Android：添加到应用程序数据库不起作用答案

【问题标题】：Android: Adding to App Database Not WorkingAndroid：添加到应用程序数据库不起作用
【发布时间】：2017-09-04 16:14:54
【问题描述】：

我正在编写一个涉及拍照的应用程序，然后将该照片的 URI 保存在数据库中。图像 URI 构成单个条目（由照片和多个音频文件 URI 组成的条目）的一部分。以下是我到目前为止这部分应用程序的代码：

数据库处理程序

package com.example.HwST_GoMo;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Environment;
import android.util.Log;

public class DatabaseHandler extends SQLiteOpenHelper {


    private SQLiteDatabase myDataBase; 

    // All Static variables
    // Database Version
    private static final int DATABASE_VERSION = 10;

    // Database Name
    private static final String DATABASE_NAME = "db";

    private static final String DB_PATH = "/mnt/sdcard/HWST/";

    // Contacts table name
    private static final String TABLE_ENTRIES = "Entries";

    // Contacts Table Columns names
    private static final String KEY_ID = "entry_id";
    private static final String KEY_IMAGE_URI = "image_uri";
    private static final String KEY_AUDIO_URI = "audio_uri";

    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_ENTRIES + "("
                + KEY_AUDIO_URI + " TEXT, " + KEY_IMAGE_URI + " TEXT," + KEY_ID + " INTEGER PRIMARY KEY" + 
                ")";
        db.execSQL(CREATE_CONTACTS_TABLE);
    }

    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_ENTRIES);

        // Create tables again
        onCreate(db);
    }

    public void openDataBase() throws SQLException{

        //Open the database
        String myPath = DB_PATH + DATABASE_NAME;
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);

    }

    public void addEntry(String URI){


        //SQLiteDatabase db = this.getWritableDatabase();
        myDataBase = this.getWritableDatabase();


        ContentValues values = new ContentValues();
        //values.put(KEY_IMAGE_URI, entry.getImageUri()); // Contact Name
        //values.put(KEY_AUDIO_URI, entry.getAudioUri()); // Contact Phone Number

        values.put(KEY_AUDIO_URI, "LOLOL");
        values.put(KEY_IMAGE_URI, URI);
        values.put(KEY_ID, 265);

        // Inserting Row

        long test = myDataBase.insert(TABLE_ENTRIES, null, values);

        System.out.println("PLEASE REACH THIS also " + test);

        this.close();
        //myDataBase.close(); // Closing database connection
    }

    // Getting single entry
    Entry getEntry(int id) {
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(TABLE_ENTRIES, new String[] { KEY_ID,
                KEY_IMAGE_URI, KEY_AUDIO_URI }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();

        Entry entry = new Entry(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2));
        // return entry
        return entry;
    }

    // Getting All Entries
    public List<Entry> getAllEntries() {
        List<Entry> entryList = new ArrayList<Entry>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_ENTRIES;

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Entry entry = new Entry();
                entry.setID(Integer.parseInt(cursor.getString(0)));
                entry.setImageUri(cursor.getString(1));
                entry.setAudioUri(cursor.getString(2));
                // Adding entry to list
                entryList.add(entry);
            } while (cursor.moveToNext());
        }

        // return entry list
        return entryList;
    }

    // Updating single entry
    public int updateEntry(Entry entry) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_IMAGE_URI, entry.getImageUri());
        values.put(KEY_AUDIO_URI, entry.getAudioUri());

        // updating row
        return db.update(TABLE_ENTRIES, values, KEY_ID + " = ?",
                new String[] { String.valueOf(entry.getID()) });
    }

    // Deleting single contact
    public void deleteEntry(Entry entry) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_ENTRIES, KEY_ID + " = ?",
                new String[] { String.valueOf(entry.getID()) });
        db.close();
    }

    // Getting contacts Count
    public int getEntriesCount() {
        String countQuery = "SELECT  * FROM " + TABLE_ENTRIES;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();

        // return count
        return cursor.getCount();
    } 
}

拍照页面

package com.example.HwST_GoMo;

import java.io.File;
import java.io.FileOutputStream;

import android.app.Activity;
import android.content.ContextWrapper;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class TakePhotographPage extends Activity {
    /** Called when the activity is first created. */

    private static final int CAMERA_REQUEST = 1888;
    private ImageView imageView;

    DatabaseHandler db = new DatabaseHandler(this);
    private TextView textView;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.takephotographpage);

        Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE); 
        startActivityForResult(cameraIntent, CAMERA_REQUEST); 

        this.imageView = (ImageView)this.findViewById(R.id.photoResultView);
        this.textView = (TextView)this.findViewById(R.id.textTest);



        Button button = (Button)findViewById(R.id.back_to_menu);
        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent intent = new Intent(view.getContext(), ControlsPage.class);
                startActivityForResult(intent, 0);
                // TODO Auto-generated method stub
            }
        });        
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
        if (requestCode == CAMERA_REQUEST) {  
            Bitmap photo = (Bitmap) data.getExtras().get("data"); 
            imageView.setImageBitmap(photo);

            int temp = (new File("/mnt/sdcard/HWST/").list().length) +1 ;
            String fileName = Integer.toString(temp);

            File file = null;
            FileOutputStream os;
            String dirName = "/HWST/";
                    try {  

                            File sdCard = Environment.getExternalStorageDirectory();

                            System.out.println(sdCard);
                            File dir = new File (sdCard.getAbsolutePath() + dirName);

                            file = new File(dir, fileName + ".png");
                            System.out.println(file);


                            FileOutputStream outStream = new FileOutputStream(file);
                            photo.compress(Bitmap.CompressFormat.PNG, 100, outStream);
                            outStream.flush();
                            outStream.close();


                            DatabaseHandler db = new DatabaseHandler(this);
                            db.openDataBase();

                            db.addEntry(file.toString());

                    }catch(Exception e){
                            System.out.println(e.toString());
                    }



            //db.addEntry(new Entry(0, "" + u + "", "test"));
        }  
    } 
}

入门类

package com.example.HwST_GoMo;

public class Entry {

    //private variables
    int _id;
    String _imageUri;
    String _audioUri;

    //Empty Constructor
    public Entry(){

    }

    //constructor
    public Entry(int id, String imageUri, String audioUri){
        this._id = id;
        this._imageUri = imageUri;
        this._audioUri = audioUri;
    }

    //get ID
    public int getID(){
        return this._id;
    }

    //set ID
    public void setID(int id){
        this._id = id;
    }

    //get imageUri
    public String getImageUri(){
        return this._imageUri;
    }

    //set imageUri
    public void setImageUri(String imageUri){
        this._imageUri = imageUri;
    }

    //get audioUri
    public String getAudioUri(){
        return this._audioUri;
    }

    //set audioUri
    public void setAudioUri(String audioUri){
        this._audioUri = audioUri;
    }   

}

我的问题是没有任何东西被添加到我的数据库中，而是似乎被添加到 /data/data 中我无权访问的数据库中。如果我将 KEY_ID 设置为我以前没有使用过的数字，然后运行应用程序并拍照，logcat 会显示以下内容：http://img26.imageshack.us/img26/6526/logcat1.png

如果我使用相同的 KEY_ID 再次运行该应用程序，我会得到以下信息： http://img706.imageshack.us/img706/1857/logcat2.png

使用 PC 上的 SQLite 数据库浏览器和手机上的 SQLite 管理器应用程序，我看到没有任何内容输入到数据库中。

第二次输入同一个 ID 时的约束错误让我相信数据正在进入数据库（虽然它是错误的），所以我的问题是，我要进行哪些更改才能强制应用将条目放入数据库中的“/mtn/sdcard/HWST/db”而不是“/data/data/com.example.HwST_GoMo/databases/db”的地址？

很抱歉不得不为 logcat 输出使用图像，但它不允许我将消息导出到 txt 文件。

【问题讨论】：

标签： android database location

【解决方案1】：

// Database Name
private static final String DATABASE_NAME = "db";

// path to db
private static final String DB_PATH = "/mnt/sdcard/HWST/";

// now both combined
private static final String DB_FILE = DB_PATH + DATABASE_NAME;

public DatabaseHandler(Context context) {
    super(context, DB_FILE, null, DATABASE_VERSION);
}

构造函数将在您指定的位置创建数据库。如果名称以/（绝对路径）开头，那么将在那里创建数据库。如果你给它别的东西，它会在/data/data/your.package.name/databases/[name] 中创建它。该路径是您的应用程序主目录，它可以在那里读/写。

另外：您应该将除构造函数/onCreate/onUpgrade 之外的所有内容从DatabaseHandler 移到一个新类中，并从那里使用DatabaseHandler。 SQLiteOpenHelper 的目的是帮助您获得具有所需表（创建/升级）的可写数据库。最好不要用于其他用途。

class TheRealDatabaseHandler {

    public void addEntry(String URI){
        DatabaseHandler helper = new DatabaseHandler(mContext);
        SQLiteDatabase db = helper.getWritableDatabase();
        db.insert...
   }

}

【讨论】：