Android App中各種數據保存方式的使用實例總結

2019-12-12 06:31:21

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少量數據保存之SharedPreferences接口實例
SharedPreferences數據保存主要是通過鍵值的方式存儲在xml文件中
xml文件在data/此程序的包名/XX.xml。
格式：

<?xml version='1.0' encoding='utf-8' standalone='yes' ?><map><int name="count" value="3" /><string name="time">寫入日期:2013年10月07日,時間:11:28:09</string></map>

SharedPreferences讀寫的基本步驟：
讀：
1.通過Context的getSharedPreferences獲取SharedPreferences接口的對象share：SharedPreferences share = this.getSharedPreferences("share",Context.MODE_PRIVATE);
"shre"保存的xml文件名 ,Context.MODE_PRIVATE 保存的類型為只被本程序訪問 (還有MODE_WORLD_READABLE表示其余的程序能夠讀不能寫,MODE
_WORLD_WRITEBLE能讀寫這兩個都在api17的時候被廢了)
2.通過share的getXXX的方法獲取指定key的值： share.getInt("count", 0);
寫：
1.通過SharedPreferences對象的edit()方法獲取Edit對象:Edit editor = share.edit();
2.通過editor對象的putXXX方法來寫入值：editor.putInt("count", 1);
3.調用Editor的commit()方法提交修改值：editor.commit();

訪問其他程序的SharedPreferences
訪問其他程序的SharedPreferences 的讀寫唯一不同的是先的獲取該程序的Context接口對象：this.createPackageContext(packageName, flags)
packageName為要該目標程序的包名,flags訪問類型
其余的就和上面的步驟差不多就不再概敘

實例

<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/write"   android:layout_width="wrap_content"   android:layout_height="wrap_content"    android:layout_gravity="center_horizontal"   android:text="寫入數據" />   <Button   android:id="@+id/read"   android:layout_width="wrap_content"   android:layout_height="wrap_content"    android:layout_gravity="center_horizontal"   android:text="讀入數據" />  <TextView   android:id="@+id/txtCount"   android:layout_width="match_parent"   android:layout_height="wrap_content"/>   <TextView   android:id="@+id/txt1"   android:layout_width="match_parent"   android:layout_height="wrap_content" />  </LinearLayout>

package com.android.xiong.sharepreferencestest;  import java.text.SimpleDateFormat; import java.util.Date;  import android.app.Activity; import android.content.Context; import android.content.SharedPreferences; import android.content.SharedPreferences.Editor; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.TextView;  public class MainActivity extends Activity {   private Button write;  private Button read;   private TextView txt1;  private TextView countTxt;    SharedPreferences share ;    Editor editor;   int countO=0;  @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);   //獲取SharedPreferences對象   share = this.getSharedPreferences("share",     Context.MODE_PRIVATE);   //獲取Editor對象   editor = share.edit();   write = (Button) findViewById(R.id.write);   read = (Button) findViewById(R.id.read);   txt1 = (TextView) findViewById(R.id.txt1);   countTxt=(TextView)findViewById(R.id.txtCount);   //獲取share中key為count的值   countO=share.getInt("count", 0);   countO++;   //修改share中key為count的值   editor.putInt("count", countO);   //提交修改   editor.commit();   System.out.println("該應用程序使用了:"+countO+"次");   countTxt.setText("該應用程序使用了:"+countO+"次");      OnClickListener writeListener = new OnClickListener() {     @Override    public void onClick(View v) {     // TODO Auto-generated method stub      SimpleDateFormat data = new SimpleDateFormat(       "寫入日期:yyyy年MM月dd日,時間:hh:mm:ss");     editor.putString("time",       data.format(new Date()));     editor.commit();     }   };   OnClickListener readListener=new OnClickListener() {        @Override    public void onClick(View v) {     // TODO Auto-generated method stub     if(!share.contains("share")){      txt1.setText(share.getString("time", null));     }         }   };   write.setOnClickListener(writeListener);   read.setOnClickListener(readListener);   }   @Override  public boolean onCreateOptionsMenu(Menu menu) {   // Inflate the menu; this adds items to the action bar if it is present.   getMenuInflater().inflate(R.menu.main, menu);   return true;  }  }

機身內存數據讀寫(Internal Storage)
1.機身內存讀取主要用個兩個類文件輸入流(FileInputStream)和文件輸出流(FileOutputStream): FileInputStream fileInput = this.openFileInput("test.txt") 第一個參數為 data/此程序包名/data/test.txt 文件下的文件名 ;
FileOutputStream fileOut = this.openFileOutput("test.txt",this.MODE_APPEND)第一個參數表示文件名第二個參數表示打開的方式
2.獲取了文件輸入輸出流之后其后的文件的讀寫和基本的IO操作一樣
機身內存數據讀寫實例

<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:layout_gravity="center_horizontal"  android:orientation="vertical"  tools:context=".MainActivity" >  <EditText   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:id="@+id/ed1"   android:inputType="textMultiLine"/>  <Button   android:id="@+id/write"   android:text="寫入"   android:layout_width="match_parent"   android:layout_height="wrap_content"/>  <Button   android:id="@+id/read"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:text="讀入"/>  <EditText   android:id="@+id/ed2"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:inputType="textMultiLine"/>  <Button   android:id="@+id/delete"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:text="刪除指定的文件"   />  <EditText   android:id="@+id/ed3"   android:layout_width="match_parent"   android:layout_height="wrap_content"   />  </LinearLayout>

package com.android.xiong.fileiotest;  import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStreamReader; import java.lang.reflect.Array; import java.util.ArrayList; import java.util.Arrays; import java.util.List;  import android.app.Activity; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText;  public class MainActivity extends Activity {   private Button read;  private Button write;  private EditText ed1;  private EditText ed2;  private EditText ed3;  private Button delete;   @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);   read = (Button) findViewById(R.id.read);   write = (Button) findViewById(R.id.write);   delete = (Button) findViewById(R.id.delete);   ed3 = (EditText) findViewById(R.id.ed3);   ed2 = (EditText) findViewById(R.id.ed2);   ed1 = (EditText) findViewById(R.id.ed1);   write.setOnClickListener(new OnClickListener() {    @Override    public void onClick(View v) {     String str = ed1.getText().toString();     if (!str.equals("")) {      write(str);     }     }   });   read.setOnClickListener(new OnClickListener() {     @Override    public void onClick(View v) {     read();     }   });   delete.setOnClickListener(new OnClickListener() {    @Override    public void onClick(View v) {     String str = ed3.getText().toString();     if (!str.equals("")) {      deleteFiles(str);     } else {      ed3.setText(str + ":該文件輸入錯誤或不存在!");     }     }   });   }   private void write(String content) {   try {    // 以追加的方式打開文件輸出流    FileOutputStream fileOut = this.openFileOutput("test.txt",      this.MODE_APPEND);    // 寫入數據    fileOut.write(content.getBytes());    // 關閉文件輸出流    fileOut.close();    } catch (Exception e) {    e.printStackTrace();   }  }   private void read() {   try {    ed2.setText("");    // 打開文件輸入流    FileInputStream fileInput = this.openFileInput("test.txt");    BufferedReader br = new BufferedReader(new InputStreamReader(      fileInput));    String str = null;    StringBuilder stb = new StringBuilder();    while ((str = br.readLine()) !=null ) {     stb.append(str);    }    ed2.setText(stb);   } catch (Exception e) {    e.printStackTrace();   }   }    //刪除指定的文件  private void deleteFiles(String fileName) {   try {    // 獲取data文件中的所有文件列表    List<String> name = Arrays.asList(this.fileList());    if (name.contains(fileName)) {     this.deleteFile(fileName);     ed3.setText(fileName + ":該文件成功刪除！");    } else     ed3.setText(fileName + ":該文件輸入錯誤或不存在!");    } catch (Exception e) {    e.printStackTrace();   }  }   @Override  public boolean onCreateOptionsMenu(Menu menu) {   getMenuInflater().inflate(R.menu.main, menu);   return true;  }  }

SDcard(External Storage)讀寫數據實例
1.SDcard數據讀寫需要注定的先要在Androidmainfest.xml文件中注冊新建刪除和讀寫的權限 :

<!-- 在SD卡上創建與刪除權限 --><uses-permission Android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" /><!-- 向SD卡上寫入權限 --><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2.讀寫的基本流程就是:
2.1 通過Environment類的getExternalStorageState()方法來判斷手機是否有SDcard:

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

2.2 最通過getExternalStorageDirectory()方法來獲取文件目錄:

復制代碼代碼如下:

File file = new File(Environment.getExternalStorageDirectory().getCanonicalPath() + "/test.txt");

讀寫的文件都在sdcrad文件夾中通過File Explorer可以導出來
2.3 其后就和基本IO操作相同了
2.4還有要注意一點的是在運行的模擬器的時候要附帶虛擬的SDcard時要在Run as->Run Configurations 中要關聯一下如下圖

SDcard數據讀寫實例

<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:gravity="center_horizontal"  android:orientation="vertical"  tools:context=".MainActivity" >  <EditText   android:id="@+id/ed1"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:inputType="textMultiLine"/>  <Button   android:id="@+id/write"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:text="寫入SD卡中"/>  <Button   android:id="@+id/read"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:text="讀取SD文件"/>  <TextView   android:id="@+id/txt1"   android:layout_width="match_parent"   android:layout_height="wrap_content"/> </LinearLayout>

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"  package="com.android.xiong.sdcardtest"  android:versionCode="1"  android:versionName="1.0" >   <uses-sdk   android:minSdkVersion="14"   android:targetSdkVersion="17" />  <!-- 在SD卡上創建與刪除權限 -->  <uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" />  <!-- 向SD卡上寫入權限 -->  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />   <application   android:allowBackup="true"   android:icon="@drawable/ic_launcher"   android:label="@string/app_name"   android:theme="@style/AppTheme" >   <activity    android:name="com.android.xiong.sdcardtest.MainActivity"    android:label="@string/app_name" >    <intent-filter>     <action android:name="android.intent.action.MAIN" />      <category android:name="android.intent.category.LAUNCHER" />    </intent-filter>   </activity>  </application>  </manifest>

package com.android.xiong.sdcardtest;  import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStreamReader;  import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView;  public class MainActivity extends Activity {   private Button write;  private Button read;   private EditText ed1;  private TextView txt1;   @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   setContentView(R.layout.activity_main);   write = (Button) findViewById(R.id.write);   read = (Button) findViewById(R.id.read);   ed1 = (EditText) findViewById(R.id.ed1);   txt1 = (TextView) findViewById(R.id.txt1);   write.setOnClickListener(new OnClickListener() {     @Override    public void onClick(View v) {     // TODO Auto-generated method stub     writeSDcard(ed1.getText().toString());     }   });   read.setOnClickListener(new OnClickListener() {     @Override    public void onClick(View v) {     // TODO Auto-generated method stub      txt1.setText(readSDcard());    }   });  }   // 把數據寫入SD卡   private void writeSDcard(String str) {    try {    // 判斷是否存在SD卡    if (Environment.getExternalStorageState().equals(      Environment.MEDIA_MOUNTED)) {     // 獲取SD卡的目錄     File file = Environment.getExternalStorageDirectory();     FileOutputStream fileW = new FileOutputStream(file.getCanonicalPath() + "/test.txt");     fileW.write(str.getBytes());     fileW.close();    }   } catch (Exception e) {    e.printStackTrace();   }   }   // 從SD卡中讀取數據  private String readSDcard() {   StringBuffer str = new StringBuffer();   try {    // 判斷是否存在SD    if (Environment.getExternalStorageState().equals(      Environment.MEDIA_MOUNTED)) {     File file = new File(Environment.getExternalStorageDirectory()       .getCanonicalPath() + "/test.txt");                     // 判斷是否存在該文件     if (file.exists()) {      // 打開文件輸入流      FileInputStream fileR = new FileInputStream(file);      BufferedReader reads = new BufferedReader(        new InputStreamReader(fileR));      String st = null;      while ((st =reads.readLine())!=null ) {       str.append(st);      }      fileR.close();     } else {      txt1.setText("該目錄下文件不存在");     }    }    } catch (Exception e) {    e.printStackTrace();   }   return str.toString();  }   @Override  public boolean onCreateOptionsMenu(Menu menu) {   // Inflate the menu; this adds items to the action bar if it is present.   getMenuInflater().inflate(R.menu.main, menu);   return true;  }  }

SQLite簡介和簡單的登錄與注冊源代碼
1.獲取SQLiteDatabase對象db創建數據庫或連接數據庫：SQLiteDatabasedb = SQLiteDatabase.openOrCreateDatabase(MainActivity.this.getFilesDir().toString()+ "/test.dbs", null);如果目錄下有test.dbs數據庫則是連接沒有就是創建
2.用對象db的方法來執行sql語句：db.execSQL(String sql) 此方法木有返回值所以查詢不好弄。查詢一般用db.rawQuery返回一個Cursor對象(相當與jdbc中的ResultSet),Cursor有如下幾個方法來查詢數據:
2.1 move ToFirst 將記錄指針跳到第一行
2.2 moveToLast將記錄指針跳到最后一行
2.3 moveNext將記錄指針移到下一行
2.4moveToPosition( int ss)將記錄指針跳到指定的ss行
2.5moveToPrevious將記錄指針跳到上一行
將記錄指針跳到指定的行之后就可以通過對象的getXXX方法來獲取數據 :如 Cursor cursor = db.rawQuery("select na,pw from user where na=? and pw=?", new String []{name,pwd});
3.回收資源close
當然以SQLiteDatabase對象還可以調用許多方法來操作數據庫，不過俺是覺得這幾個方法基本夠了

簡單的登錄與注冊源代碼：
（僅此來練習SQLite的操作一般注冊的信息都樣上傳到服務器而不會是存儲在手機數據庫）

2016423112521792.jpg (452×512)

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"   package="com.android.xiong.sqlitelogin"   android:versionCode="1"   android:versionName="1.0" >    <uses-sdk     android:minSdkVersion="8"     android:targetSdkVersion="14" />    <application     android:allowBackup="true"     android:icon="@drawable/ic_launcher"     android:label="@string/app_name"     android:theme="@style/AppTheme" >     <activity       android:name="com.android.xiong.sqlitelogin.MainActivity"       android:label="@string/app_name" >       <intent-filter>         <action android:name="android.intent.action.MAIN" />          <category android:name="android.intent.category.LAUNCHER" />       </intent-filter>     </activity>     <activity       android:name="com.android.xiong.sqlitelogin.RegistersActivity"       android:label="@string/app_name" >     </activity>   </application>  </manifest>

<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=".MainActivity" >    <TextView     android:id="@+id/login"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:layout_margin="30dp"     android:gravity="center_horizontal"     android:textColor="#8a2be2"     android:textSize="35dp"     android:text="登錄界面" />   <TextView      android:id="@+id/txtname"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@id/login"     android:layout_marginRight="5dp"     android:layout_marginBottom="30dp"     android:textSize="28dp"     android:text="用戶帳號:"/>   <EditText      android:id="@+id/edname"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_marginBottom="30dp"     android:layout_below="@id/login"     android:layout_toRightOf="@id/txtname"     android:layout_alignParentRight="true"      android:hint="請輸入用戶帳號"/>     <TextView      android:id="@+id/txtpassword"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@id/txtname"     android:layout_marginRight="5dp"     android:textSize="28dp"     android:text="用戶密碼:"/>   <EditText      android:id="@+id/edpassword"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@id/edname"     android:layout_toRightOf="@id/txtpassword"     android:layout_alignParentRight="true"     android:inputType="textPassword"     android:hint="請輸入用戶密碼"/>   <LinearLayout      android:layout_below="@id/edpassword"     android:orientation="horizontal"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:layout_marginTop="30dp"     android:gravity="center_horizontal" >   <Button      android:id="@+id/btregister"     android:layout_height="wrap_content"     android:layout_width="wrap_content"     android:layout_marginRight="20dp"     android:text="用戶注冊"/>    <Button      android:id="@+id/btlogin"     android:layout_height="wrap_content"     android:layout_width="wrap_content"     android:text="用戶登錄"/>    </LinearLayout>  </RelativeLayout>

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"   android:layout_width="match_parent"   android:layout_height="match_parent" >       <TextView     android:id="@+id/txt1"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:layout_margin="30dp"     android:gravity="center_horizontal"     android:text="注冊界面"     android:textColor="#8a2be2"     android:textSize="35dp" />    <TextView     android:id="@+id/txtname1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@id/txt1"     android:layout_marginBottom="30dp"     android:layout_marginRight="5dp"     android:text="帳號:"     android:textSize="28dp" />    <EditText     android:id="@+id/edname1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_alignParentRight="true"     android:layout_below="@id/txt1"      android:layout_toRightOf="@id/txtname1"     android:layout_marginBottom="30dp" />    <TextView     android:id="@+id/txtpassword1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@id/txtname1"     android:layout_marginRight="5dp"     android:text="密碼:"     android:textSize="28dp" />    <EditText     android:id="@+id/edpassword1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_alignParentRight="true"     android:layout_below="@id/edname1"     android:layout_toRightOf="@id/txtpassword1" />    <LinearLayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:layout_below="@id/edpassword1"     android:layout_marginTop="30dp"     android:gravity="center_horizontal"     android:orientation="horizontal" >      <Button       android:id="@+id/btregister1"       android:layout_width="wrap_content"       android:layout_height="wrap_content"       android:layout_marginRight="20dp"       android:text="提交數據" />   </LinearLayout> </RelativeLayout>

package com.android.xiong.sqlitelogin;  import android.app.Activity; import android.app.AlertDialog; import android.content.Intent; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.os.Bundle; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText;  public class MainActivity extends Activity {    // 帳號和密碼   private EditText edname;   private EditText edpassword;    private Button btregister;   private Button btlogin;   // 創建SQLite數據庫   public static SQLiteDatabase db;    @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     edname = (EditText) findViewById(R.id.edname);     edpassword = (EditText) findViewById(R.id.edpassword);     btregister = (Button) findViewById(R.id.btregister);     btlogin = (Button) findViewById(R.id.btlogin);     db = SQLiteDatabase.openOrCreateDatabase(MainActivity.this.getFilesDir().toString()         + "/test.dbs", null);     // 跳轉到注冊界面     btregister.setOnClickListener(new OnClickListener() {        @Override       public void onClick(View v) {         // TODO Auto-generated method stub         Intent intent = new Intent();         intent.setClass(MainActivity.this, RegistersActivity.class);         startActivity(intent);       }     });     btlogin.setOnClickListener(new LoginListener());   }    @Override   protected void onDestroy() {     // TODO Auto-generated method stub     super.onDestroy();     db.close();   }     class LoginListener implements OnClickListener {      @Override     public void onClick(View v) {       // TODO Auto-generated method stub       String name = edname.getText().toString();       String password = edpassword.getText().toString();       if (name.equals("") || password.equals("")) {         // 彈出消息框         new AlertDialog.Builder(MainActivity.this).setTitle("錯誤")             .setMessage("帳號或密碼不能空").setPositiveButton("確定", null)             .show();       } else {         isUserinfo(name, password);       }     }      // 判斷輸入的用戶是否正確     public Boolean isUserinfo(String name, String pwd) {       try{         String str="select * from tb_user where name=? and password=?";         Cursor cursor = db.rawQuery(str, new String []{name,pwd});         if(cursor.getCount()<=0){           new AlertDialog.Builder(MainActivity.this).setTitle("錯誤")           .setMessage("帳號或密碼錯誤！").setPositiveButton("確定", null)           .show();           return false;         }else{           new AlertDialog.Builder(MainActivity.this).setTitle("正確")           .setMessage("成功登錄").setPositiveButton("確定", null)           .show();           return true;         }                }catch(SQLiteException e){         createDb();       }       return false;     }      }   // 創建數據庫和用戶表   public void createDb() {     db.execSQL("create table tb_user( name varchar(30) primary key,password varchar(30))");   }   @Override   public boolean onCreateOptionsMenu(Menu menu) {     // Inflate the menu; this adds items to the action bar if it is present.     getMenuInflater().inflate(R.menu.main, menu);     return true;   }  }

package com.android.xiong.sqlitelogin;  import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.content.Intent; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText;  public class RegistersActivity extends Activity {    private EditText edname1;   private EditText edpassword1;   private Button btregister1;   SQLiteDatabase db;    @Override   protected void onDestroy() {     // TODO Auto-generated method stub     super.onDestroy();     db.close();   }    @Override   protected void onCreate(Bundle savedInstanceState) {     // TODO Auto-generated method stub     super.onCreate(savedInstanceState);     setContentView(R.layout.register);     edname1 = (EditText) findViewById(R.id.edname1);     edpassword1 = (EditText) findViewById(R.id.edpassword1);     btregister1 = (Button) findViewById(R.id.btregister1);     btregister1.setOnClickListener(new OnClickListener() {        @Override       public void onClick(View v) {         // TODO Auto-generated method stub         String name = edname1.getText().toString();         String password = edpassword1.getText().toString();         if (!(name.equals("") && password.equals(""))) {           if (addUser(name, password)) {             DialogInterface.OnClickListener ss = new DialogInterface.OnClickListener() {               @Override               public void onClick(DialogInterface dialog,                   int which) {                 // TODO Auto-generated method stub                 // 跳轉到登錄界面                 Intent in = new Intent();                 in.setClass(RegistersActivity.this,                     MainActivity.class);                 startActivity(in);                 // 銷毀當前activity                 RegistersActivity.this.onDestroy();               }             };             new AlertDialog.Builder(RegistersActivity.this)                 .setTitle("注冊成功").setMessage("注冊成功")                 .setPositiveButton("確定", ss).show();            } else {             new AlertDialog.Builder(RegistersActivity.this)                 .setTitle("注冊失敗").setMessage("注冊失敗")                 .setPositiveButton("確定", null);           }         } else {           new AlertDialog.Builder(RegistersActivity.this)               .setTitle("帳號密碼不能為空").setMessage("帳號密碼不能為空")               .setPositiveButton("確定", null);         }        }     });    }    // 添加用戶   public Boolean addUser(String name, String password) {     String str = "insert into tb_user values(?,?) ";     MainActivity main = new MainActivity();     db = SQLiteDatabase.openOrCreateDatabase(this.getFilesDir().toString()         + "/test.dbs", null);     main.db = db;     try {       db.execSQL(str, new String[] { name, password });       return true;     } catch (Exception e) {       main.createDb();     }     return false;   }  }

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