我是初学者并尝试在应用上工作。我想在点击imageButton上的listView时创建新的网页/活动。 （图像从网址抓取）。任何帮助表示赞赏。
以下是main.java
public class IngredientCategoryMain extends Activity {
ListView list;
String[] title;
CategoryImageAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ingredient_category_main);
list=(ListView)findViewById(R.id.listView);
title = getResources().getStringArray(R.array.titles);
adapter=new CategoryImageAdapter(this, mStrings, title);
list.setAdapter(adapter);
}
@Override
public void onDestroy() {
list.setAdapter(null);
super.onDestroy();
}
public View.OnClickListener listener=new View.OnClickListener() {
@Override
public void onClick(View arg0) {
adapter.imageLoader.clearCache();
adapter.notifyDataSetChanged();
}
};
public void onItemClick(int mPosition) {
String tempValues = title[mPosition];
Toast.makeText(IngredientCategoryMain.this, "You have clicked "+tempValues, Toast.LENGTH_LONG).show();
}
private String[] mStrings={
"https://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Ic_cake_48px.svg/2000px-Ic_cake_48px.svg.png",
"https://pixabay.com/static/uploads/photo/2013/04/01/21/30/can-99137_960_720.png",
"http://publicdomainvectors.org/photos/Gerald_G_Fast_Food_Drinks_(FF_Menu)_9.png",
"https://pixabay.com/static/uploads/photo/2014/03/25/16/59/apple-297775_960_720.png",
"https://pixabay.com/static/uploads/photo/2012/04/16/11/14/mortar-35544_960_720.png",
"https://pixabay.com/static/uploads/photo/2013/07/13/10/05/cattle-156498_960_720.png",
"https://pixabay.com/static/uploads/photo/2013/07/12/15/39/acorn-150258_960_720.png",
"http://publicdomainvectors.org/photos/johnny_automatic_bread_with_knife.png",
"https://pixabay.com/static/uploads/photo/2015/09/13/00/12/chicken-937584_960_720.jpg",
"http://publicdomainvectors.org/photos/bowl-of-steaming-soup-01.png",
"https://pixabay.com/static/uploads/photo/2014/04/02/10/38/fish-304097_960_720.png",
"http://publicdomainvectors.org/photos/Erbsen-lineart.png"
};
}
适配器
public class CategoryImageAdapter extends BaseAdapter implements OnClickListener {
private Activity activity;
private String[] data;
private String[] title;
private static LayoutInflater inflater = null;
public ImageLoader imageLoader;
public CategoryImageAdapter(Activity a, String[] d, String[] t) {
activity = a;
title = t;
data = d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader = new ImageLoader(activity.getApplicationContext());
}
@Override
public int getCount() {
return title.length;
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public void onClick(View v) {
}
public static class ViewHolder {
public ImageButton imageButton;
public TextView textView;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView;
ViewHolder holder;
if (convertView == null) {
vi = inflater.inflate(R.layout.ingcategoryrow, null);
holder = new ViewHolder();
holder.textView = (TextView) vi.findViewById(R.id.textView2);
holder.imageButton = (ImageButton) vi.findViewById(R.id.imageButton2);
vi.setTag(holder);
} else
holder = (ViewHolder) vi.getTag();
holder.textView.setText(title[position]);
ImageButton imageButton = holder.imageButton;
imageLoader.DisplayImage(data[position], imageButton);
vi.setOnClickListener(new OnItemClickListener(position));
return vi;
}
private class OnItemClickListener implements OnClickListener{
private int mPosition;
OnItemClickListener(int position) {
mPosition = position;
}
@Override
public void onClick(View arg0) {
IngredientCategoryMain sct = (IngredientCategoryMain)activity;
sct.onItemClick(mPosition);
}
}
ImageLoader的
public class ImageLoader {
MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageButton, String> imageButtons = Collections.synchronizedMap(new WeakHashMap<ImageButton, String>());
ExecutorService executorService;
Handler handler = new Handler();
public ImageLoader(Context context) {
fileCache = new FileCache(context);
executorService= Executors.newFixedThreadPool(5);
}
final int stub_id=R.drawable.bakingood;
public void DisplayImage(String url, ImageButton imageButton) {
imageButtons.put(imageButton, url);
Bitmap bitmap = memoryCache.get(url);
if(bitmap!=null) {
imageButton.setImageBitmap(bitmap);
} else {
queuePhoto(url, imageButton);
imageButton.setImageResource(stub_id);
}
}
private void queuePhoto(String url, ImageButton imageButton){
PhotoToLoad p = new PhotoToLoad(url, imageButton);
executorService.submit(new PhotosLoader(p));
}
private class PhotoToLoad {
public String url;
public ImageButton imageButton;
public PhotoToLoad(String u, ImageButton i) {
url=u;
imageButton=i;
}
}
class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad) {
this.photoToLoad=photoToLoad;
}
@Override
public void run() {
try{
if(imageButtonReused(photoToLoad))
return;
Bitmap bmp = getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if(imageButtonReused(photoToLoad))
return;
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
handler.post(bd);
} catch (Throwable th) {
th.printStackTrace();
}
}
}
private Bitmap getBitmap(String url) {
File f=fileCache.getFile(url);
Bitmap b= decodeFile(f);
if(b!=null)
return b;
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();
conn.disconnect();
bitmap = decodeFile(f);
return bitmap;
} catch (Throwable ex) {
ex.printStackTrace();
if(ex instanceof OutOfMemoryError)
memoryCache.clear();
return null;
}
}
private Bitmap decodeFile(File f) {
try {
//Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
FileInputStream stream1=new FileInputStream(f);
BitmapFactory.decodeStream(stream1,null,o);
stream1.close();
//Find the correct scale value. It should be the power of 2.
// Set width/height of recreated image
final int REQUIRED_SIZE=85;
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 current scale values
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize=scale;
FileInputStream stream2=new FileInputStream(f);
Bitmap bitmap= BitmapFactory.decodeStream(stream2, null, o2);
stream2.close();
return bitmap;
} catch (FileNotFoundException e) {
}
catch (IOException e) {
e.printStackTrace();
}
return null;
}
boolean imageButtonReused(PhotoToLoad photoToLoad){
String tag=imageButtons.get(photoToLoad.imageButton);
if (tag==null || !tag.equals(photoToLoad.url))
return true;
return false;
}
class BitmapDisplayer implements Runnable {
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p) {bitmap = b;photoToLoad = p;}
public void run() {
if (imageButtonReused(photoToLoad))
return;
if (bitmap!=null)
photoToLoad.imageButton.setImageBitmap(bitmap);
else
photoToLoad.imageButton.setImageResource(stub_id);
}
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}
的MemoryCache
public class MemoryCache {
private static final String TAG = "MemoryCache";
private Map<String, Bitmap> cache = Collections.synchronizedMap(
new LinkedHashMap<String, Bitmap>(10,1.5f, true));
private long size=0;
private long limit=1000000;
public MemoryCache () {
setLimit(Runtime.getRuntime().maxMemory() / 4);
}
public void setLimit(long limit) {
this.limit = limit;
Log.i(TAG, "MemoryCache will use up to " + limit / 1024. / 1024. + "MB");
}
public Bitmap get(String id) {
try {
if (!cache.containsKey(id))
return null;
return cache.get(id);
} catch (NullPointerException ex) {
ex.printStackTrace();
return null;
}
}
public void put(String id, Bitmap bitmap) {
try{
if(cache.containsKey(id))
size-=getSizeInBytes(cache.get(id));
cache.put(id, bitmap);
size+=getSizeInBytes(bitmap);
checkSize();
}catch (Throwable th) {
th.printStackTrace();
}
}
private void checkSize() {
Log.i(TAG, "cache size="+size+" length="+cache.size());
if(size>limit) {
Iterator<Map.Entry<String, Bitmap>> iter=cache.entrySet().iterator();
while (iter.hasNext()) {
Map.Entry<String, Bitmap> entry=iter.next();
size-=getSizeInBytes(entry.getValue());
iter.remove();
if(size<=limit)
break;
}
Log.i(TAG, "Clean cache.New size "+cache.size());
}
}
public void clear() {
try{
cache.clear();
size=0;
}catch (NullPointerException ex) {
}
}
private long getSizeInBytes(Bitmap bitmap) {
if (bitmap==null)
return 0;
return bitmap.getRowBytes()*bitmap.getHeight();
}
}
FileCache
public class FileCache {
private File cacheDir;
public FileCache(Context context) {
if (android.os.Environment.getExternalStorageState().equals(
android.os.Environment.MEDIA_MOUNTED))
{
//if SDCARD is mounted (SDCARD is present on device and mounted)
cacheDir = new File(
android.os.Environment.getExternalStorageDirectory(),"LazyList");
}
else
{
// if checking on simulator the create cache dir in your application context
cacheDir=context.getCacheDir();
}
if(!cacheDir.exists()){
// create cache dir in your application context
cacheDir.mkdirs();
}
}
public void clear() {
File[] files=cacheDir.listFiles();
if(files==null)
return;
for (File f:files)
f.delete();
}
public File getFile(String url) {
//Identify images by hashcode or encode by URLEncoder.encode.
String filename=String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
return f;
}
}
的Utils
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 (IOException e) {
e.printStackTrace();
}
}
}
答案 0 :(得分：0)
在listitem.onclick中添加'startActivity（intent）'的代码 - 您可以查看正在点击的图片或位置，然后启动相应的活动。
答案 1 :(得分：0)
在适配器中，在此行之后：
std::shared_ptr<Tony>
Movie::addTony()
{
auto tony = std::make_shared<Tony>();
attachActor(tony);
return tony;
}
做这样的事情：
ImageButton imageButton = holder.imageButton;
它的工作方式是每个视图都有一个选项来响应用户“在他身上”执行的点击事件，你需要做的就是将View.OnClickListener接口的实现传递给View（通过setOnClickListener方法）就是这样。 第二步是启动一个非常简单的活动，你需要使用当前上下文和你想要启动的活动的类创建一个intent，然后从当前上下文中调用startActivity方法。
在这种情况下，当前上下文由活动参考表示。
答案 2 :(得分：0)
这一行之后
ImageButton imageButton = holder.imageButton;
只需添加以下代码行
imageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
activity.startActivity(new Intent(activity, YourActivityClass.class));
}
});