0

更新 4

这是我的 DBhelper 类

      package com.example.dbtest;

       import java.io.File;
     import java.io.FileOutputStream;
    import java.io.IOException;
      import java.io.InputStream;
       import java.io.OutputStream;

        import android.content.Context;
        import android.database.Cursor;
       import android.database.SQLException;
      import android.database.sqlite.SQLiteDatabase;
       import android.database.sqlite.SQLiteOpenHelper;

       public class DBhelper extends SQLiteOpenHelper {

String tablename;

Cursor ch;

private static String DB_PATH = "/data/data/com.example.dbtest/databases/";
public static String DB_NAME = "photodb";
private SQLiteDatabase myDataBase;
private  Context myContext;



public DBhelper(Context cont) {
    super(cont, DB_NAME, null, 3);

}


public void createDataBase() throws IOException {

    boolean dbExist = checkDataBase();
    if (!dbExist) {
        boolean flag = isOpen();
        if(flag==false){
        //this.getWritableDatabase();
        this.getReadableDatabase();

            //myDataBase = SQLiteDatabase.openDatabase(DB_PATH,null, SQLiteDatabase.OPEN_READWRITE|SQLiteDatabase.NO_LOCALIZED_COLLATORS);


        try {

            copyDataBase();

        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
    }

}



public boolean checkDataBase()
{
    File dbFile = new File(DB_PATH + DB_NAME);
    return dbFile.exists();
}



private void copyDataBase() throws IOException  {


    InputStream myInput;

        myInput = myContext.getAssets().open("photodb");


    String outFileName = DB_PATH + DB_NAME;


    OutputStream myOutput;

        myOutput = new FileOutputStream(outFileName);



    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }


    myOutput.flush();
    myOutput.close();
    myInput.close();


}

public boolean isOpen() {
    if (myDataBase != null)
        return myDataBase.isOpen();
    return false;
}


public void openDataBase() throws SQLException {

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

}

@Override
public synchronized void close() {
    if (myDataBase != null)
        myDataBase.close();
    super.close();
}

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}



public void add_pics(String imagepath,String description,String location)

{


    myDataBase.execSQL("insert into photodetails values(null," + imagepath + ","
            + description + "," + location + ");");

}

}

这是我的 MainActivity

       package com.example.dbtest;



     import java.io.IOException;

      import android.os.Bundle;
      import android.app.Activity;
     import android.content.Context;
       import android.view.Menu;

 public class MainActivity extends Activity {


DBhelper mydb;
Context cont;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mydb = new DBhelper(cont);

    try {
        mydb.createDataBase();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    mydb.openDataBase();
}


@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;
}

}

我的 logcat 错误是

09-02 18:43:26.052: E/AndroidRuntime(25477): 致命异常: main 09-02 18:43:26.052: E/AndroidRuntime(25477): java.lang.RuntimeException: 无法启动活动 ComponentInfo{com. example.dbtest/com.example.dbtest.MainActivity}：java.lang.NullPointerException 09-02 18:43:26.052：E/AndroidRuntime(25477)：在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110) 09 -02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app .ActivityThread.access$700(ActivityThread.java:140) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237) 09-02 18: 43:26.052: E/AndroidRuntime(25477): 在 android.os.Handler.dispatchMessage(Handler.java:99) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.os.Looper.loop(Looper.java:137) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.main (ActivityThread.java:4921) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 java.lang.reflect.Method.invokeNative(Native Method) 09-02 18:43:26.052: E/AndroidRuntime( 25477): 在 java.lang.reflect.Method.invoke(Method.java:511) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:1027) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794) 09-02 18:43:26.052 : E/AndroidRuntime(25477): at dalvik.system.NativeStart.main(Native Method) 09-02 18:43:26.052: E/AndroidRuntime(25477): 引起：java.lang.NullPointerException 09-02 18:43 :26.052:E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase (SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E /AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity. java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477) ：在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)在 android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread .performLaunchActivity(ActivityThread.java:2074)在 android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread .performLaunchActivity(ActivityThread.java:2074)getDatabaseLocked(SQLiteOpenHelper.java:224) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate (MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime (25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)getDatabaseLocked(SQLiteOpenHelper.java:224) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate (MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime (25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18: 43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)在 android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.DBhelper.createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) 09-02 18: 43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java :1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)createDataBase(DBhelper.java:41) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 com.example.dbtest.MainActivity.onCreate(MainActivity.java:25) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Activity.performCreate(Activity.java:5206) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java :1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)java:1094) 09-02 18:43:26.052: E/AndroidRuntime(25477): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)

4

2 回答 2

0

尝试使用

   SQLiteDatabase db = SQLiteDatabase.openDatabase(myPath,null,  SQLiteDatabase.OPEN_READWRITE|SQLiteDatabase.NO_LOCALIZED_COLLATORS);

在清单文件中设置权限

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

您还需要在 sqlite 中创建元数据表

CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT 'en_US')

和

INSERT INTO "android_metadata" VALUES ('en_US')
于 2013-09-02T12:46:53.120 回答
0

你可以试试

public boolean checkDataBase()
{
    File dbFile = new File(DB_PATH + DB_NAME);
    return dbFile.exists();
}

代替

private boolean checkDataBase() {
        SQLiteDatabase checkDB = null;
        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READWRITE);
        } catch (SQLiteException e) {
            // database does't exist yet.
        }
        if (checkDB != null) {
            checkDB.close();
        }

        return checkDB != null ? true : false;
    }

更新：

你得到以下异常android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)

因为您试图打开多个SQLiteDatabase. 只需确保一次只打开一个实例即可。您可以DBhelper使用Singelton模式来实现。为此，您可以参考此

于 2013-09-02T10:52:53.793 回答