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Java url图像下载返回总是空的

java android

Java url图像下载返回总是空的,java,android,android-imageview,httpurlconnection,Java,Android,Android Imageview,Httpurlconnection,我做错了什么？我得到200 OK响应，但图像位图为null。我使用Asynctask检索url图像。我正在尝试将位图分配给imageview 有什么想法吗 private class loadMoreListView extends AsyncTask< Void, Void, String> { protected String doInBackground(Void... unused) { loadingMore = true;

我做错了什么？我得到200 OK响应，但图像位图为
null
。我使用
Asynctask
检索url图像。我正在尝试将位图分配给imageview

有什么想法吗

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;
        }

私有类loadMoreListView扩展了AsyncTask{
受保护字符串DOIN背景（无效…未使用）{
loadingMore=true；
位图mIcon11=null；
试一试{
URL url1=新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（“内容类型”、“应用程序/x-www-form-urlencoded”）；
int responceCode=connection.getResponseCode（）；
Log.i（“response_line”，Integer.toString（responceCode））；
InputStream isstream=null；
isstream=connection.getInputStream（）；
//名为isstream的inputstream返回null
mIcon11=BitmapFactory.decodeStream（isstream）；
}捕获（例外e）{
Log.e（“Error”，e.getMessage（））；
e、 printStackTrace（）；
}
返回结果；
}
看看/

它允许你用几行代码做你想做的事（NB注意Android 28+http URL是不可能的，除非你做一些！）

它处理图像的下载、内存或磁盘缓存和回收、线程、占位符、转换等。无需重新发明轮子。Heck您甚至可以调整图像大小并具有各种裁剪选项

Picasso.get()
  .load(url)
  .resize(50, 50)
  .centerCrop()
  .into(imageView)
更新：

dependencies {
    ...
    implementation 'com.android.volley:volley:1.1.1'
    implementation 'com.squareup.picasso:picasso:2.71828'
}

<uses-permission android:name="android.permission.INTERNET" />

<?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>

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);
    }
}
正如其他人所提到的，您不应该使用不推荐使用的
AsyncTask
。您可以使用许多其他库以线程和更可读的方式发出网络请求，如。这可以与毕加索一起使用，以实现您想要的

下面是一个从google加载一些文本以及加载文本后的图像的示例：

build.gradle:

dependencies {
    ...
    implementation 'com.android.volley:volley:1.1.1'
    implementation 'com.squareup.picasso:picasso:2.71828'
}

<uses-permission android:name="android.permission.INTERNET" />

<?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>

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);
    }
}
AndroidManifest.xml:

dependencies {
    ...
    implementation 'com.android.volley:volley:1.1.1'
    implementation 'com.squareup.picasso:picasso:2.71828'
}

<uses-permission android:name="android.permission.INTERNET" />

<?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>

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);
    }
}
fragment\u first.xml:

dependencies {
    ...
    implementation 'com.android.volley:volley:1.1.1'
    implementation 'com.squareup.picasso:picasso:2.71828'
}

<uses-permission android:name="android.permission.INTERNET" />

<?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>

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);
    }
}
FirstFragment.java:

dependencies {
    ...
    implementation 'com.android.volley:volley:1.1.1'
    implementation 'com.squareup.picasso:picasso:2.71828'
}

<uses-permission android:name="android.permission.INTERNET" />

<?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>

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);
    }
}

package com.example.myapplication；
导入android.os.Bundle；
导入android.view.LayoutInflater；
导入android.view.view；
导入android.view.ViewGroup；
导入android.widget.ImageView；
导入android.widget.TextView；
导入androidx.annotation.NonNull；
导入androidx.fragment.app.fragment；
导入com.android.volley.Request；
导入com.android.volley.RequestQueue；
导入com.android.volley.Response；
导入com.android.volley.VolleyError；
导入com.android.volley.toolbox.StringRequest；
导入com.android.volley.toolbox.volley；
导入com.squareup.picasso.picasso；
公共类FirstFragment扩展了Fragment{
@凌驾
公共视图onCreateView(
充气机、视图组容器、，
捆绑存储状态
) {
//为该碎片膨胀布局
返回充气机。充气（R.layout.fragment_first，container，false）；
}
已创建公用void onview（@NonNull视图，Bundle savedInstanceState）{
super.onViewCreated（视图，savedInstanceState）；
TextView TextView=view.findViewById（R.id.TextView）；
ImageView=view.findViewById（R.id.ImageView）；
RequestQueue=Volley.newRequestQueue（getActivity（））；
字符串url=”https://www.google.com";
//从提供的URL请求字符串响应。
StringRequest StringRequest=新的StringRequest（Request.Method.GET，url，
新的Response.Listener（）{
@凌驾
公共void onResponse（字符串响应）{
//显示响应字符串的前500个字符。
setText（“响应为：”+Response.substring（0500））；
Picasso.get（）.load（“https://i.imgur.com/DvpvklR.png）插入（图像视图）；
}
}，new Response.ErrorListener（）{
@凌驾
公共无效onErrorResponse（截击错误）{
setText（“那没用！”）；
}
});
//将请求添加到RequestQueue。
添加（stringRequest）；
}
}
图像的分辨率可能太大。请尝试较小的图像。所有图像都是这样的…需要找到一种方法…59kb是图像300x300大小300dpi您考虑过使用Glide而不是AsyncTask吗？AsyncTask已弃用。Glide？已弃用但可以使用…问题是因为AsyncTask而发生的？“Glide？已弃用，但可以使用”--Glide未弃用。
AsyncTask
已弃用。注释不用于扩展讨论；此对话已被删除。