我一直在努力解决这个问题。我有一个名为imgURLS的ArrayLIst，我想添加我使用jsoup从我的网站解析的网址。但imgURLS总是空的。我在eclipse上尝试了jsoup解析，但它确实有效。当我在create方法中添加字符串而不是在URLcollector（这是一个异步实现）中添加字符串时，arraylist工作。
我的代码假设首先从我的网站获取图片网址。然后把它们放在arrayLIst中。然后使用arrayList元素（链接）在imageView中看到。
现在除了将解析后的图像链接存储在arrayList中之外，其他所有工作都有效。我需要帮助才能做到这一点。我愿意使用另一个像arrayList这样的容器，如果这样可以让事情变得更容易。感谢
<%= form_tag( '/welcome/how_much', post: true, remote: true) do %>
<span id="questions">
<h5 class="label">Estimated new home cost?</h5>
<%= text_field(:amount, {id: "house_amount", placeholder: "ex. 100,000"}, class: "form-control form-control-lg") %>
</span>
<span id="questions">
<h5 class="label">Estimated payment for a new home?</h5>
<%= text_field(:high_rent, {id: "high_rent", placeholder: "ex. 1,200"}, class: "form-control form-control-lg") %>
</span>
<span id="questions">
<h5 class="label">Current Monthly Rent?</h5>
<%= text_field(:current_rent, {id: "current_rent", placeholder: "ex. 800"}, class: "form-control form-control-lg") %>
</span>
<%= submit_tag("See how quickly you can buy a home", data: {'data-toggle' => "modal", 'data_target' => "#savings_modal"}, class: "btn btn-success btn-lg") %>
<!-- Modal for sign-up -->
<div class="modal" id="savings_modal" tabindex="-1" role="dialog">
<div class="modal-dialog" role="document">
<div class="modal-content">
<h3 class="modal-title" id="savingsModalTitle">You could be ready to buy in <%= @months_to_buy %> months</h3>
<h5 class="modal-title">and have <%= @total_savings %>* to put towards a down payment & a drastically increased credit score using LikeHome</h5>
<div class="modal-body">
<h4>Sign-up Now to get started!</h4>
<%= render '_tenant_signup_modal_form.html.erb' %>
</div>
</div>
</div>
</div>
错误
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
ImageView imageView;
int count = 0;
String websteURL = "https://wubewallpapers.wordpress.com/";
//String url1 = "https://wubewallpapers.files.wordpress.com/2018/03/landscape.jpg?w=134&h=201&zoom=2";
ArrayList<String> imgURLS = new ArrayList<>();
//ArrayList<String> imgURLS2 = new ArrayList<>();
//ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout. ,imgURLS );
Button setBKG;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = findViewById(R.id.imageView);
setBKG = findViewById(R.id.setBKG);
new URLcollector().execute(websteURL);
loadImageFromUrl(imgURLS.get(count));
imageView.setOnTouchListener(new OnSwipeTouchListener(MainActivity.this) {
public void onSwipeRight() {
Toast.makeText(MainActivity.this, "right : " + imgURLS.size(), Toast.LENGTH_SHORT).show();
if (count == imgURLS.size() - 1) {
count = 0;
} else {
count++;
}
loadImageFromUrl(imgURLS.get(count));
}
public void onSwipeLeft() {
// Toast.makeText(MainActivity.this, "left", Toast.LENGTH_SHORT).show();
if (count == 0) {
count = imgURLS.size() - 1;
} else {
count -= 1;
}
loadImageFromUrl(imgURLS.get(count));
}
});
}
public void loadImageFromUrl(String url) {
Picasso.with(this).load(url).placeholder(R.mipmap.ic_launcher) // optional
.error(R.mipmap.ic_launcher) //if error
.into(imageView, new com.squareup.picasso.Callback() {
@Override
public void onSuccess() {
// if user clicked on set wallpaper
// then set wallpaper
setBKG.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Bitmap bitmap = ((BitmapDrawable) imageView.getDrawable()).getBitmap();
WallpaperManager myWallpaperManager = WallpaperManager
.getInstance(getApplicationContext());
try {
myWallpaperManager.setBitmap(bitmap);
Toast.makeText(MainActivity.this, "wallpaper changed", Toast.LENGTH_LONG).show();
} catch (IOException e) {
Toast.makeText(MainActivity.this, "There was an error", Toast.LENGTH_LONG).show();
}
}
});
}
@Override
public void onError() {
}
});
}
public class OnSwipeTouchListener implements OnTouchListener {
private final GestureDetector gestureDetector;
public OnSwipeTouchListener(Context ctx) {
gestureDetector = new GestureDetector(ctx, new GestureListener());
}
@Override
public boolean onTouch(View v, MotionEvent event) {
return gestureDetector.onTouchEvent(event);
}
private final class GestureListener extends SimpleOnGestureListener {
private static final int SWIPE_THRESHOLD = 100;
private static final int SWIPE_VELOCITY_THRESHOLD = 100;
@Override
public boolean onDown(MotionEvent e) {
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
boolean result = false;
try {
float diffY = e2.getY() - e1.getY();
float diffX = e2.getX() - e1.getX();
if (Math.abs(diffX) > Math.abs(diffY)) {
if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
if (diffX > 0) {
onSwipeRight();
} else {
onSwipeLeft();
}
result = true;
}
} else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
if (diffY > 0) {
onSwipeBottom();
} else {
onSwipeTop();
}
result = true;
}
} catch (Exception exception) {
exception.printStackTrace();
}
return result;
}
}
public void onSwipeRight() {
}
public void onSwipeLeft() {
}
public void onSwipeTop() {
}
public void onSwipeBottom() {
}
}
private class URLcollector extends AsyncTask<String, Void, ArrayList<String>> {
private static final String TAG = "MainActivity";
ArrayList<String> imgURLS2 = new ArrayList<>();
// these Strings / or String are / is the parameters of the task, that can be handed over via the excecute(params) method of AsyncTask
protected ArrayList<String> doInBackground(String... params) {
String param1 = params[0];
try {
Document document = Jsoup
.connect("https://wubewallpapers.wordpress.com/").get();
Elements spanElements = document.select("img");
for (Element imgElement : spanElements) {
imgURLS2.add(imgElement.attr("src"));
}
} catch (Exception e) {
Log.e(TAG, Log.getStackTraceString(e));
}
// the Integer variable is used for progress
publishProgress();
// once the data is downloaded (for example JSON data)
// parse the data and return it to the onPostExecute() method
// in this example the return data is simply a long value
// this could also be a list of your custom-objects, ...
return imgURLS;
}
// the onPostexecute method receives the return type of doInBackGround()
@Override
protected void onPostExecute(ArrayList<String> result) {
// do something with the result, for example display the received Data in a ListView
// in this case, "result" would contain the "someLong" variable returned by doInBackground();
imgURLS = imgURLS2;
}
}
}
05-28 20:52
答案 0 :(得分：0)
这里的问题很简单 - AsyncTask.execute是异步。它在一个单独的线程中启动任务，然后在任务运行之前立即返回。这就是为什么你的列表是空的并抛出IndexOutOfBoundsException。它尚未填充，因为AsyncTask尚未运行。最简单的解决方案是在执行调用后将所有内容都放在onCreate中，然后将其放在onPostExecute方法中。
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = findViewById(R.id.imageView);
setBKG = findViewById(R.id.setBKG);
new URLcollector().execute(websteURL);
// take it from here...
}
@Override
protected void onPostExecute(ArrayList<String> result) {
// do something with the result, for example display the received Data in a ListView
// in this case, "result" would contain the "someLong" variable returned by doInBackground();
imgURLS = imgURLS2;
// ...and put it here
loadImageFromUrl(imgURLS.get(count));
imageView.setOnTouchListener(new OnSwipeTouchListener(MainActivity.this) {
public void onSwipeRight() {
Toast.makeText(MainActivity.this, "right : " + imgURLS.size(), Toast.LENGTH_SHORT).show();
if (count == imgURLS.size() - 1) {
count = 0;
} else {
count++;
}
loadImageFromUrl(imgURLS.get(count));
}
public void onSwipeLeft() {
// Toast.makeText(MainActivity.this, "left", Toast.LENGTH_SHORT).show();
if (count == 0) {
count = imgURLS.size() - 1;
} else {
count -= 1;
}
loadImageFromUrl(imgURLS.get(count));
}
});
}
答案 1 :(得分：0)
嗨，请查看以下几点
1.您正在尝试访问0元素：
new URLcollector（）。execute（websteURL）; loadImageFromUrl（imgURLS.get（计数））;
但你没有把它用于imgURLS