我一直在使用 Picasso 用返回图像的 URL 填充 listview。这些 URL 是从 API 调用返回的。
适配器
public class RecipeAdapter extends BaseAdapter implements ListAdapter {
private final Activity activity;
private final JSONArray jsonArray;
public RecipeAdapter (Activity activity, JSONArray jsonArray){
assert activity !=null;
assert jsonArray != null;
this.jsonArray = jsonArray;
this.activity = activity;
}
@Override
public int getCount(){
if(null==jsonArray)
return 0;
else
return jsonArray.length();
}
@Override
public JSONObject getItem(int position){
if(null==jsonArray) return null;
else
return jsonArray.optJSONObject(position);
}
@Override
public long getItemId(int position){
return position;
}
@Override
public View getView (int position, View v, ViewGroup parent){
if (v == null) {
v = View.inflate(activity, R.layout.recipe_item, null);
}
CircularImageView icon = (CircularImageView)v.findViewById(R.id.recipeIcon);
TextView title = (TextView) v.findViewById(R.id.recipeTitle);
TextView supplier = (TextView) v.findViewById(R.id.supplier);
JSONObject JSdata = getItem(position);
if(null!=JSdata){
try {
if (JSdata.has("title")) {
title.setText(JSdata.getString("title"));
}
if (JSdata.has("publisher")) {
supplier.setText(JSdata.getString("publisher"));
}
if (JSdata.has("image_url")) {
String image = JSdata.getString("image_url");
String[] imagearray = image.split("\\.");
String extension = imagearray[imagearray.length - 1];
String tag = new String();
if (extension.equals("jpg")) {
if (URLUtil.isValidUrl(image)) {
Picasso.with(activity)
.load(image)
.centerCrop()
.tag(tag)
.error(R.drawable.icon01)
.resize(50, 50)
.into(icon);
} else {
Picasso.with(activity)
.load(R.drawable.icon01)
.centerCrop()
.resize(50, 50)
.tag(tag)
.into(icon);
}
}
}
} catch (JSONException e) {
Toast.makeText(activity, "Error finding recipes",
Toast.LENGTH_SHORT).show();
e.printStackTrace();
}
}
final ImageView fav = (ImageView)v.findViewById(R.id.favbutton);
fav.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
fav.setImageResource(R.drawable.ic_favorite_white_24dp);
Toast.makeText(activity, "Added to favourites",
Toast.LENGTH_SHORT).show();
}
});
return v;
}
}
我已经阅读了很多相关资料，并且尝试使用 .tag() 方法和滚动监听器:
class Populate extends AsyncTask<String, String, JSONArray> {
protected void onPreExecute() {
progress = ProgressDialog.show(RecipeSearch.this, "Finding Recipes", "Searching....", true);
}
@Override
protected JSONArray doInBackground(String... urls) {
JSONParser recipeParse = new JSONParser();
String rawJSON = recipeParse.getJSON(urls[0]);
try {
if (rawJSON != null) {
JSONObject object = new JSONObject(rawJSON);
JSONArray jArray = object.getJSONArray("recipes");
return jArray;
} else {
JSONArray jArray = null;
return jArray;
}
} catch(Exception e) {
System.out.println(e);
Toast.makeText(getApplicationContext(), "Error Searching for Recipes",
Toast.LENGTH_SHORT).show();
JSONArray jArray = null;
return jArray;
}
//do http request and add objects to array here.
//need to do a custom adapter
// return null;
}
@Override
protected void onPostExecute(JSONArray jArray) {
if (jArray != null) {
final ListView recipes = (ListView) findViewById(R.id.recipeView);
recipes.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
JSONObject selected = (JSONObject) (recipes.getItemAtPosition(position));
String url = null;
try {
url = selected.getString("source_url");
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
}
Intent i = new Intent(Intent.ACTION_VIEW);
i.setData(Uri.parse(url));
startActivity(i);
}
});
final String tag ="";
recipes.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
Picasso picasso = Picasso.with(getApplicationContext());
if (scrollState == SCROLL_STATE_IDLE ||
scrollState == SCROLL_STATE_TOUCH_SCROLL) {
picasso.resumeTag(tag);
} else {
picasso.pauseTag(tag);
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
Picasso picasso = Picasso.with(getApplicationContext());
picasso.pauseTag(tag);
}
});
recipeAdapter = new RecipeAdapter(RecipeSearch.this, jArray);//jArray is your json array
recipes.setAdapter(recipeAdapter);
} else {
Toast.makeText(getApplicationContext(), "No Recipes Found", Toast.LENGTH_SHORT).show();
finish();
}
progress.dismiss();
}
}
虽然这可能会解决问题，但是当我在大列表上滚动时，它会导致应用程序崩溃。登录目录:
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference
at android.graphics.Bitmap.createScaledBitmap(Bitmap.java:591)
at com.pkmmte.view.CircularImageView.refreshBitmapShader(CircularImageView.java:341)
at com.pkmmte.view.CircularImageView.invalidate(CircularImageView.java:262)
at android.widget.ImageView.setImageDrawable(ImageView.java:456)
at com.squareup.picasso.PicassoDrawable.setPlaceholder(PicassoDrawable.java:61)
at com.squareup.picasso.RequestCreator.into(RequestCreator.java:664)
at com.squareup.picasso.RequestCreator.into(RequestCreator.java:601)
at io.moffat.kitchenpal.RecipeAdapter.getView(RecipeAdapter.java:99)
at android.widget.AbsListView.obtainView(AbsListView.java:2347)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillUp(ListView.java:732)
at android.widget.ListView.fillGap(ListView.java:671)
at android.widget.AbsListView.trackMotionScroll(AbsListView.java:4991)
at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3418)
at android.widget.AbsListView.onTouchMove(AbsListView.java:3801)
at android.widget.AbsListView.onTouchEvent(AbsListView.java:3632)
at android.view.View.dispatchTouchEvent(View.java:8471)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2399)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2092)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2106)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2369)
at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1719)
at android.app.Activity.dispatchTouchEvent(Activity.java:2742)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:59)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:59)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2330)
at android.view.View.dispatchPointerEvent(View.java:8666)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4123)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3989)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
at android.view.ViewRootImpl.deliverInputEvent
欢迎任何帮助或建议
最佳答案
经过大量调试，弄明白了。
我使用的库试图在未正确加载时对 CircularImageView 资源使用方法。更改为不同的库，现在可以完美运行。
关于android - 使用 Picasso 在滚动列表中加载图像时崩溃应用程序，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32684120/