編輯：關於Android編程
第一行代碼Android學習：第七部分主要涉及到文件存儲、SharedPreferences存儲、SQLite數據庫存儲
文件存儲：DYHDM_06_00FilePersistenceTest
1.activity_main.xml2.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();
// 一次可以判斷兩種空值null或""
if (!TextUtils.isEmpty(inputText)) {
et.setText(inputText);
// 光標移動到文本的末尾
et.setSelection(inputText.length());
Toast.makeText(MainActivity.this, inputText, Toast.LENGTH_SHORT)
.show();
}
}
/**
* 在頁面關閉的時候保存輸入的數據 重載方法
*/
@Override
protected void onDestroy() {
super.onDestroy();
String inputText = et.getText().toString();
save(inputText);
}
/**
* TODO 保存數據到文件
*
* @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 從文件中讀取數據
*
* @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存儲：DYHDM_06_01SharedPreferencesTest
1.activity_main.xml2.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存儲和獲取數據
*
* @author 張志安
* @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) {
/**
* 存儲 Android中提供了三種方法得到SharedPreferences對象
* 1.Context類中的getSharedPreferences() 兩個參數：名稱和操作模式
* 2.Activity類中的getPreferences() 一個參數：操作模式 默認使用類名做文件名
* 3.PreferenceManager類中的getDefaultSharedPreferences() 靜態方法
* 接受一個Context參數，使用包名為前綴命名
*
* 獲得SharedPreferences對象後，存儲數據分為三步：
* 1.調用SharedPreferences對象的edit(
* )方法獲取一個SharedPreferences.Editor對象
* 2.向SharedPreferences.Editor對象中添加數據，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) {
// 獲取數據
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數據庫存儲：DYHDM_06_02MyDatabaseHelper
1.activity_main.xml2.MyDatabaseHelper.java
/*
* @Title: MyDatabaseHelper.java
* @Description: TODO
* @author: 張志安
* @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 用於數據庫的創建
*
* @author 張志安
* @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)";
/**
* <默認構造函數>
*/
public MyDatabaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
mContext = context;
}
/**
* 重載方法
*/
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_BOOK2);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
/**
* 重載方法
*/
@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) {
// 創建數據庫
dbHelper.getWritableDatabase();
}
});
bt_add = (Button) findViewById(R.id.bt_add);
bt_add.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// 添加數據
db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
// 第一條數據
values.put("name", "zza");
values.put("author", "zzzzz");
values.put("pages", 444);
values.put("price", 15.5);
db.insert("Book", null, values);
// 第二條數據
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) {
// 更新數據
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) {
// 刪除數據
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();
// 查詢book表中所有數據
Cursor cursor = db.query("Book", null, null, null, null, null,
null);
if (cursor.moveToFirst()) {
do {
// 遍歷Cursor對象，取出數據
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();
// 事務可以保證某一系列操作要麼都完成，要麼都不完成
// 開始事務
db.beginTransaction();
try {
// 添加操作
// 。。。
// 事務已經執行成功
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
} finally {
// 結束事務
db.endTransaction();
}
}
});
}
}
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