如何在android imageview中显示数据库中的图像

Question

嗨，在我的应用程序中，我得到了该图像中的 json 响应。我想在 android imageview 中显示该图像。在该图像中我想为 imageView 设置。

图片":"547150_156322317826149_1332901104_n.jpg

谁能帮帮我

Answer 1

好吧，我假设您从 url 获取图片，所以我建议您尝试以下代码： 在你的 main.xml 文件中创建一个简单的 ImageView：

ma​​in.xml：

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

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Loading image from url"
        android:layout_margin="10dip" />

    <ImageView android:id="@+id/image"
        android:layout_height="wrap_content"
        android:layout_width="fill_parent"
        android:layout_margin="10dip"/>

</LinearLayout>

打开您的主要活动并输入以下代码。每当您不想显示来自 url 的图像时，只需调用以下代码：

AndroidLoadImageFromURLActivity.java：

package com.androidhive.imagefromurl;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ImageView;

public class AndroidLoadImageFromURLActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Loader image - will be shown before loading image
        int loader = R.drawable.loader;

        // Imageview to show
        ImageView image = (ImageView) findViewById(R.id.image);

        // Image url
        String image_url = "http://url of the image here";

        // ImageLoader class instance
        ImageLoader imgLoader = new ImageLoader(getApplicationContext());

        // whenever you want to load an image from url
        // call DisplayImage function
        // url - image url to load
        // loader - loader image, will be displayed before getting image
        // image - ImageView 
        imgLoader.DisplayImage(image_url, loader, image);
    }
}

在您的项目中添加以下类并运行该项目：

ImageLoader.java

package com.androidhive.imagefromurl;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;

public class ImageLoader {

    MemoryCache memoryCache=new MemoryCache();
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService; 

    public ImageLoader(Context context){
        fileCache=new FileCache(context);
        executorService=Executors.newFixedThreadPool(5);
    }

    int stub_id = R.drawable.ic_launcher;
    public void DisplayImage(String url, int loader, ImageView imageView)
    {
        stub_id = loader;
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(loader);
        }
    }

    private void queuePhoto(String url, ImageView imageView)
    {
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        executorService.submit(new PhotosLoader(p));
    }

    private Bitmap getBitmap(String url)
    {
        File f=fileCache.getFile(url);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;

        //from web
        try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex){
           ex.printStackTrace();
           return null;
        }
    }

    //decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f){
        try {
            //decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f),null,o);

            //Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE=70;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {}
        return null;
    }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u;
            imageView=i;
        }
    }

    class PhotosLoader implements Runnable {
        PhotoToLoad photoToLoad;
        PhotosLoader(PhotoToLoad photoToLoad){
            this.photoToLoad=photoToLoad;
        }

        @Override
        public void run() {
            if(imageViewReused(photoToLoad))
                return;
            Bitmap bmp=getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if(imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
            Activity a=(Activity)photoToLoad.imageView.getContext();
            a.runOnUiThread(bd);
        }
    }

    boolean imageViewReused(PhotoToLoad photoToLoad){
        String tag=imageViews.get(photoToLoad.imageView);
        if(tag==null || !tag.equals(photoToLoad.url))
            return true;
        return false;
    }

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        PhotoToLoad photoToLoad;
        public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
        public void run()
        {
            if(imageViewReused(photoToLoad))
                return;
            if(bitmap!=null)
                photoToLoad.imageView.setImageBitmap(bitmap);
            else
                photoToLoad.imageView.setImageResource(stub_id);
        }
    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }

}

FileCache.java

package com.androidhive.imagefromurl;

import java.io.File;
import android.content.Context;

public class FileCache {

    private File cacheDir;

    public FileCache(Context context){
        //Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
            cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"TempImages");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }

    public File getFile(String url){
        String filename=String.valueOf(url.hashCode());
        File f = new File(cacheDir, filename);
        return f;

    }

    public void clear(){
        File[] files=cacheDir.listFiles();
        if(files==null)
            return;
        for(File f:files)
            f.delete();
    }

}

MemoryCache.java

package com.androidhive.imagefromurl;

import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import android.graphics.Bitmap;

public class MemoryCache {
    private Map<String, SoftReference<Bitmap>> cache=Collections.synchronizedMap(new HashMap<String, SoftReference<Bitmap>>());

    public Bitmap get(String id){
        if(!cache.containsKey(id))
            return null;
        SoftReference<Bitmap> ref=cache.get(id);
        return ref.get();
    }

    public void put(String id, Bitmap bitmap){
        cache.put(id, new SoftReference<Bitmap>(bitmap));
    }

    public void clear() {
        cache.clear();
    }
}

Utils.java

package com.androidhive.imagefromurl;

import java.io.InputStream;
import java.io.OutputStream;

public class Utils {
    public static void CopyStream(InputStream is, OutputStream os)
    {
        final int buffer_size=1024;
        try
        {
            byte[] bytes=new byte[buffer_size];
            for(;;)
            {
              int count=is.read(bytes, 0, buffer_size);
              if(count==-1)
                  break;
              os.write(bytes, 0, count);
            }
        }
        catch(Exception ex){}
    }
}

希望对你有所帮助，问候

Answer 2

您可以使用this library。

从 JSON 获取照片名称后，您应该创建正确的 http 链接并使用我上面提到的库。

Answer 3

RecyclerViewAdapter.java

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
Context context;
ArrayList<DataList> arrName;

public RecyclerViewAdapter(Context context, ArrayList<DataList> arrName) {
    this.context = context;
    this.arrName = arrName;
}


@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    return new ViewHolder(LayoutInflater.from(context).inflate(R.layout.name_row, viewGroup, false));
}

@Override
public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
    viewHolder.name.setText(arrName.get(i).getName());
    viewHolder.address.setText(arrName.get(i).getAddress());
    DataList datalist = arrName.get(i);

    byte[] recordImage = datalist.getImage();
    Bitmap bitmap = BitmapFactory.decodeByteArray(recordImage, 0, recordImage.length);
    viewHolder.img.setImageBitmap(bitmap);
}

@Override
public int getItemCount() {
    return arrName.size();
}

public class ViewHolder extends RecyclerView.ViewHolder {
    TextView name, address;
    ImageView img;

    public ViewHolder(@NonNull View itemView) {
        super(itemView);
        name = itemView.findViewById(R.id.name);
        address = itemView.findViewById(R.id.addr);
        img = itemView.findViewById(R.id.image);
    }
}}

MainActivity.java

public class MainActivity extends AppCompatActivity {
TextView txtChage;
Button btnChage, RemoveRecylerView;
RecyclerView recyclerView;
ArrayList<DataList> arrnames = new ArrayList<>();

ArrayList<DataList> arrData = new ArrayList<>();

dbHelper dbhelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    txtChage = findViewById(R.id.txt);
    btnChage = findViewById(R.id.ShowRecylerView);
    recyclerView = findViewById(R.id.recyclerView);
    RemoveRecylerView = findViewById(R.id.RemoveRecylerView);


    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    RecyclerViewAdapter adapter = new RecyclerViewAdapter(this, arrnames);
    recyclerView.setAdapter(adapter);

    dbhelper = dbHelper.getDb(this);
    if (!dbhelper.CheckDb()) {
        dbhelper.CreateDb(this);
    }
    dbhelper.openDb();
    arrData = dbhelper.getData();

    for (int i = 0; i < arrData.size(); i++) {
        String name = arrData.get(i).getName();
        String address = arrData.get(i).getAddress();
        byte[] img = arrData.get(i).getImage();

        arrnames.add(new DataList(name, address, img));
        adapter.notifyDataSetChanged();
    }


    adapter.notifyDataSetChanged();

    btnChage.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            txtChage.setText("Recycler Visible");
            recyclerView.setVisibility(View.VISIBLE);
            btnChage.setVisibility(View.GONE);
            RemoveRecylerView.setVisibility(View.VISIBLE);
        }
    });
    RemoveRecylerView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            txtChage.setText("Recycler Gone");
            recyclerView.setVisibility(View.GONE);
            btnChage.setVisibility(View.VISIBLE);
            RemoveRecylerView.setVisibility(View.GONE);

        }
    });
}

dbHelper.java

public class dbHelper extends SQLiteOpenHelper {
private static String Dbname = "StudentInfo.sqlite";
private String DbPath;
private SQLiteDatabase mainDb;

public dbHelper(Context context) {
    super(context, Dbname, null, 1);
    DbPath = "/data/data/" + context.getPackageName() + "/databases";
}

public static synchronized dbHelper getDb(Context context) {
    return new dbHelper(context);
}

public boolean CheckDb() {
    SQLiteDatabase database;
    try {
        database = SQLiteDatabase.openDatabase(DbPath + "/" + Dbname, null, SQLiteDatabase.OPEN_READONLY);
    } catch (Exception e) {
        database = null;
    }
    return database != null;
}

public void CreateDb(Context context) {
    this.getReadableDatabase();
    this.close();

    try {


        InputStream inputStream = context.getAssets().open(Dbname);

        String filepath = DbPath + "/" + Dbname;

        FileOutputStream fos = new FileOutputStream(filepath);

        byte[] bytes = new byte[1024];

        int length;

        while ((length = inputStream.read(bytes)) > 0) {
            fos.write(bytes, 0, length);
        }

        fos.close();
        fos.flush();
        inputStream.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public ArrayList<DataList> getData() {
    Cursor cursor = mainDb.rawQuery("Select * from Profile", null);
    ArrayList<DataList> arrData = new ArrayList<>();

    while (cursor.moveToNext()) {
        String name = cursor.getString(1);
        String Address = cursor.getString(2);
        byte[] img = cursor.getBlob(3);
        arrData.add(new DataList(name, Address, img));

    }
    return arrData;
}

public void openDb() {
    mainDb = SQLiteDatabase.openDatabase(DbPath + "/" + Dbname, null, SQLiteDatabase.OPEN_READWRITE);
}


@Override
public void onCreate(SQLiteDatabase db) {


}

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

}}

DataList.java

public class DataList {

private int id;
private byte[] image;
private String name;
private String Address;

public DataList(String name, String Address, byte[] image) {

    this.name = name;
    this.Address = Address;
    this.image = image;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public byte[] getImage() {
    return image;
}

public void setImage(byte[] image) {
    this.image = image;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getAddress() {
    return Address;
}

public void setAddress(String Address) {
    this.Address = Address;
}

}