[英]url image download returns always null android
我究竟做錯了什么? 我得到 200 OK 響應,但圖像位圖為null
。 我使用Asynctask
來檢索 url 圖像。 我正在嘗試將位圖分配給 imageview。
有什么想法嗎?
private class loadMoreListView extends AsyncTask< Void, Void, String> {
protected String doInBackground(Void... unused) {
loadingMore = true;
Bitmap mIcon11 = null;
try {
URL url1 = new URL("https://imgaz2.staticbg.com/thumb/view/oaupload/ser1/banggood/images/E4/21/c5424852-82af-47a1-8a13-54da3d1bc049.jpg");
HttpURLConnection connection = (HttpURLConnection) url1.openConnection();
connection.setReadTimeout(10000);
connection.setConnectTimeout(10000);
connection.setDoInput(true);
connection.setRequestMethod("GET");
connection.setUseCaches(false);
connection.setAllowUserInteraction(false);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
int responceCode = connection.getResponseCode();
Log.i("response_line", Integer.toString(responceCode));
InputStream isstream =null;
isstream=connection.getInputStream();
//inputstream named isstream returns null
mIcon11 = BitmapFactory.decodeStream(isstream);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return result;
}
看看畢加索/畢加索 Github 。
它允許你用幾行代碼做你想做的事情(注意Android 28+ http urls 是不行的,除非你做一些額外的工作!):
Picasso.get().load("https://i.imgur.com/DvpvklR.png").into(imageView);
它處理圖像的下載、內存或磁盤緩存和回收、線程、占位符、轉換等。 無需重新發明輪子。 哎呀,您甚至可以調整圖像大小並有各種裁剪選項
Picasso.get()
.load(url)
.resize(50, 50)
.centerCrop()
.into(imageView)
更新:
正如其他人所提到的,您不應該使用AsyncTask
作為其已棄用。 您可以使用許多其他庫以線程化和更具可讀性的方式發出網絡請求,例如Volley 。 這可以與畢加索結合使用來實現你想要的。
下面是一個示例,它從谷歌加載一些文本以及加載文本后的圖像:
構建.gradle:
dependencies {
...
implementation 'com.android.volley:volley:1.1.1'
implementation 'com.squareup.picasso:picasso:2.71828'
}
AndroidManifest.xml:
<uses-permission android:name="android.permission.INTERNET" />
fragment_first.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".FirstFragment">
<ImageView
android:id="@+id/imageview"
android:layout_width="200dp"
android:layout_height="200dp"
app:layout_constraintBottom_toTopOf="@id/textview"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_first_fragment"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/textview"/>
</androidx.constraintlayout.widget.ConstraintLayout>
FirstFragment.java:
package com.example.myapplication;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.squareup.picasso.Picasso;
public class FirstFragment extends Fragment {
@Override
public View onCreateView(
LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState
) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
TextView textView = view.findViewById(R.id.textview);
ImageView imageView = view.findViewById(R.id.imageview);
RequestQueue queue = Volley.newRequestQueue(getActivity());
String url = "https://www.google.com";
// Request a string response from the provided URL.
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
// Display the first 500 characters of the response string.
textView.setText("Response is: " + response.substring(0, 500));
Picasso.get().load("https://i.imgur.com/DvpvklR.png").into(imageView);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
textView.setText("That didn't work!");
}
});
// Add the request to the RequestQueue.
queue.add(stringRequest);
}
}
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