivity" > <Button android:id="@+id/save_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Save data" /> <Button android:id="@+id/get_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Get data" /> </LinearLayout> 2.MainActivity.java package com.example.dyhdm_sharedpreferencestest; import android.app.Activity; import android.content.SharedPreferences; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast; /** * TODO SharedPreferences存储和获取数据 * * @author 张志安 * @date: 2016-8-16 下午12:52:13 */ public class MainActivity extends Activity { private Button saveData; private Button getData; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); saveData = (Button) findViewById(R.id.save_data); saveData.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { /** * 存储 Android中提供了三种方法得到SharedPreferences对象 * 1.Context类中的getSharedPreferences() 两个参数：名称和操作模式 * 2.Activity类中的getPreferences() 一个参数：操作模式 默认使用类名做文件名 * 3.PreferenceManager类中的getDefaultSharedPreferences() 静态方法 * 接受一个Context参数，使用包名为前缀命名 * * 获得SharedPreferences对象后，存储数据分为三步： * 1.调用SharedPreferences对象的edit( * )方法获取一个SharedPreferences.Editor对象 * 2.向SharedPreferences.Editor对象中添加数据，putString() 3.commit()提交 * */ SharedPreferences.Editor editor = getSharedPreferences("data", MODE_PRIVATE).edit(); editor.putString("name", "zza"); editor.putInt("age", 21); editor.commit(); } }); getData = (Button) findViewById(R.id.get_data); getData.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 获取数据 SharedPreferences sp = getSharedPreferences("data", MODE_PRIVATE); String name = sp.getString("name", ""); int age = sp.getInt("age", 0); Toast.makeText(MainActivity.this, name + "==" + age, Toast.LENGTH_SHORT).show(); } }); } }

SQLite数据库存储：DYHDM_06_02MyDatabaseHelper

1.activity_main.xml <LinearLayout 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:orientation="vertical" tools:context=".MainActivity" > <Button android:id="@+id/bt_create" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="创建数据库" /> <Button android:id="@+id/bt_add" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="添加数据" /> <Button android:id="@+id/bt_update" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="更改数据" /> <Button android:id="@+id/bt_delete" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="删除数据" /> <Button android:id="@+id/bt_query" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="查询数据" /> <Button android:id="@+id/bt_replace" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="置换数据" /> </LinearLayout> 2.MyDatabaseHelper.java /* * @Title: MyDatabaseHelper.java * @Description: TODO * @author: 张志安 * @date: 2016-8-16 下午1:20:05 * */ package com.example.dyhdm_06_02mydatabasehelper; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; import android.widget.Toast; /** * TODO 用于数据库的创建 * * @author 张志安 * @date: 2016-8-16 下午1:20:05 */ public class MyDatabaseHelper extends SQLiteOpenHelper { private Context mContext; public static final String CREATE_BOOK = "create table Book (" + "id integer primary key autoincrement," + "author text," + "price real," + "pages integer," + "name text)"; public static final String CREATE_BOOK2 = "create table Book2 (" + "id integer primary key autoincrement," + "author text," + "price real," + "name text)"; /** * <默认构造函数> */ public MyDatabaseHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); mContext = context; } /** * 重载方法 */ @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_BOOK); db.execSQL(CREATE_BOOK2); Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show(); } /** * 重载方法 */ @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // db.execSQL("drop table if exists Book"); // db.execSQL("drop table if exists Book2"); // onCreate(db); switch (oldVersion) { case 1: db.execSQL(CREATE_BOOK2); break; default: break; } } } 3.MainActivity.java package com.example.dyhdm_06_02mydatabasehelper; import java.util.Currency; import android.app.Activity; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.Toast; public class MainActivity extends Activity { private MyDatabaseHelper dbHelper; private Button bt_create; private Button bt_add; private Button bt_update; private Button bt_delete; private Button bt_query; private Button bt_replace; private SQLiteDatabase db; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2); bt_create = (Button) findViewById(R.id.bt_create); bt_create.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 创建数据库 dbHelper.getWritableDatabase(); } }); bt_add = (Button) findViewById(R.id.bt_add); bt_add.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 添加数据 db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); // 第一条数据 values.put("name", "zza"); values.put("author", "zzzzz"); values.put("pages", 444); values.put("price", 15.5); db.insert("Book", null, values); // 第二条数据 values.clear(); values.put("name", "zzza"); values.put("author", "zzz"); values.put("pages", 4444); values.put("price", 15.54); db.insert("Book", null, values); } }); bt_update = (Button) findViewById(R.id.bt_update); bt_update.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 更新数据 db = dbHelper.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("pages", "555"); db.update("Book", values, "name = ?", new String[] { "zza" }); } }); bt_delete = (Button) findViewById(R.id.bt_delete); bt_delete.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 删除数据 db = dbHelper.getWritableDatabase(); db.delete("Book", "pages > ?", new String[] { "500" }); } }); bt_query = (Button) findViewById(R.id.bt_query); bt_query.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { db = dbHelper.getWritableDatabase(); // 查询book表中所有数据 Cursor cursor = db.query("Book", null, null, null, null, null, null); if (cursor.moveToFirst()) { do { // 遍历Cursor对象，取出数据 Log.e("zza", cursor.getString(cursor.getColumnIndex("name")) + "===" + cursor.getString(cursor .getColumnIndex("author")) + "===" + cursor.getInt(cursor .getColumnIndex("pages")) + "===" + cursor.getDouble(cursor .getColumnIndex("price"))); } while (cursor.moveToNext()); } cursor.close(); } }); bt_replace = (Button) findViewById(R.id.bt_replace); bt_replace.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { db = dbHelper.getWritableDatabase(); // 事务可以保证某一系列操作要么都完成，要么都不完成 // 开始事务 db.beginTransaction(); try { // 添加操作 // 。。。 // 事务已经执行成功 db.setTransactionSuccessful(); } catch (Exception e) { e.printStackTrace(); } finally { // 结束事务 db.endTransaction(); } } }); } }

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