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android - 如何在android imageview中显示来自数据库的图像

转载 作者:搜寻专家 更新时间:2023-11-01 07:56:36 26 4
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您好,在我的应用程序中,我在该图像中获得了 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

最佳答案

好吧,我会假设你从一个 url 得到你的图片,所以我建议你试试这个代码:在 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 Activity 并键入以下代码。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();
}

}

文件缓存.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();
}

}

内存缓存.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){}
}
}

希望对你有帮助,祝好

关于android - 如何在android imageview中显示来自数据库的图像,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/27168303/

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