1

各位程序员。

我正在开发一个显示挪威鱼类信息的应用程序。我有一个 SQLite 数据库，并使用以下结构运行：

CREATE TABLE fisk(image TEXT, id INTEGER PRIMARY KEY AUTOINCREMENT, navn TEXT, familie TEXT, latin TEXT, engelsk TEXT, habitat TEXT, notat TEXT);

我已经成功读取了我需要的数据，但是如果你理解我的话，我想在特定行上设置 ImageView 等于 R.drawable.STRING_FROM_IMAGE_COLUMN。

关于如何做到这一点的任何提示？我不知道我应该在代码中的哪个位置引用图像。所有图像都存储在 res/drawable 文件夹中，文件名与数据库中图像列中的名称相同。除了图像之外，Everyting 工作正常，我尝试了许多解决方案但没有成功

我的原型和当前工作进度的图像：

代码：

MainActivity.java 包 com.dbtes.lol；

import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteException;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;

public class MainActivity extends Activity
{
private TextView tvTest;
private DataBaseHelper myDbHelper;
private SimpleCursorAdapter dataAdapter;
private ImageView ivFisk;


/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);


   tvTest = (TextView) findViewById(R.id.tvTest);
   myDbHelper = new DataBaseHelper(this);

   try {
       myDbHelper.createDataBase();
       tvTest.setText("DB created");
   }
   catch(IOException ioe) {
       throw new Error("Unable to create database");


   }

   try {
       myDbHelper.openDataBase();
       tvTest.setText("DB opened");
       displayListView();


   }
   catch(SQLiteException sqle) {
       throw sqle;
   }
}

public void displayListView() {
     Cursor cursor = myDbHelper.fetchAllFishes();

     // Bind columns to array
     String[] columns = new String[] {
         DataBaseHelper.KEY_IMAGE,
         DataBaseHelper.KEY_NAME,
         DataBaseHelper.KEY_FAMILY,
         DataBaseHelper.KEY_LATIN,
         DataBaseHelper.KEY_ENGLISH,
         DataBaseHelper.KEY_HABITAT,
         DataBaseHelper.KEY_NOTE
     };

     // Reference to XML layout binds
     int[] to = new int[] {
       R.id.ivFish,
       R.id.tvName,
       R.id.tvFamily,
       R.id.tvLatin,
       R.id.tvEnglish,
       R.id.tvHabitat,
       R.id.tvNote

     };

     dataAdapter = new SimpleCursorAdapter(this, R.layout.fish_info, cursor, columns, to, 0);

     ListView listView = (ListView) findViewById(R.id.listView1);
     listView.setAdapter(dataAdapter); 

     ivFisk = (ImageView) findViewById(R.id.ivFish);


     listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
         ListView listView1 = (ListView) findViewById(R.id.listView1);
         @Override
         public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Cursor cursor = (Cursor) listView1.getItemAtPosition(position);

          //  String name = cursor.getString(cursor.getColumnIndexOrThrow("navn"));
           // Toast.makeText(getApplicationContext(), name.toLowerCase(), Toast.LENGTH_LONG).show();

         }
     });

}
}

数据库助手.java

package com.dbtes.lol;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


public class DataBaseHelper extends SQLiteOpenHelper{

private static String DB_PATH = "/data/data/com.dbtes.lol/databases/";
private static String DB_NAME = "fiskDBv1.db";

// Lagd i ettertid
private static String TABLE_NAME = "fisk";
private static final String TAG = "CountriesDbAdapter";

// Table tags - lagd i ettertid
public static String KEY_ID = "_id";
public static String KEY_NAME = "navn";
public static String KEY_FAMILY = "familie";
public static String KEY_LATIN = "latin";
public static String KEY_ENGLISH = "engelsk";
public static String KEY_HABITAT = "habitat";
public static String KEY_NOTE = "notat";
public static String KEY_IMAGE = "image";



private SQLiteDatabase myDataBase;

private final Context myContext;

// Constructor
public DataBaseHelper(Context context) {
    super(context, DB_NAME, null, 1);
    this.myContext = context;
}

public void createDataBase() throws IOException {
    boolean dbExist = checkDataBase();

    if(dbExist) {
        // Do nothing, DB exist
    }
    else {
        // Lager en tom database som vi overskriver med min egen DB
        this.getReadableDatabase();

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

private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }
    catch(SQLiteException e) {
        // Database dosen't exist
    }

    if(checkDB != null) {
        checkDB.close();
    }

    return checkDB != null ? true : false;
}


private void copyDatabase() throws IOException {
    //Open DB as InputStream
    InputStream myInput = myContext.getAssets().open(DB_NAME);

    // Path to empty DB created by JVM
    String outFileName = DB_PATH + DB_NAME;

    // Åpne tom DB som utstrøm
    OutputStream myOutput = new FileOutputStream(outFileName);

    // Overføre data fra eksisterende til tom DB
    byte[] buffer = new byte[1024];
    int length;

    while((length = myInput.read(buffer))>0) {
        myOutput.write(buffer, 0, length);
    }

    // Close streams
    myOutput.flush();
    myOutput.close();
    myInput.close();  
}

public void openDataBase() throws SQLiteException {
    //Open db
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}

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

// Lagd i ettertid
public Cursor fetchAllFishes() {
    Cursor myCursor = myDataBase.query(TABLE_NAME, new String[] 
    {KEY_IMAGE, KEY_ID, KEY_NAME, KEY_FAMILY, KEY_LATIN, KEY_ENGLISH, KEY_HABITAT, KEY_NOTE}, 
     null, null, null, null, "navn");

    if(myCursor !=  null) {
        myCursor.moveToFirst();
    }
    return myCursor;
}

// Fetch names
public Cursor fetchFishName() {
    Log.w(TAG, "Feil her");

    Cursor myCursor =
          myCursor = myDataBase.query(TABLE_NAME, new String[]{KEY_NAME},null,null,null,null, "navn");

    if(myCursor != null) {
        myCursor.moveToFirst();
    }
    return myCursor;
}

// Standard implemented methods
@Override
public void onCreate(SQLiteDatabase db) {  
}

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

主要的.xml

<?xml version="1.0" encoding="utf-8"?>
        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            >
        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:id="@+id/tvTest"
            />

        <TextView 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="@string/some_text"
            android:textSize="20sp" />

        <ListView 
            android:id="@+id/listView1"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" />

        </LinearLayout>

鱼信息.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="6dip" >


<!-- Data labels --> 
<TextView 
    android:id="@+id/tvNameInfo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:text="Navn: "
    android:textAppearance="?android:attr/textAppearanceMedium" />

<TextView 
    android:id="@+id/tvFamilyInfo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/tvNameInfo"
    android:layout_below="@+id/tvNameInfo"
    android:text="Famile: "
    android:textAppearance="?android:attr/textAppearanceMedium" />

<TextView 
    android:id="@+id/tvLatinInfo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/tvFamilyInfo"
    android:layout_below="@+id/tvFamilyInfo"
    android:text="Latin: "
    android:textAppearance="?android:attr/textAppearanceMedium" />


<TextView 
    android:id="@+id/tvEnglishInfo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/tvLatinInfo" 
    android:layout_below="@+id/tvLatinInfo"
    android:text="Engelsk: "
    android:textAppearance="?android:attr/textAppearanceMedium" />


<TextView 
    android:id="@+id/tvHabitatInfo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/tvEnglishInfo"
    android:layout_below="@+id/tvEnglishInfo"
    android:text="Habitat: "
    android:textAppearance="?android:attr/textAppearanceMedium" />




<!-- Actual data bindings -->
<TextView 
    android:id="@+id/tvName"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/tvFamilyInfo"
    android:layout_alignLeft="@+id/tvFamily"
     />



<TextView 
    android:id="@+id/tvFamily"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/tvLatinInfo"
    android:layout_toRightOf="@+id/tvFamilyInfo"
     />

<TextView 
    android:id="@+id/tvLatin"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/tvLatinInfo"
    android:layout_alignBottom="@+id/tvLatinInfo"
    android:layout_toRightOf="@+id/tvLatinInfo"
     />


<TextView 
    android:id="@+id/tvEnglish"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/tvEnglishInfo"
   android:layout_alignBottom="@+id/tvEnglishInfo"
    android:layout_toRightOf="@+id/tvEnglishInfo"
     />


<TextView 
    android:id="@+id/tvHabitat"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/tvHabitatInfo"
    android:layout_alignBottom="@+id/tvHabitatInfo"
    android:layout_toRightOf="@+id/tvHabitatInfo"
     />

<TextView
    android:id="@+id/tvNote"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/tvHabitat"
    android:layout_marginTop="10dp"
    />


<ImageView
  android:id="@+id/ivFish"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true"
  android:layout_below="@+id/tvNote"
  android:layout_marginTop="15dp"
  android:layout_gravity="center"
/>

</RelativeLayout>

编辑

我将此方法添加到 DataBaseHelper.java 类中，以从数据库中返回带有图像名称的 ArrayList（我尝试将其打印到控制台，这很好，所有名称都在）：

public ArrayList<String> getNames() {
       ArrayList<String> nameList = null;

       Cursor cursor = null;
       try {
           String query = "SELECT image FROM fisk ORDER BY navn";

           cursor = myDataBase.rawQuery(query, null);
           if(cursor != null && cursor.moveToFirst()) {
               nameList = new ArrayList<String>();
               do {
                   nameList.add(cursor.getString(0));
               } while(cursor.moveToNext());
           }
           else{
               nameList.add("testimage");
           }
       }catch(Exception e) {
           e.printStackTrace();
           nameList = null;
       }
       finally{
           if(cursor != null && !cursor.isClosed()) {
               cursor.close();
               cursor = null;
           }
           close();
       }
       return nameList; 
   }

我已将此添加到 MainActivity.java 中的方法 displayListView() 中，并附有答案中的提示。

try { 
        ArrayList<String> testNames = new ArrayList<String>();
        testNames = myDbHelper.getNames();

        ivFisk = (ImageView) findViewById(R.id.ivFish);
        context = this;

              if(!testNames.isEmpty()) {

                        for(String s : testNames) {
               int id = context.getResources().getIdentifier(s, "drawable", context.getPackageName());

               if(id != 0) {
                   System.out.println("MyTAG: Adding: " + id); // if name and image exist, just print for debug

                            /* #####Everything is matching fine, but when I try to run the next two lines, I get NPE ####*/

                             //Drawable drawable = getResources().getDrawable(id);
               //ivFisk.setImageDrawable(drawable);

               }
               else if(id == 0) { //just running with a few images in drawable-folder just for testing. Takes long to load if I have all, there for a dummy test image.
                   System.out.println("MyTag: Setting test image");

                 //  ivFisk.setImageResource(R.drawable.testimage);
               }

            }
        }
       } 
       catch(Exception ex)
       {
           System.out.println("MyTag: " + ex);
       }

如果您在评论中看到，当我尝试将现有图像添加到视图时，我会得到一个 NPE：

Drawable drawable = getResources().getDrawable(id);
ivFisk.setImageDrawable(drawable);

日志说：

MyTag: Adding: 2130837504
MyTag: java.lang.NullPointerException

它清楚地读取并匹配第一项，然后停止。我觉得我是如此接近，无法理解为什么会发生这种情况。在过去的 7 个小时里，我已经尝试了很多解决方案和“修复”。请指点我一个方向或提供一些帮助。非常感谢你。

4

1 回答 1

2

如果我没有错，那么您想使用图像名称设置图像。如果是这样，那么这就是解决方案。

您可以使用Resources.getIdentifier方法。像下面这样使用它

int id = getResources().getIdentifier(myString, your_string, getPackageName());
Drawable drawable = getResources().getDrawable(id);
yourImageView.setImageDrawable(drawable);

另一个较慢的解决方案（如果有人想知道），使用反射

 Field field = R.drawable.class.getDeclaredField(your_string);
 int id  = field.getInt(this); // use this id to set background resource
于 2013-07-08T14:39:22.797 回答